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Forbes LM, Bull TM, Lahm T, Sisson T, O'Gean K, Lawley JS, Hunter K, Levine BD, Lovering A, Roach RC, Subudhi AW, Cornwell WK. Right ventricular performance during acute hypoxic exercise. J Physiol 2024. [PMID: 38409819 DOI: 10.1113/jp284943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 02/01/2024] [Indexed: 02/28/2024] Open
Abstract
Acute hypoxia increases pulmonary arterial (PA) pressures, though its effect on right ventricular (RV) function is controversial. The objective of this study was to characterize exertional RV performance during acute hypoxia. Ten healthy participants (34 ± 10 years, 7 males) completed three visits: visits 1 and 2 included non-invasive normoxic (fraction of inspired oxygen (F i O 2 ${F_{{\mathrm{i}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) = 0.21) and isobaric hypoxic (F i O 2 ${F_{{\mathrm{i}}{{\mathrm{O}}_{\mathrm{2}}}}}$ = 0.12) cardiopulmonary exercise testing (CPET) to determine normoxic/hypoxic maximal oxygen uptake (V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ ). Visit 3 involved invasive haemodynamic assessments where participants were randomized 1:1 to either Swan-Ganz or conductance catheterization to quantify RV performance via pressure-volume analysis. Arterial oxygen saturation was determined by blood gas analysis from radial arterial catheterization. During visit 3, participants completed invasive submaximal CPET testing at 50% normoxicV ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ and again at 50% hypoxicV ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ (F i O 2 ${F_{{\mathrm{i}}{{\mathrm{O}}_{\mathrm{2}}}}}$ = 0.12). Median (interquartile range) values for non-invasiveV ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ values during normoxic and hypoxic testing were 2.98 (2.43, 3.66) l/min and 1.84 (1.62, 2.25) l/min, respectively (P < 0.0001). Mean PA pressure increased significantly when transitioning from rest to submaximal exercise during normoxic and hypoxic conditions (P = 0.0014). Metrics of RV contractility including preload recruitable stroke work, dP/dtmax , and end-systolic pressure increased significantly during the transition from rest to exercise under normoxic and hypoxic conditions. Ventricular-arterial coupling was maintained during normoxic exercise at 50%V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ . During submaximal exercise at 50% of hypoxicV ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ , ventricular-arterial coupling declined but remained within normal limits. In conclusion, resting and exertional RV functions are preserved in response to acute exposure to hypoxia at anF i O 2 ${F_{{\mathrm{i}}{{\mathrm{O}}_{\mathrm{2}}}}}$ = 0.12 and the associated increase in PA pressures. KEY POINTS: The healthy right ventricle augments contractility, lusitropy and energetics during periods of increased metabolic demand (e.g. exercise) in acute hypoxic conditions. During submaximal exercise, ventricular-arterial coupling decreases but remains within normal limits, ensuring that cardiac output and systemic perfusion are maintained. These data describe right ventricular physiological responses during submaximal exercise under conditions of acute hypoxia, such as occurs during exposure to high altitude and/or acute hypoxic respiratory failure.
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Affiliation(s)
- Lindsay M Forbes
- Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado, Aurora, CO, USA
| | - Todd M Bull
- Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado, Aurora, CO, USA
| | - Tim Lahm
- Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado, Aurora, CO, USA
- Division of Pulmonary, Critical Care and Sleep Medicine, National Jewish Health, Denver, CO, USA
- Rocky Mountain Regional Veterans Affairs Medical Center, Aurora, CO, USA
| | - Tyler Sisson
- Clinical Translational Research Center, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Katie O'Gean
- Clinical Translational Research Center, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Justin S Lawley
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Kendall Hunter
- Department of Bioengineering, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Benjamin D Levine
- Division of Cardiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, TX, USA
| | - Andrew Lovering
- Department of Physiology, University of Oregon, Eugene, OR, USA
| | - Robert C Roach
- Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado, Aurora, CO, USA
| | - Andrew W Subudhi
- Department of Physiology, University of Colorado, Colorado Springs, CO, USA
| | - William K Cornwell
- Clinical Translational Research Center, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- Division of Cardiology, Department of Medicine, University of Colorado, Aurora, CO, USA
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Bourdillon N, Subudhi AW, Fan JL, Evero O, Elliott JE, Lovering AT, Roach RC, Kayser B. AltitudeOmics: effects of 16 days acclimatization to hypobaric hypoxia on muscle oxygen extraction during incremental exercise. J Appl Physiol (1985) 2023; 135:823-832. [PMID: 37589059 PMCID: PMC10642515 DOI: 10.1152/japplphysiol.00100.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 07/11/2023] [Accepted: 08/03/2023] [Indexed: 08/18/2023] Open
Abstract
Acute altitude exposure lowers arterial oxygen content ([Formula: see text]) and cardiac output ([Formula: see text]) at peak exercise, whereas O2 extraction from blood to working muscles remains similar. Acclimatization normalizes [Formula: see text] but not peak [Formula: see text] nor peak oxygen consumption (V̇o2peak). To what extent acclimatization impacts muscle O2 extraction remains unresolved. Twenty-one sea-level residents performed an incremental cycling exercise to exhaustion near sea level (SL), in acute (ALT1) and chronic (ALT16) hypoxia (5,260 m). Arterial blood gases, gas exchange at the mouth and oxy- (O2Hb) and deoxyhemoglobin (HHb) of the vastus lateralis were recorded to assess arterial O2 content ([Formula: see text]), [Formula: see text], and V̇o2. The HHb-V̇o2 slope was taken as a surrogate for muscle O2 extraction. During moderate-intensity exercise, HHb-V̇o2 slope increased to a comparable extent at ALT1 (2.13 ± 0.94) and ALT16 (2.03 ± 0.88) compared with SL (1.27 ± 0.12), indicating increased O2 extraction. However, the HHb/[Formula: see text] ratio increased from SL to ALT1 and then tended to go back to SL values at ALT16. During high-intensity exercise, HHb-V̇o2 slope reached a break point beyond which it decreased at SL and ALT1, but not at ALT16. Increased muscle O2 extraction during submaximal exercise was associated with decreased [Formula: see text] in acute hypoxia. The significantly greater muscle O2 extraction during maximal exercise in chronic hypoxia is suggestive of an O2 reserve.NEW & NOTEWORTHY During incremental exercise muscle deoxyhemoglobin (HHb) and oxygen consumption (V̇o2) both increase linearly, and the slope of their relationship is an indirect index of local muscle O2 extraction. The latter was assessed at sea level, in acute and during chronic exposure to 5,260 m. The demonstrated presence of a muscle O2 extraction reserve during chronic exposure is coherent with previous studies indicating both limited muscle oxidative capacity and decrease in motor drive.
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Affiliation(s)
- Nicolas Bourdillon
- Institute of Sports Sciences, University of Lausanne, Lausanne, Switzerland
| | - Andrew W Subudhi
- Hybl Sports Medicine and Performance Center, Department of Human Physiology and Nutrition, University of Colorado, Colorado Springs, Colorado, United States
| | - Jui-Lin Fan
- Department of Physiology, Faculty of Medical & Health Sciences, Manaaki Manawa-The Centre for Heart Research, University of Auckland, Auckland, New Zealand
| | - Oghenero Evero
- Altitude Research Center, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States
| | - Jonathan E Elliott
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States
| | - Andrew T Lovering
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States
| | - Robert C Roach
- Altitude Research Center, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States
| | - Bengt Kayser
- Institute of Sports Sciences, University of Lausanne, Lausanne, Switzerland
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Forbes LM, Bull TM, Lahm T, Lawley JS, Hunter K, Levine BD, Lovering A, Roach RC, Subudhi AW, Cornwell WK. Right Ventricular Response to Acute Hypoxia among Healthy Humans. Am J Respir Crit Care Med 2023; 208:333-336. [PMID: 37311248 PMCID: PMC10395728 DOI: 10.1164/rccm.202303-0599le] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Accepted: 06/07/2023] [Indexed: 06/15/2023] Open
Affiliation(s)
| | - Todd M. Bull
- Division of Pulmonary Sciences and Critical Care Medicine
| | - Tim Lahm
- Division of Pulmonary Sciences and Critical Care Medicine
- Division of Pulmonary, Critical Care and Sleep Medicine, National Jewish Health, Denver, Colorado
- Rocky Mountain Regional Veterans Affairs Medical Center, Aurora, Colorado
| | - Justin S. Lawley
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
| | | | - Benjamin D. Levine
- Division of Cardiology, University of Texas Southwestern Medical Center, Dallas, Texas
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, Texas
| | - Andrew Lovering
- Department of Physiology, University of Oregon, Eugene, Oregon; and
| | | | - Andrew W. Subudhi
- Department of Physiology, University of Colorado, Colorado Springs, Colorado
| | - William K. Cornwell
- Division of Cardiology
- Clinical Translational Research Center, University of Colorado Anschutz Medical Campus, Aurora, Colorado
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4
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Subudhi AW, Batterson PM, Hubbell ED, Jacobs RA. Reliability Of Cycling Time Trials Performed At Maximal And Submaximal Intensities. Med Sci Sports Exerc 2020. [DOI: 10.1249/01.mss.0000670436.51071.0e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Subudhi AW, Evero O, Reitinger J, Davis C, Gronewold J, Nichols AJ, Van‐Houten SJ, Roach RC. Combined methazolamide and theophylline improves oxygen saturation but not exercise performance or altitude illness in acute hypobaric hypoxia. Exp Physiol 2020; 106:117-125. [DOI: 10.1113/ep088461] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Accepted: 04/29/2020] [Indexed: 01/04/2023]
Affiliation(s)
- Andrew W. Subudhi
- Altitude Research Center University of Colorado Anschutz Medical Campus Aurora CO USA
- Department of Human Physiology and Nutrition University of Colorado Colorado Springs Colorado Springs CO USA
| | - Oghenero Evero
- Altitude Research Center University of Colorado Anschutz Medical Campus Aurora CO USA
| | - Jeremy Reitinger
- Altitude Research Center University of Colorado Anschutz Medical Campus Aurora CO USA
| | - Christopher Davis
- Altitude Research Center University of Colorado Anschutz Medical Campus Aurora CO USA
| | - Jeffrey Gronewold
- Altitude Research Center University of Colorado Anschutz Medical Campus Aurora CO USA
| | - Andrew J. Nichols
- Altitude Research Center University of Colorado Anschutz Medical Campus Aurora CO USA
| | | | - Robert C. Roach
- Altitude Research Center University of Colorado Anschutz Medical Campus Aurora CO USA
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Bourdillon N, Yazdani S, Vesin JM, Subudhi AW, Lovering AT, Roach RC, Kayser B. AltitudeOmics: Spontaneous Baroreflex Sensitivity During Acclimatization to 5,260 m: A Comparison of Methods. Front Physiol 2020; 10:1505. [PMID: 31920710 PMCID: PMC6914841 DOI: 10.3389/fphys.2019.01505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Accepted: 11/28/2019] [Indexed: 11/13/2022] Open
Abstract
Introduction Baroreflex sensitivity (BRS) is essential to ensure rapid adjustment to variations in blood pressure (BP). Spontaneous baroreflex function can be assessed using continuous recordings of blood pressure. The goal of this study was to compare four methods for BRS quantification [the sequence, Bernardi's (BER), frequency and transfer function methods] to identify the most consistent method across an extreme range of conditions: rest and exercise, in normoxia, hypoxia, hypocapnia, and hypercapnia. Methods Using intra-radial artery BP in young healthy participants, BRS was calculated and compared using the four methods in normoxia, acute and chronic hypoxia (terrestrial altitude of 5,260 m) in hypocapnia (hyperventilation), hypercapnia (rebreathing) and during ramp exercise to exhaustion. Results The sequence and BER methods for BRS estimation showed good agreement during the resting and exercise protocols, whilst the ultra- and very-low frequency bands of the frequency and transfer function methods were more discrepant. Removing respiratory frequency from the blood pressure traces affected primarily the sequence and BER methods and occasionally the frequency and transfer function methods. Discussion/Conclusion The sequence and BER methods contained more respiratory related information than the frequency and transfer function methods, indicating that the former two methods predominantly rely on respiratory effects of BRS. BER method is recommended because it is the easiest to compute and even though it tends to overestimate BRS compared to the sequence method, it is consistent with the other methods, whilst its interquartile range is the smallest.
