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Panza GS, Kissane DM, Puri S, Mateika JH. The hypoxic ventilatory response and hypoxic burden are predictors of the magnitude of ventilatory long-term facilitation in humans. J Physiol 2023; 601:4611-4623. [PMID: 37641466 PMCID: PMC11006398 DOI: 10.1113/jp285192] [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: 06/22/2023] [Accepted: 08/16/2023] [Indexed: 08/31/2023] Open
Abstract
Mild intermittent hypoxia initiates progressive augmentation (PA) and ventilatory long-term facilitation (vLTF) in humans. The magnitude of these forms of plasticity might be influenced by anthropometric and physiological variables, as well as protocol elements. However, the impact of many of these variables on the magnitude of respiratory plasticity has not been established in humans. A meta-analysis was completed using anthropometric and physiological variables obtained from 124 participants that completed one of three intermittent hypoxia protocols. Simple correlations between the aggregate variables and the magnitude of PA and vLTF standardized to baseline was completed. Thereafter, the variables correlated to PA or vLTF were input into a multilinear regression equation. Baseline measures of the hypoxic ventilatory response was the sole predictor of PA (R = 0.370, P = 0.012). Similarly, this variable along with the hypoxic burden predicted the magnitude of vLTF (R = 0.546, P < 0.006 for both variables). In addition, the magnitude of PA was strongly correlated to vLTF (R = 0.617, P < 0.001). Anthropometric measures do not predict the magnitude of PA and vLTF in humans. Alternatively, the hypoxic ventilatory response was the sole predictor of PA, and in combination with the hypoxic burden, predicted the magnitude of vLTF. These influences should be considered in the design of mild intermittent hypoxia protocol studies in humans. Moreover, the strong correlation between PA and vLTF suggests that a common mechanistic pathway may have a role in the initiation of these forms of plasticity. KEY POINTS: Mild intermittent hypoxia initiates progressive augmentation (PA) and ventilatory long-term facilitation (vLTF) in humans. Many of the anthropometric and physiological variables that could impact the magnitude of these forms of plasticity are unknown. Anthropometric and physiological variables were measured from a total of 124 participants that completed one of three distinct intermittent hypoxia protocols. The variables correlated to PA or vLTF were input into a multilinear regression analysis. The hypoxic ventilatory response was the sole predictor of PA, while this variable in addition to the average hypoxic burden predicted the magnitude of vLTF. A strong correlation between PA and vLTF was also revealed. These influences should be considered in the design of mild intermittent hypoxia protocol studies in humans. Moreover, the strong correlation between PA and vLTF suggests that a common mechanistic pathway may have a role in the initiation of these forms of plasticity.
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Affiliation(s)
- Gino S Panza
- John D. Dingell Veterans Affairs Medical Center, Detroit, MI, USA
- Department of Health Care Sciences, Program of Occupational Therapy, Wayne State University, Detroit, MI, USA
| | - Dylan M Kissane
- John D. Dingell Veterans Affairs Medical Center, Detroit, MI, USA
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Shipra Puri
- John D. Dingell Veterans Affairs Medical Center, Detroit, MI, USA
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Jason H Mateika
- John D. Dingell Veterans Affairs Medical Center, Detroit, MI, USA
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI, USA
- Department of Internal Medicine, Wayne State University School of Medicine, Detroit, MI, USA
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Guluzade NA, Huggard JD, Duffin J, Keir DA. A test of the interaction between central and peripheral respiratory chemoreflexes in humans. J Physiol 2023; 601:4591-4609. [PMID: 37566804 DOI: 10.1113/jp284772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 07/25/2023] [Indexed: 08/13/2023] Open
Abstract
How central and peripheral chemoreceptor drives to breathe interact in humans remains contentious. We measured the peripheral chemoreflex sensitivity to hypoxia (PChS) at various isocapnic CO2 tensions (P C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) to determine the form of the relationship between PChS and centralP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ . Twenty participants (10F) completed three repetitions of modified rebreathing tests with end-tidalP O 2 ${P_{{{\mathrm{O}}_{\mathrm{2}}}}}$ (P ET O 2 ${P_{{\mathrm{ET}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) clamped at 150, 70, 60 and 45 mmHg. End-tidalP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ (P ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ),P ET O 2 ${P_{{\mathrm{ET}}{{\mathrm{O}}_{\mathrm{2}}}}}$ , ventilation (V ̇ $\dot{V}$ E ) and calculated oxygen saturation (SC O2 ) were measured breath-by-breath by gas-analyser and pneumotach. TheV ̇ $\dot{V}$ E -P ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ relationship of repeat-trials were linear-interpolated, combined, averaged into 1 mmHg bins, and fitted with a double-linear function (V ̇ $\dot{V}$ E S, L min-1 mmHg-1 ). PChS was computed at intervals of 1 mmHg ofP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ as follows: the difference inV ̇ $\dot{V}$ E between the three hypoxic profiles and the hyperoxic profile (∆V ̇ $\dot{V}$ E ) was calculated; three ∆V ̇ $\dot{V}$ E values were plotted against corresponding SC O2 ; and linear regression determined PChS (Lmin-1 mmHg-1 %SC O2 -1 ). These processing steps were repeated at eachP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ to produce the PChS vs. isocapnicP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ relationship. These were fitted with linear and polynomial functions, and Akaike information criterion identified the best-fit model. One-way repeated measures analysis of variance assessed between-condition differences.V ̇ $\dot{V}$ E S increased (P < 0.0001) with isoxicP ET O 2 ${P_{{\mathrm{ET}}{{\mathrm{O}}_{\mathrm{2}}}}}$ from 3.7 ± 1.5 L min-1 mmHg-1 at 150 mmHg to 4.4 ± 1.8, 5.0 ± 1.6 and 6.0 ± 2.2 Lmin-1 mmHg-1 at 70, 60 and 45 mmHg, respectively. Mean SC O2 fell progressively (99.3 ± 0%, 93.7 ± 0.1%, 90.4 ± 0.1% and 80.5 ± 0.1%; P < 0.0001). In all individuals, PChS increased withP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ , and this relationship was best described by a linear model in 75%. Despite increasing central chemoreflex activation, PChS increased linearly withP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ indicative of an additive central-peripheral chemoreflex response. KEY POINTS: How central and peripheral chemoreceptor drives to breathe interact in humans remains contentious. We measured peripheral chemoreflex sensitivity to hypoxia (PChS) at various isocapnic carbon dioxide tensions (P C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) to determine the form of the relationship between PChS and centralP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ . Participants performed three repetitions of modified rebreathing with end-tidalP O 2 ${P_{{{\mathrm{O}}_{\mathrm{2}}}}}$ fixed at 150, 70, 60 and 45 mmHg. PChS was computed at intervals of 1 mmHg of end-tidalP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ (P ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) as follows: the difference inV ̇ $\dot{V}$ E between the three hypoxic profiles and the hyperoxic profile (∆V ̇ $\dot{V}$ E ) was calculated; three ∆V ̇ $\dot{V}$ E values were plotted against corresponding calculated oxygen saturation (SC O2 ); and linear regression determined PChS (Lmin-1 mmHg-1 %SC O2 -1 ). In all individuals, PChS increased withP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ , and this relationship was best described by a linear (rather than polynomial) model in 15 of 20. Most participants did not exhibit a hypo- or hyper-additive effect of central chemoreceptors on the peripheral chemoreflex indicating that the interaction was additive.
