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Lie SL, Hisdal J, Rehn M, Høiseth LØ. Effect of systemic vascular resistance on the agreement between stroke volume by non-invasive pulse wave analysis and Doppler ultrasound in healthy volunteers. PLoS One 2024; 19:e0302159. [PMID: 38713665 DOI: 10.1371/journal.pone.0302159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 03/27/2024] [Indexed: 05/09/2024] Open
Abstract
BACKGROUND Stroke volume can be estimated beat-to-beat and non-invasively by pulse wave analysis (PWA). However, its reliability has been questioned during marked alterations in systemic vascular resistance (SVR). We studied the effect of SVR on the agreement between stroke volume by PWA and Doppler ultrasound during reductions in stroke volume in healthy volunteers. METHODS In a previous study we simultaneously measured stroke volume by PWA (SVPWA) and suprasternal Doppler ultrasound (SVUS). We exposed 16 healthy volunteers to lower body negative pressure (LBNP) to reduce stroke volume in combination with isometric hand grip to elevate SVR. LBNP was increased by 20 mmHg every 6 minutes from 0 to 80 mmHg, or until hemodynamic decompensation. The agreement between SVPWA and SVUS was examined using Bland-Altman analysis with mixed regression. Within-subject limits of agreement (LOA) was calculated from the residual standard deviation. SVRUS was calculated from SVUS. We allowed for a sloped bias line by introducing the mean of the methods and SVRUS as explanatory variables to examine whether the agreement was dependent on the magnitude of stroke volume and SVRUS. RESULTS Bias ± limits of agreement (LOA) was 27.0 ± 30.1 mL. The within-subject LOA was ±11.1 mL. The within-subject percentage error was 14.6%. The difference between methods decreased with higher means of the methods (-0.15 mL/mL, confidence interval (CI): -0.19 to -0.11, P<0.001). The difference between methods increased with higher SVRUS (0.60 mL/mmHg × min × L-1, 95% CI: 0.48 to 0.72, P<0.001). CONCLUSION PWA overestimated stroke volume compared to Doppler ultrasound during reductions in stroke volume and elevated SVR in healthy volunteers. The agreement between SVPWA and SVUS decreased during increases in SVR. This is relevant in settings where a high level of reliability is required.
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Affiliation(s)
- Sole Lindvåg Lie
- Norwegian Air Ambulance Foundation, Department of Research and Development, Oslo, Norway
- Institute of Clinical Medicine, University of Oslo, Oslo, Norway
- Section of Vascular Investigations, Oslo University Hospital, Oslo, Norway
| | - Jonny Hisdal
- Institute of Clinical Medicine, University of Oslo, Oslo, Norway
- Section of Vascular Investigations, Oslo University Hospital, Oslo, Norway
| | - Marius Rehn
- Norwegian Air Ambulance Foundation, Department of Research and Development, Oslo, Norway
- Institute of Clinical Medicine, University of Oslo, Oslo, Norway
- Air Ambulance Department, Division of Prehospital Services, Oslo University Hospital, Oslo, Norway
| | - Lars Øivind Høiseth
- Institute of Clinical Medicine, University of Oslo, Oslo, Norway
- Department of Anesthesia and Intensive Care Medicine, Division of Emergencies and Critical Care, Oslo University Hospital, Oslo, Norway
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DeConne TM, Fancher IS, Edwards DG, Trott DW, Martens CR. CD8 + T-cell metabolism is related to cerebrovascular reactivity in middle-aged adults. Am J Physiol Regul Integr Comp Physiol 2024; 326:R416-R426. [PMID: 38406845 DOI: 10.1152/ajpregu.00267.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 02/13/2024] [Accepted: 02/22/2024] [Indexed: 02/27/2024]
Abstract
Cerebrovascular reactivity (CVR) decreases with advancing age, contributing to increased risk of cognitive impairment; however, the mechanisms underlying the age-related decrease in CVR are incompletely understood. Age-related changes to T cells, such as impaired mitochondrial respiration, increased inflammation, likely contribute to peripheral and cerebrovascular dysfunction in animals. However, whether T-cell mitochondrial respiration is related to cerebrovascular function in humans is not known. Therefore, we hypothesized that peripheral T-cell mitochondrial respiration would be positively associated with CVR and that T-cell glycolytic metabolism would be negatively associated with CVR. Twenty middle-aged adults (58 ± 5 yr) were recruited for this study. T cells were separated from peripheral blood mononuclear cells. Cellular oxygen consumption rate (OCR) and extracellular acidification rate (ECAR, a marker of glycolytic activity) were measured using extracellular flux analysis. CVR was quantified using the breath-hold index (BHI), which reflects the change in blood velocity in the middle-cerebral artery (MCAv) during a 30-s breath-hold. In contrast to our hypothesis, we found that basal OCR in CD8+ T cells (β = -0.59, R2 = 0.27, P = 0.019) was negatively associated with BHI. However, in accordance with our hypothesis, we found that basal ECAR (β = -2.20, R2 = 0.29, P = 0.015) and maximum ECAR (β = -50, R2 = 0.24, P = 0.029) were negatively associated with BHI in CD8+ T cells. There were no associations observed in CD4+ T cells. These associations appeared to be primarily mediated by an association with the pressor response to the breath-hold test. Overall, our findings suggest that CD8+ T-cell respiration and glycolytic activity may influence CVR in humans.NEW & NOTEWORTHY Peripheral T-cell metabolism is related to in vivo cerebrovascular reactivity in humans. Higher glycolytic metabolism in CD8+ T cells was associated with lower cerebrovascular reactivity to a breath-hold in middle-aged adults, which is possibly reflective of a more proinflammatory state in midlife.
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Affiliation(s)
- Theodore M DeConne
- Department of Internal Medicine, Wake Forest University School of Medicine, Winston-Salem, North Carolina, United States
| | - Ibra S Fancher
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, Delaware, United States
| | - David G Edwards
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, Delaware, United States
| | - Daniel W Trott
- Department of Kinesiology, University of Texas at Arlington, Arlington, Texas, United States
| | - Christopher R Martens
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, Delaware, United States
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3
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Tourula E, Lenzini M, Rhodes A, Hetz SE, Pearson J. Facial fanning reduces heart rate but not tolerance to a simulated hemorrhagic challenge following exercise heat stress in young healthy humans. Am J Physiol Regul Integr Comp Physiol 2024; 326:R210-R219. [PMID: 38105763 DOI: 10.1152/ajpregu.00180.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 11/02/2023] [Accepted: 12/12/2023] [Indexed: 12/19/2023]
Abstract
We investigated whether reducing face skin temperature alters arterial blood pressure control and lower body negative pressure (LBNP) tolerance after exercise heat stress. Eight subjects (1 female; age, 27 ± 9 yr) exercised at ∼63% V̇o2max until core temperature had increased ∼1.5°C before undergoing LBNP to presyncope either with fanning to return face skin temperature to baseline (Δ-5°C, Fan trial) or without (No Fan trial). LBNP tolerance was quantified as cumulative stress index (CSI; mmHg·min). Before LBNP, whole body and face skin temperatures were elevated from baseline in both trials (38.0 ± 0.5°C and 36.3 ± 0.5°C, respectively, both P < 0.001). During LBNP, face skin temperature decreased in the Fan trial (30.9 ± 1.0°C) but was unchanged in the No Fan trial (36.1 ± 0.6°C, between trials P < 0.001). Mean arterial pressure was not different between trials (P = 0.237) and was similarly reduced at presyncope in both trials (from 82 ± 7 to 67 ± 8 mmHg, P < 0.001). During LBNP, heart rate was attenuated in the Fan trial at Mid LBNP (146 ± 16 vs. 158 ± 12 beats/min, P = 0.036) and at peak heart rate (158 ± 15 vs. 170 ± 15 beats/min; P < 0.001). LBNP tolerance was not different between trials (321 ± 248 vs. 328 ± 115 mmHg·min, P = 0.851). In exercise heat-stressed individuals, lowering face skin temperature to normothermic values suppressed heart rate thereby altering cardiovascular control during a simulated hemorrhagic challenge without reducing tolerance.
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Affiliation(s)
- Erica Tourula
- William J. Hybl Sports Medicine and Performance Center, Department of Human Physiology and Nutrition, University of Colorado Colorado Springs, Colorado, United States
- Department of Kinesiology, H. H. Morris Human Performance Laboratories, School of Public Health, Indiana University, Bloomington, Indiana, United States
| | - Miramani Lenzini
- William J. Hybl Sports Medicine and Performance Center, Department of Human Physiology and Nutrition, University of Colorado Colorado Springs, Colorado, United States
| | - Addison Rhodes
- William J. Hybl Sports Medicine and Performance Center, Department of Human Physiology and Nutrition, University of Colorado Colorado Springs, Colorado, United States
| | - Sarah E Hetz
- William J. Hybl Sports Medicine and Performance Center, Department of Human Physiology and Nutrition, University of Colorado Colorado Springs, Colorado, United States
| | - James Pearson
- William J. Hybl Sports Medicine and Performance Center, Department of Human Physiology and Nutrition, University of Colorado Colorado Springs, Colorado, United States
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Meng L, Sun Y, Zhao X, Meng DM, Liu Z, Adams DC, McDonagh DL, Rasmussen M. Effects of phenylephrine on systemic and cerebral circulations in humans: a systematic review with mechanistic explanations. Anaesthesia 2024; 79:71-85. [PMID: 37948131 DOI: 10.1111/anae.16172] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/03/2023] [Indexed: 11/12/2023]
Abstract
We conducted a systematic review of the literature reporting phenylephrine-induced changes in blood pressure, cardiac output, cerebral blood flow and cerebral tissue oxygen saturation as measured by near-infrared spectroscopy in humans. We used the proportion change of the group mean values reported by the original studies in our analysis. Phenylephrine elevates blood pressure whilst concurrently inducing a reduction in cardiac output. Furthermore, despite increasing cerebral blood flow, it decreases cerebral tissue oxygen saturation. The extent of phenylephrine's influence on cardiac output (r = -0.54 and p = 0.09 in awake humans; r = -0.55 and p = 0.007 in anaesthetised humans), cerebral blood flow (r = 0.65 and p = 0.002 in awake humans; r = 0.80 and p = 0.003 in anaesthetised humans) and cerebral tissue oxygen saturation (r = -0.72 and p = 0.03 in awake humans; r = -0.24 and p = 0.48 in anaesthetised humans) appears closely linked to the magnitude of phenylephrine-induced blood pressure changes. When comparing the effects of phenylephrine in awake and anaesthetised humans, we found no evidence of a significant difference in cardiac output, cerebral blood flow or cerebral tissue oxygen saturation. There was also no evidence of a significant difference in effect on systemic and cerebral circulations whether phenylephrine was given by bolus or infusion. We explore the underlying mechanisms driving the phenylephrine-induced cardiac output reduction, cerebral blood flow increase and cerebral tissue oxygen saturation decrease. Individualised treatment approaches, close monitoring and consideration of potential risks and benefits remain vital to the safe and effective use of phenylephrine in acute care.
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Affiliation(s)
- L Meng
- Department of Anesthesia, Indiana University School of Medicine, IA, Indianapolis, USA
| | - Y Sun
- Department of Anesthesiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Nanjing University Medical School, Nanjing, China
| | - X Zhao
- Department of Anesthesiology, First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - D M Meng
- Choate Rosemary Hall School, CT, Wallingford, USA
| | - Z Liu
- Department of Biostatistics and Health Data Science, Indiana University School of Medicine, IA, Indianapolis, USA
| | - D C Adams
- Department of Anesthesia, Indiana University School of Medicine, IA, Indianapolis, USA
| | - D L McDonagh
- Departments of Anesthesiology and Pain Management, Neurological Surgery, Neurology and Neurotherapeutics, UT Southwestern Medical Center, TX, Dallas, USA
| | - M Rasmussen
- Department of Anesthesiology, Section of Neuroanesthesia, Aarhus University Hospital, Aarhus, Denmark
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Anderson GK, Davis KA, Bhuiyan N, Rusy R, Rosenberg AJ, Rickards CA. The effect of oscillatory hemodynamics on the cardiovascular responses to simulated hemorrhage during isocapnia. J Appl Physiol (1985) 2023; 135:1312-1322. [PMID: 37881852 PMCID: PMC10911761 DOI: 10.1152/japplphysiol.00241.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 10/17/2023] [Accepted: 10/20/2023] [Indexed: 10/27/2023] Open
Abstract
During cerebral hypoperfusion induced by lower body negative pressure (LBNP), cerebral tissue oxygenation is protected with oscillatory arterial pressure and cerebral blood flow at low frequencies (0.1 Hz and 0.05 Hz), despite no protection of cerebral blood flow or oxygen delivery. However, hypocapnia induced by LBNP contributes to cerebral blood flow reductions, and may mask potential protective effects of hemodynamic oscillations on cerebral blood flow. We hypothesized that under isocapnic conditions, forced oscillations of arterial pressure and blood flow at 0.1 Hz and 0.05 Hz would attenuate reductions in extra- and intracranial blood flow during simulated hemorrhage using LBNP. Eleven human participants underwent three LBNP profiles: a nonoscillatory condition (0 Hz) and two oscillatory conditions (0.1 Hz and 0.05 Hz). End-tidal (et) CO2 and etO2 were clamped at baseline values using dynamic end-tidal forcing. Cerebral tissue oxygenation (ScO2), internal carotid artery (ICA) blood flow, and middle cerebral artery velocity (MCAv) were measured. With clamped etCO2, neither ICA blood flow (ANOVA P = 0.93) nor MCAv (ANOVA P = 0.36) decreased with LBNP, and these responses did not differ between the three profiles (ICA blood flow: 0 Hz: 2.2 ± 5.4%, 0.1 Hz: -0.4 ± 6.6%, 0.05 Hz: 0.2 ± 4.8%; P = 0.56; MCAv: 0 Hz: -2.3 ± 7.8%, 0.1 Hz: -1.3 ± 6.1%, 0.05 Hz: -3.1 ± 5.0%; P = 0.87). Similarly, ScO2 did not decrease with LBNP (ANOVA P = 0.21) nor differ between the three profiles (0 Hz: -2.6 ± 3.3%, 0.1 Hz: -1.6 ± 1.5%, 0.05 Hz: -0.2 ± 2.8%; P = 0.13). Contrary to our hypothesis, cerebral blood flow and tissue oxygenation were protected during LBNP with isocapnia, regardless of whether hemodynamic oscillations were induced.NEW & NOTEWORTHY We examined the role of forcing oscillations in arterial pressure and blood flow at 0.1 Hz and 0.05 Hz on extra- and intracranial blood flow and cerebral tissue oxygenation during simulated hemorrhage (using lower body negative pressure, LBNP) under isocapnic conditions. Contrary to our hypothesis, both cerebral blood flow and cerebral tissue oxygenation were completely protected during simulated hemorrhage with isocapnia, regardless of whether oscillations in arterial pressure and cerebral blood flow were induced. These findings highlight the protective effect of preventing hypocapnia on cerebral blood flow under simulated hemorrhage conditions.