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Affiliation(s)
- Nicolas Bourdillon
- Institue of Sport Sciences, University of Lausanne, Lausanne, Switzerland
| | - Sasan Yazdani
- Applied Signal Processing Group, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Jean-Marc Vesin
- Applied Signal Processing Group, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Andrew W Subudhi
- Altitude Research Center, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States.,Human Physiology and Nutrition, University of Colorado Colorado Springs, Colorado Springs, CO, United States
| | - Andrew T Lovering
- Department of Human Physiology, University of Oregon, Eugene, OR, United States
| | - Robert C Roach
- Altitude Research Center, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Bengt Kayser
- Institue of Sport Sciences, University of Lausanne, Lausanne, Switzerland
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7
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Batterson PM, Norton MR, Hetz SE, Rohilla S, Lindsay KG, Subudhi AW, Jacobs RA. Improving biologic predictors of cycling endurance performance with near-infrared spectroscopy derived measures of skeletal muscle respiration: E pluribus unum. Physiol Rep 2020; 8:e14342. [PMID: 31960629 PMCID: PMC6971325 DOI: 10.14814/phy2.14342] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The study aim was to compare the predictive validity of the often referenced traditional model of human endurance performance (i.e. oxygen consumption, VO2 , or power at maximal effort, fatigue threshold values, and indices of exercise efficiency) versus measures of skeletal muscle oxidative potential in relation to endurance cycling performance. We hypothesized that skeletal muscle oxidative potential would more completely explain endurance performance than the traditional model, which has never been collectively verified with cycling. Accordingly, we obtained nine measures of VO2 or power at maximal efforts, 20 measures reflective of various fatigue threshold values, 14 indices of cycling efficiency, and near-infrared spectroscopy-derived measures reflecting in vivo skeletal muscle oxidative potential. Forward regression modeling identified variable combinations that best explained 25-km time trial time-to-completion (TTC) across a group of trained male participants (n = 24). The time constant for skeletal muscle oxygen consumption recovery, a validated measure of maximal skeletal muscle respiration, explained 92.7% of TTC variance by itself (Adj R2 = .927, F = 294.2, SEE = 71.2, p < .001). Alternatively, the best complete traditional model of performance, including VO2max (L·min-1 ), %VO2max determined by the ventilatory equivalents method, and cycling economy at 50 W, only explained 76.2% of TTC variance (Adj R2 = .762, F = 25.6, SEE = 128.7, p < .001). These results confirm our hypothesis by demonstrating that maximal rates of skeletal muscle respiration more completely explain cycling endurance performance than even the best combination of traditional variables long postulated to predict human endurance performance.
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Affiliation(s)
- Philip M. Batterson
- Department of BiologyUniversity of Colorado Colorado SpringsColorado SpringsCOUSA
| | - Michael R. Norton
- Department of BiologyUniversity of Colorado Colorado SpringsColorado SpringsCOUSA
| | - Sarah E. Hetz
- Department of BiologyUniversity of Colorado Colorado SpringsColorado SpringsCOUSA
| | - Sachi Rohilla
- Department of BiologyUniversity of Colorado Colorado SpringsColorado SpringsCOUSA
| | - Keston G. Lindsay
- Department of Human Physiology and NutritionUniversity of Colorado Colorado SpringsColorado SpringsCOUSA
- Department of Health SciencesUniversity of Colorado Colorado SpringsColorado SpringsCOUSA
| | - Andrew W. Subudhi
- Department of BiologyUniversity of Colorado Colorado SpringsColorado SpringsCOUSA
- Department of Human Physiology and NutritionUniversity of Colorado Colorado SpringsColorado SpringsCOUSA
| | - Robert A. Jacobs
- Department of BiologyUniversity of Colorado Colorado SpringsColorado SpringsCOUSA
- Department of Human Physiology and NutritionUniversity of Colorado Colorado SpringsColorado SpringsCOUSA
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8
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Chung S, Nelson MD, Hamaoka T, Jacobs RA, Pearson J, Subudhi AW, Jenkins NT, Bartlett MF, Fitzgerald LF, Miehm JD, Kent JA, Lucero AA, Rowlands DS, Stoner L, McCully KK, Call J, Rodriguez-Miguelez P, Harris RA, Porcelli S, Rasica L, Marzorati M, Quaresima V, Ryan TE, Vernillo G, Millet GP, Malatesta D, Millet GY, Zuo L, Chuang CC. Commentaries on Viewpoint: Principles, insights, and potential pitfalls of the noninvasive determination of muscle oxidative capacity by near-infrared spectroscopy. J Appl Physiol (1985) 2019; 124:249-255. [PMID: 29364790 DOI: 10.1152/japplphysiol.00857.2017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | - Lee Stoner
- Massey University,University of North Carolina at Chapel Hill
| | | | | | | | | | | | - Letizia Rasica
- National Research Council, Italy,University of Milan, Italy
| | | | | | | | | | | | | | | | - Li Zuo
- The Ohio State University College of Medicine
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9
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Batterson PM, Norton MR, Hetz SE, Rohilla S, Lindsay K, Subudhi AW, Jacobs RA. Redefining Physiologic Predictors of Endurance Performance with Measures of Skeletal Muscle Oxygenation: E pluribus unum. Med Sci Sports Exerc 2019. [DOI: 10.1249/01.mss.0000560724.81978.40] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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10
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Pizzey FK, Tourula EN, Theorin TJ, Subudhi AW, Pearson J. The Impact of Caffeine on Dynamic Cerebral Autoregulation in Habitual Consumers. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.855.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Faith K Pizzey
- BiologyUniversity of Colorado Colorado SpringsColorado SpringsCO
| | - Erica N Tourula
- BiologyUniversity of Colorado Colorado SpringsColorado SpringsCO
| | - Tyler J Theorin
- BiologyUniversity of Colorado Colorado SpringsColorado SpringsCO
| | - Andrew W Subudhi
- BiologyUniversity of Colorado Colorado SpringsColorado SpringsCO
| | - James Pearson
- BiologyUniversity of Colorado Colorado SpringsColorado SpringsCO
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11
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Williams KA, Bell K, Jacobs RA, Subudhi AW. Supplemental Oxygen Does Not Influence Self-selected Work Rate at Moderate Altitude. Med Sci Sports Exerc 2018; 51:575-581. [PMID: 30299413 DOI: 10.1249/mss.0000000000001801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
INTRODUCTION It is well known that supplemental oxygen can increase aerobic power output during high-intensity and/or maximal efforts at moderate altitude, yet the effects on self-selected work rate during lower-intensity, submaximal exercise are unknown. We reasoned that if the degree of arterial oxygen saturation (SaO2) influences teleoanticipatory regulation of power output, supplemental oxygen given at moderate altitude would increase average power output during exercise performed at self-selected work rates corresponding to RPE 9 (very light) and 13 (somewhat hard). METHODS Twenty-three subjects (17 males, 6 females) completed one familiarization [fraction of inspired O2 (FIO2) = 0.209] and two blinded, experimental trials (FIO2 = 0.209 and FIO2 = 0.267). In each trial, subjects self-regulated their work rate on a cycle ergometer to maintain RPE 9 for 5 min and RPE 13 for 10 min, before performing an incremental step test to exhaustion (25 W·min). Oxygen consumption (V˙O2) and SaO2 via pulse oximetry (SpO2) were continuously monitored. Subjects were asked to guess the experimental condition after each stage of the protocol. RESULTS Supplemental oxygen increased SpO2 throughout exercise (~4%; P < 0.001) and was associated with greater peak power output (4% ± 4%; P < 0.001) and V˙O2 (5% ± 10%; P = 0.010) during the incremental test, but did not increase average power output selected during exercise at RPE 9 (P = 0.235) or 13 (P = 0.992). Subjects were unable to perceive the difference in FIO2 at any stage (P > 0.14). CONCLUSIONS Small increases in inspired oxygen concentration at moderate altitude are imperceptible and do not appear to influence selection of submaximal work rates at RPE ≤ 13.
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Affiliation(s)
- Kirsten A Williams
- University of Colorado Colorado Springs, Department of Biology, Colorado Springs, CO
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12
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Bourdillon N, Yazdani S, Subudhi AW, Lovering AT, Roach RC, Vesin JM, Kayser B. AltitudeOmics: Baroreflex Sensitivity During Acclimatization to 5,260 m. Front Physiol 2018; 9:767. [PMID: 29977210 PMCID: PMC6021743 DOI: 10.3389/fphys.2018.00767] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Accepted: 05/31/2018] [Indexed: 11/13/2022] Open
Abstract
Introduction: Baroreflex sensitivity (BRS) is essential to ensure rapid adjustment to variations in blood pressure (BP). Little is known concerning the adaptive responses of BRS during acclimatization to high altitude at rest and during exercise. Methods: Twenty-one healthy sea-level residents were tested near sea level (SL, 130 m), the 1st (ALT1) and 16th day (ALT16) at 5,260 m using radial artery catheterization. BRS was calculated using the sequence method (direct interpretation of causal link between BP and heartrate). At rest, subjects breathed a hyperoxic mixture (250 mmHg O2, end tidal) to isolate the preponderance of CO2 chemoreceptors. End-tidal CO2 varied from 20 to 50 mmHg to assess peripheral chemoreflex. Rebreathing provoked incremental increase in CO2, increasing BP to assess baroreflex. During incremental cycling exercise to exhaustion, subjects breathed room air. Results: Resting BRS decreased in ALT1 which was exacerbated in ALT16. This decrease in ALT1 was reversible upon additional inspired CO2, but not in ALT16. BRS decrease during exercise was greater and occurred at lower workloads in ALT1 compared to SL. At ALT16, this decrease returned toward SL values. Discussion/Conclusion: This study is the first to report attenuated BRS in acute hypoxia, exacerbated in chronic hypoxia. In ALT1, hypocapnia triggered BRS reduction whilst in ALT16 resetting of chemoreceptor triggered BRS reduction. The exercise BRS resetting was impaired in ALT1 but normalized in ALT16. These BRS decreases indicate decreased control of BP and may explain deteriorations of cardiovascular status during exposure to high altitude.
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Affiliation(s)
- Nicolas Bourdillon
- Institute of Sports Sciences of the University of Lausanne, Lausanne, Switzerland
| | - Sasan Yazdani
- Applied Signal Processing Group, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Andrew W Subudhi
- Department of Biology, University of Colorado, Colorado Springs, CO, United States.,Altitude Research Center, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Andrew T Lovering
- Department of Human Physiology, University of Oregon, Eugene, OR, United States
| | - Robert C Roach
- Altitude Research Center, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Jean-Marc Vesin
- Applied Signal Processing Group, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Bengt Kayser
- Institute of Sports Sciences of the University of Lausanne, Lausanne, Switzerland
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13
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Chicco AJ, Le CH, Gnaiger E, Dreyer HC, Muyskens JB, D'Alessandro A, Nemkov T, Hocker AD, Prenni JE, Wolfe LM, Sindt NM, Lovering AT, Subudhi AW, Roach RC. Adaptive remodeling of skeletal muscle energy metabolism in high-altitude hypoxia: Lessons from AltitudeOmics. J Biol Chem 2018. [PMID: 29540485 DOI: 10.1074/jbc.ra117.000470] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Metabolic responses to hypoxia play important roles in cell survival strategies and disease pathogenesis in humans. However, the homeostatic adjustments that balance changes in energy supply and demand to maintain organismal function under chronic low oxygen conditions remain incompletely understood, making it difficult to distinguish adaptive from maladaptive responses in hypoxia-related pathologies. We integrated metabolomic and proteomic profiling with mitochondrial respirometry and blood gas analyses to comprehensively define the physiological responses of skeletal muscle energy metabolism to 16 days of high-altitude hypoxia (5260 m) in healthy volunteers from the AltitudeOmics project. In contrast to the view that hypoxia down-regulates aerobic metabolism, results show that mitochondria play a central role in muscle hypoxia adaptation by supporting higher resting phosphorylation potential and enhancing the efficiency of long-chain acylcarnitine oxidation. This directs increases in muscle glucose toward pentose phosphate and one-carbon metabolism pathways that support cytosolic redox balance and help mitigate the effects of increased protein and purine nucleotide catabolism in hypoxia. Muscle accumulation of free amino acids favor these adjustments by coordinating cytosolic and mitochondrial pathways to rid the cell of excess nitrogen, but might ultimately limit muscle oxidative capacity in vivo Collectively, these studies illustrate how an integration of aerobic and anaerobic metabolism is required for physiological hypoxia adaptation in skeletal muscle, and highlight protein catabolism and allosteric regulation as unexpected orchestrators of metabolic remodeling in this context. These findings have important implications for the management of hypoxia-related diseases and other conditions associated with chronic catabolic stress.