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Affiliation(s)
- Nasimi A Guluzade
- School of Kinesiology, The University of Western Ontario, London, ON, Canada
| | - Joshua D Huggard
- School of Kinesiology, The University of Western Ontario, London, ON, Canada
| | - James Duffin
- Department of Anaesthesia and Pain Management, University of Toronto, Toronto, ON, Canada
- Department of Physiology, University of Toronto, Toronto, ON, Canada
- Thornhill Research Inc., Toronto, ON, Canada
| | - Daniel A Keir
- School of Kinesiology, The University of Western Ontario, London, ON, Canada
- Toronto General Research Institute, Toronto General Hospital, Toronto, ON, Canada
- Lawson Health Research Institute, London, ON, Canada
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Dempsey JA, Gibbons TD. Rethinking O 2 , CO 2 and breathing during wakefulness and sleep. J Physiol 2023. [PMID: 37750243 DOI: 10.1113/jp284551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 09/11/2023] [Indexed: 09/27/2023] Open
Abstract
We have examined the importance of three long-standing questions concerning chemoreceptor influences on cardiorespiratory function which are currently experiencing a resurgence of study among physiologists and clinical investigators. Firstly, while carotid chemoreceptors (CB) are required for hypoxic stimulation of breathing, use of an isolated, extracorporeally perfused CB preparation in unanaesthetized animals with maintained tonic input from the CB, reveals that extra-CB hypoxaemia also provides dose-dependent ventilatory stimulation sufficient to account for 40-50% of the total ventilatory response to steady-state hypoxaemia. Extra-CB hyperoxia also provides a dose- and time-dependent hyperventilation. Extra-CB sites of O2 -driven ventilatory stimulation identified to date include the medulla, kidney and spinal cord. Secondly, using the isolated or denervated CB preparation in awake animals and humans has demonstrated a hyperadditive effect of CB sensory input on central CO2 sensitivity, so that tonic CB activity accounts for as much as 35-40% of the normal, air-breathing eupnoeic drive to breathe. Thirdly, we argue for a key role for CO2 chemoreception and the neural drive to breathe in the pathogenesis of upper airway obstruction during sleep (OSA), based on the following evidence: (1) removal of the wakefulness drive to breathe enhances the effects of transient CO2 changes on breathing instability; (2) oscillations in respiratory motor output precipitate pharyngeal obstruction in sleeping subjects with compliant, collapsible airways; and (3) in the majority of patients in a large OSA cohort, a reduced neural drive to breathe accompanied reductions in both airflow and pharyngeal airway muscle dilator activity, precipitating airway obstruction.
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Affiliation(s)
| | - Travis D Gibbons
- University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
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Ni YN, Yang H, Thomas RJ. The role of acetazolamide in sleep apnea at sea level: a systematic review and meta-analysis. J Clin Sleep Med 2021; 17:1295-1304. [PMID: 33538687 DOI: 10.5664/jcsm.9116] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
STUDY OBJECTIVES The recognition of specific endotypes as drivers of sleep apnea suggests the need of therapies targeting individual mechanisms. Acetazolamide is known to stabilize respiration at high altitude but benefits at sea level are less well understood. METHODS All controlled studies of acetazolamide in obstructive sleep apnea and/or central sleep apnea (CSA) were evaluated. The primary outcome was the apnea-hypopnea index. RESULTS Fifteen trials with a total of 256 patients were pooled in our systematic review. Acetazolamide reduced the overall apnea-hypopnea index (mean difference [MD] -15.82, 95% CI: -21.91 to -9.74, P < .00001) in central sleep apnea (MD -22.60, 95% CI: -29.11 to -16.09, P < .00001), but not in obstructive sleep apnea (MD -10.29, 95% CI: -33.34 to 12.77, P = .38). Acetazolamide reduced the respiratory related arousal index (MD -0.82, 95% CI: -1.56 to -0.08, P = .03), improved partial arterial of oxygen (MD 11.62, 95% CI: 9.13-14.11, P < .00001), mean oxygen saturation (MD 1.78, 95% CI: 0.53-3.04, P = .005), total sleep time (MD 25.74, 95% CI: 4.10-47.38, P = .02), N2 sleep (MD 3.34, 95% CI: 0.12-6.56, P = .04) and sleep efficiency (MD 4.83, 95% CI: 0.53-9.13, P = .03). CONCLUSIONS Acetazolamide improves the apnea-hypopnea index and several sleep metrics in central sleep apnea. The drug may be of clinical benefit in patients with high loop gain apnea of various etiologies and patterns. The existence of high heterogeneity is an important limitation in applicability of our analysis. SYSTEMATIC REVIEW REGISTRATION Registry: PROSPERO; Name: The effect of acetazolamide in patients with sleep apnea at sea level: a systematic review and meta analysis; URL: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020163316; Identifier: CRD42020163316.