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Affiliation(s)
- Garen K Anderson
- Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, Texas, United States
| | - K Austin Davis
- Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, Texas, United States
| | - Nasrul Bhuiyan
- Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, Texas, United States
| | - Ryan Rusy
- Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, Texas, United States
| | - Alexander J Rosenberg
- Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, Texas, United States
- Physiology Department, Midwestern University, Downers Grove, Illinois, United States
- Integrative Physiology Laboratory, Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Caroline A Rickards
- Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, Texas, United States
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6
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Metzler-Wilson K, Fang MM, Alibegovic K, Daggett JW, Narra SC, Dazé RP, Miller OG, Wilson TE. Effect of reflex and mechanical decreases in skin perfusion on thermal- and agonist-induced eccrine sweating in humans. Am J Physiol Regul Integr Comp Physiol 2023; 324:R271-R280. [PMID: 36622082 PMCID: PMC9970189 DOI: 10.1152/ajpregu.00066.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 12/07/2022] [Accepted: 01/02/2023] [Indexed: 01/10/2023]
Abstract
In humans, skin blood flux (SkBF) and eccrine sweating are tightly coupled, suggesting common neural control and regulation. This study was designed to separate these two sympathetic nervous system end-organ responses via nonadrenergic SkBF-decreasing mechanical perturbations during heightened sudomotor drive. We induced sweating physiologically via whole body heat stress using a high-density tube-lined suit (protocol 1; 2 women, 4 men), and pharmacologically via forearm intradermal microdialysis of two steady-state doses of a cholinergic agonist, pilocarpine (protocol 2; 4 women, 3 men). During sweating induction, we decreased SkBF via three mechanical perturbations: arm and leg dependency to engage the cutaneous venoarteriolar response (CVAR), limb venous occlusion to engage the CVAR and decrease perfusion pressure, and limb arterial occlusion to cause ischemia. In protocol 1, heat stress increased arm cutaneous vascular conductance and forearm sweat rate (capacitance hygrometry). During heat stress, despite decreases in SkBF during each of the acute (3 min) mechanical perturbations, eccrine sweat rate was unaffected. During heat stress with extended (10 min) ischemia, sweat rate decreased. In protocol 2, both pilocarpine doses (ED50 and EMAX) increased SkBF and sweat rate. Each mechanical perturbation resulted in decreased SkBF but minimal changes in eccrine sweat rate. Taken together, these data indicate that a wide range of acute decreases in SkBF do not appear to proportionally decrease either physiologically- or pharmacologically induced eccrine sweating in peripheral skin. This preservation of evaporative cooling despite acutely decreased SkBF could have consequential impacts for heat storage and balance during changes in body posture, limb position, or blood flow restrictive conditions.
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Affiliation(s)
- Kristen Metzler-Wilson
- Department of Physical Therapy, Indiana University School of Health and Human Sciences, Indianapolis, Indiana
- Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Milie M Fang
- Division of Biomedical Sciences, Marian University College of Osteopathic Medicine, Indianapolis, Indiana
| | - Kenan Alibegovic
- Division of Biomedical Sciences, Marian University College of Osteopathic Medicine, Indianapolis, Indiana
| | - James W Daggett
- Division of Biomedical Sciences, Marian University College of Osteopathic Medicine, Indianapolis, Indiana
| | - Seetharam C Narra
- Division of Biomedical Sciences, Marian University College of Osteopathic Medicine, Indianapolis, Indiana
| | - Robert P Dazé
- Division of Biomedical Sciences, Marian University College of Osteopathic Medicine, Indianapolis, Indiana
| | - Olivia G Miller
- Department of Physical Therapy, Indiana University School of Health and Human Sciences, Indianapolis, Indiana
| | - Thad E Wilson
- Division of Biomedical Sciences, Marian University College of Osteopathic Medicine, Indianapolis, Indiana
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
- Saha Cardiovascular Research Center, University of Kentucky College of Medicine, Lexington, Kentucky
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MacNamara JP, Dias KA, Hearon CM, Hieda M, Turer AT, Link MS, Sarma S, Levine BD. Limits to Submaximal and Maximal Exercise in Patients with Hypertrophic Cardiomyopathy. J Appl Physiol (1985) 2022; 133:787-797. [PMID: 35952351 DOI: 10.1152/japplphysiol.00566.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Patients with hypertrophic cardiomyopathy (HCM) often have reduced exercise capacity, and it is unclear whether cardiovascular regulation during exercise is intact in these patients. We aimed to determine the relationship between cardiac output (Q̇c) and oxygen uptake (V̇O2), and stroke volume (SV) reserve in HCMcompared to healthy participants and participants with left ventricular hypertrophy (LVH) but not HCM. METHODS Sixteen patients with HCM (48±7 years, 44% female), 16 participants with LVH (49±5 years, 44% female), and 61 healthy controls (CON: 52±5 years, 52% female) completed submaximal steady-state treadmill exercise followed by a maximal exercise test. V̇O2, Q̇c,SV and arterio-venous oxygen difference were measured during rest and exercise, and Q̇c/V̇O2 slopes were constructed. RESULTS The Q̇c/V̇O2 slopewas blunted in HCM compared to CON and LVH (HCM 4.9±0.7 vs. CON 5.5± 1.0 [P = 0.027], vs LVH 6.0±1.0AU [P = 0.002]) and participants with HCM had a lower SV reserve (HCM 53±33%, controls 83±33%, LVH 82±22%; HCM vs. controls P = 0.002; HCM vs. LVH P = 0.015). Despite a blunted Q̇c/V̇O2 slope, 75% of patients with HCM achieved ≥80% predicted V̇O2max by augmenting a-vO2 difference at maximal exercise (16.0±0.8 mL/100mL vs 13.8±2.7 mL/100mL, P = 0.021). CONCLUSIONS Patients with HCM do not appropriately match Q̇c to metabolic demand, primarily due to inadequate stroke volume augmentation. Despite this central limitation, many patients achieve normal exercise capacities by significantly increasing peripheral oxygen extraction.
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Affiliation(s)
- James P MacNamara
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas, United States.,University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Katrin A Dias
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas, United States.,University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Christopher M Hearon
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas, United States.,University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Michinari Hieda
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas, United States.,University of Texas Southwestern Medical Center, Dallas, TX, United States.,Kyushu University, School of Medicine, Department of Medicine and Biosystemic Science, Fukuoka, Japan
| | - Aslan T Turer
- University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Mark S Link
- University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Satyam Sarma
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas, United States.,University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Benjamin D Levine
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas, United States.,University of Texas Southwestern Medical Center, Dallas, TX, United States
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Fujii N, Fujimoto T, Yinhang C, Dobashi K, Matsutake R, Amano T, Watanabe K, Nishiyasu T. Caffeine Exacerbates Hyperventilation and Reductions in Cerebral Blood Flow in Physically Fit Men Exercising in the Heat. Med Sci Sports Exerc 2021; 53:845-852. [PMID: 33044440 DOI: 10.1249/mss.0000000000002537] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
INTRODUCTION Caffeine is an exercise performance enhancer widely used by individuals engaged in training or competition under heat-stressed conditions. Caffeine ingestion during exercise in the heat is believed to be safe because it does not greatly affect body temperature responses, heart rate, or body fluid status. However, it remains unknown whether caffeine affects hyperthermia-induced hyperventilation or reductions in the cerebral blood flow index. We tested the hypothesis that under conditions inducing severe hyperthermia, caffeine exacerbates hyperthermia-induced hyperventilation and reduces the cerebral blood flow index during exercise. METHODS Using a randomized, single-blind, crossover design, 12 physically active healthy young men (23 ± 2 yr) consumed a moderate dose of caffeine (5 mg·kg-1) or placebo in the heat (37°C). Approximately 60 min after the ingestion, they cycled for ~45 min at a workload equal to ~55% of their predetermined peak oxygen uptake (moderate intensity) until their core temperature increased to 2.0°C above its preexercise baseline level. RESULTS In both trials, ventilation increased and the cerebral blood flow index assessed by middle cerebral artery mean blood velocity decreased as core temperature rose during exercise (P < 0.05), indicating that hyperthermia-induced hyperventilation and lowering of the cerebral blood flow occurred. When core temperature was elevated by 1.5°C or more (P < 0.05), ventilation was higher and the cerebral blood flow was lower throughout the caffeine trial than the placebo trial (P < 0.05). CONCLUSIONS A moderate dose of caffeine exacerbates hyperthermia-induced hyperventilation and reductions in the cerebral blood flow index during exercise in the heat with severe hyperthermia.
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Affiliation(s)
- Naoto Fujii
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, JAPAN
| | | | | | - Kohei Dobashi
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, JAPAN
| | - Ryoko Matsutake
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, JAPAN
| | - Tatsuro Amano
- Laboratory for Exercise and Environmental Physiology, Faculty of Education, Niigata University, Niigata, JAPAN
| | - Koichi Watanabe
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, JAPAN
| | - Takeshi Nishiyasu
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, JAPAN
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Babcock MC, Robinson AT, Migdal KU, Watso JC, Martens CR, Edwards DG, Pescatello LS, Farquhar WB. High Salt Intake Augments Blood Pressure Responses During Submaximal Aerobic Exercise. J Am Heart Assoc 2020; 9:e015633. [PMID: 32406312 PMCID: PMC7660875 DOI: 10.1161/jaha.120.015633] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Background High sodium (Na+) intake is a widespread cardiovascular disease risk factor. High Na+ intake impairs endothelial function and exaggerates sympathetic reflexes, which may augment exercising blood pressure (BP) responses. Therefore, this study examined the influence of high dietary Na+ on BP responses during submaximal aerobic exercise. Methods and Results Twenty adults (8F/12M, age=24±4 years; body mass index 23.0±0.6 kg·m−2; VO2peak=39.7±9.8 mL·min−1·kg−1; systolic BP=111±10 mm Hg; diastolic BP=64±8 mm Hg) participated in this randomized, double‐blind, placebo‐controlled crossover study. Total Na+ intake was manipulated via ingestion of capsules containing either a placebo (dextrose) or table salt (3900 mg Na+/day) for 10 days each, separated by ≥2 weeks. On day 10 of each intervention, endothelial function was assessed via flow‐mediated dilation followed by BP measurement at rest and during 50 minutes of cycling at 60% VO2peak. Throughout exercise, BP was assessed continuously via finger photoplethysmography and every 5 minutes via auscultation. Venous blood samples were collected at rest and during the final 10 minutes of exercise for assessment of norepinephrine. High Na+ intake increased urinary Na+ excretion (placebo=140±68 versus Na+=282±70 mmol·24H−1; P<0.001) and reduced flow‐mediated dilation (placebo=7.2±2.4 versus Na+=4.2±1.7%; P<0.001). Average exercising systolic BP was augmented following high Na+ (placebo=Δ30.0±16.3 versus Na+=Δ38.3±16.2 mm Hg; P=0.03) and correlated to the reduction in flow‐mediated dilation (R=−0.71, P=0.002). Resting norepinephrine concentration was not different between conditions (P=0.82). Norepinephrine increased during exercise (P=0.002), but there was no Na+ effect (P=0.26). Conclusions High dietary Na+ augments BP responses during submaximal aerobic exercise, which may be mediated, in part, by impaired endothelial function.
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Affiliation(s)
- Matthew C Babcock
- Department of Kinesiology and Applied Physiology University of Delaware Newark DE
| | - Austin T Robinson
- Department of Kinesiology and Applied Physiology University of Delaware Newark DE.,School of Kinesiology Auburn University Auburn AL
| | - Kamila U Migdal
- Department of Kinesiology and Applied Physiology University of Delaware Newark DE
| | - Joseph C Watso
- Department of Kinesiology and Applied Physiology University of Delaware Newark DE
| | | | - David G Edwards
- Department of Kinesiology and Applied Physiology University of Delaware Newark DE
| | | | - William B Farquhar
- Department of Kinesiology and Applied Physiology University of Delaware Newark DE
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10
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Babcock MC, Robinson AT, Watso JC, Migdal KU, Martens CR, Edwards DG, Pescatello LS, Farquhar WB. Salt Loading Blunts Central and Peripheral Postexercise Hypotension. Med Sci Sports Exerc 2020; 52:935-943. [PMID: 31609296 PMCID: PMC7144834 DOI: 10.1249/mss.0000000000002187] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
INTRODUCTION High salt intake is a widespread cardiovascular risk factor with systemic effects. These effects include an expansion of plasma volume, which may interfere with postexercise hypotension (PEH). However, the effects of high salt intake on central and peripheral indices of PEH remain unknown. We tested the hypothesis that high salt intake would attenuate central and peripheral PEH. METHODS Nineteen healthy adults (7 female/12 male; age, 25 ± 4 yr; body mass index, 23.3 ± 2.2 kg·m; V[Combining Dot Above]O2peak, 41.6 ± 8.7 mL·min·kg; systolic blood pressure (BP), 112 ± 9 mm Hg; diastolic BP, 65 ± 9 mm Hg) participated in this double-blind, randomized, placebo-controlled crossover study. Participants were asked to maintain a 2300 mg·d sodium diet for 10 d on two occasions separated by ≥2 wk. Total salt intake was manipulated via ingestion of capsules containing either table salt (3900 mg·d) or placebo (dextrose) during each diet. On the 10th day, participants completed 50 min of cycling at 60% V[Combining Dot Above]O2peak. A subset of participants (n = 8) completed 60 min of seated rest (sham trial). Beat-to-beat BP was measured in-laboratory for 60 min after exercise via finger photoplethysmography. Brachial and central BPs were measured for 24 h after exercise via ambulatory BP monitor. RESULTS Ten days of high salt intake increased urinary sodium excretion (134 ± 70 (dextrose) vs 284 ± 74 mmol per 24 h (salt), P < 0.001), expanded plasma volume (7.2% ± 10.8%), and abolished PEH during in-laboratory BP monitoring (main effect of diet, P < 0.001). Ambulatory systolic BPs were higher for 12 h after exercise during the salt and sham trials compared with the dextrose trial (average change, 3.6 ± 2.1 mm Hg (dextrose), 9.9 ± 1.4 mm Hg (salt), 9.8 ± 2.5 mm Hg (sham); P = 0.01). Ambulatory central systolic BP was also higher during the salt trial compared with dextrose trial. CONCLUSION High salt intake attenuates peripheral and central PEH, potentially reducing the beneficial cardiovascular effects of acute aerobic exercise.