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Affiliation(s)
- Adam J Chicco
- From the Departments of Biomedical Sciences, .,Cell and Molecular Biology, and
| | | | - Erich Gnaiger
- the Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Hans C Dreyer
- the Department of Human Physiology, University of Oregon, Eugene, Oregon 97403-1240, and
| | - Jonathan B Muyskens
- the Department of Human Physiology, University of Oregon, Eugene, Oregon 97403-1240, and
| | | | - Travis Nemkov
- the Department of Biochemistry and Molecular Genetics and
| | - Austin D Hocker
- the Department of Human Physiology, University of Oregon, Eugene, Oregon 97403-1240, and
| | - Jessica E Prenni
- Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523
| | - Lisa M Wolfe
- Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523
| | - Nathan M Sindt
- Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523
| | - Andrew T Lovering
- the Department of Human Physiology, University of Oregon, Eugene, Oregon 97403-1240, and
| | - Andrew W Subudhi
- the Department of Biology, University of Colorado, Colorado Springs, Colorado 80918
| | - Robert C Roach
- Altitude Research Center, University of Colorado-Anschutz Medical Campus, Aurora 80045, Colorado 80045
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14
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Bell K, Subudhi AW. Effects Of Supplemental Oxygen On Submaximal And Maximal Cycling Performance At Altitude. Med Sci Sports Exerc 2017. [DOI: 10.1249/01.mss.0000517523.38543.c2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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15
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Horiuchi M, Subudhi AW. Reply. Exp Physiol 2017; 102:384. [PMID: 28247478 DOI: 10.1113/ep086243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Masahiro Horiuchi
- Division of Human Environmental Science, Mount Fuji Research Institute, Yamanshi, Japan
| | - Andrew W Subudhi
- Department of Biology, University of Colorado, Colorado Springs, CO, USA.,Altitude Research Center, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
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16
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Garrett ZK, Pearson J, Subudhi AW. Postural effects on cerebral blood flow and autoregulation. Physiol Rep 2017; 5:5/4/e13150. [PMID: 28242827 PMCID: PMC5328778 DOI: 10.14814/phy2.13150] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2016] [Revised: 01/10/2017] [Accepted: 01/13/2017] [Indexed: 11/24/2022] Open
Abstract
Cerebral autoregulation (CA) is thought to maintain relatively constant cerebral blood flow (CBF) across normal blood pressures. To determine if postural changes alter CA, we measured cerebral blood flow velocity (CBFv) in the middle cerebral arteries, mean arterial blood pressure (MABP), cardiac output (Q), and end‐tidal carbon dioxide (PETCO2) in 18 healthy individuals (11 female and seven male; 26 ± 9 years) during repeated periods of supine and seated rest. Multiple regression was used to evaluate the influence of PETCO2, MABP, Q, and hydrostatic pressure on CBFv. Static CA was assessed by evaluating absolute changes in steady‐state CBFv. Dynamic CA was assessed by transfer function analysis of the CBFv response to spontaneous oscillations in MABP. In the seated versus supine posture, MABP (67.2 ± 7.2 vs. 84.2 ± 12.1 mmHg; P < 0.001), CBFv (55.2 ± 9.1 vs. 63.6 ± 10.6 cm/sec; P < 0.001) and PETCO2 (29.1 ± 2.6 vs. 30.9 ± 2.3 mmHg; P < 0.001) were reduced. Changes in CBFv were not explained by variance in PETCO2, MABP, Q, or hydrostatic pressure. A reduction in MABP to CBFv transfer function gain while seated (P < 0.01) was explained by changes in the power spectrum of MABP, not CBFv. Our findings suggest that changes in steady‐state cerebral hemodynamics between postures do not appear to have a large functional consequence on the dynamic regulation of CBF.
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Affiliation(s)
- Zachary K Garrett
- Department of Biology, University of Colorado Colorado Springs, Colorado Springs, Colorado
| | - James Pearson
- Department of Biology, University of Colorado Colorado Springs, Colorado Springs, Colorado
| | - Andrew W Subudhi
- Department of Biology, University of Colorado Colorado Springs, Colorado Springs, Colorado
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17
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Song A, Zhang Y, Han L, Yegutkin GG, Liu H, Sun K, D'Alessandro A, Li J, Karmouty-Quintana H, Iriyama T, Weng T, Zhao S, Wang W, Wu H, Nemkov T, Subudhi AW, Jameson-Van Houten S, Julian CG, Lovering AT, Hansen KC, Zhang H, Bogdanov M, Dowhan W, Jin J, Kellems RE, Eltzschig HK, Blackburn M, Roach RC, Xia Y. Erythrocytes retain hypoxic adenosine response for faster acclimatization upon re-ascent. Nat Commun 2017; 8:14108. [PMID: 28169986 PMCID: PMC5309698 DOI: 10.1038/ncomms14108] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Accepted: 11/29/2016] [Indexed: 12/19/2022] Open
Abstract
Faster acclimatization to high altitude upon re-ascent is seen in humans; however, the molecular basis for this enhanced adaptive response is unknown. We report that in healthy lowlanders, plasma adenosine levels are rapidly induced by initial ascent to high altitude and achieved even higher levels upon re-ascent, a feature that is positively associated with quicker acclimatization. Erythrocyte equilibrative nucleoside transporter 1 (eENT1) levels are reduced in humans at high altitude and in mice under hypoxia. eENT1 deletion allows rapid accumulation of plasma adenosine to counteract hypoxic tissue damage in mice. Adenosine signalling via erythrocyte ADORA2B induces PKA phosphorylation, ubiquitination and proteasomal degradation of eENT1. Reduced eENT1 resulting from initial hypoxia is maintained upon re-ascent in humans or re-exposure to hypoxia in mice and accounts for erythrocyte hypoxic memory and faster acclimatization. Our findings suggest that targeting identified purinergic-signalling network would enhance the hypoxia adenosine response to counteract hypoxia-induced maladaptation. Humans that reach high altitude soon after the first ascent show faster adaptation to hypoxia. Song et al. show that this adaptive response relies on decreased red blood cell uptake of plasma adenosine due to reduced levels of nucleoside transporter ENT1 resulting from coordinated adenosine generation by ectonucleotidase CD73 and activation of A2B receptors.
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Affiliation(s)
- Anren Song
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Yujin Zhang
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Leng Han
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | | | - Hong Liu
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Graduate School of Biomedical Sciences, University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Kaiqi Sun
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Graduate School of Biomedical Sciences, University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Angelo D'Alessandro
- Department of Biochemistry and Molecular Genetics, University of Colorado, Aurora, Colorado 80045, USA
| | - Jessica Li
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Harry Karmouty-Quintana
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Takayuki Iriyama
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Department of Obstetrics and Gynecology, Faculty of Medicine, The University of Tokyo, Tokyo 113-8655, Japan
| | - Tingting Weng
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Shushan Zhao
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Department of Orthopedics, Xiangya Hospital, Central South University, Changsha, 410008 Hunan, China
| | - Wei Wang
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Department of Nephrology, Xiangya Hospital, Central South University, Changsha, 410008 Hunan, China
| | - Hongyu Wu
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Travis Nemkov
- Altitude Research Center, Department of Emergency Medicine University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Andrew W Subudhi
- Altitude Research Center, Department of Emergency Medicine University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Sonja Jameson-Van Houten
- Altitude Research Center, Department of Emergency Medicine University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Colleen G Julian
- Altitude Research Center, Department of Emergency Medicine University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Andrew T Lovering
- Altitude Research Center, Department of Emergency Medicine University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Kirk C Hansen
- Department of Biochemistry and Molecular Genetics, University of Colorado, Aurora, Colorado 80045, USA
| | - Hong Zhang
- Department of Pathology, MD Anderson Cancer Center, Houston, Texas 77030, USA
| | - Mikhail Bogdanov
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - William Dowhan
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Jianping Jin
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Rodney E Kellems
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Graduate School of Biomedical Sciences, University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Holger K Eltzschig
- Organ Protection Program, Department of Anesthesiology, University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Michael Blackburn
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Graduate School of Biomedical Sciences, University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Robert C Roach
- Altitude Research Center, Department of Emergency Medicine University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Yang Xia
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Graduate School of Biomedical Sciences, University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.,Department of Nephrology, Xiangya Hospital, Central South University, Changsha, 410008 Hunan, China
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18
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Liu H, Zhang Y, Wu H, D'Alessandro A, Yegutkin GG, Song A, Sun K, Li J, Cheng NY, Huang A, Edward Wen Y, Weng TT, Luo F, Nemkov T, Sun H, Kellems RE, Karmouty-Quintana H, Hansen KC, Zhao B, Subudhi AW, Jameson-Van Houten S, Julian CG, Lovering AT, Eltzschig HK, Blackburn MR, Roach RC, Xia Y. Beneficial Role of Erythrocyte Adenosine A2B Receptor-Mediated AMP-Activated Protein Kinase Activation in High-Altitude Hypoxia. Circulation 2016; 134:405-21. [PMID: 27482003 DOI: 10.1161/circulationaha.116.021311] [Citation(s) in RCA: 107] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 06/14/2016] [Indexed: 12/18/2022]
Abstract
BACKGROUND High altitude is a challenging condition caused by insufficient oxygen supply. Inability to adjust to hypoxia may lead to pulmonary edema, stroke, cardiovascular dysfunction, and even death. Thus, understanding the molecular basis of adaptation to high altitude may reveal novel therapeutics to counteract the detrimental consequences of hypoxia. METHODS Using high-throughput, unbiased metabolomic profiling, we report that the metabolic pathway responsible for production of erythrocyte 2,3-bisphosphoglycerate (2,3-BPG), a negative allosteric regulator of hemoglobin-O2 binding affinity, was significantly induced in 21 healthy humans within 2 hours of arrival at 5260 m and further increased after 16 days at 5260 m. RESULTS This finding led us to discover that plasma adenosine concentrations and soluble CD73 activity rapidly increased at high altitude and were associated with elevated erythrocyte 2,3-BPG levels and O2 releasing capacity. Mouse genetic studies demonstrated that elevated CD73 contributed to hypoxia-induced adenosine accumulation and that elevated adenosine-mediated erythrocyte A2B adenosine receptor activation was beneficial by inducing 2,3-BPG production and triggering O2 release to prevent multiple tissue hypoxia, inflammation, and pulmonary vascular leakage. Mechanistically, we demonstrated that erythrocyte AMP-activated protein kinase was activated in humans at high altitude and that AMP-activated protein kinase is a key protein functioning downstream of the A2B adenosine receptor, phosphorylating and activating BPG mutase and thus inducing 2,3-BPG production and O2 release from erythrocytes. Significantly, preclinical studies demonstrated that activation of AMP-activated protein kinase enhanced BPG mutase activation, 2,3-BPG production, and O2 release capacity in CD73-deficient mice, in erythrocyte-specific A2B adenosine receptor knockouts, and in wild-type mice and in turn reduced tissue hypoxia and inflammation. CONCLUSIONS Together, human and mouse studies reveal novel mechanisms of hypoxia adaptation and potential therapeutic approaches for counteracting hypoxia-induced tissue damage.
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Affiliation(s)
- Hong Liu
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Yujin Zhang
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Hongyu Wu
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Angelo D'Alessandro
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Gennady G Yegutkin
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Anren Song
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Kaiqi Sun
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Jessica Li
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Ning-Yuan Cheng
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Aji Huang
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Yuan Edward Wen
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Ting Ting Weng
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Fayong Luo
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Travis Nemkov
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Hong Sun
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Rodney E Kellems
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Harry Karmouty-Quintana
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Kirk C Hansen
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Bihong Zhao
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Andrew W Subudhi
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Sonja Jameson-Van Houten
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Colleen G Julian
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Andrew T Lovering
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Holger K Eltzschig
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Michael R Blackburn
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Robert C Roach
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.)
| | - Yang Xia
- From the Department of Biochemistry and Molecular Biology (H.L., Y.Z., H.W., A.S., K.S., J.L., N.-Y.C., A.H., Y.E.W., T.T.W., F.L., R.E.K., H.K.-Q., M.R.B., Y.X.), Graduate School of Biomedical Sciences (H.L., K.S., R.E.K., M.R.B., Y.X.), and Department of Pathology (B.Z.), University of Texas Health Science Center at Houston; Departments of Otolaryngology (H.L., H.S.) and Nephrology (Y.X.), Xiangya Hospital, Central South University, Changsha, Hunan, China; Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora (A.D., T.N., K.C.H.); Medicity Research Laboratory, University of Turku, Turku, Finland (G.G.Y.); Altitude Research Center, Department of Emergency Medicine (A.W.S., S.J.-V.H., C.G.J., R.C.R.), and Organ Protection Program, Department of Anesthesiology (H.K.E.), University of Colorado School of Medicine, Aurora; and Department of Human Physiology, University of Oregon, Eugene (A.TL.).