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Affiliation(s)
- Yue-Nan Ni
- Division of Pulmonary, Critical Care and Sleep Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts.,Department of Respiratory and Critical Care Medicine, West China School of Medicine and West China Hospital, Sichuan University, China
| | - Huan Yang
- Department of Respiratory and Critical Care Medicine, West China School of Medicine and West China Hospital, Sichuan University, China
| | - Robert Joseph Thomas
- Division of Pulmonary, Critical Care and Sleep Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts
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Caldwell HG, Smith KJ, Lewis NCS, Hoiland RL, Willie CK, Lucas SJE, Stembridge M, Burgess KR, MacLeod DB, Ainslie PN. Regulation of cerebral blood flow by arterial PCO 2 independent of metabolic acidosis at 5050 m. J Physiol 2021; 599:3513-3530. [PMID: 34047356 DOI: 10.1113/jp281446] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Accepted: 05/21/2021] [Indexed: 12/23/2022] Open
Abstract
KEY POINTS We investigated the influence of arterial PCO2 (PaCO2 ) with and without experimentally altered pH on cerebral blood flow (CBF) regulation at sea level and with acclimatization to 5050 m. At sea level and high altitude, we assessed stepwise alterations in PaCO2 following metabolic acidosis (via 2 days of oral acetazolamide; ACZ) with and without acute restoration of pH (via intravenous sodium bicarbonate; ACZ+HCO3 - ). Total resting CBF was unchanged between trials at each altitude even though arterial pH and [HCO3 - ] (i.e. buffering capacity) were effectively altered. The cerebrovascular responses to changes in arterial [H+ ]/pH were consistent with the altered relationship between PaCO2 and [H+ ]/pH following ACZ at high altitude (i.e. leftward x-intercept shifts). Absolute cerebral blood velocity (CBV) and the sensitivity of CBV to PaCO2 was unchanged between trials at high altitude, indicating that CBF is acutely regulated by PaCO2 rather than arterial pH. ABSTRACT Alterations in acid-base balance with progressive acclimatization to high altitude have been well-established. However, how respiratory alkalosis and the resultant metabolic compensation interact to regulate cerebral blood flow (CBF) is uncertain. We addressed this via three separate experimental trials at sea level and following partial acclimatization (14 to 20 days) at 5050 m; involving: (1) resting acid-base balance (control); (2) following metabolic acidosis via 2 days of oral acetazolamide at 250 mg every 8 h (ACZ; pH: Δ -0.07 ± 0.04 and base excess: Δ -5.7 ± 1.9 mEq⋅l-1 , trial effects: P < 0.001 and P < 0.001, respectively); and (3) after acute normalization of arterial acidosis via intravenous sodium bicarbonate (ACZ + HCO3 - ; pH: Δ -0.01 ± 0.04 and base excess: Δ -1.5 ± 2.1 mEq⋅l-1 , trial effects: P = 1.000 and P = 0.052, respectively). Within each trial, we utilized transcranial Doppler ultrasound to assess the cerebral blood velocity (CBV) response to stepwise alterations in arterial PCO2 (PaCO2 ), i.e. cerebrovascular CO2 reactivity. Resting CBF (via Duplex ultrasound) was unaltered between trials within each altitude, indicating that respiratory compensation (i.e. Δ -3.4 ± 2.3 mmHg PaCO2 , trial effect: P < 0.001) was sufficient to offset any elevations in CBF induced via the ACZ-mediated metabolic acidosis. Between trials at high altitude, we observed consistent leftward shifts in both the PaCO2 -pH and CBV-pH responses across the CO2 reactivity tests with experimentally reduced arterial pH via ACZ. When indexed against PaCO2 - rather than pH - the absolute CBV and sensitivity of CBV-PaCO2 was unchanged between trials at high altitude. Taken together, following acclimatization, CO2 -mediated changes in cerebrovascular tone rather than arterial [H+ ]/pH is integral to CBF regulation at high altitude.
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Affiliation(s)
- Hannah G Caldwell
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Kurt J Smith
- Integrative Physiology Laboratory, Department of Kinesiology and Nutrition, University of Illinois Chicago, Chicago, Illinois, USA
| | - Nia C S Lewis
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Ryan L Hoiland
- Department of Anesthesiology, Pharmacology and Therapeutics, Vancouver General Hospital, West 12th Avenue, University of British Columbia, Vancouver, British Columbia, Canada.,Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Christopher K Willie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Samuel J E Lucas
- Department of Physiology, University of Otago, Dunedin, New Zealand.,School of Sport, Exercise and Rehabilitation Sciences & Centre for Human Brain Health, University of Birmingham, Birmingham, UK
| | - Michael Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - Keith R Burgess
- Peninsula Sleep Clinic, Sydney, New South Wales, Australia.,Department of Medicine, University of Sydney, Sydney, New South Wales, Australia
| | - David B MacLeod
- Human Pharmacology and Physiology Lab, Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
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Methazolamide in high-altitude illnesses. Eur J Pharm Sci 2020; 148:105326. [PMID: 32251722 DOI: 10.1016/j.ejps.2020.105326] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 03/26/2020] [Accepted: 03/26/2020] [Indexed: 11/24/2022]
Abstract
As a carbonic anhydrase inhibitor and a methylated lipophilic analogue of acetazolamide, Methazolamide has higher lipid solubility, less plasma protein binding and renal excretion, and fewer side effects, compared to acetazolamide. Methazolamide can increase systemic metabolic acidosis and sequentially improve ventilation and oxygenation level. The increased oxygenation level leads to reduced reactive oxygen species (ROS) production, relived cerebral edema, mitigated hypoxic pulmonary vasoconstriction, abrogated hypoxic fatigue, and decreased excessive erythrocytosis. In addition to the effect as a carbonic anhydrase inhibitor, methazolamide directly activates the transcription factor anti-oxidative nuclear factor-related factor 2 (Nrf2) and inhibits interleukin-1β (IL-1β) release. These pharmacological functions of methazolamide are beneficial for the prevention and treatment of high-altitude illnesses. Besides, methazolamide causes less fatigue side effects than acetazolamide does. It is also worth noting that several studies suggested that a lower dose of methazolamide has similar prophylaxis and treatment efficacy in acute mountain sickness (AMS) to a higher dose of acetazolamide. Given methazolamide's advantages over acetazolamide, methazolamide may thus represent an alternative for acetazolamide when taken for high-altitude illnesses prophylaxis and treatment. However, more in-depth clinical trials are needed to fully evaluate this efficacy of methazolamide.
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Clarke A, Ladha C, Wright A, Pattinson K. Losartan may attenuate altitude-related sleep disturbance. BMJ Mil Health 2020; 167:424-428. [PMID: 32086272 DOI: 10.1136/jramc-2019-001308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 11/12/2019] [Accepted: 11/15/2019] [Indexed: 11/04/2022]
Abstract
INTRODUCTION Sleep disturbance is common at high altitude and likely driven by an exaggerated peripheral chemoreceptor response which leads to apnoeic episodes and arousal. We hypothesised that this heightened response is in part mediated through angiotensin II receptors in the carotid body. To examine this link, we studied the effect of angiotensin II receptor blocker on sleep disturbance. METHODS Twenty participants paired by age, gender and ACE phenotype ascended to the Whymper Hut (5000 m) on Chimborazo in the Ecuadorean Andes as part of a double-blinded randomised placebo-controlled study of physiological mechanisms. Subjects were randomised to either losartan 100 mg daily or placebo. The primary outcome of sleep efficiency was measured using wrist-mounted actigraphs. One pair was excluded from analysis after descending before the end of the study due to acute mountain sickness. RESULTS There was a significantly different response to altitude between the two groups (F=3.274, p=0.029), as a decline in sleep efficiency in the placebo group (F=10.259, p<0.001) was not replicated in the angiotensin II receptor blocker group (F=0.459, p=0.713). CONCLUSION The absence of any significant sleep disturbance in the intervention group suggests that peripheral chemoreceptor hypersensitivity is largely mediated by angiotensin II receptor activation. However, further research is needed to confirm our findings and to study the potential mechanisms of action.