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Affiliation(s)
- Matthew C. Babcock
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE
| | - Austin T. Robinson
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE
| | - Joseph C. Watso
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE
| | - Kamila U. Migdal
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE
| | | | - David G. Edwards
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE
| | | | - William B. Farquhar
- Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE
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11
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Engelland RE, Hemingway HW, Tomasco OG, Olivencia-Yurvati AH, Romero SA. Neural control of blood pressure is altered following isolated leg heating in aged humans. Am J Physiol Heart Circ Physiol 2020; 318:H976-H984. [PMID: 32142377 DOI: 10.1152/ajpheart.00019.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
There is a sustained reduction in arterial blood pressure that occurs in aged adults following exposure to acute leg heating. We tested the hypothesis that acute leg heating would decrease arterial blood pressure in aged adults secondary to sympathoinhibition. We exposed 13 young and 10 aged adults to 45 min of leg heating. Muscle sympathetic nerve activity (radial nerve) was measured before leg heating (preheat) and 30 min after (recovery) and is expressed as burst frequency. Neurovascular transduction was examined by assessing the slope of the relation between muscle sympathetic nerve activity and leg vascular conductance measured at rest and during isometric handgrip exercise performed to fatigue. Arterial blood pressure was well maintained in young adults (preheat, 86 ± 6 mmHg vs. recovery, 88 ± 7 mmHg; P = 0.4) due to increased sympathetic nerve activity (preheat, 16 ± 7 bursts/min vs. recovery, 22 ± 10 bursts/min; P < 0.01). However, in aged adults, sympathetic nerve activity did not differ from preheat (37 ± 5 bursts/min) to recovery (33 ± 6 bursts/min, P = 0.1), despite a marked reduction in arterial blood pressure (preheat, 101 ± 7 mmHg vs. recovery, 94 ± 6 mmHg; P < 0.01). Neurovascular transduction did not differ from preheat to recovery for either age group (P ≥ 0.1). The reduction in arterial blood pressure that occurs in aged adults following exposure to acute leg heating is mediated, in part, by a sympathoinhibitory effect that alters the compensatory neural response to hypotension.NEW & NOTEWORTHY There is a sustained reduction in arterial blood pressure that occurs in aged adults following exposure to acute leg heating. However, the neurovascular mechanisms mediating this response remain unknown. Our findings demonstrate for the first time that this reduction in arterial blood pressure is mediated, in part, by a sympathoinhibitory effect that alters the compensatory neural response to hypotension in aged adults.
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Affiliation(s)
- Rachel E Engelland
- Department of Physiology and Anatomy, Human Vascular Physiology Laboratory, University of North Texas Health Science Center, Ft. Worth, Texas
| | - Holden W Hemingway
- Department of Physiology and Anatomy, Human Vascular Physiology Laboratory, University of North Texas Health Science Center, Ft. Worth, Texas
| | - Olivia G Tomasco
- Department of Physiology and Anatomy, Human Vascular Physiology Laboratory, University of North Texas Health Science Center, Ft. Worth, Texas
| | - Albert H Olivencia-Yurvati
- Department of Physiology and Anatomy, Human Vascular Physiology Laboratory, University of North Texas Health Science Center, Ft. Worth, Texas.,Department of Surgery, University of North Texas Health Science Center, Ft. Worth, Texas
| | - Steven A Romero
- Department of Physiology and Anatomy, Human Vascular Physiology Laboratory, University of North Texas Health Science Center, Ft. Worth, Texas
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12
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Cherouveim ED, Botonis PG, Tsakiris T, Koskolou MD, Geladas ND. The effect of menstrual cycle on maximal breath-hold time. Respir Physiol Neurobiol 2020; 274:103381. [DOI: 10.1016/j.resp.2020.103381] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 12/26/2019] [Accepted: 01/05/2020] [Indexed: 11/26/2022]
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13
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Trotter CE, Tourula E, Pizzey FK, Batterson PM, Jacobs RA, Pearson J. High‐intensity interval exercise reduces tolerance to a simulated haemorrhagic challenge in heat‐stressed individuals. Exp Physiol 2020; 106:212-221. [DOI: 10.1113/ep088377] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 01/28/2020] [Indexed: 11/08/2022]
Affiliation(s)
- Claire E. Trotter
- Department of Human Physiology and Nutrition University of Colorado at Colorado Springs Colorado Springs CO USA
- Department of Applied Physiology and Wellness Southern Methodist University Dallas TX USA
| | - Erica Tourula
- Department of Human Physiology and Nutrition University of Colorado at Colorado Springs Colorado Springs CO USA
| | - Faith K. Pizzey
- Department of Human Physiology and Nutrition University of Colorado at Colorado Springs Colorado Springs CO USA
- School of Human Movement and Nutrition Sciences The University of Queensland Brisbane Australia
| | - Philip M. Batterson
- Department of Human Physiology and Nutrition University of Colorado at Colorado Springs Colorado Springs CO USA
- College of Biological and Population Health Sciences Oregon State University Corvallis OR USA
| | - Robert A. Jacobs
- Department of Human Physiology and Nutrition University of Colorado at Colorado Springs Colorado Springs CO USA
| | - James Pearson
- Department of Human Physiology and Nutrition University of Colorado at Colorado Springs Colorado Springs CO USA
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14
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Engelland RE, Hemingway HW, Tomasco OG, Olivencia-Yurvati AH, Romero SA. Acute lower leg hot water immersion protects macrovascular dilator function following ischaemia-reperfusion injury in humans. Exp Physiol 2019; 105:302-311. [PMID: 31707732 DOI: 10.1113/ep088154] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Accepted: 11/08/2019] [Indexed: 12/14/2022]
Abstract
NEW FINDINGS • What is the central question of this study? What is the effect of lower leg hot water immersion on vascular ischaemia-reperfusion injury induced in the arm of young healthy humans? • What is the main finding and its importance? Lower leg hot water immersion successfully protects against vascular ischaemia-reperfusion injury in humans. This raises the possibility that targeted heating of the lower legs may be an alternative therapeutic approach to whole-body heating that is equally efficacious at protecting against vascular ischaemia-reperfusion injury. ABSTRACT Reperfusion that follows a period of ischaemia paradoxically reduces vasodilator function in humans and contributes to the tissue damage associated with an ischaemic event. Acute whole-body hot water immersion protects against vascular ischaemia-reperfusion (I-R) injury in young healthy humans. However, the effect of acute lower leg heating on I-R injury is unclear. Therefore, the purpose of this study was to test the hypothesis that, compared with thermoneutral control immersion, acute lower leg hot water immersion would prevent the decrease in macro- and microvascular dilator functions following I-R injury in young healthy humans. Ten young healthy subjects (5 female) immersed their lower legs into a circulated water bath for 60 min under two randomized conditions: (1) thermoneutral control immersion (∼33°C) and (2) hot water immersion (∼42°C). Macrovascular (brachial artery flow-mediated dilatation) and microvascular (forearm reactive hyperaemia) dilator functions were assessed using Doppler ultrasound at three time points: (1) pre-immersion, (2) 60 min post-immersion, and (3) post-I/R (20 min of arm ischaemia followed by 20 min of reperfusion). Ischaemia-reperfusion injury reduced macrovascular dilator function following control immersion (pre-immersion 6.0 ± 2.1% vs. post-I/R 3.6 ± 2.1%; P < 0.05), but was well-maintained with prior hot water immersion (pre-immersion 5.8 ± 2.1% vs. post-I/R 5.3 ± 2.1%; P = 0.8). Microvascular dilator function did not differ between conditions or across time. Taken together, acute lower leg hot water immersion prevents the decrease in macrovascular dilator function that occurs following I-R injury in young healthy humans.
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Affiliation(s)
- Rachel E Engelland
- Human Vascular Physiology Laboratory, Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Holden W Hemingway
- Human Vascular Physiology Laboratory, Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Olivia G Tomasco
- Human Vascular Physiology Laboratory, Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Albert H Olivencia-Yurvati
- Human Vascular Physiology Laboratory, Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA.,Department of Surgery, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Steven A Romero
- Human Vascular Physiology Laboratory, Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
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15
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Gibbons TD, Zuj KA, Peterson SD, Hughson RL. Comparison of pulse contour, aortic Doppler ultrasound and bioelectrical impedance estimates of stroke volume during rapid changes in blood pressure. Exp Physiol 2019; 104:368-378. [PMID: 30582758 DOI: 10.1113/ep087240] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Accepted: 12/18/2018] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Pulse contour analysis of the finger arterial pressure by Windkessel modelling is commonly used to estimate stroke volume continuously. But is it valid during dynamic changes in blood pressure? What is the main finding and its importance? Second-by-second analysis revealed that pulse contour analysis underestimated stroke volume by up to 25% after standing from a squat, and 16% after standing thigh-cuff release, when compared with aortic Doppler ultrasound estimates. These results reveal that pulse contour analysis of stroke volume should be interpreted with caution during rapid changes in physiological state. ABSTRACT Dynamic measurements of stroke volume (SV) and cardiac output provide an index of central haemodynamics during transitional states, such as postural changes and onset of exercise. The most widely used method to assess dynamic fluctuations in SV is the Modelflow method, which uses the arterial blood pressure waveform along with age- and sex-specific aortic properties to compute beat-to-beat estimates of aortic flow. Modelflow has been validated against more direct methods in steady-state conditions, but not during dynamic changes in physiological state, such as active orthostatic stress testing. In the present study, we compared the dynamic SV responses from Modelflow (SVMF ), aortic Doppler ultrasound (SVU/S ) and bioelectrical impedance analysis (SVBIA ) during two different orthostatic stress tests, a squat-to-stand (S-S) transition and a standing bilateral thigh-cuff release (TCR), in 15 adults (six females). Second-by-second analysis revealed that when compared with estimates of SV by aortic Doppler ultrasound, Modelflow underestimated SV by up to 25% from 3 to 11 s after standing from the squat position and by up to 16% from 3 to 7 s after TCR (P < 0.05). The SVMF and SVBIA were similar during the first minute of the S-S transition, but were different 3 s after TCR and at intermittent time points between 34 and 44 s (P < 0.05). These findings indicate that the physiological conditions elicited by orthostatic stress testing violate some of the inherent assumptions of Modelflow and challenge models used to interpret bioelectrical impedance responses, resulting in an underestimation in SV during rapid changes in physiological state.
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Affiliation(s)
- Travis D Gibbons
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo, ON, Canada
| | - Kathryn A Zuj
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo, ON, Canada
| | - Sean D Peterson
- Department of Mechanical and Mechatronic Engineering, University of Waterloo, Waterloo, ON, Canada
| | - Richard L Hughson
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo, ON, Canada.,Schlegel-University of Waterloo Research Institute for Aging, Waterloo, ON, Canada
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16
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Trotter CE, Pizzey FK, Batterson PM, Jacobs RA, Pearson J. Small reductions in skin temperature after onset of a simulated hemorrhagic challenge improve tolerance in exercise heat-stressed individuals. Am J Physiol Regul Integr Comp Physiol 2018; 315:R539-R546. [DOI: 10.1152/ajpregu.00182.2018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated whether small reductions in skin temperature 60 s after the onset of a simulated hemorrhagic challenge would improve tolerance to lower body negative pressure (LBNP) after exercise heat stress. Eleven healthy subjects completed two trials (High and Reduced). Subjects cycled at ~55% maximal oxygen uptake wearing a warm water-perfused suit until core temperatures increased by ~1.2°C before lying supine and undergoing LBNP to presyncope. LBNP tolerance was quantified as cumulative stress index (CSI; product of each LBNP level multiplied by time; mmHg·min). Skin temperature was similarly elevated from baseline before LBNP and remained elevated 60 s after the onset of LBNP in both High (37.72 ± 0.52°C) and Reduced (37.95 ± 0.54°C) trials (both P < 0.0001). At 60%CSI skin temperature remained elevated in the High trial (37.51 ± 0.56°C) but was reduced to 34.97 ± 0.72°C by the water-perfused suit in the Reduced trial ( P < 0.0001 between trials). Cutaneous vascular conductance was not different between trials [High: 1.57 ± 0.43 vs. Reduced: 1.39 ± 0.38 arbitrary units (AU)/mmHg; P = 0.367] before LBNP but decreased to 0.67 ± 0.19 AU/mmHg at 60%CSI in the Reduced trial while remaining unchanged in the High trial ( P = 0.002 between trials). CSI was higher in the Reduced (695 ± 386 mmHg·min) relative to the High (441 ± 290 mmHg·min; P = 0.023) trial. Mean arterial pressure was not different between trials at presyncope (High: 62 ± 10 vs. Reduced: 62 ± 9 mmHg; P = 0.958). Small reductions in skin temperature after the onset of a simulated hemorrhagic challenge improve LBNP tolerance after exercise heat stress. This may have important implications regarding treatment of an exercise heat-stressed individual (e.g., soldier) who has experienced a hemorrhagic injury.