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D'Alessandro A, Nemkov T, Sun K, Liu H, Song A, Monte AA, Subudhi AW, Lovering AT, Dvorkin D, Julian CG, Kevil CG, Kolluru GK, Shiva S, Gladwin MT, Xia Y, Hansen KC, Roach RC. AltitudeOmics: Red Blood Cell Metabolic Adaptation to High Altitude Hypoxia. J Proteome Res 2016; 15:3883-3895. [PMID: 27646145 DOI: 10.1021/acs.jproteome.6b00733] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Red blood cells (RBCs) are key players in systemic oxygen transport. RBCs respond to in vitro hypoxia through the so-called oxygen-dependent metabolic regulation, which involves the competitive binding of deoxyhemoglobin and glycolytic enzymes to the N-terminal cytosolic domain of band 3. This mechanism promotes the accumulation of 2,3-DPG, stabilizing the deoxygenated state of hemoglobin, and cytosol acidification, triggering oxygen off-loading through the Bohr effect. Despite in vitro studies, in vivo adaptations to hypoxia have not yet been completely elucidated. Within the framework of the AltitudeOmics study, erythrocytes were collected from 21 healthy volunteers at sea level, after exposure to high altitude (5260 m) for 1, 7, and 16 days, and following reascent after 7 days at 1525 m. UHPLC-MS metabolomics results were correlated to physiological and athletic performance parameters. Immediate metabolic adaptations were noted as early as a few hours from ascending to >5000 m, and maintained for 16 days at high altitude. Consistent with the mechanisms elucidated in vitro, hypoxia promoted glycolysis and deregulated the pentose phosphate pathway, as well purine catabolism, glutathione homeostasis, arginine/nitric oxide, and sulfur/H2S metabolism. Metabolic adaptations were preserved 1 week after descent, consistently with improved physical performances in comparison to the first ascendance, suggesting a mechanism of metabolic memory.
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Affiliation(s)
- Angelo D'Alessandro
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver , Anschutz Medical Campus, Aurora, Colorado 80045, United States
| | - Travis Nemkov
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver , Anschutz Medical Campus, Aurora, Colorado 80045, United States
| | - Kaiqi Sun
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston , Houston, Texas, United States
| | - Hong Liu
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston , Houston, Texas, United States
| | - Anren Song
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston , Houston, Texas, United States
| | - Andrew A Monte
- Altitude Research Center, Department of Emergency Medicine, University of Colorado , Anschutz Medical Campus, Aurora, Colorado, United States
| | - Andrew W Subudhi
- Altitude Research Center, Department of Emergency Medicine, University of Colorado , Anschutz Medical Campus, Aurora, Colorado, United States.,Department of Biology, University of Colorado Colorado Springs , Colorado Springs, Colorado, United States
| | - Andrew T Lovering
- Department of Human Physiology, University of Oregon , Eugene, Oregon, United States
| | - Daniel Dvorkin
- Altitude Research Center, Department of Emergency Medicine, University of Colorado , Anschutz Medical Campus, Aurora, Colorado, United States
| | - Colleen G Julian
- Altitude Research Center, Department of Emergency Medicine, University of Colorado , Anschutz Medical Campus, Aurora, Colorado, United States
| | - Christopher G Kevil
- Department of Pathology, Centre for Cardiovascular Diseases and Sciences, LSU Health , Shreveport, Louisiana, United States
| | - Gopi K Kolluru
- Department of Pathology, Centre for Cardiovascular Diseases and Sciences, LSU Health , Shreveport, Louisiana, United States
| | - Sruti Shiva
- Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania, United States
| | - Mark T Gladwin
- Department of Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania, United States
| | - Yang Xia
- Department of Biochemistry and Molecular Biology, The University of Texas Health Science Center at Houston , Houston, Texas, United States
| | - Kirk C Hansen
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver , Anschutz Medical Campus, Aurora, Colorado 80045, United States
| | - Robert C Roach
- Altitude Research Center, Department of Emergency Medicine, University of Colorado , Anschutz Medical Campus, Aurora, Colorado, United States
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20
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Horiuchi M, Endo J, Dobashi S, Kiuchi M, Koyama K, Subudhi AW. Effect of progressive normobaric hypoxia on dynamic cerebral autoregulation. Exp Physiol 2016; 101:1276-1284. [DOI: 10.1113/ep085789] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Accepted: 07/12/2016] [Indexed: 01/05/2023]
Affiliation(s)
- Masahiro Horiuchi
- Division of Human Environmental Science; Mount Fuji Research Institute; Japan
| | - Junko Endo
- Division of Human Environmental Science; Mount Fuji Research Institute; Japan
| | - Shohei Dobashi
- Integrated Graduate School Department of Medicine; Engineering, and Agricultural Sciences; University of Yamanashi; Japan
| | - Masataka Kiuchi
- Integrated Graduate School Department of Medicine; Engineering, and Agricultural Sciences; University of Yamanashi; Japan
| | - Katsuhiro Koyama
- Integrated Graduate School Department of Medicine; Engineering, and Agricultural Sciences; University of Yamanashi; Japan
| | - Andrew W. Subudhi
- Department of Biology; University of Colorado; Colorado Springs CO USA
- Altitude Research Center; University of Colorado Anschutz Medical Campus; Aurora CO USA
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21
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Lawley JS, Levine BD, Williams MA, Malm J, Eklund A, Polaner DM, Subudhi AW, Hackett PH, Roach RC. Cerebral spinal fluid dynamics: effect of hypoxia and implications for high-altitude illness. J Appl Physiol (1985) 2016; 120:251-62. [DOI: 10.1152/japplphysiol.00370.2015] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 08/17/2015] [Indexed: 12/24/2022] Open
Abstract
The pathophysiology of acute mountain sickness and high-altitude cerebral edema, the cerebral forms of high-altitude illness, remain uncertain and controversial. Persistently elevated or pathological fluctuations in intracranial pressure are thought to cause symptoms similar to those reported by individuals suffering cerebral forms of high-altitude illness. This review first focuses on the basic physiology of the craniospinal system, including a detailed discussion of the long-term and dynamic regulation of intracranial pressure. Thereafter, we critically examine the available literature, based primarily on invasive pressure monitoring, that suggests intracranial pressure is acutely elevated at altitude due to brain swelling and/or elevated sagittal sinus pressure, but normalizes over time. We hypothesize that fluctuations in intracranial pressure occur around a slightly elevated or normal mean intracranial pressure, in conjunction with oscillations in arterial Po2 and arterial blood pressure. Then these modest fluctuations in intracranial pressure, in concert with direct vascular stretch due to dilatation and/or increased blood pressure transmission, activate the trigeminal vascular system and cause symptoms of acute mountain sickness. Elevated brain water (vasogenic edema) may be due to breakdown of the blood-brain barrier. However, new information suggests cerebral spinal fluid flux into the brain may be an important factor. Regardless of the source (or mechanisms responsible) for the excess brain water, brain swelling occurs, and a “tight fit” brain would be a major risk factor to produce symptoms; activities that produce large changes in brain volume and cause fluctuations in blood pressure are likely contributing factors.
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Affiliation(s)
- Justin S. Lawley
- Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, Dallas, Texas
- UT Southwestern Medical Center, Dallas, Texas
| | - Benjamin D. Levine
- Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, Dallas, Texas
- UT Southwestern Medical Center, Dallas, Texas
| | - Michael A. Williams
- Sandra and Malcolm Berman Brain & Spine Institute, Dept. of Neurology, Sinai Hospital, Baltimore, Maryland
| | - Jon Malm
- Department of Clinical Neuroscience, Umeå University, Umeå, Sweden
| | - Anders Eklund
- Department of Radiation Sciences, Umeå University, Umeå, Sweden
| | - David M. Polaner
- Departments of Anesthesiology and Pediatrics, University of Colorado School of Medicine and Children's Hospital Colorado, Aurora, Colorado
| | - Andrew W. Subudhi
- Department of Biology, University of Colorado, Colorado Springs, Colorado
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado; and
| | | | - Robert C. Roach
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado; and
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22
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Fan JL, Subudhi AW, Duffin J, Lovering AT, Roach RC, Kayser B. AltitudeOmics: Resetting of Cerebrovascular CO2 Reactivity Following Acclimatization to High Altitude. Front Physiol 2016; 6:394. [PMID: 26779030 PMCID: PMC4705915 DOI: 10.3389/fphys.2015.00394] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 12/03/2015] [Indexed: 12/25/2022] Open
Abstract
Previous studies reported enhanced cerebrovascular CO2 reactivity upon ascent to high altitude using linear models. However, there is evidence that this response may be sigmoidal in nature. Moreover, it was speculated that these changes at high altitude are mediated by alterations in acid-base buffering. Accordingly, we reanalyzed previously published data to assess middle cerebral blood flow velocity (MCAv) responses to modified rebreathing at sea level (SL), upon ascent (ALT1) and following 16 days of acclimatization (ALT16) to 5260 m in 21 lowlanders. Using sigmoid curve fitting of the MCAv responses to CO2, we found the amplitude (95 vs. 129%, SL vs. ALT1, 95% confidence intervals (CI) [77, 112], [111, 145], respectively, P = 0.024) and the slope of the sigmoid response (4.5 vs. 7.5%/mmHg, SL vs. ALT1, 95% CIs [3.1, 5.9], [6.0, 9.0], respectively, P = 0.026) to be enhanced at ALT1, which persisted with acclimatization at ALT16 (amplitude: 177, 95% CI [139, 215], P < 0.001; slope: 10.3%/mmHg, 95% CI [8.2, 12.5], P = 0.003) compared to SL. Meanwhile, the sigmoidal response midpoint was unchanged at ALT1 (SL: 36.5 mmHg; ALT1: 35.4 mmHg, 95% CIs [34.0, 39.0], [33.1, 37.7], respectively, P = 0.982), while it was reduced by ~7 mmHg at ALT16 (28.6 mmHg, 95% CI [26.4, 30.8], P = 0.001 vs. SL), indicating leftward shift of the cerebrovascular CO2 response to a lower arterial partial pressure of CO2 (PaCO2) following acclimatization to altitude. Sigmoid fitting revealed a leftward shift in the midpoint of the cerebrovascular response curve which could not be observed with linear fitting. These findings demonstrate that there is resetting of the cerebrovascular CO2 reactivity operating point to a lower PaCO2 following acclimatization to high altitude. This cerebrovascular resetting is likely the result of an altered acid-base buffer status resulting from prolonged exposure to the severe hypocapnia associated with ventilatory acclimatization to high altitude.
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Affiliation(s)
- Jui-Lin Fan
- Centre for Translational Physiology, University of OtagoWellington, New Zealand; Department of Surgery and Anaesthesia, University of OtagoWellington, New Zealand
| | - Andrew W Subudhi
- Department of Emergency Medicine, Altitude Research Center, University of Colorado DenverAurora, CO, USA; Department of Biology, University of Colorado Colorado SpringsColorado Springs, CO, USA
| | - James Duffin
- Department of Physiology, University of TorontoToronto, ON, Canada; Department of Anaesthesiology, University of TorontoToronto, ON, Canada; University Health NetworkToronto, ON, Canada
| | - Andrew T Lovering
- Department of Human Physiology, University of Oregon Eugene, Oregon, OR, USA
| | - Robert C Roach
- Department of Emergency Medicine, Altitude Research Center, University of Colorado DenverAurora, CO, USA; Department of Biology, University of Colorado Colorado SpringsColorado Springs, CO, USA
| | - Bengt Kayser
- Institute of Sports Sciences, Faculty of Biology and Medicine, University of LausanneLausanne, Switzerland; Department of Physiology, Faculty of Biology and Medicine, University of LausanneLausanne, Switzerland
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Sedighian P, Subudhi AW, Scalzo F, Asgari S. Pediatric heart sound segmentation using hidden Markov model. Annu Int Conf IEEE Eng Med Biol Soc 2015; 2014:5490-3. [PMID: 25571237 DOI: 10.1109/embc.2014.6944869] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Recent advances in technology have enabled automatic cardiac auscultation using digital stethoscopes. This in turn creates the need for development of algorithms capable of automatic segmentation of heart sounds. Pediatric heart sound segmentation is a challenging task due to various confounding factors including the significant influence of respiration on children's heart sounds. The current work investigates the application of homomorphic filtering and Hidden Markov Model for the purpose of segmenting pediatric heart sounds. The efficacy of the proposed method is evaluated on the publicly available Pascal Challenge dataset and its performance is compared with those of three other existing methods. The results show that our proposed method achieves an accuracy of 92.4%±1.1% and 93.5%±1.1% in identifying the first and second heart sound components, respectively, and is superior to three other existing methods in terms of accuracy or computational complexity.