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Affiliation(s)
- Alexander Clarke
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, Tyne and Wear, UK
| | - C Ladha
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, Tyne and Wear, UK
| | - A Wright
- College of Medical and Dental Sciences, University of Birmingham, Birmingham, Birmingham, UK
| | - K Pattinson
- Nuffield Department of Clinical Neurosciences, Oxford University, Oxford, Oxfordshire, UK
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Dominelli PB, Baker SE, Wiggins CC, Stewart GM, Sajgalik P, Shepherd JRA, Roberts SK, Roy TK, Curry TB, Hoyer JD, Oliveira JL, Foster GE, Joyner MJ. Dissociating the effects of oxygen pressure and content on the control of breathing and acute hypoxic response. J Appl Physiol (1985) 2019; 127:1622-1631. [PMID: 31647724 PMCID: PMC6962610 DOI: 10.1152/japplphysiol.00569.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 10/18/2019] [Accepted: 10/20/2019] [Indexed: 11/22/2022] Open
Abstract
Arterial oxygen tension and oxyhemoglobin saturation (S a O 2 ) decrease in parallel during hypoxia. Distinguishing between changes in oxygen tension and oxygen content as the relevant physiological stimulus for cardiorespiratory alterations remains challenging. To overcome this, we recruited nine individuals with hemoglobinopathy manifesting as high-affinity hemoglobin [HAH; partial pressure at 50% S a O 2 (P50) = 16 ± 0.4 mmHg] causing greater S a O 2 at a given oxygen partial pressure compared with control subjects (n = 12, P50 = 26 ± 0.4 mmHg). We assessed ventilatory and cardiovascular responses to acute isocapnic hypoxia, iso-oxic hypercapnia, and 20 min of isocapnic hypoxia (arterial Po2 = 50 mmHg). Blood gas alterations were achieved with dynamic end-tidal forcing. When expressed as a function of the logarithm of oxygen partial pressure, ventilatory sensitivity to hypoxia was not different between groups. However, there was a significant difference when expressed as a function of S a O 2 . Conversely, the rise in heart rate was blunted in HAH subjects when expressed as a function of partial pressure but similar when expressed as a function of S a O 2 . Ventilatory sensitivity to hypercapnia was not different between groups. During sustained isocapnic hypoxia, the rise in minute ventilation was similar between groups; however, heart rate was significantly greater in the controls during 3 to 9 min of exposure. Our results support the notion that oxygen tension, not content, alters cellular Po2 in the chemosensors and drives the hypoxic ventilatory response. Our study suggests that in addition to oxygen partial pressure, oxygen content may also influence the heart rate response to hypoxia.NEW & NOTEWORTHY We dissociated the effects of oxygen content and pressure of cardiorespiratory regulation studying individuals with high-affinity hemoglobin (HAH). During hypoxia, the ventilatory response, expressed as a function of oxygen tension, was similar between HAH variants and controls; however, the rise in heart rate was blunted in the variants. Our work supports the notion that the hypoxic ventilatory response is regulated by oxygen tension, whereas cardiovascular regulation may be influenced by arterial oxygen content and tension.
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Affiliation(s)
- Paolo B Dominelli
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| | - Sarah E Baker
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| | - Chad C Wiggins
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| | - Glenn M Stewart
- Department of Cardiovascular Disease, Mayo Clinic, Rochester, Minnesota
| | - Pavol Sajgalik
- Department of Cardiovascular Disease, Mayo Clinic, Rochester, Minnesota
| | - John R A Shepherd
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| | - Shelly K Roberts
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| | - Tuhin K Roy
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| | - Timothy B Curry
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| | - James D Hoyer
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
| | - Jennifer L Oliveira
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
| | - Glen E Foster
- School of Health and Exercise Science, University of British Columbia, Kelowna, British Columbia, Canada
| | - Michael J Joyner
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
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Teppema LJ, Boulet LM, Hackett HK, Dominelli PB, Cheyne WS, Dominelli GS, Swenson ER, Foster GE. Influence of methazolamide on the human control of breathing: A comparison to acetazolamide. Exp Physiol 2019; 105:293-301. [PMID: 31595565 DOI: 10.1113/ep088058] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Accepted: 10/04/2019] [Indexed: 01/15/2023]
Abstract
NEW FINDINGS What is the central question of this study? Acetazolamide and methazolamide both reduce hypoxic pulmonary vasoconstriction equally, but methazolamide does not impair skeletal muscle function. The effect of methazolamide on respiratory control in humans is not yet known. What is the main finding and its importance? Similar to acetazolamide after chronic oral administration, methazolamide causes a metabolic acidosis and shifts the ventilatory CO2 response curve leftwards without reducing O2 sensitivity. The change in ventilation over the change in log P O 2 provides a more accurate measure of hypoxic sensitivity than the change in ventilation over the change in arterial oxyhaemoglobin saturation. ABSTRACT Acetazolamide is used to prevent/treat acute mountain sickness and both central and obstructive sleep apnoea. Methazolamide, like acetazolamide, reduces hypoxic pulmonary vasoconstriction, but has fewer side-effects, including less impairment of skeletal muscle function. Given that the effects of methazolamide on respiratory control in humans are unknown, we compared the effects of oral methazolamide and acetazolamide on ventilatory control and determined the ventilation-log P O 2 relationship in humans. In a double-blind, placebo-controlled, randomized cross-over design, we studied the effects of acetazolamide (250 mg three times daily), methazolamide (100 mg twice daily) and placebo in 14 young male subjects who were exposed to 7 min of normoxic hypercapnia and to three levels of eucapnia and hypercapnic hypoxia. With placebo, methazolamide and acetazolamide, the CO2 sensitivities were 2.39 ± 1.29, 3.27 ± 1.82 and 2.62 ± 1.79 l min-1 mmHg-1 (n.s.) and estimated apnoeic thresholds 32 ± 3, 28 ± 3 and 26 ± 3 mmHg, respectively (P < 0.001, placebo versus methazolamide and acetazolamide). The relationship between ventilation ( V ̇ I ) and log P O 2 (using arterialized venous P O 2 in hypoxia) was linear, and neither agent influenced the relationship between hypoxic sensitivity ( Δ V ̇ I / Δ log P O 2 ) and arterial [H+ ]. Using Δ V ̇ I / Δ log P O 2 rather than Δ V ̇ I /Δ arterial oxyhaemoglobin saturation enables a more accurate estimation of oxygenation and ventilatory control in metabolic acidosis/alkalosis when right- or leftward shifts of the oxyhaemoglobin saturation curve occur. Given that acetazolamide and methazolamide have similar effects on ventilatory control, methazolamide might be preferred for indications requiring the use of a carbonic anhydrase inhibitor, avoiding some of the negative side-effects of acetazolamide.