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Affiliation(s)
- Claire E. Trotter
- Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, Colorado
| | - Faith K. Pizzey
- Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, Colorado
| | - Philip M. Batterson
- Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, Colorado
| | - Robert A. Jacobs
- Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, Colorado
| | - James Pearson
- Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, Colorado
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17
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Schlader ZJ, O'Leary MC, Sackett JR, Johnson BD. Face cooling reveals a relative inability to increase cardiac parasympathetic activation during passive heat stress. Exp Physiol 2018; 103:701-713. [PMID: 29450933 DOI: 10.1113/ep086865] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 02/12/2018] [Indexed: 01/31/2023]
Abstract
NEW FINDINGS What is the central question of this study? Does passive heat stress attenuate the increase in cardiac parasympathetic stimulation, vascular resistance and blood pressure evoked by face cooling? What is the main finding and its importance? Passive heat stress attenuates the capacity to increase cardiac parasympathetic activation and impairs the ability to increase vascular resistance during sympathoexcitation, which ultimately results in a relative inability to increase blood pressure. These findings cast doubt on the efficacy of face cooling at augmenting blood pressure during orthostasis while heat stressed. ABSTRACT We tested the hypothesis that passive heat stress attenuates the increase in cardiac parasympathetic stimulation, vascular resistance and blood pressure evoked by face cooling. During normothermia and when intestinal temperature was elevated by 1.0 ± 0.2°C, 10 healthy young adults underwent 3 min of face cooling. Face cooling was accomplished by placing a 2.5 litre bag of ice water (0 ± 0°C) over the cheeks, eyes and forehead. Primary variables included forehead skin temperature, mean arterial pressure and systemic, forearm and cutaneous vascular resistances. Indices of heart rate variability in the time domain provided an index of cardiac parasympathetic activity. The magnitude of reduction in forehead skin temperature during face cooling was slightly greater during normothermia (-17.6 ± 1.9 versus -16.3 ± 3.0°C, P = 0.03). Increases in heart rate variability evoked by face cooling were attenuated during heat stress. Changes in systemic, forearm and cutaneous vascular resistances during face cooling were virtually abolished during heat stress (P < 0.01). However, when forearm and vascular data were reported as conductance, differences between normothermia and heat stress were not apparent (P ≥ 0.62). Nevertheless, the increase in mean arterial pressure was attenuated during heat stress with face cooling (at 3 min: 2 ± 7 mmHg) compared with normothermia (at 3 min: 19 ± 7 mmHg, P < 0.01). These data indicate that passive heat stress attenuates face cooling-evoked increases in cardiac parasympathetic activation, vascular resistance and blood pressure. However, they also indicate that changes in indices of vascular resistance do not always reflect equivalent changes in conductance.
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Affiliation(s)
- Zachary J Schlader
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
| | - Morgan C O'Leary
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
| | - James R Sackett
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
| | - Blair D Johnson
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
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18
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MacEwen C, Sutherland S, Daly J, Pugh C, Tarassenko L. Validation of Modelflow Estimates of Cardiac Output in Hemodialysis Patients. Ther Apher Dial 2018; 22:337-344. [DOI: 10.1111/1744-9987.12650] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 09/10/2017] [Accepted: 10/17/2017] [Indexed: 12/15/2022]
Affiliation(s)
- Clare MacEwen
- Oxford Kidney Unit; Oxford University Hospitals NHS Trust; Oxford UK
- Department of Engineering Science; Institute of Biomedical Engineering, Oxford University; Oxford UK
| | - Sheera Sutherland
- Oxford Kidney Unit; Oxford University Hospitals NHS Trust; Oxford UK
| | - Jonathan Daly
- Department of Engineering Science; Institute of Biomedical Engineering, Oxford University; Oxford UK
| | - Christopher Pugh
- Oxford Kidney Unit; Oxford University Hospitals NHS Trust; Oxford UK
- Nuffield Department of Medicine; Oxford University; Oxford UK
| | - Lionel Tarassenko
- Department of Engineering Science; Institute of Biomedical Engineering, Oxford University; Oxford UK
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19
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Lucas RAI, Wilson LC, Ainslie PN, Fan JL, Thomas KN, Cotter JD. Independent and interactive effects of incremental heat strain, orthostatic stress, and mild hypohydration on cerebral perfusion. Am J Physiol Regul Integr Comp Physiol 2017; 314:R415-R426. [PMID: 29212807 DOI: 10.1152/ajpregu.00109.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of this study was to identify the dose-dependent effects of heat strain and orthostasis [via lower body negative pressure (LBNP)], with and without mild hypohydration, on systemic function and cerebral perfusion. Eleven men (means ± SD: 27 ± 7 y; body mass 77 ± 6 kg), resting supine in a water-perfused suit, underwent progressive passive heating [0.5°C increments in core temperature (Tc; esophageal to +2.0°C)] while euhydrated (EUH) or hypohydrated (HYPO; 1.5-2% body mass deficit). At each thermal state, mean cerebral artery blood velocity (MCAvmean; transcranial Doppler), partial pressure of end-tidal carbon dioxide ([Formula: see text]), heart rate (HR) and mean arterial blood pressure (MAP; photoplethysmography) were measured continuously during LBNP (0, -15, -30, and -45 mmHg). Four subjects became intolerant before +2.0°C Tc, unrelated to hydration status. Without LBNP, decreases in [Formula: see text] accounted fully for reductions in MCAvmean across all Tc. With LBNP at heat tolerance (+1.5 or +2.0°C), [Formula: see text] accounted for 69 ± 25% of the change in MCAvmean. The HYPO condition did not affect MCAvmean or any cardiovascular variables during combined LBNP and passive heat stress (all P > 0.13). These findings indicate that hypocapnia accounted fully for the reduction in MCAvmean when passively heat stressed in the absence of LBNP and for two- thirds of the reduction when at heat tolerance combined with LBNP. Furthermore, when elevations in Tc are matched, mild hypohydration does not influence cerebrovascular or cardiovascular responses to LBNP, even when stressed by a combination of hyperthermia and LBNP.
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Affiliation(s)
- R A I Lucas
- Department of Physiology, University of Otago , Dunedin , New Zealand.,School of Physical Education, Sport and Exercise Sciences, University of Otago , Dunedin , New Zealand.,School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham , Birmingham , United Kingdom
| | - L C Wilson
- Department of Physiology, University of Otago , Dunedin , New Zealand.,School of Physical Education, Sport and Exercise Sciences, University of Otago , Dunedin , New Zealand.,Department of Medicine, University of Otago , Dunedin , New Zealand
| | - P N Ainslie
- Department of Physiology, University of Otago , Dunedin , New Zealand.,Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia Okanagan , Kelowna , Canada
| | - J L Fan
- Department of Physiology, University of Otago , Dunedin , New Zealand.,Institute of Sports Science, Faculty of Biology and Medicine, University of Lausanne , Lausanne , Switzerland.,Lemanic Neuroscience Doctoral School, University of Lausanne , Lausanne , Switzerland
| | - K N Thomas
- Department of Physiology, University of Otago , Dunedin , New Zealand.,School of Physical Education, Sport and Exercise Sciences, University of Otago , Dunedin , New Zealand.,Department of Surgical Sciences, Dunedin School of Medicine, University of Otago . New Zealand
| | - J D Cotter
- School of Physical Education, Sport and Exercise Sciences, University of Otago , Dunedin , New Zealand
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20
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Schlader ZJ, Coleman GL, Sackett JR, Sarker S, Chapman CL, Hostler D, Johnson BD. Behavioral thermoregulation in older adults with cardiovascular co-morbidities. Temperature (Austin) 2017; 5:70-85. [PMID: 29687045 PMCID: PMC5902208 DOI: 10.1080/23328940.2017.1379585] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2017] [Revised: 09/01/2017] [Accepted: 09/06/2017] [Indexed: 12/21/2022] Open
Abstract
We tested the hypotheses that older adults with cardiovascular co-morbidities will demonstrate greater changes in body temperature and exaggerated changes in blood pressure before initiating thermal behavior. We studied twelve healthy younger adults (Younger, 25 ± 4 y) and six older adults ('At Risk', 67 ± 4 y) taking prescription medications for at least two of the following conditions: hypertension, type II diabetes, hypercholesterolemia. Subjects underwent a 90-min test in which they voluntarily moved between cool (18.1 ± 1.8°C, RH: 29 ± 5%) and warm (40.2 ± 0.3°C, RH: 20 ± 0%) rooms when they felt 'too cool' (C→W) or 'too warm' (W→C). Mean skin and intestinal temperatures and blood pressure were measured. Data were analyzed as a change from pretest baseline. Changes in mean skin temperature were not different between groups at C→W (Younger: +0.2 ± 0.8°C, 'At Risk': +0.7 ± 1.8°C, P = 0.51) or W→C (Younger: +2.7 ± 0.6°C, 'At Risk': +2.9 ± 1.9°C, P = 0.53). Changes in intestinal temperature were not different at C→W (Younger: 0.0 ± 0.1°C, 'At Risk': +0.1 ± 0.2, P = 0.11), but differed at W→C (-0.1 ± 0.2°C vs. +0.1 ± 0.3°C, P = 0.02). Systolic pressure at C→W increased (Younger: +10 ± 9 mmHg, 'At Risk': +24 ± 17 mmHg) and at W→C decreased (Younger: -4 ± 13 mmHg, 'At Risk': -23 ± 19 mmHg) to a greater extent in 'At Risk' (P ≤ 0.05). Differences were also apparent for diastolic pressure at C→W (Younger: -2 ± 4 mmHg, 'At Risk': +17 ± 23 mmHg, P < 0.01), but not at W→C (Younger Y: +4 ± 13 mmHg, 'At Risk': -1 ± 6 mmHg, P = 0.29). Despite little evidence for differential control of thermal behavior, the initiation of behavior in 'at risk' older adults is preceded by exaggerated blood pressure responses.
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Affiliation(s)
- Zachary J. Schlader
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
| | - Gregory L. Coleman
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
| | - James R. Sackett
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
| | - Suman Sarker
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
| | - Christopher L. Chapman
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
| | - David Hostler
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
| | - Blair D. Johnson
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
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21
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Zuj KA, Prince CN, Hughson RL, Peterson SD. Enhanced muscle blood flow with intermittent pneumatic compression of the lower leg during plantar flexion exercise and recovery. J Appl Physiol (1985) 2017; 124:302-311. [PMID: 29122964 DOI: 10.1152/japplphysiol.00784.2017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study tested the hypothesis that intermittent compression of the lower limb would increase blood flow during exercise and postexercise recovery. Data were collected from 12 healthy individuals (8 men) who performed 3 min of standing plantar flexion exercise. The following three conditions were tested: no applied compression (NoComp), compression during the exercise period only (ExComp), and compression during 2 min of standing postexercise recovery. Doppler ultrasound was used to determine superficial femoral artery (SFA) blood flow responses. Mean arterial pressure (MAP) and cardiac stroke volume (SV) were assessed using finger photoplethysmography, with vascular conductance (VC) calculated as VC = SFA flow/MAP. Compared with the NoComp condition, compression resulted in increased MAP during exercise [+3.5 ± 4.1 mmHg (mean ± SD)] but not during postexercise recovery (+1.6 ± 5.9 mmHg). SV increased with compression during both exercise (+4.8 ± 5.1 ml) and recovery (+8.0 ± 6.6 ml) compared with NoComp. There was a greater increase in SFA flow with compression during exercise (+52.1 ± 57.2 ml/min) and during recovery (+58.6 ± 56.7 ml/min). VC immediately following exercise was also significantly greater in the ExComp condition compared with the NoComp condition (+0.57 ± 0.42 ml·min-1·mmHg-1), suggesting the observed increase in blood flow during exercise was in part because of changes in VC. Results from this study support the hypothesis that intermittent compression applied during exercise and recovery from exercise results in increased limb blood flow, potentially contributing to changes in exercise performance and recovery. NEW & NOTEWORTHY Blood flow to working skeletal muscle is achieved in part through the rhythmic actions of the skeletal muscle pump. This study demonstrated that the application of intermittent pneumatic compression during the diastolic phase of the cardiac cycle, to mimic the mechanical actions of the muscle pump, accentuates muscle blood flow during exercise and elevates blood flow during the postexercise recovery period. Intermittent compression during and after exercise might have implications for exercise performance and recovery.
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Affiliation(s)
- K A Zuj
- University of Waterloo, Department of Kinesiology , Waterloo, Ontario , Canada
| | - C N Prince
- University of Waterloo, Department of Mechanical and Mechatronics Engineering , Waterloo, Ontario , Canada
| | - R L Hughson
- University of Waterloo, Department of Kinesiology , Waterloo, Ontario , Canada.,Schlegel-University of Waterloo Research Institute for Aging , Waterloo, Ontario , Canada
| | - S D Peterson
- University of Waterloo, Department of Mechanical and Mechatronics Engineering , Waterloo, Ontario , Canada
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22
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Hughson RL, Peterson SD, Yee NJ, Greaves DK. Cardiac output by pulse contour analysis does not match the increase measured by rebreathing during human spaceflight. J Appl Physiol (1985) 2017; 123:1145-1149. [PMID: 28798205 DOI: 10.1152/japplphysiol.00651.2017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 08/03/2017] [Accepted: 08/04/2017] [Indexed: 11/22/2022] Open
Abstract
Pulse contour analysis of the noninvasive finger arterial pressure waveform provides a convenient means to estimate cardiac output (Q̇). The method has been compared with standard methods under a range of conditions but never before during spaceflight. We compared pulse contour analysis with the Modelflow algorithm to estimates of Q̇ obtained by rebreathing during preflight baseline testing and during the final month of long-duration spaceflight in nine healthy male astronauts. By Modelflow analysis, stroke volume was greater in supine baseline than seated baseline or inflight. Heart rate was reduced in supine baseline so that there were no differences in Q̇ by Modelflow estimate between the supine (7.02 ± 1.31 l/min, means ± SD), seated (6.60 ± 1.95 l/min), or inflight (5.91 ± 1.15 l/min) conditions. In contrast, rebreathing estimates of Q̇ increased from seated baseline (4.76 ± 0.67 l/min) to inflight (7.00 ± 1.39 l/min, significant interaction effect of method and spaceflight, P < 0.001). Pulse contour analysis utilizes a three-element Windkessel model that incorporates parameters dependent on aortic pressure-area relationships that are assumed to represent the entire circulation. We propose that a large increase in vascular compliance in the splanchnic circulation invalidates the model under conditions of spaceflight. Future spaceflight research measuring cardiac function needs to consider this important limitation for assessing absolute values of Q̇ and stroke volume.NEW & NOTEWORTHY Noninvasive assessment of cardiac function during human spaceflight is an important tool to monitor astronaut health. This study demonstrated that pulse contour analysis of finger arterial blood pressure to estimate cardiac output failed to track the 46% increase measured by a rebreathing method. These results strongly suggest that alternative methods not dependent on pulse contour analysis are required to track cardiac function in spaceflight.