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Korbel S, Curry D, Mitchell M, Butler W, Davis JE, Subudhi AW. Effect of Altitude Acclimatization on Work Completed at a Constant Perceived Exertion during Moderate-Intensity Exercise. Med Sci Sports Exerc 2015. [DOI: 10.1249/01.mss.0000477434.15545.ba] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Langolf RJ, Subudhi AW, Grajzel K, Roach RC, Panerai RB, Davis JE. Cerebral Autoregulation Index at High Altitude Assessed by Leg Cuff and Transfer Function Analysis Techniques. Med Sci Sports Exerc 2015. [DOI: 10.1249/01.mss.0000478362.52975.60] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Roach RC, Dvorkin D, Julian CG, Gronewold J, Bourdillon N, Bucher J, Elliott JE, Evero O, Fan JL, Jameson‐Van Houten S, Kayser B, Kern JP, Kim SE, Laurie SS, Lovering AT, Ryan B, Wachsmuth NB, Subudhi AW. Transcriptomic and Epigenomic Reponses During Human Adaptation to High‐Altitude Hypoxia. FASEB J 2015. [DOI: 10.1096/fasebj.29.1_supplement.1051.5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- RC Roach
- Altitude Research Center U Colorado AMCUnited States
| | - D Dvorkin
- Altitude Research Center U Colorado AMCUnited States
| | - C G Julian
- Altitude Research Center U Colorado AMCUnited States
| | - J Gronewold
- Altitude Research Center U Colorado AMCUnited States
| | | | - J Bucher
- Dept HumanPhysiol U OregonUnited States
| | | | - O Evero
- Altitude Research Center U Colorado AMCUnited States
| | - JL Fan
- Inst Sports Sci ULausanneSwitzerland
| | | | - B Kayser
- Inst Sports Sci ULausanneSwitzerland
| | - JP Kern
- Dept HumanPhysiol U OregonUnited States
| | - SE Kim
- Dept HumanPhysiol U OregonUnited States
| | - SS Laurie
- Dept HumanPhysiol U OregonUnited States
| | | | - B Ryan
- Dept IntegrPhysiol U Colorado BoulderUnited States
| | | | - A W Subudhi
- Altitude Research Center U Colorado AMCUnited States
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Abstract
This brief review traces the last 50 years of research related to cerebral blood flow (CBF) in humans exposed to high altitude. The increase in CBF within the first 12 hours at high altitude and its return to near sea level values after 3-5 days of acclimatization was first documented with use of the Kety-Schmidt technique in 1964. The degree of change in CBF at high altitude is influenced by many variables, including arterial oxygen and carbon dioxide tensions, oxygen content, cerebral spinal fluid pH, and hematocrit, but can be collectively summarized in terms of the relative strengths of four key integrated reflexes: 1) hypoxic cerebral vasodilatation; 2) hypocapnic cerebral vasoconstriction; 3) hypoxic ventilatory response; and 4) hypercapnic ventilatory response. Understanding the mechanisms underlying these reflexes and their interactions with one another is critical to advance our understanding of global and regional CBF regulation. Whether high altitude populations exhibit cerebrovascular adaptations to chronic levels of hypoxia or if changes in CBF are related to the development of acute mountain sickness are currently unknown; yet overall, the integrated CBF response to high altitude appears to be sufficient to meet the brain's large and consistent demand for oxygen. This short review is organized as follows: An historical overview of the earliest CBF measurements collected at high altitude introduces a summary of reported CBF changes at altitude over the last 50 years in both lowlanders and high-altitude natives. The most tenable candidate mechanism(s) regulating CBF at altitude are summarized with a focus on available data in humans, and a role for these mechanisms in the pathophysiology of AMS is considered. Finally, suggestions for future directions are provided.
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Affiliation(s)
- Philip N Ainslie
- 1 School of Health and Exercise Sciences, University of British Columbia , Okanagan Campus, Kelowna, British Columbia, Canada
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Elliott JE, Laurie SS, Kern JP, Beasley KM, Goodman RD, Kayser B, Subudhi AW, Roach RC, Lovering AT. AltitudeOmics: impaired pulmonary gas exchange efficiency and blunted ventilatory acclimatization in humans with patent foramen ovale after 16 days at 5,260 m. J Appl Physiol (1985) 2015; 118:1100-12. [PMID: 25678698 DOI: 10.1152/japplphysiol.00879.2014] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 02/08/2015] [Indexed: 12/29/2022] Open
Abstract
A patent foramen ovale (PFO), present in ∼40% of the general population, is a potential source of right-to-left shunt that can impair pulmonary gas exchange efficiency [i.e., increase the alveolar-to-arterial Po2 difference (A-aDO2)]. Prior studies investigating human acclimatization to high-altitude with A-aDO2 as a key parameter have not investigated differences between subjects with (PFO+) or without a PFO (PFO-). We hypothesized that in PFO+ subjects A-aDO2 would not improve (i.e., decrease) after acclimatization to high altitude compared with PFO- subjects. Twenty-one (11 PFO+) healthy sea-level residents were studied at rest and during cycle ergometer exercise at the highest iso-workload achieved at sea level (SL), after acute transport to 5,260 m (ALT1), and again at 5,260 m after 16 days of high-altitude acclimatization (ALT16). In contrast to PFO- subjects, PFO+ subjects had 1) no improvement in A-aDO2 at rest and during exercise at ALT16 compared with ALT1, 2) no significant increase in resting alveolar ventilation, or alveolar Po2, at ALT16 compared with ALT1, and consequently had 3) an increased arterial Pco2 and decreased arterial Po2 and arterial O2 saturation at rest at ALT16. Furthermore, PFO+ subjects had an increased incidence of acute mountain sickness (AMS) at ALT1 concomitant with significantly lower peripheral O2 saturation (SpO2). These data suggest that PFO+ subjects have increased susceptibility to AMS when not taking prophylactic treatments, that right-to-left shunt through a PFO impairs pulmonary gas exchange efficiency even after acclimatization to high altitude, and that PFO+ subjects have blunted ventilatory acclimatization after 16 days at altitude compared with PFO- subjects.
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Affiliation(s)
| | - Steven S Laurie
- Department of Human Physiology, University of Oregon, Eugene, Oregon
| | - Julia P Kern
- Department of Human Physiology, University of Oregon, Eugene, Oregon
| | - Kara M Beasley
- Department of Human Physiology, University of Oregon, Eugene, Oregon
| | - Randall D Goodman
- Oregon Heart and Vascular Institute, Echocardiography, Springfield, Oregon
| | - Bengt Kayser
- University of Lausanne, Department of Physiology and Institute of Sports Sciences, Lausanne, Switzerland
| | - Andrew W Subudhi
- Altitude Research Center, University of Colorado Anschutz Medical Campus, Denver, Colorado; and Department of Biology, University of Colorado, Colorado Springs, Colorado
| | - Robert C Roach
- Altitude Research Center, University of Colorado Anschutz Medical Campus, Denver, Colorado; and
| | - Andrew T Lovering
- Department of Human Physiology, University of Oregon, Eugene, Oregon;
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Subudhi AW, Grajzel K, Langolf RJ, Roach RC, Panerai RB, Davis JE. Cerebral autoregulation index at high altitude assessed by thigh-cuff and transfer function analysis techniques. Exp Physiol 2015; 100:173-81. [DOI: 10.1113/expphysiol.2014.082479] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Accepted: 11/27/2014] [Indexed: 11/08/2022]
Affiliation(s)
- Andrew W. Subudhi
- Department of Biology; University of Colorado Colorado Springs; Colorado Springs CO USA
- Department of Emergency Medicine; University of Colorado Altitude Research Center; Aurora CO USA
| | - Katalin Grajzel
- Department of Psychology; University of Colorado Colorado Springs; Colorado Springs CO USA
| | - Robert J. Langolf
- Alma College; Department of Integrative Physiology and Health Science; Alma MI USA
| | - Robert C. Roach
- Department of Emergency Medicine; University of Colorado Altitude Research Center; Aurora CO USA
| | - Ronney B. Panerai
- Department of Cardiovascular Sciences and NIHR Biomedical Research Unit; University of Leicester; UK
| | - John E. Davis
- Alma College; Department of Integrative Physiology and Health Science; Alma MI USA
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Ryan BJ, Wachsmuth NB, Schmidt WF, Byrnes WC, Julian CG, Lovering AT, Subudhi AW, Roach RC. AltitudeOmics: rapid hemoglobin mass alterations with early acclimatization to and de-acclimatization from 5260 m in healthy humans. PLoS One 2014; 9:e108788. [PMID: 25271637 PMCID: PMC4182755 DOI: 10.1371/journal.pone.0108788] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Accepted: 08/26/2014] [Indexed: 01/09/2023] Open
Abstract
It is classically thought that increases in hemoglobin mass (Hbmass) take several weeks to develop upon ascent to high altitude and are lost gradually following descent. However, the early time course of these erythropoietic adaptations has not been thoroughly investigated and data are lacking at elevations greater than 5000 m, where the hypoxic stimulus is dramatically increased. As part of the AltitudeOmics project, we examined Hbmass in healthy men and women at sea level (SL) and 5260 m following 1, 7, and 16 days of high altitude exposure (ALT1/ALT7/ALT16). Subjects were also studied upon return to 5260 m following descent to 1525 m for either 7 or 21 days. Compared to SL, absolute Hbmass was not different at ALT1 but increased by 3.7±5.8% (mean ± SD; n = 20; p<0.01) at ALT7 and 7.6±6.6% (n = 21; p<0.001) at ALT16. Following descent to 1525 m, Hbmass was reduced compared to ALT16 (−6.0±3.7%; n = 20; p = 0.001) and not different compared to SL, with no difference in the loss in Hbmass between groups that descended for 7 (−6.3±3.0%; n = 13) versus 21 days (−5.7±5.0; n = 7). The loss in Hbmass following 7 days at 1525 m was correlated with an increase in serum ferritin (r = −0.64; n = 13; p<0.05), suggesting increased red blood cell destruction. Our novel findings demonstrate that Hbmass increases within 7 days of ascent to 5260 m but that the altitude-induced Hbmass adaptation is lost within 7 days of descent to 1525 m. The rapid time course of these adaptations contrasts with the classical dogma, suggesting the need to further examine mechanisms responsible for Hbmass adaptations in response to severe hypoxia.
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Affiliation(s)
- Benjamin J. Ryan
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, Colorado, United States of America
- * E-mail:
| | - Nadine B. Wachsmuth
- Department of Sports Medicine/Sports Physiology, University of Bayreuth, Bayreuth, Germany
| | - Walter F. Schmidt
- Department of Sports Medicine/Sports Physiology, University of Bayreuth, Bayreuth, Germany
| | - William C. Byrnes
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, Colorado, United States of America
| | - Colleen G. Julian
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Andrew T. Lovering
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States of America
| | - Andrew W. Subudhi
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
- Department of Biology, University of Colorado Colorado Springs, Colorado Springs, Colorado, United States of America
| | - Robert C. Roach
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
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Subudhi AW, Fan JL, Evero O, Bourdillon N, Kayser B, Julian CG, Lovering AT, Panerai RB, Roach RC. AltitudeOmics: cerebral autoregulation during ascent, acclimatization, and re-exposure to high altitude and its relation with acute mountain sickness. J Appl Physiol (1985) 2014; 116:724-9. [DOI: 10.1152/japplphysiol.00880.2013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Cerebral autoregulation (CA) acts to maintain brain blood flow despite fluctuations in perfusion pressure. Acute hypoxia is thought to impair CA, but it is unclear if CA is affected by acclimatization or related to the development of acute mountain sickness (AMS). We assessed changes in CA using transfer function analysis of spontaneous fluctuations in radial artery blood pressure (indwelling catheter) and resulting changes in middle cerebral artery blood flow velocity (transcranial Doppler) in 21 active individuals at sea level upon arrival at 5,260 m (ALT1), after 16 days of acclimatization (ALT16), and upon re-exposure to 5,260 m after 7 days at 1,525 m (POST7). The Lake Louise Questionnaire was used to evaluate AMS symptom severity. CA was impaired upon arrival at ALT1 ( P < 0.001) and did not change with acclimatization at ALT16 or upon re-exposure at POST7. CA was not associated with AMS symptoms (all R < 0.50, P > 0.05). These findings suggest that alterations in CA are an intrinsic consequence of hypoxia and are not directly related to the occurrence or severity of AMS.