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Affiliation(s)
- Luc J Teppema
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Lindsey M Boulet
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
| | - Heather K Hackett
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
| | - Paolo B Dominelli
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada.,Department of Kinesiology, University of Waterloo, Waterloo, ON, Canada
| | - William S Cheyne
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
| | - Giulio S Dominelli
- Southern Medical Program, University of British Columbia, Kelowna, BC, Canada
| | - Erik R Swenson
- Division of Pulmonary & Critical Care Medicine, VA Puget Sound Health Care System, University of Washington, Seattle, WA, USA
| | - Glen E Foster
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
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10
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Abstract
The ventilatory control system is highly vulnerable to exogenous administered opioid analgesics. Particularly respiratory depression is a potentially lethal complication that may occur when opioids are overdosed or consumed in combination with other depressants such as sleep medication or alcohol. Fatalities occur in acute and chronic pain patients on opioid therapy and individuals that abuse prescription or illicit opioids for their hedonistic pleasure. One important strategy to mitigate opioid-induced respiratory depression is cotreatment with nonopioid respiratory stimulants. Effective stimulants prevent respiratory depression without affecting the analgesic opioid response. Several pharmaceutical classes of nonopioid respiratory stimulants are currently under investigation. The majority acts at sites within the brainstem respiratory network including drugs that act at α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (ampakines), 5-hydroxytryptamine receptor agonists, phospodiesterase-4 inhibitors, D1-dopamine receptor agonists, the endogenous peptide glycyl-glutamine, and thyrotropin-releasing hormone. Others act peripherally at potassium channels expressed on oxygen-sensing cells of the carotid bodies, such as doxapram and GAL021 (Galleon Pharmaceuticals Corp., USA). In this review we critically appraise the efficacy of these agents. We conclude that none of the experimental drugs are adequate for therapeutic use in opioid-induced respiratory depression and all need further study of efficacy and toxicity. All discussed drugs, however, do highlight potential mechanisms of action and possible templates for further study and development.
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11
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Boulet LM, Teppema LJ, Hackett HK, Dominelli PB, Cheyne WS, Dominelli GS, Irwin DC, Buehler PW, Baek JH, Swenson ER, Foster GE. Attenuation of human hypoxic pulmonary vasoconstriction by acetazolamide and methazolamide. J Appl Physiol (1985) 2018; 125:1795-1803. [PMID: 30236048 DOI: 10.1152/japplphysiol.00509.2018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
RATIONALE Acetazolamide, a carbonic anhydrase inhibitor used for preventing altitude illness attenuates hypoxic pulmonary vasoconstriction (HPV) while improving oxygenation. Methazolamide, an analog of acetazolamide, is more lipophilic, has a longer half-life, and activates a major antioxidant transcription factor. However, its influence on the hypoxic pulmonary response in humans is unknown. OBJECTIVE To determine if a clinically relevant dosing of methazolamide improves oxygenation, attenuates HPV and augments plasma antioxidant capacity in men exposed to hypoxia when compared to an established dosing of acetazolamide known to suppress HPV. METHODS In this double-blind, placebo-controlled, cross-over trial, eleven participants were randomized to treatments with methazolamide (100mg b.i.d.) and acetazolamide (250mg t.i.d.) for two days prior to 60 minutes of hypoxia (FIO2≈0.12). MEASUREMENTS Pulmonary artery systolic pressure (PASP), alveolar ventilation (V̇A), blood gases and markers of redox status were measured. Pulmonary vascular sensitivity to hypoxia was determined by indexing PASP to alveolar PO2. RESULTS Acetazolamide caused greater metabolic acidosis compared with methazolamide, but the augmented V̇A and improved oxygenation with hypoxia were similar. The rise in PASP with hypoxia was lower with methazolamide (9.0 ± 0.9 mmHg) and acetazolamide (8.0 ± 0.7 mmHg) compared with placebo (14.1 ± 1.3 mmHg; P < 0.05). The pulmonary vascular sensitivity to hypoxia (ΔPASP/ΔPAO2) was reduced equally by both drugs. Only acetazolamide improved the non-enzymatic plasma antioxidant capacity. CONCLUSIONS Although acetazolamide only had plasma antioxidant properties, methazolamide led to similar improvements in oxygenation and reduction in HPV at a dose causing less metabolic acidosis than acetazolamide in humans.
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Affiliation(s)
| | - Luc J Teppema
- Anesthesiology, Leiden University Medical Center, Netherlands
| | - Heather K Hackett
- School of Health and Exercise Sciences, University of British Columbia
| | | | | | | | - David C Irwin
- Division of Cardiovascular Pulmonary Research, University of Colorado Denver Health Sciences Center, United States
| | | | | | | | - Glen Edward Foster
- School of Health and Exercise Science, University of British Columbia, Canada
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12
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Wilson RJA, Teppema LJ. Integration of Central and Peripheral Respiratory Chemoreflexes. Compr Physiol 2016; 6:1005-41. [PMID: 27065173 DOI: 10.1002/cphy.c140040] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
A debate has raged since the discovery of central and peripheral respiratory chemoreceptors as to whether the reflexes they mediate combine in an additive (i.e., no interaction), hypoadditive or hyperadditive manner. Here we critically review pertinent literature related to O2 and CO2 sensing from the perspective of system integration and summarize many of the studies on which these seemingly opposing views are based. Despite the intensity and quality of this debate, we have yet to reach consensus, either within or between species. In reviewing this literature, we are struck by the merits of the approaches and preparations that have been brought to bear on this question. This suggests that either the nature of combination is not important to system responses, contrary to what has long been supposed, or that the nature of the combination is more malleable than previously assumed, changing depending on physiological state and/or respiratory requirement.
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Affiliation(s)
- Richard J A Wilson
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute and Alberta Children Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Luc J Teppema
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands
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13
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Affiliation(s)
- Luc J. Teppema
- Department Anesthesiology, Leiden University Medical Centre, Leiden, The Netherlands
| | - Remco R. Berendsen
- Department Anesthesiology, Leiden University Medical Centre, Leiden, The Netherlands
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14
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Swenson ER. Reply to Drs. Teppema and Berendsen. J Appl Physiol (1985) 2016; 120:565. [DOI: 10.1152/japplphysiol.00872.2015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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15
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Teppema LJ, Swenson ER. The noncarbonic anhydrase inhibiting acetazolamide analog N-methylacetazolamide reduces the hypercapnic, but not hypoxic, ventilatory response. Physiol Rep 2015; 3:3/8/e12484. [PMID: 26290531 PMCID: PMC4562570 DOI: 10.14814/phy2.12484] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Previous studies have shown that the carbonic anhydrase (CA) inhibitors acetazolamide (AZ) and methazolamide (MZ) have inhibiting actions on breathing. Classically these have been attributed to CA inhibition, but other effects unrelated to CA inhibition have been identified in other tissues. To explore this possibility in the control of ventilation by the central nervous system, we investigated whether an AZ-analog without CA inhibiting properties, by virtue of a single methylation on the sulfonamide moiety, N-methylacetazolamide (NMA), would still display similar actions to acetazolamide and methazolamide. NMA (20 mg kg−1) was given intravenously to anesthetized cats and we measured the responses to steady-state isocapnic hypoxia and stepwise changes in end-tidal pco2 before and after infusion of this AZ analog using the technique of end-tidal forcing. NMA caused a large decrease in the apneic threshold and CO2 sensitivity very similar to those previously observed with AZ and MZ, suggesting that these effects are mediated independently of CA inhibition. In contrast to acetazolamide, but similar to methazolamide, NMA did not affect the steady-state isocapnic hypoxic response. In conclusion, our data reveal complex effects of sulfonamides with very similar structure to AZ that reveal both CA-dependent and CA-independent effects, which need to be considered when using AZ as a probe for the role of CA in the control of ventilation.