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Affiliation(s)
- Richard L Hughson
- Schlegel-University of Waterloo Research Institute for Aging, Waterloo, Ontario Canada; and
| | - Sean D Peterson
- Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario, Canada
| | - Nicholas J Yee
- Schlegel-University of Waterloo Research Institute for Aging, Waterloo, Ontario Canada; and
| | - Danielle K Greaves
- Schlegel-University of Waterloo Research Institute for Aging, Waterloo, Ontario Canada; and
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23
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Rokamp KZ, Staalsø JM, Zaar M, Rasmussen P, Petersen LG, Nielsen RV, Secher NH, Olsen NV, Nielsen HB. The Gly 16 Allele of the G16R Single Nucleotide Polymorphism in the β 2 -Adrenergic Receptor Gene Augments the Glycemic Response to Adrenaline in Humans. Front Physiol 2017; 8:661. [PMID: 28928674 PMCID: PMC5591882 DOI: 10.3389/fphys.2017.00661] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 08/21/2017] [Indexed: 11/25/2022] Open
Abstract
Cerebral non-oxidative carbohydrate consumption may be driven by a β2-adrenergic mechanism. This study tested whether the 46G > A (G16R) single nucleotide polymorphism of the β2-adrenergic receptor gene (ADRB2) influences the metabolic and cerebrovascular responses to administration of adrenaline. Forty healthy Caucasian men were included from a group of genotyped individuals. Cardio- and cerebrovascular variables at baseline and during a 60-min adrenaline infusion (0.06 μg kg−1 min−1) were measured by Model flow, near-infrared spectroscopy and transcranial Doppler sonography. Blood samples were obtained from an artery and a retrograde catheter in the right internal jugular vein. The ADRB2 G16R variation had no effect on baseline arterial glucose, but during adrenaline infusion plasma glucose was up to 1.2 mM (CI95: 0.36–2.1, P < 0.026) higher in the Gly16 homozygotes compared with Arg16 homozygotes. The extrapolated steady-state levels of plasma glucose was 1.9 mM (CI95: 1.0 –2.9, PNLME < 0.0026) higher in the Gly16 homozygotes compared with Arg16 homozygotes. There was no change in the cerebral oxygen glucose index and the oxygen carbohydrate index during adrenaline infusion and the two indexes were not affected by G16R polymorphism. No difference between genotype groups was found in cardiac output at baseline or during adrenaline infusion. The metabolic response of glucose during adrenergic stimulation with adrenaline is associated to the G16R polymorphism of ADRB2, although without effect on cerebral metabolism. The differences in adrenaline-induced blood glucose increase between genotypes suggest an elevated β2-adrenergic response in the Gly16 homozygotes with increased adrenaline-induced glycolysis compared to Arg16 homozygotes.
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Affiliation(s)
- Kim Z Rokamp
- Department of Anesthesia, Rigshospitalet, University of CopenhagenCopenhagen, Denmark
| | - Jonatan M Staalsø
- Department of Neuroanesthesia, Rigshospitalet, University of CopenhagenCopenhagen, Denmark
| | - Morten Zaar
- Department of Anesthesia, Rigshospitalet, University of CopenhagenCopenhagen, Denmark
| | - Peter Rasmussen
- Department of Anesthesia, Rigshospitalet, University of CopenhagenCopenhagen, Denmark
| | - Lonnie G Petersen
- Department of Anesthesia, Rigshospitalet, University of CopenhagenCopenhagen, Denmark
| | - Rikke V Nielsen
- Department of Neuroanesthesia, Rigshospitalet, University of CopenhagenCopenhagen, Denmark
| | - Niels H Secher
- Department of Anesthesia, Rigshospitalet, University of CopenhagenCopenhagen, Denmark
| | - Niels V Olsen
- Department of Neuroanesthesia, Rigshospitalet, University of CopenhagenCopenhagen, Denmark.,Department of Neuroscience and Pharmacology, University of CopenhagenCopenhagen, Denmark
| | - Henning B Nielsen
- Department of Anesthesia, Rigshospitalet, University of CopenhagenCopenhagen, Denmark
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24
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Charkoudian N, Usselman CW, Skow RJ, Staab JS, Julian CG, Stickland MK, Chari RS, Khurana R, Davidge ST, Davenport MH, Steinback CD. Muscle sympathetic nerve activity and volume-regulating factors in healthy pregnant and nonpregnant women. Am J Physiol Heart Circ Physiol 2017; 313:H782-H787. [PMID: 28733450 DOI: 10.1152/ajpheart.00312.2017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 07/18/2017] [Accepted: 07/18/2017] [Indexed: 11/22/2022]
Abstract
Healthy, normotensive human pregnancies are associated with striking increases in both plasma volume and vascular sympathetic nerve activity (SNA). In nonpregnant humans, volume-regulatory factors including plasma osmolality, vasopressin, and the renin-angiotensin-aldosterone system have important modulatory effects on control of sympathetic outflow. We hypothesized that pregnancy would be associated with changes in the relationships between SNA (measured as muscle SNA) and volume-regulating factors, including plasma osmolality, plasma renin activity, and arginine vasopressin (AVP). We studied 46 healthy, normotensive young women (23 pregnant and 23 nonpregnant). We measured SNA, arterial pressure, plasma osmolality, plasma renin activity, AVP, and other volume-regulatory factors in resting, semirecumbent posture. Pregnant women had significantly higher resting SNA (38 ± 12 vs. 23 ± 6 bursts/min in nonpregnant women), lower osmolality, and higher plasma renin activity and aldosterone (all P < 0.05). Group mean values for AVP were not different between groups [4.64 ± 2.57 (nonpregnant) vs. 5.17 ± 2.03 (pregnant), P > 0.05]. However, regression analysis detected a significant relationship between individual values for SNA and AVP in pregnant (r = 0.71, P < 0.05) but not nonpregnant women (r = 0.04). No relationships were found for other variables. These data suggest that the link between AVP release and resting SNA becomes stronger in pregnancy, which may contribute importantly to blood pressure regulation in healthy women during pregnancy.NEW & NOTEWORTHY Sympathetic nerve activity and blood volume are both elevated during pregnancy, but blood pressure is usually normal. Here, we identified a relationship between vasopressin and sympathetic nerve activity in pregnant but not nonpregnant women. This may provide mechanistic insights into blood pressure regulation in normal pregnancy and in pregnancy-related hypertension.
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Affiliation(s)
- Nisha Charkoudian
- United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Charlotte W Usselman
- Neurovascular Health Laboratory, Program for Pregnancy and Postpartum Health, Faculty of Physical Education and Recreation, Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Rachel J Skow
- Neurovascular Health Laboratory, Program for Pregnancy and Postpartum Health, Faculty of Physical Education and Recreation, Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Jeffery S Staab
- United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Colleen G Julian
- Department of Medicine, University of Colorado Denver School of Medicine, Denver, Colorado; and
| | - Michael K Stickland
- Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Radha S Chari
- Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada.,Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Rshmi Khurana
- Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada.,Department of Medicine, University of Colorado Denver School of Medicine, Denver, Colorado; and
| | - Sandra T Davidge
- Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada.,Department of Medicine, University of Colorado Denver School of Medicine, Denver, Colorado; and
| | - Margie H Davenport
- Neurovascular Health Laboratory, Program for Pregnancy and Postpartum Health, Faculty of Physical Education and Recreation, Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Craig D Steinback
- Neurovascular Health Laboratory, Program for Pregnancy and Postpartum Health, Faculty of Physical Education and Recreation, Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada; .,Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada
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25
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Olesen ND, Sørensen H, Ambrus R, Svendsen LB, Lund A, Secher NH. A mesenteric traction syndrome affects near-infrared spectroscopy evaluated cerebral oxygenation because skin blood flow increases. J Clin Monit Comput 2017; 32:261-268. [PMID: 28293809 DOI: 10.1007/s10877-017-0014-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 03/07/2017] [Indexed: 11/30/2022]
Abstract
During abdominal surgery manipulation of internal organs may induce a "mesenteric traction syndrome" (MTS) including a triad of flushing, hypotension, and tachycardia that lasts for about 30 min. We evaluated whether MTS affects near-infrared spectroscopy (NIRS) assessed frontal lobe oxygenation (ScO2) by an increase in forehead skin blood flow (SkBF). The study intended to include 10 patients who developed MTS during pancreaticoduodenectomy and 22 patients were enrolled (age 61 ± 8 years; mean ± SD). NIRS determined ScO2, laser Doppler flowmetry determined SkBF, cardiac output (CO) was evaluated by pulse-contour analysis (Modelflow), and transcranial Doppler assessed middle cerebral artery mean flow velocity (MCA Vmean). MTS was identified by flushing within 60 min after start of surgery. MTS developed 20 min (12-24; median with range) after the start of surgery and heart rate (78 ± 16 vs. 68 ± 17 bpm; P = 0.0032), CO (6.2 ± 1.4 vs. 5.3 ± 1.1 L min-1; P = 0.0086), SkBF (98 ± 35 vs. 80 ± 23 PU; P = 0.0271), and ScO2 (71 ± 6 vs. 67 ± 8%; P < 0.0001), but not MCA Vmean (32 ± 8 vs. 32 ± 7; P = 0.1881) were largest in the patients who developed MTS. In some patients undergoing abdominal surgery NIRS-determined ScO2 is at least temporarily affected by an increase in extra-cranial perfusion independent of cerebral blood flow as indicated by MCA Vmean. Thus, NIRS evaluation of ScO2 may overestimate cerebral oxygenation if patients flush during surgery.
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Affiliation(s)
- Niels D Olesen
- Department of Anaesthesia, Rigshospitalet 2043, University of Copenhagen, Blegdamsvej 9, 2100, Copenhagen, Denmark. .,Department of Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark.
| | - Henrik Sørensen
- Department of Anaesthesia, Rigshospitalet 2043, University of Copenhagen, Blegdamsvej 9, 2100, Copenhagen, Denmark
| | - Rikard Ambrus
- Department of Surgical Gastroenterology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Lars B Svendsen
- Department of Surgical Gastroenterology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Anton Lund
- Department of Anaesthesia, Rigshospitalet 2043, University of Copenhagen, Blegdamsvej 9, 2100, Copenhagen, Denmark
| | - Niels H Secher
- Department of Anaesthesia, Rigshospitalet 2043, University of Copenhagen, Blegdamsvej 9, 2100, Copenhagen, Denmark
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26
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Wiles JD, Goldring N, Coleman D. Home-based isometric exercise training induced reductions resting blood pressure. Eur J Appl Physiol 2016; 117:83-93. [PMID: 27853886 DOI: 10.1007/s00421-016-3501-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 11/09/2016] [Indexed: 01/03/2023]
Abstract
PURPOSE Isometric exercise training (IET) reduces resting blood pressure (BP). Most previous protocols impose exercise barriers which undermine its effectiveness as a potential physical therapy for altering BP. An inexpensive, home-based programme would promote IET as a valuable tool in the fight against hypertension. The aims of this study were: (a) to investigate whether home-based wall squat training could successfully reduce resting BP and (b) to explore the physiological variables that might mediate a change in resting BP. METHODS Twenty-eight healthy normotensive males were randomly assigned to a control and a 4 week home-based IET intervention using a crossover design with a 4 week 'washout' period in-between. Wall squat training was completed 3 × weekly over 4 weeks with 48 h between sessions. Each session comprised 4 × 2 min bouts of wall squat exercise performed at a participant-specific knee joint angle relative to a target HR of 95% HRpeak, with 2 min rest between bouts. Resting heart rate, BP, cardiac output, total peripheral resistance, and stroke volume were taken at baseline and post each condition. RESULTS Resting BP (systolic -4 ± 5, diastolic -3 ± 3 and mean arterial -3 ± 3 mmHg), cardiac output (-0.54 ± 0.66 L min-1) and heart rate (-5 ± 7 beats min-1) were all reduced following IET, with no change in total peripheral resistance or stroke volume compared to the control. CONCLUSION These findings suggest that the wall squat provides an effective method for reducing resting BP in the home resulting primarily from a reduction in resting heart rate.
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Affiliation(s)
- Jonathan D Wiles
- Section of Sport and Exercise Sciences, School of Human and Life Sciences, Canterbury Christ Church University, North Holmes Road, Canterbury, CT1 1QU, UK.
| | - Natalie Goldring
- Section of Sport and Exercise Sciences, School of Human and Life Sciences, Canterbury Christ Church University, North Holmes Road, Canterbury, CT1 1QU, UK
| | - Damian Coleman
- Section of Sport and Exercise Sciences, School of Human and Life Sciences, Canterbury Christ Church University, North Holmes Road, Canterbury, CT1 1QU, UK
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27
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Romero SA, Gagnon D, Adams AN, Cramer MN, Kouda K, Crandall CG. Acute limb heating improves macro- and microvascular dilator function in the leg of aged humans. Am J Physiol Heart Circ Physiol 2016; 312:H89-H97. [PMID: 27836894 DOI: 10.1152/ajpheart.00519.2016] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 10/21/2016] [Accepted: 11/10/2016] [Indexed: 01/14/2023]
Abstract
Local heating of an extremity increases blood flow and vascular shear stress throughout the arterial tree. Local heating acutely improves macrovascular dilator function in the upper limbs of young healthy adults through a shear stress-dependent mechanism but has no such effect in the lower limbs of this age group. The effect of acute limb heating on dilator function within the atherosclerotic prone vasculature of the lower limbs of aged adults is unknown. Therefore, the purpose of this study was to test the hypothesis that acute lower limb heating improves macro- and microvascular dilator function within the leg vasculature of aged adults. Nine young and nine aged adults immersed their lower limbs at a depth of ~33 cm into a heated (~42°C) circulated water bath for 45 min. Before and 30 min after heating, macro (flow-mediated dilation)- and microvascular (reactive hyperemia) dilator functions were assessed in the lower limb, following 5 min of arterial occlusion, via Doppler ultrasound. Compared with preheat, macrovascular dilator function was unchanged following heating in young adults (P = 0.6) but was improved in aged adults (P = 0.04). Similarly, microvascular dilator function, as assessed by peak reactive hyperemia, was unchanged following heating in young adults (P = 0.1) but was improved in aged adults (P < 0.01). Taken together, these data suggest that acute lower limb heating improves both macro- and microvascular dilator function in an age dependent manner. NEW & NOTEWORTHY We demonstrate that lower limb heating acutely improves macro- and microvascular dilator function within the atherosclerotic prone vasculature of the leg in aged adults. These findings provide evidence for a potential therapeutic use of chronic lower limb heating to improve vascular health in primary aging and various disease conditions.