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Affiliation(s)
- Andrew W. Subudhi
- University of Colorado Altitude Research Center, Department of Emergency Medicine, Anschutz Medical Campus, Aurora, Colorado
- University of Colorado Colorado Springs, Department of Biology, Colorado Springs, Colorado
| | - Jui-Lin Fan
- University of Lausanne, Institute of Sports Sciences, Lausanne, Switzerland
- University of Geneva, Lemanic Doctoral School of Neuroscience, Geneva, Switzerland
| | - Oghenero Evero
- University of Colorado Altitude Research Center, Department of Emergency Medicine, Anschutz Medical Campus, Aurora, Colorado
| | - Nicolas Bourdillon
- University of Lausanne, Institute of Sports Sciences, Lausanne, Switzerland
| | - Bengt Kayser
- University of Lausanne, Institute of Sports Sciences, Lausanne, Switzerland
| | - Colleen G. Julian
- University of Colorado Altitude Research Center, Department of Emergency Medicine, Anschutz Medical Campus, Aurora, Colorado
| | - Andrew T. Lovering
- University of Oregon, Department of Human Physiology, Eugene, Oregon; and
| | - Ronney B. Panerai
- University of Leicester, Leicester Royal Infirmary, Department of Cardiovascular Sciences, Leicester, United Kingdom
| | - Robert C. Roach
- University of Colorado Altitude Research Center, Department of Emergency Medicine, Anschutz Medical Campus, Aurora, Colorado
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Subudhi AW, Bourdillon N, Bucher J, Davis C, Elliott JE, Eutermoster M, Evero O, Fan JL, Houten SJV, Julian CG, Kark J, Kark S, Kayser B, Kern JP, Kim SE, Lathan C, Laurie SS, Lovering AT, Paterson R, Polaner DM, Ryan BJ, Spira JL, Tsao JW, Wachsmuth NB, Roach RC. AltitudeOmics: the integrative physiology of human acclimatization to hypobaric hypoxia and its retention upon reascent. PLoS One 2014; 9:e92191. [PMID: 24658407 PMCID: PMC3962396 DOI: 10.1371/journal.pone.0092191] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 02/19/2014] [Indexed: 11/19/2022] Open
Abstract
An understanding of human responses to hypoxia is important for the health of millions of people worldwide who visit, live, or work in the hypoxic environment encountered at high altitudes. In spite of dozens of studies over the last 100 years, the basic mechanisms controlling acclimatization to hypoxia remain largely unknown. The AltitudeOmics project aimed to bridge this gap. Our goals were 1) to describe a phenotype for successful acclimatization and assess its retention and 2) use these findings as a foundation for companion mechanistic studies. Our approach was to characterize acclimatization by measuring changes in arterial oxygenation and hemoglobin concentration [Hb], acute mountain sickness (AMS), cognitive function, and exercise performance in 21 subjects as they acclimatized to 5260 m over 16 days. We then focused on the retention of acclimatization by having subjects reascend to 5260 m after either 7 (n = 14) or 21 (n = 7) days at 1525 m. At 16 days at 5260 m we observed: 1) increases in arterial oxygenation and [Hb] (compared to acute hypoxia: PaO2 rose 9±4 mmHg to 45±4 while PaCO2 dropped a further 6±3 mmHg to 21±3, and [Hb] rose 1.8±0.7 g/dL to 16±2 g/dL; 2) no AMS; 3) improved cognitive function; and 4) improved exercise performance by 8±8% (all changes p<0.01). Upon reascent, we observed retention of arterial oxygenation but not [Hb], protection from AMS, retention of exercise performance, less retention of cognitive function; and noted that some of these effects lasted for 21 days. Taken together, these findings reveal new information about retention of acclimatization, and can be used as a physiological foundation to explore the molecular mechanisms of acclimatization and its retention.
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Affiliation(s)
- Andrew W. Subudhi
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
- Department of Biology, University of Colorado Colorado Springs, Colorado Springs, Colorado, United States of America
| | - Nicolas Bourdillon
- Institute of Sports Sciences and Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Jenna Bucher
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States of America
| | - Christopher Davis
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Jonathan E. Elliott
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States of America
| | - Morgan Eutermoster
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Oghenero Evero
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Jui-Lin Fan
- Institute of Sports Sciences and Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
- Lemanic Doctoral School of Neuroscience, University of Lausanne, Lausanne, Switzerland
| | - Sonja Jameson-Van Houten
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Colleen G. Julian
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Jonathan Kark
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Sherri Kark
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Bengt Kayser
- Institute of Sports Sciences and Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Julia P. Kern
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States of America
| | - See Eun Kim
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States of America
| | - Corinna Lathan
- AnthroTronix, Inc., Silver Spring, Maryland, United States of America
| | - Steven S. Laurie
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States of America
| | - Andrew T. Lovering
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States of America
| | - Ryan Paterson
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - David M. Polaner
- Departments of Anesthesiology and Pediatrics, University of Colorado School of Medicine and Children's Hospital Colorado, Aurora, Colorado, United States of America
| | - Benjamin J. Ryan
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, Colorado, United States of America
| | - James L. Spira
- United States Department of Veterans Affairs, National Center for PTSD, Pacific Islands Health Care System, and Department of Psychiatry, University of Hawaii John A. Burns School of Medicine, Honolulu, Hawaii, United States of America
| | - Jack W. Tsao
- Wounded, Ill & Injured Directorate (M9), United States Navy Bureau of Medicine and Surgery, Falls Church, Virginia, United States of America
| | - Nadine B. Wachsmuth
- Department of Sports Medicine/Sports Physiology, University of Bayreuth, Bayreuth, Germany
| | - Robert C. Roach
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
- * E-mail:
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Ogoh S, Nakahara H, Ueda S, Okazaki K, Shibasaki M, Subudhi AW, Miyamoto T. Effects of acute hypoxia on cerebrovascular responses to carbon dioxide. Exp Physiol 2014; 99:849-58. [PMID: 24632495 DOI: 10.1113/expphysiol.2013.076802] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In normoxic conditions, a reduction in arterial carbon dioxide tension causes cerebral vasoconstriction, thereby reducing cerebral blood flow and modifying dynamic cerebral autoregulation (dCA). It is unclear to what extent these effects are altered by acute hypoxia and the associated hypoxic ventilatory response (respiratory chemoreflex). This study tested the hypothesis that acute hypoxia attenuates arterial CO2 tension-mediated regulation of cerebral blood flow to help maintain cerebral O2 homeostasis. Eight subjects performed three randomly assigned respiratory interventions following a resting baseline period, as follows: (1) normoxia (21% O2); (2) hypoxia (12% O2); and (3) hypoxia with wilful restraint of the respiratory chemoreflex. During each intervention, 0, 2.0, 3.5 or 5.0% CO2 was sequentially added (8 min stages) to inspired gas mixtures to assess changes in steady-state cerebrovascular CO2 reactivity and dCA. During normoxia, the addition of CO2 increased internal carotid artery blood flow and middle cerebral artery mean blood velocity (MCA Vmean), while reducing dCA (change in phase = -0.73 ± 0.22 rad, P = 0.005). During acute hypoxia, internal carotid artery blood flow and MCA Vmean remained unchanged, but cerebrovascular CO2 reactivity (internal carotid artery, P = 0.003; MCA Vmean, P = 0.031) and CO2-mediated effects on dCA (P = 0.008) were attenuated. The effects of hypoxia were not further altered when the respiratory chemoreflex was restrained. These findings support the hypothesis that arterial CO2 tension-mediated effects on the cerebral vasculature are reduced during acute hypoxia. These effects could limit the degree of hypocapnic vasoconstriction and may help to regulate cerebral blood flow and cerebral O2 homeostasis during acute periods of hypoxia.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan
| | | | - Shinya Ueda
- Morinomiya University of Medical Sciences, Osaka, Japan
| | - Kazunobu Okazaki
- Department of Environmental Physiology for Exercise, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - Manabu Shibasaki
- Department of Environmental Health, Nara Women's University, Nara, Japan
| | - Andrew W Subudhi
- Department of Biology, University of Colorado, Colorado Springs, CO, USA
| | - Tadayoshi Miyamoto
- Morinomiya University of Medical Sciences, Osaka, Japan Department of Cardiovascular Dynamics, National Cardiovascular Center Research Institute, Osaka, Japan
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Fan JL, Subudhi AW, Evero O, Bourdillon N, Kayser B, Lovering AT, Roach RC. AltitudeOmics: enhanced cerebrovascular reactivity and ventilatory response to CO2 with high-altitude acclimatization and reexposure. J Appl Physiol (1985) 2013; 116:911-8. [PMID: 24356520 DOI: 10.1152/japplphysiol.00704.2013] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The present study is the first to examine the effect of high-altitude acclimatization and reexposure on the responses of cerebral blood flow and ventilation to CO2. We also compared the steady-state estimates of these parameters during acclimatization with the modified rebreathing method. We assessed changes in steady-state responses of middle cerebral artery velocity (MCAv), cerebrovascular conductance index (CVCi), and ventilation (V(E)) to varied levels of CO2 in 21 lowlanders (9 women; 21 ± 1 years of age) at sea level (SL), during initial exposure to 5,260 m (ALT1), after 16 days of acclimatization (ALT16), and upon reexposure to altitude following either 7 (POST7) or 21 days (POST21) at low altitude (1,525 m). In the nonacclimatized state (ALT1), MCAv and V(E) responses to CO2 were elevated compared with those at SL (by 79 ± 75% and 14.8 ± 12.3 l/min, respectively; P = 0.004 and P = 0.011). Acclimatization at ALT16 further elevated both MCAv and Ve responses to CO2 compared with ALT1 (by 89 ± 70% and 48.3 ± 32.0 l/min, respectively; P < 0.001). The acclimatization gained for V(E) responses to CO2 at ALT16 was retained by 38% upon reexposure to altitude at POST7 (P = 0.004 vs. ALT1), whereas no retention was observed for the MCAv responses (P > 0.05). We found good agreement between steady-state and modified rebreathing estimates of MCAv and V(E) responses to CO2 across all three time points (P < 0.001, pooled data). Regardless of the method of assessment, altitude acclimatization elevates both the cerebrovascular and ventilatory responsiveness to CO2. Our data further demonstrate that this enhanced ventilatory CO2 response is partly retained after 7 days at low altitude.
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Affiliation(s)
- Jui-Lin Fan
- Institute of Sports Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
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Julian CG, Subudhi AW, Hill RC, Wilson MJ, Dimmen AC, Hansen KC, Roach RC. Exploratory proteomic analysis of hypobaric hypoxia and acute mountain sickness in humans. J Appl Physiol (1985) 2013; 116:937-44. [PMID: 24265281 DOI: 10.1152/japplphysiol.00362.2013] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Our objective in this exploratory study was to identify novel biomarkers of importance for acute mountain sickness (AMS) using discovery-based proteomic methods. Peripheral blood samples were collected and AMS symptoms were assessed in 20 healthy volunteers prior to [-15 h (baseline) and 0 h; 1,609 m; barometric pressure = 625 mmHg] and after a 9-h exposure to hypobaric hypoxia (9 h; 4,875 m; barometric pressure = 425 mmHg). AMS status was assessed using the Lake Louise Questionnaire. Plasma samples were pooled according to AMS status at each time point. Protein composition of the samples was determined by a GeLC-MS/MS approach using two analytical platforms (LTQ-XL linear ion trap mass spectrometer and a LTQ-FT ultra hybrid mass spectrometer) for technical replication. Spectral counting was used to make semiquantitative comparisons of protein abundance between AMS-susceptible (AMS) and AMS-resistant (AMS·R) subjects with exposure to hypobaric hypoxia. After 9 h of hypoxia, the abundance of proteins with antioxidant properties (i.e., peroxiredoxin 6, glutathione peroxidase, and sulfhydryl oxidase 1) rose in AMS but not AMS·R. Our exploratory analyses suggest that exposure to hypobaric hypoxia enhances enzymatic antioxidant systems in AMS vs. AMS·R, which, we propose, may be an overcompensation for hypoxia-induced oxidant production. On the basis of our findings we 1) speculate that quenching oxidant activity may have adverse downstream effects that are of pathophysiological importance for AMS such as interrupting oxidant-sensitive cell signaling and gene transcription and 2) question the existing assumption that increased oxidant production in AMS is pathological.
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Affiliation(s)
- Colleen G Julian
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Denver, Aurora, Colorado
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Subudhi AW, Fan JL, Evero O, Bourdillon N, Kayser B, Julian CG, Lovering AT, Roach RC. AltitudeOmics: effect of ascent and acclimatization to 5260 m on regional cerebral oxygen delivery. Exp Physiol 2013; 99:772-81. [PMID: 24243839 DOI: 10.1113/expphysiol.2013.075184] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Cerebral hypoxaemia associated with rapid ascent to high altitude can be life threatening; yet, with proper acclimatization, cerebral function can be maintained well enough for humans to thrive. We investigated adjustments in global and regional cerebral oxygen delivery (DO2) as 21 healthy volunteers rapidly ascended and acclimatized to 5260 m. Ultrasound indices of cerebral blood flow in internal carotid and vertebral arteries were measured at sea level, upon arrival at 5260 m (ALT1; atmospheric pressure 409 mmHg) and after 16 days of acclimatization (ALT16). Cerebral DO2 was calculated as the product of arterial oxygen content and flow in each respective artery and summed to estimate global cerebral blood flow. Vascular resistances were calculated as the quotient of mean arterial pressure and respective flows. Global cerebral blood flow increased by ∼70% upon arrival at ALT1 (P < 0.001) and returned to sea-level values at ALT16 as a result of changes in cerebral vascular resistance. A reciprocal pattern in arterial oxygen content maintained global cerebral DO2 throughout acclimatization, although DO2 to the posterior cerebral circulation was increased by ∼25% at ALT1 (P = 0.032). We conclude that cerebral DO2 is well maintained upon acute exposure and acclimatization to hypoxia, particularly in the posterior and inferior regions of the brain associated with vital homeostatic functions. This tight regulation of cerebral DO2 was achieved through integrated adjustments in local vascular resistances to alter cerebral perfusion during both acute and chronic exposure to hypoxia.