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Affiliation(s)
- Luc J Teppema
- Department of Anesthesiology, Leiden University Medical Centre, Leiden, The Netherlands
| | - Erik R Swenson
- Pulmonary and Critical Care Medicine, VA Puget Sound Health Care System, University of Washington, Seattle, Washington, USA
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16
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Sasso E, Vitale M, Monteleone F, Boffo FL, Santoriello M, Sarnataro D, Garbi C, Sabatella M, Crifò B, Paolella LA, Minopoli G, Winum JY, Zambrano N. Binding of carbonic anhydrase IX to 45S rDNA genes is prevented by exportin-1 in hypoxic cells. BIOMED RESEARCH INTERNATIONAL 2015; 2015:674920. [PMID: 25793203 PMCID: PMC4352447 DOI: 10.1155/2015/674920] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 09/09/2014] [Indexed: 11/17/2022]
Abstract
Carbonic anhydrase IX (CA IX) is a surrogate marker of hypoxia, involved in survival and pH regulation in hypoxic cells. We have recently characterized its interactome, describing a set of proteins interacting with CA IX, mainly in hypoxic cells, including several members of the nucleocytoplasmic shuttling apparatuses. Accordingly, we described complex subcellular localization for this enzyme in human cells, as well as the redistribution of a carbonic anhydrase IX pool to nucleoli during hypoxia. Starting from this evidence, we analyzed the possible contribution of carbonic anhydrase IX to transcription of the 45 S rDNA genes, a process occurring in nucleoli. We highlighted the binding of carbonic anhydrase IX to nucleolar chromatin, which is regulated by oxygen levels. In fact, CA IX was found on 45 S rDNA gene promoters in normoxic cells and less represented on these sites, in hypoxic cells and in cells subjected to acetazolamide-induced acidosis. Both conditions were associated with increased representation of carbonic anhydrase IX/exportin-1 complexes in nucleoli. 45 S rRNA transcript levels were accordingly downrepresented. Inhibition of nuclear export by leptomycin B suggests a model in which exportin-1 acts as a decoy, in hypoxic cells, preventing carbonic anhydrase IX association with 45 S rDNA gene promoters.
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MESH Headings
- Acidosis/genetics
- Acidosis/metabolism
- Antigens, Neoplasm/genetics
- Antigens, Neoplasm/metabolism
- Biomarkers, Tumor/genetics
- Biomarkers, Tumor/metabolism
- Carbonic Anhydrase IX
- Carbonic Anhydrases/genetics
- Carbonic Anhydrases/metabolism
- Cell Hypoxia/genetics
- Cell Hypoxia/physiology
- Cell Line, Tumor
- Cell Nucleus/genetics
- Cell Nucleus/metabolism
- Chromatin/genetics
- Chromatin/metabolism
- DNA, Ribosomal/genetics
- DNA, Ribosomal/metabolism
- HEK293 Cells
- Humans
- Karyopherins/genetics
- Karyopherins/metabolism
- Promoter Regions, Genetic/drug effects
- Receptors, Cytoplasmic and Nuclear/genetics
- Receptors, Cytoplasmic and Nuclear/metabolism
- Transcription, Genetic/genetics
- Exportin 1 Protein
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Affiliation(s)
- Emanuele Sasso
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli Federico II, 80131 Napoli, Italy
- CEINGE Biotecnologie Avanzate, Via Gaetano Salvatore 486, 80145 Napoli, Italy
- Associazione Culturale DiSciMuS RFC, 80026 Casoria, Italy
| | - Monica Vitale
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli Federico II, 80131 Napoli, Italy
- CEINGE Biotecnologie Avanzate, Via Gaetano Salvatore 486, 80145 Napoli, Italy
| | - Francesca Monteleone
- CEINGE Biotecnologie Avanzate, Via Gaetano Salvatore 486, 80145 Napoli, Italy
- Associazione Culturale DiSciMuS RFC, 80026 Casoria, Italy
| | - Francesca Ludovica Boffo
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli Federico II, 80131 Napoli, Italy
- CEINGE Biotecnologie Avanzate, Via Gaetano Salvatore 486, 80145 Napoli, Italy
| | - Margherita Santoriello
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli Federico II, 80131 Napoli, Italy
| | - Daniela Sarnataro
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli Federico II, 80131 Napoli, Italy
- CEINGE Biotecnologie Avanzate, Via Gaetano Salvatore 486, 80145 Napoli, Italy
| | - Corrado Garbi
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli Federico II, 80131 Napoli, Italy
| | - Mariangela Sabatella
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli Federico II, 80131 Napoli, Italy
- CEINGE Biotecnologie Avanzate, Via Gaetano Salvatore 486, 80145 Napoli, Italy
| | - Bianca Crifò
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli Federico II, 80131 Napoli, Italy
- CEINGE Biotecnologie Avanzate, Via Gaetano Salvatore 486, 80145 Napoli, Italy
| | - Luca Alfredo Paolella
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli Federico II, 80131 Napoli, Italy
- CEINGE Biotecnologie Avanzate, Via Gaetano Salvatore 486, 80145 Napoli, Italy
| | - Giuseppina Minopoli
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli Federico II, 80131 Napoli, Italy
- CEINGE Biotecnologie Avanzate, Via Gaetano Salvatore 486, 80145 Napoli, Italy
| | - Jean-Yves Winum
- Institut des Biomolécules Max Mousseron, UMR 5247 CNRS, Université Montpellier I & II, ENSCM, 34296 Montpellier, France
| | - Nicola Zambrano
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli Federico II, 80131 Napoli, Italy
- CEINGE Biotecnologie Avanzate, Via Gaetano Salvatore 486, 80145 Napoli, Italy
- Associazione Culturale DiSciMuS RFC, 80026 Casoria, Italy
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17
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Teppema LJ, Smith CA. CrossTalk opposing view: peripheral and central chemoreceptors have hyperadditive effects on respiratory motor control. J Physiol 2014; 591:4359-61. [PMID: 24037128 DOI: 10.1113/jphysiol.2013.256818] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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18
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19
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Abstract
This paper describes the interactions between ventilation and acid-base balance under a variety of conditions including rest, exercise, altitude, pregnancy, and various muscle, respiratory, cardiac, and renal pathologies. We introduce the physicochemical approach to assessing acid-base status and demonstrate how this approach can be used to quantify the origins of acid-base disorders using examples from the literature. The relationships between chemoreceptor and metaboreceptor control of ventilation and acid-base balance summarized here for adults, youth, and in various pathological conditions. There is a dynamic interplay between disturbances in acid-base balance, that is, exercise, that affect ventilation as well as imposed or pathological disturbances of ventilation that affect acid-base balance. Interactions between ventilation and acid-base balance are highlighted for moderate- to high-intensity exercise, altitude, induced acidosis and alkalosis, pregnancy, obesity, and some pathological conditions. In many situations, complete acid-base data are lacking, indicating a need for further research aimed at elucidating mechanistic bases for relationships between alterations in acid-base state and the ventilatory responses.