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Affiliation(s)
- Steven A Romero
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, Texas
| | - Daniel Gagnon
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, Texas
| | - Amy N Adams
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, Texas
| | - Matthew N Cramer
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, Texas
| | - Ken Kouda
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, Texas
| | - Craig G Crandall
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, Texas
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28
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Staalsø JM, Rokamp KZ, Olesen ND, Lonn L, Secher NH, Olsen NV, Mantoni T, Helgstrand U, Nielsen HB. ADRB2 gly16gly Genotype, Cardiac Output, and Cerebral Oxygenation in Patients Undergoing Anesthesia for Abdominal Aortic Aneurysm Surgery. Anesth Analg 2016; 123:1408-1415. [PMID: 27632347 DOI: 10.1213/ane.0000000000001563] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Gly16arg polymorphism of the adrenergic β2-receptor is associated with the elevated cardiac output (Q) in healthy gly16-homozygotic subjects. We questioned whether this polymorphism also affects Q and regional cerebral oxygen saturation (SCO2) during anesthesia in vascular surgical patients. METHODS One hundred sixty-eight patients (age 71 ± 6 years) admitted for elective surgery were included. Cardiovascular variables were determined before and during anesthesia by intravascular pulse contour analysis (Nexfin) and SCO2 by cerebral oximetry (INVOS 5100C). Genotyping was performed with the TaqMan assay. RESULTS Before anesthesia, Q and SCO2 were 4.7 ± 1.2 L/min and 66% ± 8%, respectively, and linearly correlated (r = 0.35, P < .0001). In patients with the gly16gly genotype baseline, Q was approximately 0.4 L/min greater than in arg16 carriers (CI95: 0.0-0.8, Pt test = .03), but during anesthesia, the difference was 0.3 L/min (Pmixed-model = .07). Post hoc analysis revealed the change in SCO2 from baseline to the induction of anesthesia to be on average 2% greater in gly16gly homozygotes than in arg16 patients when adjusted for the change in Q (P = .03; CI95: 0.2-4.0%). CONCLUSIONS This study suggests that the β2-adrenoceptor gly16gly genotype is associated with the elevated resting Q. An interesting trend to greater frontal lobe oxygenation at induction of anesthesia in patients with gly16gly genotype was found, but because of insufficient sample size and lack of PCO2 control throughout the measurements, the presented data may only serve as the hypothesis generating for future studies. The confidence limits indicate that the magnitude of the effects may range from clinically insignificant to potentially important.
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Affiliation(s)
- Jonatan Myrup Staalsø
- From the *Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark; †Department of Anesthesia Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark; Departments of ‡Radiology and §Vascular Surgery Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark; and ‖Department of Neuroanesthesia Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
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29
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Schlader ZJ, Sarker S, Mündel T, Coleman GL, Chapman CL, Sackett JR, Johnson BD. Hemodynamic responses upon the initiation of thermoregulatory behavior in young healthy adults. Temperature (Austin) 2016; 3:271-285. [PMID: 27857957 PMCID: PMC4965002 DOI: 10.1080/23328940.2016.1148938] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Revised: 01/26/2016] [Accepted: 01/27/2016] [Indexed: 11/30/2022] Open
Abstract
We tested the hypotheses that thermoregulatory behavior is initiated before changes in blood pressure and that skin blood flow upon the initiation of behavior is reflex mediated. Ten healthy young subjects moved between 40°C and 17°C rooms when they felt 'too warm' (W→C) or 'too cool' (C→W). Blood pressure, cardiac output, skin and rectal temperatures were measured. Changes in skin blood flow between locations were not different at 2 forearm locations. One was clamped at 34°C ensuring responses were reflex controlled. The temperature of the other was not clamped ensuring responses were potentially local and/or reflex controlled. Relative to pre-test Baseline, skin temperature was not different at C→W (33.5 ± 0.7°C, P = 0.24), but was higher at W→C (36.1 ± 0.5°C, P < 0.01). Rectal temperature was different from Baseline at C→W (-0.2 ± 0.1°C, P < 0.01) and W→C (-0.2 ± 0.1°C, P < 0.01). Blood pressure was different from Baseline at C→W (+7 ± 4 mmHg, P < 0.01) and W→C (-5 ± 5 mmHg, P < 0.01). Cardiac output was not different from Baseline at C→W (-0.1 ± 0.4 L/min, P = 0.56), but higher at W→C (0.4 ± 0.4 L/min, P < 0.01). Skin blood flow between locations was not different from Baseline at C→W (clamped: -6 ± 15 PU, not clamped: -3 ± 6 PU, P = 0.46) or W→C (clamped: +21 ± 23 PU, not clamped: +29 ± 15 PU, P = 0.26). These data indicate that the initiation of thermoregulatory behavior is preceded by moderate changes in blood pressure and that skin blood flow upon the initiation of this behavior is under reflex control.
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Affiliation(s)
- Zachary J. Schlader
- Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
| | - Suman Sarker
- Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
| | - Toby Mündel
- School of Sport and Exercise, Massey University, Palmerston North, New Zealand`
| | - Gregory L. Coleman
- Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
| | | | - James R. Sackett
- Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
| | - Blair D. Johnson
- Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
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30
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Sato K, Oue A, Yoneya M, Sadamoto T, Ogoh S. Heat stress redistributes blood flow in arteries of the brain during dynamic exercise. J Appl Physiol (1985) 2016; 120:766-73. [DOI: 10.1152/japplphysiol.00353.2015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 01/31/2016] [Indexed: 11/22/2022] Open
Abstract
We hypothesized that heat stress would decrease anterior and posterior cerebral blood flow (CBF) during exercise, and the reduction in anterior CBF would be partly associated with large increase in extracranial blood flow (BF). Nine subjects performed 40 min of semirecumbent cycling at 60% of the peak oxygen uptake in hot (35°C; Heat) and thermoneutral environments (25°C; Control). We evaluated BF and conductance (COND) in the external carotid artery (ECA), internal carotid artery (ICA), and vertebral artery (VA) using ultrasonography. During the Heat condition, ICA and VA BF were significantly increased 10 min after the start of exercise ( P < 0.05) and thereafter gradually decreased. ICA COND was significantly decreased ( P < 0.05), whereas VA COND remained unchanged throughout Heat. Compared with the Control, either BF or COND of ICA and VA at the end of Heat tended to be lower, but not significantly. In contrast, ECA BF and COND at the end of Heat were both higher than levels in the Control condition ( P < 0.01). During Heat, a reduction in ICA BF appears to be associated with a decline in end-tidal CO2 tension ( r = 0.84), whereas VA BF appears to be affected by a change in cardiac output ( r = 0.87). In addition, a change in ECA BF during Heat was negatively correlated with a change in ICA BF ( r = −0.75). Heat stress resulted in modification of the vascular response of head and brain arteries to exercise, which resulted in an alteration in the distribution of cardiac output. Moreover, a hyperthermia-induced increase in extracranial BF might compromise anterior CBF during exercise with heat stress.
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Affiliation(s)
- Kohei Sato
- Research Institute of Physical Fitness, Japan Women's College of Physical Education, Tokyo, Japan; and
| | - Anna Oue
- Research Institute of Physical Fitness, Japan Women's College of Physical Education, Tokyo, Japan; and
| | - Marina Yoneya
- Research Institute of Physical Fitness, Japan Women's College of Physical Education, Tokyo, Japan; and
| | - Tomoko Sadamoto
- Research Institute of Physical Fitness, Japan Women's College of Physical Education, Tokyo, Japan; and
| | - Shigehiko Ogoh
- Research Institute of Physical Fitness, Japan Women's College of Physical Education, Tokyo, Japan; and
- Department of Biomedical Engineering, Toyo University, Saitama, Japan
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31
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Chiesa ST, Trangmar SJ, González-Alonso J. Temperature and blood flow distribution in the human leg during passive heat stress. J Appl Physiol (1985) 2016; 120:1047-58. [PMID: 26823344 PMCID: PMC4894946 DOI: 10.1152/japplphysiol.00965.2015] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 01/22/2016] [Indexed: 01/19/2023] Open
Abstract
The ability of direct heat stress to increase limb blood flow is well known, but the magnitude and profile of hemodynamic responses within the major vessels of the leg have not been explored. Here, we systematically characterize these responses through a wide range of heat stress levels and show that isolated leg heating confers potentially beneficial hemodynamic changes equivalent to those of moderate whole body hyperthermia, with these hemodynamic adjustments being predominantly driven by local temperature-sensitive mechanisms. The influence of temperature on the hemodynamic adjustments to direct passive heat stress within the leg's major arterial and venous vessels and compartments remains unclear. Fifteen healthy young males were tested during exposure to either passive whole body heat stress to levels approaching thermal tolerance [core temperature (Tc) + 2°C; study 1; n = 8] or single leg heat stress (Tc + 0°C; study 2; n = 7). Whole body heat stress increased perfusion and decreased oscillatory shear index in relation to the rise in leg temperature (Tleg) in all three major arteries supplying the leg, plateauing in the common and superficial femoral arteries before reaching severe heat stress levels. Isolated leg heat stress increased arterial blood flows and shear patterns to a level similar to that obtained during moderate core hyperthermia (Tc + 1°C). Despite modest increases in great saphenous venous (GSV) blood flow (0.2 l/min), the deep venous system accounted for the majority of returning flow (common femoral vein 0.7 l/min) during intense to severe levels of heat stress. Rapid cooling of a single leg during severe whole body heat stress resulted in an equivalent blood flow reduction in the major artery supplying the thigh deep tissues only, suggesting central temperature-sensitive mechanisms contribute to skin blood flow alone. These findings further our knowledge of leg hemodynamic responses during direct heat stress and provide evidence of potentially beneficial vascular alterations during isolated limb heat stress that are equivalent to those experienced during exposure to moderate levels of whole body hyperthermia.
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Affiliation(s)
- Scott T Chiesa
- Centre for Human Performance, Exercise and Rehabilitation, Brunel University London, Uxbridge, United Kingdom
| | - Steven J Trangmar
- Centre for Human Performance, Exercise and Rehabilitation, Brunel University London, Uxbridge, United Kingdom
| | - José González-Alonso
- Centre for Human Performance, Exercise and Rehabilitation, Brunel University London, Uxbridge, United Kingdom
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Greaney JL, Stanhewicz AE, Proctor DN, Alexander LM, Kenney WL. Impairments in central cardiovascular function contribute to attenuated reflex vasodilation in aged skin. J Appl Physiol (1985) 2015; 119:1411-20. [PMID: 26494450 PMCID: PMC4683344 DOI: 10.1152/japplphysiol.00729.2015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Accepted: 10/20/2015] [Indexed: 01/08/2023] Open
Abstract
During supine passive heating, increases in skin blood flow (SkBF) and cardiac output (Qc) are both blunted in older adults. The aim here was to determine the effect of acutely correcting the peripheral vasodilatory capacity of aged skin on the integrated cardiovascular responses to passive heating. A secondary aim was to examine the SkBF-Qc relation during hyperthermia in the presence (upright posture) and absence (dynamic exercise) of challenges to central venous pressure. We hypothesized that greater increases in SkBF would be accompanied by greater increases in Qc. Eleven healthy older adults (69 ± 3 yr) underwent supine passive heating (0.8°C rise in core temperature; water-perfused suit) after ingesting sapropterin (BH4, a nitric oxide synthase cofactor; 10 mg/kg) or placebo (randomized double-blind crossover design). Twelve young (24 ± 1 yr) subjects served as a comparison group. SkBF (laser-Doppler flowmetry) and Qc (open-circuit acetylene wash-in) were measured during supine heating, heating + upright posture, and heating + dynamic exercise. Throughout supine and upright heating, sapropterin fully restored the SkBF response of older adults to that of young adults but Qc remained blunted. During heat + upright posture, SkBF failed to decrease in untreated older subjects. There were no age- or treatment-related differences in SkBF-Qc during dynamic exercise. The principal finding of this study was that the blunted Qc response to passive heat stress is directly related to age as opposed to the blunted peripheral vasodilatory capacity of aged skin. Furthermore, peripheral impairments to SkBF in the aged may contribute to inapposite responses during challenges to central venous pressure during hyperthermia.