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Affiliation(s)
- Andrew W Subudhi
- University of Colorado Denver Anschutz Medical Campus, Department of Emergency Medicine, Altitude Research Center, Aurora, CO, USA University of Colorado Colorado Springs, Department of Biology, Colorado Springs, CO, USA
| | - Jui-Lin Fan
- University of Lausanne, Institute of Sport Sciences, Lausanne, Switzerland University of Geneva, Lemanic Doctoral School of Neuroscience, Geneva, Switzerland
| | - Oghenero Evero
- University of Colorado Denver Anschutz Medical Campus, Department of Emergency Medicine, Altitude Research Center, Aurora, CO, USA
| | - Nicolas Bourdillon
- University of Lausanne, Institute of Sport Sciences, Lausanne, Switzerland
| | - Bengt Kayser
- University of Lausanne, Institute of Sport Sciences, Lausanne, Switzerland
| | - Colleen G Julian
- University of Colorado Denver Anschutz Medical Campus, Department of Emergency Medicine, Altitude Research Center, Aurora, CO, USA
| | - Andrew T Lovering
- University of Oregon, Department of Human Physiology, Eugene, OR, USA
| | - Robert C Roach
- University of Colorado Denver Anschutz Medical Campus, Department of Emergency Medicine, Altitude Research Center, Aurora, CO, USA
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Amann M, Goodall S, Twomey R, Subudhi AW, Lovering AT, Roach RC. AltitudeOmics: on the consequences of high-altitude acclimatization for the development of fatigue during locomotor exercise in humans. J Appl Physiol (1985) 2013; 115:634-42. [PMID: 23813531 DOI: 10.1152/japplphysiol.00606.2013] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The development of muscle fatigue is oxygen (O2)-delivery sensitive [arterial O2 content (CaO2) × limb blood flow (QL)]. Locomotor exercise in acute hypoxia (AH) is, compared with sea level (SL), associated with reduced CaO2 and exaggerated inspiratory muscle work (Winsp), which impairs QL, both of which exacerbate fatigue individually by compromising O2 delivery. Since chronic hypoxia (CH) normalizes CaO2 but exacerbates Winsp, we investigated the consequences of a 14-day exposure to high altitude on exercise-induced locomotor muscle fatigue. Eight subjects performed the identical constant-load cycling exercise (138 ± 14 W; 11 ± 1 min) at SL (partial pressure of inspired O2, 147.1 ± 0.5 Torr), in AH (73.8 ± 0.2 Torr), and in CH (75.7 ± 0.1 Torr). Peripheral fatigue was expressed as pre- to postexercise percent reduction in electrically evoked potentiated quadriceps twitch force (ΔQtw,pot). Central fatigue was expressed as the exercise-induced percent decrease in voluntary muscle activation (ΔVA). Resting CaO2 at SL and CH was similar, but CaO2 in AH was lower compared with SL and CH (17.3 ± 0.5, 19.3 ± 0.7, 20.3 ± 1.3 ml O2/dl, respectively). Winsp during exercise increased with acclimatization (SL: 387 ± 36, AH: 503 ± 53, CH: 608 ± 67 cmH2O·s(-1)·min(-1); P < 0.01). Exercise at SL did not induce central or peripheral fatigue. ΔQtw,pot was significant but similar in AH and CH (21 ± 2% and 19 ± 3%; P = 0.24). ΔVA was significant in both hypoxic conditions but smaller in CH vs. AH (4 ± 1% vs. 8 ± 2%; P < 0.05). In conclusion, acclimatization to severe altitude does not attenuate the substantial impact of hypoxia on the development of peripheral fatigue. In contrast, acclimatization attenuates, but does not eliminate, the exacerbation of central fatigue associated with exercise in severe AH.
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Affiliation(s)
- Markus Amann
- Department of Medicine, University of Utah, Salt Lake City, Utah
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Asgari S, Gonzalez N, Subudhi AW, Hamilton R, Vespa P, Bergsneider M, Roach RC, Hu X. Continuous detection of cerebral vasodilatation and vasoconstriction using intracranial pulse morphological template matching. PLoS One 2012; 7:e50795. [PMID: 23226385 PMCID: PMC3511284 DOI: 10.1371/journal.pone.0050795] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Accepted: 10/23/2012] [Indexed: 12/05/2022] Open
Abstract
Although accurate and continuous assessment of cerebral vasculature status is highly desirable for managing cerebral vascular diseases, no such method exists for current clinical practice. The present work introduces a novel method for real-time detection of cerebral vasodilatation and vasoconstriction using pulse morphological template matching. Templates consisting of morphological metrics of cerebral blood flow velocity (CBFV) pulse, measured at middle cerebral artery using Transcranial Doppler, are obtained by applying a morphological clustering and analysis of intracranial pulse algorithm to the data collected during induced vasodilatation and vasoconstriction in a controlled setting. These templates were then employed to define a vasodilatation index (VDI) and a vasoconstriction index (VCI) for any inquiry data segment as the percentage of the metrics demonstrating a trend consistent with those obtained from the training dataset. The validation of the proposed method on a dataset of CBFV signals of 27 healthy subjects, collected with a similar protocol as that of training dataset, during hyperventilation (and CO2 rebreathing tests) shows a sensitivity of 92% (and 82%) for detection of vasodilatation (and vasoconstriction) and the specificity of 90% (and 92%), respectively. Moreover, the proposed method of detection of vasodilatation (vasoconstriction) is capable of rejecting all the cases associated with vasoconstriction (vasodilatation) and outperforms other two conventional techniques by at least 7% for vasodilatation and 19% for vasoconstriction.
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Affiliation(s)
- Shadnaz Asgari
- Department of Computer Engineering and Computer Science, California State University, Long Beach, California, United States of America
- Department of Neurosurgery, University of California Los Angeles, Los Angeles, California, United States of America
| | - Nestor Gonzalez
- Department of Neurosurgery, University of California Los Angeles, Los Angeles, California, United States of America
| | - Andrew W. Subudhi
- Department of Biology, University of Colorado, Colorado Springs, Colorado, United States of America
- Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Denver, Colorado, United States of America
| | - Robert Hamilton
- Department of Neurosurgery, University of California Los Angeles, Los Angeles, California, United States of America
- Department of Bioengineering, University of California Los Angeles, Los Angeles, California, United States of America
| | - Paul Vespa
- Department of Neurosurgery, University of California Los Angeles, Los Angeles, California, United States of America
| | - Marvin Bergsneider
- Department of Neurosurgery, University of California Los Angeles, Los Angeles, California, United States of America
- Department of Bioengineering, University of California Los Angeles, Los Angeles, California, United States of America
| | - Robert C. Roach
- Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Denver, Colorado, United States of America
| | - Xiao Hu
- Department of Neurosurgery, University of California Los Angeles, Los Angeles, California, United States of America
- Department of Bioengineering, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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Abstract
Hypoxia changes the regional distribution of cerebral blood flow and stimulates the ventilatory chemoreflex, thereby reducing CO2 tension. We examined the effects of both hypoxia and isocapnic hypoxia on acute changes in internal carotid (ICA) and vertebral artery (VA) blood flow. Ten healthy male subjects underwent the following two randomly assigned respiratory interventions after a resting baseline period with room air: (i) hypoxia; and (ii) isocapnic hypoxia with a controlled gas mixture (12% O2; inspiratory mmHg). In the isocapnic hypoxia intervention, subjects were instructed to maintain the rate and depth of breathing to maintain the level of end-tidal partial pressure of CO2 ( ) during the resting baseline period. The ICA and VA blood flow (velocity × cross-sectional area) were measured using Doppler ultrasonography. The was decreased (-6.3 ± 0.9%, P < 0.001) during hypoxia by hyperventilation (minute ventilation +12.9 ± 2.2%, P < 0.001), while was unchanged during isocapnic hypoxia. The ICA blood flow was unchanged (P = 0.429), while VA blood flow increased (+10.3 ± 3.1%, P = 0.010) during hypoxia. In contrast, isocapnic hypoxia increased both ICA (+14.5 ± 1.4%, P < 0.001) and VA blood flows (+10.9 ± 2.4%, P < 0.001). Thus, hypoxic vasodilatation outweighed hypocapnic vasoconstriction in the VA, but not in the ICA. These findings suggest that acute hypoxia elicits an increase in posterior cerebral blood flow, possibly to maintain essential homeostatic functions of the brainstem.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, 2100 Kujirai, Kawagoe-shi, Saitama 350-8585, Japan.
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Miyazawa T, Horiuchi M, Ichikawa D, Subudhi AW, Sugawara J, Ogoh S. Face cooling with mist water increases cerebral blood flow during exercise: effect of changes in facial skin blood flow. Front Physiol 2012; 3:308. [PMID: 22934059 PMCID: PMC3429079 DOI: 10.3389/fphys.2012.00308] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Accepted: 07/13/2012] [Indexed: 11/21/2022] Open
Abstract
Facial cooling (FC) increases cerebral blood flow (CBF) at rest and during exercise; however, the mechanism of this response remains unclear. The purpose of the present study was to test our hypothesis that FC causes facial vasoconstriction that diverts skin blood flow (SkBFface) toward the middle cerebral artery (MCA Vmean) at rest and to a greater extent during exercise. Nine healthy young subjects (20 ± 2 years) underwent 3 min of FC by fanning and spraying the face with a mist of cold water (~4°C) at rest and during steady-state exercise [heart rate (HR) of 120 bpm]. We focused on the difference between the averaged data acquired from 1 min immediately before FC and last 1 min of FC. SkBFface, MCA Vmean, and mean arterial blood pressure (MAP) were higher during exercise than at rest. As hypothesized, FC decreased SkBFface at rest (−32 ± 4%) and to a greater extent during exercise (−64 ± 10%, P = 0.012). Although MCA Vmean was increased by FC (Rest, +1.4 ± 0.5 cm/s; Exercise, +1.4 ± 0.6 cm/s), the amount of the FC-evoked changes in MCA Vmean at rest and during exercise differed among subjects. In addition, changes in MCA Vmean with FC did not correlate with concomitant changes in SkBFface (r = 0.095, P = 0.709). MAP was also increased by FC (Rest, +6.2 ± 1.4 mmHg; Exercise, +4.2 ± 1.2 mmHg). These findings suggest that the FC-induced increase in CBF during exercise could not be explained only by change in SkBFface.
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Affiliation(s)
- Taiki Miyazawa
- Center for Biomedical Engineering Research, Toyo University Kawagoe, Japan
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Abstract
Altitudes at which athletes compete or train do usually not exceed 2000-2500 m. At these moderate altitudes acute mountain sickness (AMS) is mild, transient and affects at the most 25% of a tourist population at risk. Unpublished data included in this review paper demonstrate that more intense physical activity associated with high-altitude training or mountaineering does not increase prevalence or severity of AMS at these altitudes. These conclusions can also be extended to the use of normobaric hypoxia, as data in this paper suggest that the severity of AMS is not significantly different between hypobaric and normobaric hypoxia at the same ambient pO(2). Furthermore, high-altitude cerebral or pulmonary oedema do not occur at these altitudes and intermittent exposure to considerably higher altitudes (4000-6000 m) used by athletes for hypoxic training are too short to cause acute high-altitude illnesses. Even moderate altitude between 2000 and 3000 m can, however, exacerbate cardiovascular or pulmonary disease or lead to a first manifestation of undiagnosed illness in older people that may belong to the accompanying staff of athletes. Moderate altitudes may also lead to splenic infarctions in healthy athletes with sickle cell trait.
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Affiliation(s)
- Kai Schommer
- Department of Internal Medicine, Division of Sports Medicine, University Hospital Heidelberg, Germany
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Abstract
The general practice of altitude training is widely accepted as a means to enhance sport performance despite a lack of rigorous scientific studies. For example, the scientific gold-standard design of a double-blind, placebo-controlled, cross-over trial has never been conducted on altitude training. Given that few studies have utilised appropriate controls, there should be more scepticism concerning the effects of altitude training methodologies. In this brief review we aim to point out weaknesses in theories and methodologies of the various altitude training paradigms and to highlight the few well-designed studies to give athletes, coaches and sports medicine professionals the current scientific state of knowledge on common forms of altitude training. Another aim is to encourage investigators to design well-controlled studies that will enhance our understanding of the mechanisms and potential benefits of altitude training.