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Affiliation(s)
- Michael I Lindinger
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada.
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20
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Gulsvik R, Skjørten I, Undhjem K, Holø L, Frostad A, Saure EW, Lejlic V, Humerfelt S, Hansen G, Bruun Wyller T. Acetazolamide improves oxygenation in patients with respiratory failure and metabolic alkalosis. CLINICAL RESPIRATORY JOURNAL 2013; 7:390-6. [PMID: 23578004 DOI: 10.1111/crj.12025] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Revised: 02/18/2013] [Accepted: 04/07/2013] [Indexed: 01/30/2023]
Abstract
INTRODUCTION Coexistent respiratory failure and metabolic alkalosis is a common finding. Acidotic diuretics cause a fall in pH that may stimulate respiration. OBJECTIVE The purpose of the study was to evaluate the effectiveness of short-term treatment with acetazolamide for combined respiratory failure and metabolic alkalosis. METHODS A randomised, placebo-controlled and double-blind parallel group trial where oral acetazolamide 250 mg three times a day for 5 days were administered to patients hospitalised for respiratory failure because of a pulmonary disease (Pa O2 ≤ 8 kPa and/or Pa CO2 ≥ 7 kPa) who had concurrent metabolic alkalosis [base excess (BE) ≥ 8 mmol/L]. Pa O2 after 5 days was the primary effect variable. Secondary effect variables were Pa CO2 , BE and pH on day 5, and the total number of days in hospital. RESULTS Of 70 patients enrolled (35 in each group), data from 54 were analysed per protocol, while last observation carried forward was used for the remaining 16. During the 5-day treatment, Pa O2 increased on average 0.81 kPa in the placebo group and 1.41 kPa in the acetazolamide group. After adjustment for baseline skewness, the difference was statistically significant (adjusted mean difference 0.55 kPa, 95% confidence interval 0.03-1.06). Pa CO2 decreased in both groups, but the difference was not statistically significant. As expected, pH and BE decreased markedly in the acetazolamide group. CONCLUSION Acetazolamide may constitute a useful adjuvant treatment mainly to be considered in selected patients with respiratory failure combined with prominent metabolic alkalosis or where non-invasive ventilation is insufficient or infeasible.
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Affiliation(s)
- Ragnhild Gulsvik
- Department of Pulmonary Medicine, Oslo University Hospital, Oslo, Norway
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21
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Teppema LJ, Berendsen RR. Acetazolamide and cerebrovascular function at high altitude. J Physiol 2012; 590:2945-6; author reply 2947. [PMID: 22707596 DOI: 10.1113/jphysiol.2012.233569] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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22
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Tin C, Song G, Poon CS. Hypercapnia attenuates inspiratory amplitude and expiratory time responsiveness to hypoxia in vagotomized and vagal-intact rats. Respir Physiol Neurobiol 2012; 181:79-87. [PMID: 22326640 DOI: 10.1016/j.resp.2012.01.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Revised: 01/19/2012] [Accepted: 01/24/2012] [Indexed: 10/14/2022]
Abstract
A negative influence of central chemosensitivity on peripheral chemoreflex response has been demonstrated recently in a decerebrate-vagotomized rat preparation in situ with separate carotid body and brainstem perfusions. Here, we report similar negative influences of hypercapnia on the hypoxic respiratory response in anesthetized, spontaneously breathing rats before and after vagotomy and anesthetized, artificially ventilated rats after vagotomy. Baseline breathing patterns and responsiveness to hypercapnia and hypoxia varied widely between the three respiratory modes. Despite this, the responses in inspiratory amplitude and expiratory duration (and hence respiratory frequency and neural ventilation) to hypoxia varied inversely with the background CO2 level in all three groups. Results demonstrate a hypoadditive hypercapnic-hypoxic interaction in vivo that resembles the hypoadditive central-peripheral chemoreceptor interaction in situ for these respiratory variables in the rat, regardless of differences in vagal feedback, body temperature and ventilation method. These observations stand in contrast to previous reports of hyperadditive peripheral-central chemoreceptor interaction.
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Affiliation(s)
- Chung Tin
- Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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23
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Fan JL, Burgess KR, Thomas KN, Lucas SJE, Cotter JD, Kayser B, Peebles KC, Ainslie PN. Effects of acetazolamide on cerebrovascular function and breathing stability at 5050 m. J Physiol 2012; 590:1213-25. [PMID: 22219343 DOI: 10.1113/jphysiol.2011.219923] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
One of the many actions of the carbonic anhydrase inhibitor, acetazolamide (ACZ), is to accelerate acclimatisation and reduce periodic breathing during sleep. The mechanism(s) by which ACZ may improve breathing stability, especially at high altitude, remain unclear. We tested the hypothesis that acute I.V. ACZ would enhance cerebrovascular reactivity to CO₂ at altitude, and thereby lower ventilatory drive and improve breathing stability during wakefulness. We measured arterial blood gases, minute ventilation (˙VE) and middle cerebral artery blood flow velocity (MCAv) before and 30 min following ACZ administration (I.V. 10 mg kg⁻¹) in 12 healthy participants at sea level and following partial acclimatisation to altitude (5050 m).Measures were made at rest and during changes in end-tidal PCO₂ and PO₂ (isocapnic hypoxia). At sea level, ACZ increased resting MCAv and its reactivity to both hypocapnia and hypercapnia (P < 0.05), and lowered resting VE, arterial O₂ saturation (Sa,O₂ ) and arterial PO₂ (Pa,O₂) (P < 0.05); arterial PCO₂ (Pa,CO₂ ) was unaltered (P > 0.05). At altitude, ACZ also increased resting MCAv and its reactivity to both hypocapnia and hypercapnia (resting MCAv and hypocapnia reactivity to a greater extent than at sea level). Moreover, ACZ at altitude elevated Pa,CO₂ and again lowered resting Pa,O₂ and Sa,O₂ (P <0.05). Although the ˙VE sensitivity to hypercapnia or isocapnic hypoxia was unaltered following ACZ at both sea level and altitude (P > 0.05), breathing stability at altitude was improved (e.g. lower incidence of ventilatory oscillations and variability of tidal volume; P < 0.05). Our data indicate that I.V. ACZ elevates cerebrovascular reactivity and improves breathing stability at altitude, independent of changes in peripheral or central chemoreflex sensitivities. We speculate that Pa,CO₂-mediated elevations in cerebral perfusion and an enhanced cerebrovascular reactivity may partly account for the improved breathing stability following ACZ at high altitude.