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Affiliation(s)
- Jody L Greaney
- Department of Kinesiology, Noll Laboratory, The Pennsylvania State University, University Park, Pennsylvania
| | - Anna E Stanhewicz
- Department of Kinesiology, Noll Laboratory, The Pennsylvania State University, University Park, Pennsylvania
| | - David N Proctor
- Department of Kinesiology, Noll Laboratory, The Pennsylvania State University, University Park, Pennsylvania
| | - Lacy M Alexander
- Department of Kinesiology, Noll Laboratory, The Pennsylvania State University, University Park, Pennsylvania
| | - W Larry Kenney
- Department of Kinesiology, Noll Laboratory, The Pennsylvania State University, University Park, Pennsylvania
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Mündel T, Perry BG, Ainslie PN, Thomas KN, Sikken ELG, Cotter JD, Lucas SJE. Postexercise orthostatic intolerance: influence of exercise intensity. Exp Physiol 2015; 100:915-25. [DOI: 10.1113/ep085143] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 05/29/2015] [Indexed: 11/08/2022]
Affiliation(s)
- Toby Mündel
- School of Sport and Exercise; Massey University; Palmerston North New Zealand
| | - Blake G. Perry
- School of Sport and Exercise; Massey University; Palmerston North New Zealand
| | - Philip N. Ainslie
- Centre for Heart, Lung and Vascular Health; School of Health and Exercise Sciences, University of British Columbia; Okanagan British Columbia Canada
- Department of Physiology; University of Otago; Dunedin New Zealand
| | - Kate N. Thomas
- School of Physical Education, Sport and Exercise Sciences; University of Otago; Dunedin New Zealand
- Department of Surgical Sciences; University of Otago; Dunedin New Zealand
| | - Elisabeth L. G. Sikken
- Department of Physiology; University of Otago; Dunedin New Zealand
- Department of Physiology; Radboud University Nijmegen Medical Centre; The Netherlands
| | - James D. Cotter
- School of Physical Education, Sport and Exercise Sciences; University of Otago; Dunedin New Zealand
| | - Samuel J. E. Lucas
- Department of Physiology; University of Otago; Dunedin New Zealand
- School of Sport, Exercise and Rehabilitation Sciences; College of Life and Environmental Sciences, University of Birmingham; UK
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Siebenmann C, Rasmussen P, Sørensen H, Zaar M, Hvidtfeldt M, Pichon A, Secher NH, Lundby C. Cardiac output during exercise: A comparison of four methods. Scand J Med Sci Sports 2014; 25:e20-7. [DOI: 10.1111/sms.12201] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/27/2014] [Indexed: 12/21/2022]
Affiliation(s)
- C. Siebenmann
- Center for Integrative Human Physiology; Institute of Physiology; University of Zürich; Zürich Switzerland
| | - P. Rasmussen
- Center for Integrative Human Physiology; Institute of Physiology; University of Zürich; Zürich Switzerland
| | - H. Sørensen
- Department of Anesthesia; The Copenhagen Muscle Research Center; Rigshospitalet; University of Copenhagen; Copenhagen Denmark
| | - M. Zaar
- Department of Anesthesia; The Copenhagen Muscle Research Center; Rigshospitalet; University of Copenhagen; Copenhagen Denmark
| | - M. Hvidtfeldt
- Department of Anesthesia; The Copenhagen Muscle Research Center; Rigshospitalet; University of Copenhagen; Copenhagen Denmark
| | - A. Pichon
- Laboratoire Réponses Cellulaires et Fonctionnelles à l'Hypoxie; Université Paris 13; Bobigny France
| | - N. H. Secher
- Department of Anesthesia; The Copenhagen Muscle Research Center; Rigshospitalet; University of Copenhagen; Copenhagen Denmark
| | - C. Lundby
- Center for Integrative Human Physiology; Institute of Physiology; University of Zürich; Zürich Switzerland
- Food & Nutrition & Sport Science; Gothenburg University; Gothenburg Sweden
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Relationship between sympathetic nerve activity and aortic wave reflection characteristics in postmenopausal women. Menopause 2014; 20:967-72. [PMID: 23531685 DOI: 10.1097/gme.0b013e3182843b59] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Aortic wave reflection characteristics, such as augmentation index, are positively related to muscle sympathetic nerve activity in young men. In young women, there is an inverse relationship. We investigated whether this inverse relationship persisted in postmenopausal women. METHODS Muscle sympathetic nerve activity (peroneal microneurography) and arterial pressure (brachial catheter) were measured in 16 postmenopausal women (mean [SEM] age, 60 [2] y). Aortic blood pressure and wave form characteristics were synthesized from radial arterial pressure waves (applanation tonometry). Specifically, augmentation index, wave reflection amplitude, and estimated wasted left ventricular energy were calculated. These data were compared with our previously published work from an identical protocol in 23 young women (mean [SEM] age, 25 [1] y). RESULTS Tonic sympathetic activity was higher in postmenopausal women than in young women (64 [3] vs 24 [4] bursts/100 heartbeats). All indices of aortic wave reflection were higher in postmenopausal women than in young women (P < 0.05). Baseline sympathetic activity was inversely related to augmentation index (r = -0.63, P < 0.05), augmented pressure (r = -0.62, P < 0.05), and wasted left ventricular energy (r = -0.61, P < 0.05) in young women. Conversely, baseline sympathetic activity was positively related to augmentation index (r = 0.63, P = 0.09), augmented pressure (r = 0.69, P < 0.05), and wasted left ventricular energy (r = 0.79, P < 0.05) in postmenopausal women. CONCLUSIONS High levels of sympathetic activity are associated with higher indices of aortic wave reflection in postmenopausal women. Consequently, postmenopausal women with high sympathetic activity may be more at risk for developing cardiovascular diseases or experiencing adverse cardiovascular system-related events.
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Lacewell AN, Buck TM, Romero SA, Halliwill JR. Postexercise syncope: Wingate syncope test and effective countermeasure. Exp Physiol 2013; 99:172-86. [PMID: 24078670 DOI: 10.1113/expphysiol.2013.075333] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Altered systemic haemodynamics following exercise can compromise cerebral perfusion and result in syncope. As the Wingate anaerobic test often induces presyncope, we hypothesized that a modified Wingate test could form the basis of a novel model for the study of postexercise syncope and a test bed for potential countermeasures. Along these lines, breathing through an impedance threshold device has been shown to increase tolerance to hypovolaemia, and could prove beneficial in the setting of postexercise syncope. Therefore, we hypothesized that a modified Wingate test followed by head-up tilt would produce postexercise syncope, and that breathing through an impedance threshold device (countermeasure) would prevent postexercise syncope in healthy individuals. Nineteen recreationally active men and women underwent a 60 deg head-up tilt during recovery from the Wingate test while arterial pressure, heart rate, end-tidal CO2 and cerebral tissue oxygenation were measured on a control day and a countermeasure day. The duration of tolerable tilt was increased by a median time of 3 min 48 s with countermeasure in comparison to the control (P < 0.05), and completion of the tilt test increased from 42 to 67% with the countermeasure. During the tilt, mean arterial pressure was greater (108.0 ± 4.1 versus 100.4 ± 2.4 mmHg; P < 0.05) with the countermeasure in comparison to the control. These data suggest that the Wingate syncope test produces a high incidence of presyncope, which is sensitive to countermeasures such as inspiratory impedance.
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Affiliation(s)
- Alisha N Lacewell
- J. R. Halliwill: 122 Esslinger Hall, 1240 University of Oregon, Eugene, OR 97403-1240, USA.
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G16R single nucleotide polymorphism but not haplotypes of the β(2)-adrenergic receptor gene alters cardiac output in humans. Clin Sci (Lond) 2013; 125:191-8. [PMID: 23438238 DOI: 10.1042/cs20120555] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Variation in genes encoding the β(2)-adrenergic receptor (ADRB2) and angiotensin-converting enzyme (ACE) may influence Q (cardiac output). The 46G>A (G16R) SNP (single nucleotide polymorphism) has been associated with β(2)-mediated vasodilation, but the effect of ADRB2 haplotypes on Q has not been studied. Five SNPs within ADRB2 (46G>A, 79C>G, 491C>T, 523C>A and 1053G>C by a pairwise tagging principle) and the I/D (insertion/deletion) polymorphism in ACE were genotyped in 143 subjects. Cardiovascular variables were evaluated by the Model flow method at rest and during incremental cycling exercise. Only the G16R polymorphism was associated with Q. In carriers of the Arg(16) allele, Q(rest) (resting Q) was 0.4 [95% CI (confidence interval), 0.0-0.7] l/min lower than in G16G homozygotes (P=0.048). During exercise, the increase in Q was by 4.7 (95% CI, 4.3-5.2) l/min per litre increase in pulmonary Vo(2) (oxygen uptake) in G16G subjects, but the increase was 0.5 (0.0-0.9) l/min lower in Arg16 carriers (P=0.035). A similar effect size was observed for the Arg16 haplotypes ACCCG and ACCCC. No interaction was found between ADRB2 and ACE polymorphisms. During exercise, the increase in Q was 0.5 (CI, 0.0 -1.0) l/min greater in ACE I/I carriers compared with I/D and D/D subjects (P=0.054). In conclusion, the ADRB2 Arg16 allele in humans is associated with a lower Q both at rest and during exercise, overriding the effects of haplotypes.
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38
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Pearson J, Kalsi KK, Stöhr EJ, Low DA, Barker H, Ali L, González-Alonso J. Haemodynamic responses to dehydration in the resting and exercising human leg. Eur J Appl Physiol 2013; 113:1499-509. [PMID: 23288036 DOI: 10.1007/s00421-012-2579-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Accepted: 12/26/2012] [Indexed: 10/27/2022]
Abstract
Dehydration and hyperthermia reduces leg blood flow (LBF), cardiac output ([Formula: see text]) and arterial pressure during whole-body exercise. It is unknown whether the reductions in blood flow are associated with dehydration-induced alterations in arterial blood oxygen content (C aO2) and O2-dependent signalling. This study investigated the impact of dehydration and concomitant alterations in C aO2 upon LBF and [Formula: see text]. Haemodynamics, arterial and femoral venous blood parameters and plasma [ATP] were measured at rest and during one-legged knee-extensor exercise in 7 males in four conditions: (1) control, (2) mild dehydration, (3) moderate dehydration, and (4) rehydration. Relative to control, C aO2 and LBF increased with dehydration at rest and during exercise (C aO2: from 199 ± 1 to 208 ± 2, and 202 ± 2 to 210 ± 2 ml L(-1) and LBF: from 0.38 ± 0.04 to 0.77 ± 0.09, and 1.64 ± 0.09 to 1.88 ± 0.1 L min(-1), respectively). Similarly, [Formula: see text] was unchanged or increased with dehydration at rest and during exercise, whereas arterial and leg perfusion pressures declined. Following rehydration, C aO2 declined (to 193 ± 2 mL L(-1)) but LBF remained elevated. Alterations in LBF were unrelated to C aO2 (r (2) = 0.13-0.27, P = 0.48-0.64) and plasma [ATP]. These findings suggest dehydration and concomitant alterations in C aO2 do not compromise LBF despite reductions in plasma [ATP]. While an additive or synergistic effect cannot be excluded, reductions in LBF during exercise with dehydration may not necessarily be associated with alterations in C aO2 and/or intravascular [ATP].
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Affiliation(s)
- James Pearson
- Centre for Sports Medicine and Human Performance, Brunel University, Uxbridge, Middlesex, UB8 3PH, UK
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39
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Francescato M, Cettolo V, di Prampero P. Oxygen uptake kinetics at work onset: Role of cardiac output and of phosphocreatine breakdown. Respir Physiol Neurobiol 2013; 185:287-95. [DOI: 10.1016/j.resp.2012.09.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Revised: 09/27/2012] [Accepted: 09/27/2012] [Indexed: 12/16/2022]
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40
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Cherouveim ED, Botonis PG, Koskolou MD, Geladas ND. Effect of gender on maximal breath-hold time. Eur J Appl Physiol 2012. [DOI: 10.1007/s00421-012-2552-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Fujii N, Honda Y, Delliaux S, Tsuji B, Watanabe K, Sugihara A, Kondo N, Nishiyasu T. Effect of voluntary hypocapnic hyperventilation on cutaneous circulation in resting heated humans. Am J Physiol Regul Integr Comp Physiol 2012; 303:R975-83. [DOI: 10.1152/ajpregu.00169.2012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hypocapnia attenuates the sweat response normally seen in hyperthermic resting subjects, but its effect on the blood flow response in their nonglabrous skin under the same hyperthermic conditions remains unclear. In the present study, we investigated whether hypocapnia induced by voluntary hyperventilation affects the blood flow response to heat stress in the nonglabrous skin of resting humans. Nine healthy male subjects were passively heated using legs-only hot water immersion and a water-perfused suit, which caused esophageal temperature (Tes) to increase by as much as 1.0°C. During normothermia and at +0.6°C Tes and +1.0°C Tes, the subjects performed two voluntary 7-min hyperventilation (minute ventilation = 40 l/min) trials (hypocapnic and eucapnic) in random order. End-tidal CO2 pressure was reduced by 23–25 torr during hypocapnic hyperventilation, but it was maintained at the spontaneous breathing level during eucapnic hyperventilation. Cutaneous blood flow was evaluated as the cutaneous red blood cell flux in the forearm (CBFforearm) or forehead (CBFforehead) and was normalized to the normothermic spontaneous breathing value. Hypocapnic hyperventilation at +0.6°C Tes was associated with significantly reduced CBFforearm, compared with eucapnic hyperventilation, after 5–7 min of hyperventilation (395 to 429 vs. 487 to 525% baseline, P < 0.05). No significant difference in CBFforehead was seen during hypocapnic hyperventilation compared with eucapnic hyperventilation at +0.6°C Tes or +1.0°C Tes. These results suggest that in resting humans, hypocapnia achieved through voluntary hyperventilation attenuates the increase in cutaneous blood flow elicited by moderate heat stress in the nonglabrous skin of the forearm, but not the forehead.