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Affiliation(s)
- Carsten Lundby
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Winterthurerstrasse 190, 8057 - Zürich, Switzerland.
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Olin JT, Dimmen AC, Subudhi AW, Roach RC. A simple method to clamp end-tidal carbon dioxide during rest and exercise. Eur J Appl Physiol 2012; 112:3439-44. [PMID: 22736248 DOI: 10.1007/s00421-012-2433-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Accepted: 05/23/2012] [Indexed: 11/25/2022]
Abstract
Carbon dioxide regulates ventilation and cerebral blood flow during exercise. There are significant limitations in breathing systems designed to control end-tidal gas concentrations when used during high-intensity exercise. We designed a simple, inexpensive breathing system which controls end-tidal carbon dioxide (PET CO2) during exercise from rest to peak work capacity (W(max)). The system is operated by an investigator who, in response to breath-by-breath PET CO2, titrates flow of a 10 % CO(2), 21 % O(2) mixture into an open-ended 5-L inspiratory reservoir. To demonstrate system efficacy, nine fit male subjects performed two maximal, incremental exercise tests (25 W min(-1) ramp) on a cycle ergometer: a poikilocapnic control trial in which PET CO2 varied with work intensity, and an experimental trial, in which we planned to clamp PET CO2 at 50 mmHg. With our breathing system, we maintained PET CO2 at 51 ± 2 mmHg throughout exercise (rest, 50 ± 2; W(max), 52 ± 5 mmHg; mean ± SD) despite large changes in ventilation (range 27-65 at rest, 134-185 L min(-1) BTPS at W (max)) and carbon dioxide production (range 0.3-0.7 at rest, 4.5-5.5 L min(-1) at W (max)). This simple, inexpensive system achieves PET CO2 control at rest and throughout exercise.
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Affiliation(s)
- J Tod Olin
- Altitude Research Center, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
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Bergeron MF, Bahr R, Bärtsch P, Bourdon L, Calbet JAL, Carlsen KH, Castagna O, González-Alonso J, Lundby C, Maughan RJ, Millet G, Mountjoy M, Racinais S, Rasmussen P, Subudhi AW, Young AJ, Soligard T, Engebretsen L. International Olympic Committee consensus statement on thermoregulatory and altitude challenges for high-level athletes. Br J Sports Med 2012; 46:770-9. [DOI: 10.1136/bjsports-2012-091296] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Sato K, Sadamoto T, Hirasawa A, Oue A, Subudhi AW, Miyazawa T, Ogoh S. Differential blood flow responses to CO₂ in human internal and external carotid and vertebral arteries. J Physiol 2012; 590:3277-90. [PMID: 22526884 DOI: 10.1113/jphysiol.2012.230425] [Citation(s) in RCA: 151] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Arterial CO2 serves as a mediator of cerebral blood flow(CBF), and its relative influence on the regulation of CBF is defined as cerebral CO2 reactivity. Our previous studies have demonstrated that there are differences in CBF responses to physiological stimuli (i.e. dynamic exercise and orthostatic stress) between arteries in humans. These findings suggest that dynamic CBF regulation and cerebral CO2 reactivity may be different in the anterior and posterior cerebral circulation. The aim of this study was to identify cerebral CO2 reactivity by measuring blood flow and examine potential differences in CO2 reactivity between the internal carotid artery (ICA), external carotid artery (ECA) and vertebral artery (VA). In 10 healthy young subjects, we evaluated the ICA, ECA, and VA blood flow responses by duplex ultrasonography (Vivid-e, GE Healthcare), and mean blood flow velocity in middle cerebral artery (MCA) and basilar artery (BA) by transcranial Doppler (Vivid-7, GE healthcare) during two levels of hypercapnia (3% and 6% CO2), normocapnia and hypocapnia to estimate CO2 reactivity. To characterize cerebrovascular reactivity to CO2,we used both exponential and linear regression analysis between CBF and estimated partial pressure of arterial CO2, calculated by end-tidal partial pressure of CO2. CO2 reactivity in VA was significantly lower than in ICA (coefficient of exponential regression 0.021 ± 0.008 vs. 0.030 ± 0.008; slope of linear regression 2.11 ± 0.84 vs. 3.18 ± 1.09% mmHg−1: VA vs. ICA, P <0.01). Lower CO2 reactivity in the posterior cerebral circulation was persistent in distal intracranial arteries (exponent 0.023 ± 0.006 vs. 0.037 ± 0.009; linear 2.29 ± 0.56 vs. 3.31 ± 0.87% mmHg−1: BA vs. MCA). In contrast, CO2 reactivity in ECA was markedly lower than in the intra-cerebral circulation (exponent 0.006 ± 0.007; linear 0.63 ± 0.64% mmHg−1, P <0.01). These findings indicate that vertebro-basilar circulation has lower CO2 reactivity than internal carotid circulation, and that CO2 reactivity of the external carotid circulation is markedly diminished compared to that of the cerebral circulation, which may explain different CBF responses to physiological stress.
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Affiliation(s)
- Kohei Sato
- Research Institute of Physical Fitness, Japan Women's College of Physical Education, Kita-Karasuyama, Setagaya-ku, Tokyo 157-8565, Japan.
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Subudhi AW, Olin JT, Dimmen AC, Polaner DM, Kayser B, Roach RC. Does cerebral oxygen delivery limit incremental exercise performance? J Appl Physiol (1985) 2011; 111:1727-34. [PMID: 21921244 DOI: 10.1152/japplphysiol.00569.2011] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous studies have suggested that a reduction in cerebral oxygen delivery may limit motor drive, particularly in hypoxic conditions, where oxygen transport is impaired. We hypothesized that raising end-tidal Pco(2) (Pet(CO(2))) during incremental exercise would increase cerebral blood flow (CBF) and oxygen delivery, thereby improving peak power output (W(peak)). Amateur cyclists performed two ramped exercise tests (25 W/min) in a counterbalanced order to compare the normal, poikilocapnic response against a clamped condition, in which Pet(CO(2)) was held at 50 Torr throughout exercise. Tests were performed in normoxia (barometric pressure = 630 mmHg, 1,650 m) and hypoxia (barometric pressure = 425 mmHg, 4,875 m) in a hypobaric chamber. An additional trial in hypoxia investigated effects of clamping at a lower Pet(CO(2)) (40 Torr) from ∼75 to 100% W(peak) to reduce potential influences of respiratory acidosis and muscle fatigue imposed by clamping Pet(CO(2)) at 50 Torr. Metabolic gases, ventilation, middle cerebral artery CBF velocity (transcranial Doppler), forehead pulse oximetry, and cerebral (prefrontal) and muscle (vastus lateralis) hemoglobin oxygenation (near infrared spectroscopy) were monitored across trials. Clamping Pet(CO(2)) at 50 Torr in both normoxia (n = 9) and hypoxia (n = 11) elevated CBF velocity (∼40%) and improved cerebral hemoglobin oxygenation (∼15%), but decreased W(peak) (6%) and peak oxygen consumption (11%). Clamping at 40 Torr near maximal effort in hypoxia (n = 6) also improved cerebral oxygenation (∼15%), but again limited W(peak) (5%). These findings demonstrate that increasing mass cerebral oxygen delivery via CO(2)-mediated vasodilation does not improve incremental exercise performance, at least when accompanied by respiratory acidosis.
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Affiliation(s)
- Andrew W Subudhi
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
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Julian CG, Subudhi AW, Wilson MJ, Dimmen AC, Pecha T, Roach RC. Acute mountain sickness, inflammation, and permeability: new insights from a blood biomarker study. J Appl Physiol (1985) 2011; 111:392-9. [PMID: 21636566 DOI: 10.1152/japplphysiol.00391.2011] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The pathophysiology of acute mountain sickness (AMS) is unknown. One hypothesis is that hypoxia induces biochemical changes that disrupt the blood-brain barrier (BBB) and, subsequently, lead to the development of cerebral edema and the defining symptoms of AMS. This study explores the relationship between AMS and biomarkers thought to protect against or contribute to BBB disruption. Twenty healthy volunteers participated in a series of hypobaric hypoxia trials distinguished by pretreatment with placebo, acetazolamide (250 mg), or dexamethasone (4 mg), administered using a randomized, double-blind, placebo-controlled, crossover design. Each trial included peripheral blood sampling and AMS assessment before (-15 and 0 h) and during (0.5, 4, and 9 h) a 10-h hypoxic exposure (barometric pressure = 425 mmHg). Anti-inflammatory and/or anti-permeability [interleukin (IL)-1 receptor agonist (IL-1RA), heat shock protein (HSP)-70, and adrenomedullin], proinflammatory (IL-6, IL-8, IL-2, IL-1β, and substance P), angiogenic, or chemotactic biomarkers (macrophage inflammatory protein-1β, VEGF, TNF-α, monocyte chemotactic protein-1, and matrix metalloproteinase-9) were assessed. AMS-resistant subjects had higher IL-1RA (4 and 9 h and overall), HSP-70 (0 h and overall), and adrenomedullin (overall) compared with AMS-susceptible subjects. Acetazolamide raised IL-1RA and HSP-70 compared with placebo in AMS-susceptible subjects. Dexamethasone also increased HSP-70 and adrenomedullin in AMS-susceptible subjects. Macrophage inflammatory protein-1β was higher in AMS-susceptible than AMS-resistant subjects after 4 h of hypoxia; dexamethasone minimized this difference. Other biomarkers were unrelated to AMS. Resistance to AMS was accompanied by a marked anti-inflammatory and/or anti-permeability response that may have prevented downstream pathophysiological events leading to AMS. Conversely, AMS susceptibility does not appear to be related to an exaggerated inflammatory response.
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Affiliation(s)
- Colleen Glyde Julian
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, 12469 East 17 Place, Bldg 400, Aurora, CO 80045-0508, USA
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Subudhi AW, Olin JT, Dimmen AC, Kayser B, Roach RC. Does Cerebral Blood Flow Limit Maximal Aerobic Power Output? Med Sci Sports Exerc 2011. [DOI: 10.1249/01.mss.0000402920.14578.55] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Subudhi AW, Dimmen AC, Julian CG, Wilson MJ, Panerai RB, Roach RC. Effects of acetazolamide and dexamethasone on cerebral hemodynamics in hypoxia. J Appl Physiol (1985) 2011; 110:1219-25. [PMID: 21393464 DOI: 10.1152/japplphysiol.01393.2010] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous attempts to detect global cerebral hemodynamic differences between those who develop headache, nausea, and fatigue following rapid exposure to hypoxia [acute mountain sickness (AMS)] and those who remain healthy have been inconclusive. In this study, we investigated the effects of two drugs known to reduce symptoms of AMS to determine if a common cerebral hemodynamic mechanism could explain the prophylactic effect within individuals. With the use of randomized, placebo-controlled, double-blind, crossover design, 20 healthy volunteers were given oral acetazolamide (250 mg), dexamethasone (4 mg), or placebo every 8 h for 24 h prior to and during a 10-h exposure to a simulated altitude of 4,875 m in a hypobaric chamber, which included 2 h of exercise at 50% of altitude-specific VO(2max). Cerebral hemodynamic parameters derived from ultrasound assessments of dynamic cerebral autoregulation and vasomotor reactivity were recorded 15 h prior to and after 9 h of hypoxia. AMS symptoms were scored using the Lake Louise Questionnaire (LLQ). It was found that both drugs prevented AMS in those who became ill on placebo (~70% decrease in LLQ), yet a common cerebral hemodynamic mechanism was not identified. Compared with placebo, acetazolamide reduced middle cerebral artery blood flow velocity (11%) and improved dynamic cerebral autoregulation after 9 h of hypoxia, but these effects appeared independent of AMS. Dexamethasone had no measureable cerebral hemodynamic effects in hypoxia. In conclusion, global cerebral hemodynamic changes resulting from hypoxia may not explain the development of AMS.
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Affiliation(s)
- Andrew W Subudhi
- Altitude Research Center, University of Colorado Anschutz Medical Campus, Colorado, USA.
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Subudhi AW, Panerai RB, Roach RC. Response to Letter by Bailey. Stroke 2010. [DOI: 10.1161/strokeaha.110.587501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Andrew W. Subudhi
- Altitude Research Center University of Colorado at Denver School of Medicine Denver, Colo and Department of Biology University of Colorado at Colorado Springs Colorado Springs, Colo
| | - Ronney B. Panerai
- Department of Cardiovascular Sciences University of Leicester Leicester Royal Infirmary Leicester, UK
| | - Robert C. Roach
- Altitude Research Center University of Colorado at Denver School of Medicine Denver, Colo
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