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Affiliation(s)
- Jui-Lin Fan
- Department of Physiology, Otago School of Medical Science, University of Otago, Dunedin, New Zealand.
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24
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Nussbaumer-Ochsner Y, Latshang TD, Ulrich S, Kohler M, Thurnheer R, Bloch KE. Patients with obstructive sleep apnea syndrome benefit from acetazolamide during an altitude sojourn: a randomized, placebo-controlled, double-blind trial. Chest 2011; 141:131-138. [PMID: 21659435 DOI: 10.1378/chest.11-0375] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
BACKGROUND Many patients with obstructive sleep apnea syndrome (OSA) are unable or unwilling to use continuous positive airway pressure (CPAP) therapy when traveling to the mountains for work or recreation even though they risk pronounced hypoxemia and exacerbation of sleep apnea. Because the treatment of OSA at altitude has not been established, we tested the hypothesis that acetazolamide improves hypoxemia, sleep, and breathing disturbances in otherwise untreated patients with OSA at altitude. METHODS Forty-five patients with OSA on long-term CPAP, median age 64 years, living at < 600 m underwent a placebo-controlled, double-blind, crossover trial randomized for the sequence of drug and altitude exposure (490 m, 1,860 m, and 2,590 m). Patients spent two 3-day periods at altitude and a 2-week wash-out period at < 600 m. At altitude, patients discontinued CPAP and received acetazolamide 2 × 250 mg daily or placebo. Polysomnography, vigilance, and symptoms were evaluated. RESULTS At 490 m, off CPAP, median nocturnal oxygen saturation was 93%, and the apnea/hypopnea index was 51.2/h. On placebo at 1,860 m and 2,590 m, the corresponding values were 89% and 85% and 63.6/h and 86.2/h, respectively (P < .01 vs 490 m, both instances). On acetazolamide at 1,860 m and 2,590 m, oxygen saturation was higher (91% and 88%) and apnea/hypopnea indices were lower (48.0/h and 61.4/h) than on placebo (P < .01 all instances). Acetazolamide reduced nocturnal transcutaneous Pco(2), improved sleep efficiency and subjective insomnia, and prevented excessive BP elevations at altitude. CONCLUSIONS In patients with OSA discontinuing CPAP during an altitude sojourn, acetazolamide improves oxygenation, breathing disturbances, and sleep quality by stimulating ventilation. Therefore, patients with OSA may benefit from acetazolamide at altitude if CPAP therapy is not feasible. TRIAL REGISTRY ClinicalTrials.gov; No.: NCT00714740; URL: www.clinicaltrials.gov.
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Affiliation(s)
- Yvonne Nussbaumer-Ochsner
- Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Zurich; Center for Human Integrative Physiology, University of Zurich, Zurich
| | - Tsogyal D Latshang
- Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Zurich; Center for Human Integrative Physiology, University of Zurich, Zurich
| | - Silvia Ulrich
- Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Zurich; Center for Human Integrative Physiology, University of Zurich, Zurich
| | - Malcolm Kohler
- Center for Human Integrative Physiology, University of Zurich, Zurich
| | - Robert Thurnheer
- Pulmonary Division, Cantonal Hospital Munsterlingen, Munsterlingen, Switzerland
| | - Konrad E Bloch
- Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Zurich; Center for Human Integrative Physiology, University of Zurich, Zurich.
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25
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Teppema LJ, Baby S. Anesthetics and control of breathing. Respir Physiol Neurobiol 2011; 177:80-92. [PMID: 21514403 DOI: 10.1016/j.resp.2011.04.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Revised: 04/04/2011] [Accepted: 04/07/2011] [Indexed: 12/18/2022]
Abstract
An important side effect of general anesthetics is respiratory depression. Anesthetics have multiple membrane targets of which ionotropic receptors such as gamma-aminobutyric acid-A (GABA(A)), glycine, N-methyl-D-aspartate and nicotinic acetylcholinergic (nACh) receptors are important members. GABA, glutamate and ACh are crucial neurotransmitters in the respiratory neuronal network, and the ability of anesthetics to modulate their release and interact with their receptors implies complex effects on respiration. Metabotropic receptors and intracellular proteins are other important targets for anesthetics suggesting complex effects on intracellular signaling pathways. Here we briefly overview the effects of general anesthetics on protein targets as far as these are relevant for respiratory control. Subsequently, we describe some methods with which the overall effect of anesthetics on the control of breathing can be measured, as well as some promising in vivo approaches to study their synaptic effects. Finally, we summarize the most important respiratory effects of volatile anesthetics in humans and animals and those of some intravenous anesthetics in animals.
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Affiliation(s)
- Luc J Teppema
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands.
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26
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Teppema LJ, Dahan A. The Ventilatory Response to Hypoxia in Mammals: Mechanisms, Measurement, and Analysis. Physiol Rev 2010; 90:675-754. [DOI: 10.1152/physrev.00012.2009] [Citation(s) in RCA: 257] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The respiratory response to hypoxia in mammals develops from an inhibition of breathing movements in utero into a sustained increase in ventilation in the adult. This ventilatory response to hypoxia (HVR) in mammals is the subject of this review. The period immediately after birth contains a critical time window in which environmental factors can cause long-term changes in the structural and functional properties of the respiratory system, resulting in an altered HVR phenotype. Both neonatal chronic and chronic intermittent hypoxia, but also chronic hyperoxia, can induce such plastic changes, the nature of which depends on the time pattern and duration of the exposure (acute or chronic, episodic or not, etc.). At adult age, exposure to chronic hypoxic paradigms induces adjustments in the HVR that seem reversible when the respiratory system is fully matured. These changes are orchestrated by transcription factors of which hypoxia-inducible factor 1 has been identified as the master regulator. We discuss the mechanisms underlying the HVR and its adaptations to chronic changes in ambient oxygen concentration, with emphasis on the carotid bodies that contain oxygen sensors and initiate the response, and on the contribution of central neurotransmitters and brain stem regions. We also briefly summarize the techniques used in small animals and in humans to measure the HVR and discuss the specific difficulties encountered in its measurement and analysis.
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Affiliation(s)
- Luc J. Teppema
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Albert Dahan
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands
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