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Affiliation(s)
- Naoto Fujii
- Institute of Health and Sports Science, University of Tsukuba, Tsukuba, Japan
| | - Yasushi Honda
- Institute of Health and Sports Science, University of Tsukuba, Tsukuba, Japan
| | - Stephane Delliaux
- Institute of Health and Sports Science, University of Tsukuba, Tsukuba, Japan
- UMR L'Université de la Méditerranée Secteur Nord Physiologie et Physiopathologie en conditions d'oxygénation extrêmes, Institut fédératif de recherche Jean Roche, Faculté de Médecine, Université de la Méditerranée, Marseille, France; and
| | - Bun Tsuji
- Institute of Health and Sports Science, University of Tsukuba, Tsukuba, Japan
| | - Kazuhito Watanabe
- Institute of Health and Sports Science, University of Tsukuba, Tsukuba, Japan
| | - Akira Sugihara
- Institute of Health and Sports Science, University of Tsukuba, Tsukuba, Japan
| | - Narihiko Kondo
- Faculty of Human Development, Kobe University, Kobe, Japan
| | - Takeshi Nishiyasu
- Institute of Health and Sports Science, University of Tsukuba, Tsukuba, Japan
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Morrison SA, Ainslie PN, Lucas RAI, Cheung SS, Cotter JD. Compression garments do not alter cerebrovascular responses to orthostatic stress after mild passive heating. Scand J Med Sci Sports 2012; 24:291-300. [DOI: 10.1111/sms.12001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/14/2012] [Indexed: 11/26/2022]
Affiliation(s)
- S. A. Morrison
- School of Physical Education; University of Otago; Dunedin New Zealand
- Jozef Stefan Institute; Ljubljana Slovenia
| | - P. N. Ainslie
- School of Health and Exercise Sciences; University of British Columbia; Kelowna BC Canada
| | - R. A. I. Lucas
- School of Physical Education; University of Otago; Dunedin New Zealand
| | - S. S. Cheung
- Department of Kinesiology; Brock University; St. Catharines ON Canada
| | - J. D. Cotter
- School of Physical Education; University of Otago; Dunedin New Zealand
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Endotoxemia reduces cerebral perfusion but enhances dynamic cerebrovascular autoregulation at reduced arterial carbon dioxide tension. Crit Care Med 2012; 40:1873-8. [PMID: 22610190 DOI: 10.1097/ccm.0b013e3182474ca7] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
OBJECTIVE The administration of endotoxin to healthy humans reduces cerebral blood flow but its influence on dynamic cerebral autoregulation remains unknown. We considered that a reduction in arterial carbon dioxide tension would attenuate cerebral perfusion and improve dynamic cerebral autoregulation in healthy subjects exposed to endotoxemia. DESIGN Prospective descriptive study. SETTING Hospital research laboratory. SUBJECTS Ten healthy young subjects (age: 32 ± 8 yrs [mean ± SD]; weight: 84 ± 10 kg; weight: 184 ± 5 cm; body mass index: 25 ± 2 kg/m2) participated in the study. INTERVENTIONS Systemic hemodynamics, middle cerebral artery mean flow velocity, and dynamic cerebral autoregulation evaluated by transfer function analysis in the very low (<0.07 Hz), low (0.07-0.15 Hz), and high (>0.15 Hz) frequency ranges were monitored in these volunteers before and after an endotoxin bolus (2 ng/kg; Escherichia coli). MEASUREMENTS AND MAIN RESULTS Endotoxin increased body temperature of the subjects from 36.8 ± 0.4°C to 38.6 ± 0.5°C (p < .001) and plasma tumor necrosis factor-α from 5.6 (2.8-6.7) pg/mL to 392 (128-2258) pg/mL (p < .02). Endotoxemia had no influence on mean arterial pressure (95 [74-103] mm Hg vs. 92 [78-104] mm Hg; p = .75), but increased cardiac output (8.3 [6.1-9.5] L·min(-1) vs. 6.0 [4.5-8.2] L·min(-1); p = .02) through an elevation in heart rate (82 ± 9 beats·min(-1) vs. 63 ± 10 beats·min(-1); p < .001), whereas arterial carbon dioxide tension (37 ± 5 mm Hg vs. 41 ± 2 mm Hg; p < .05) and middle cerebral artery mean flow velocity (37 ± 9 cm·sec(-1) vs. 47 ± 10 cm·sec(-1); p < .01) were reduced. In regard to dynamic cerebral autoregulation, endotoxemia was associated with lower middle cerebral artery mean flow velocity variability (1.0 ± 1.0 [cm·sec(-1)] Hz vs. 2.8 ± 1.5 [cm·sec(-1)] Hz; p < .001), reduced gain (0.52 ± 0.11 cm·sec(-1) x mm Hg(-1) vs. 0.74 ± 0.17 cm·sec(-1) x mm Hg(-1); p < .05), normalized gain (0.22 ± 0.05 vs. 0.40 ± 0.17%·%; p < .05), and higher mean arterial pressure-to-middle cerebral artery mean flow velocity phase difference (p < .05) in the low frequency range (0.07-0.15 Hz). CONCLUSIONS These data support that the reduction in arterial carbon dioxide tension explains the improved dynamic cerebral autoregulation and the reduced cerebral perfusion encountered in healthy subjects during endotoxemia.
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Yang H, Cooke WH, Reed KS, Carter JR. Sex differences in hemodynamic and sympathetic neural firing patterns during orthostatic challenge in humans. J Appl Physiol (1985) 2012; 112:1744-51. [DOI: 10.1152/japplphysiol.01407.2011] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Recent evidence suggests that young men and women may have different strategies for regulating arterial blood pressure, and the purpose of the present study was to determine if sex differences exist in diastolic arterial pressure (DAP) and muscle sympathetic nerve activity (MSNA) relations during simulated orthostatic stress. We hypothesized that young men would demonstrate stronger DAP-MSNA coherence and a greater percentage of “consecutive integrated bursts” during orthostatic stress. Fourteen men and 14 women (age 23 ± 1 yr) were examined at rest and during progressive lower body negative pressure (LBNP; −5 to −40 mmHg). Progressive LBNP did not alter mean arterial pressure (MAP) in either sex. Heart rate increased and stroke volume decreased to a greater extent during LBNP in women (interactions, P < 0.05). DAP-MSNA coherence was strong (i.e., r ≥ 0.5) at rest and increased throughout all LBNP stages in men. In contrast, DAP-MSNA coherence was lower in women, and responses to progressive LBNP were attenuated compared with men (time × sex, P = 0.029). Men demonstrated a higher percentage of consecutive bursts during all stages of LBNP (sex, P < 0.05), although the percentage of consecutive bursts increased similarly during progressive LBNP between sexes. In conclusion, men and women demonstrate different firing patterns of integrated MSNA during LBNP that appear to be related to differences in DAP oscillatory patterns. Men tend to have more consecutive bursts, which likely contribute to a stronger DAP-MSNA coherence. These findings may help explain why young women are more prone to orthostatic intolerance.
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Affiliation(s)
- Huan Yang
- Department of Kinesiology and Integrated Physiology, Michigan Technological University, Houghton, Michigan; and
| | - William H. Cooke
- Department of Health and Kinesiology, University of Texas at San Antonio, San Antonio, Texas
| | - Kristen S. Reed
- Department of Kinesiology and Integrated Physiology, Michigan Technological University, Houghton, Michigan; and
| | - Jason R. Carter
- Department of Kinesiology and Integrated Physiology, Michigan Technological University, Houghton, Michigan; and
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Stewart JM, Medow MS, Messer ZR, Baugham IL, Terilli C, Ocon AJ. Postural neurocognitive and neuronal activated cerebral blood flow deficits in young chronic fatigue syndrome patients with postural tachycardia syndrome. Am J Physiol Heart Circ Physiol 2011; 302:H1185-94. [PMID: 22180650 DOI: 10.1152/ajpheart.00994.2011] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Neurocognition is impaired in chronic fatigue syndrome (CFS). We propose that the impairment relates to postural cerebral hemodynamics. Twenty-five CFS subjects and twenty control subjects underwent incremental upright tilt at 0, 15, 30, 45, 60, and 75° with continuous measurement of arterial blood pressure and cerebral blood flow velocity (CBFV). We used an n-back task with n ranging from 0 to 4 (increased n = increased task difficulty) to test working memory and information processing. We measured n-back outcomes by the number of correct answers and by reaction time. We measured CBFV, critical closing pressure (CCP), and CBFV altered by neuronal activity (activated CBFV) during each n value and every tilt angle using transcranial Doppler ultrasound. N-back outcome in control subjects decreased with n valve but was independent of tilt angle. N-back outcome in CFS subjects decreased with n value but deteriorated as orthostasis progressed. Absolute mean CBFV was slightly less than in control subjects in CFS subject at each angle. Activated CBFV in control subjects was independent of tilt angle and increased with n value. In contrast, activated CBFV averaged 0 in CFS subjects, decreased with angle, and was less than in control subjects. CCP was increased in CFS subjects, suggesting increased vasomotor tone and decreased metabolic control of CBFV. CCP did not change with orthostasis in CFS subjects but decreased monotonically in control subjects, consistent with vasodilation as compensation for the orthostatic reduction of cerebral perfusion pressure. Increasing orthostatic stress impairs neurocognition in CFS subjects. CBFV activation, normally tightly linked to cognitive neuronal activity, is unrelated to cognitive performance in CFS subjects; the increased CCP and vasomotor tone may indicate an uncoupling of the neurovascular unit during orthostasis.
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Affiliation(s)
- Julian M Stewart
- Departments of Physiology, New York Medical College, Valhalla, New York. USA.
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Minimally- and non-invasive assessment of maternal cardiac output: go with the flow! Int J Obstet Anesth 2011; 20:330-40. [DOI: 10.1016/j.ijoa.2011.07.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Revised: 06/29/2011] [Accepted: 07/05/2011] [Indexed: 10/17/2022]
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Hart EC, Charkoudian N, Wallin BG, Curry TB, Eisenach J, Joyner MJ. Sex and ageing differences in resting arterial pressure regulation: the role of the β-adrenergic receptors. J Physiol 2011; 589:5285-97. [PMID: 21859824 DOI: 10.1113/jphysiol.2011.212753] [Citation(s) in RCA: 244] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
In men, muscle sympathetic nerve activity (MSNA) is positively related to total peripheral resistance (TPR) and inversely related to cardiac output (CO). However, this relationship was not observed in young women. We aimed to investigate whether simultaneous β-adrenergic stimulation offsets this balance in young women. Furthermore, we aimed to examine whether the ability of the β-adrenergic receptors to offset the transduction of MSNA into vasoconstrictor tone was lost in postmenopausal women. We measured MSNA (peroneal microneurography), arterial pressure (brachial line), CO (Modelflow), TPR and changes in forearm vascular conductance (FVC) to increasing doses of noradrenaline (NA; 2, 4 and 8 ng (100 ml)(-1) min(-1)) before and after systemic β-blockade with propranolol in 17 young men, 17 young women and 15 postmenopausal (PM) women. The percentage and absolute change in FVC to the last two doses of NA were greater during β-blockade in young women (P < 0.05), whereas the change in FVC was similar before and during β-blockade in young men and PM women (P > 0.05). Before β-blockade there was no relationship of MSNA to TPR or mean arterial pressure (MAP) in young women. Following β-blockade, MSNA became positively related to TPR (r = 0.59, P < 0.05) and MAP (r = 0.58, P < 0.05). In the PM women and young men, MSNA was positively associated with TPR. β-Blockade had no effect on this relationship. Our data suggest that the β-adrenergic receptors offset α-adrenergic vasoconstriction in young women but not young men or PM women. These findings may explain in part the tendency for blood pressure to rise after menopause in women.
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Affiliation(s)
- Emma C Hart
- Department of Anaesthesiology, Mayo Clinic, Rochester, MN, USA.
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Ganio MS, Brothers RM, Shibata S, Hastings JL, Crandall CG. Effect of passive heat stress on arterial stiffness. Exp Physiol 2011; 96:919-26. [PMID: 21685446 DOI: 10.1113/expphysiol.2011.057091] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Arterial compliance, the inverse of arterial stiffness, is a prognostic indicator of arterial health. Central and peripheral arterial compliance decrease with acute cold stress and may increase postexercise when exercise-induced elevations in core temperature are likely still to be present. Increased blood flow through the conduit arteries associated with elevated core temperature increases shear stress, which in turn releases nitric oxide and other endothelium-derived factors. These changes, in conjunction with supportive in vitro data, suggest that elevated core temperature may indirectly increase central and peripheral arterial compliance (i.e. decrease arterial stiffness). The purpose of this study was to test the hypothesis that increased core temperature decreases central and peripheral arterial stiffness, as measured with pulse wave velocity (PWV). Using Doppler ultrasound, carotid-femoral (central) and carotid-radial (peripheral) arterial PWVs were measured from eight subjects (age 37 ± 11 years; mass 68.8 ± 11.1 kg; height 171 ± 3 cm) before and during passive heat-stress-induced increases in core temperature of 0.47 ± 0.05, 1.03 ± 0.12 and 1.52 ± 0.07°C (i.e. baseline, 0.5, 1.0 and 1.5°C, respectively). Changes in PWV were evaluated with one-way repeated-measures ANOVA. When analysed as group means, neither central (677 ± 161, 617 ± 72, 659 ± 74 and 766 ± 207 cm s(-1); P = 0.12) nor peripheral PWV (855 ± 192, 772 ± 95, 759 ± 49 and 858 ± 247 cm s(-1); P = 0.56) changed as core temperature increased from baseline to 0.5, 1.0 and 1.5°C, respectively. However, individual changes in central (average r = -0.89, P < 0.05) and peripheral PWV (average r = -0.93, P < 0.05) with heat stress were significantly correlated with normothermic baseline PWV. In conclusion, these data suggest that the magnitude by which heat stress reduced PWV was predicated upon normothermic PWV, with the individuals having the highest normothermic PWV being most responsive to the heat-stress-induced reductions in PWV.
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Affiliation(s)
- Matthew S Ganio
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, 7232 Greenville Avenue, Dallas, TX 75231, USA
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Amann M, Runnels S, Morgan DE, Trinity JD, Fjeldstad AS, Wray DW, Reese VR, Richardson RS. On the contribution of group III and IV muscle afferents to the circulatory response to rhythmic exercise in humans. J Physiol 2011; 589:3855-66. [PMID: 21646407 DOI: 10.1113/jphysiol.2011.209353] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
We investigated the role of skeletal muscle afferent feedback in circulatory control during rhythmic exercise in humans. Nine healthy males performed single leg knee-extensor exercise (15/30/45 watts, 3 min each) under both control conditions (Ctrl) and with lumbar intrathecal fentanyl impairing μ-opioid receptor-sensitive muscle afferents. Cardiac output and femoral blood flow were determined, and femoral arterial/venous blood samples were collected during the final minute of each workload. To rule out cephalad migration of fentanyl to the brainstem,we documented unchanged resting ventilatory responses to different levels of hypercapnia. There were no haemodynamic differences between conditions at rest. However, during exercise cardiac output was -2 % lower with fentanyl blockade compared to control (P < 0.05), secondary to a 6% and 13% reduction in heart rate and stroke volume, respectively. Throughout exercise mean arterial pressure (MAP) was reduced by 7% (P < 0.01) which is likely to have contributed to the 15% fall in femoral blood flow. However, MAP was not completely responsible for this peripheral haemodynamic change as vascular conductance was also attenuated (-9%). Evidence of increasing noradrenaline spillover (P = 0.09) implicated an elevation in sympathetic outflow in this response. The attenuated femoral blood flow during exercise with fentanyl was associated with a 17%reduction in leg O2 delivery (P < 0.01) and a concomitant rise in the arteriovenous O2 difference (4–9%), but leg O2 consumption remained 7–13% lower than control (P < 0.05). Our findings reveal an essential contribution of continuous muscle afferent feedback to ensure the appropriate haemodynamic and ultimately metabolic response to rhythmic exercise in humans
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Affiliation(s)
- Markus Amann
- Department of Medicine, University of Utah, Salt Lake City, UT,
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