Normo- and hypobaric hypoxia: are there any physiological differences?

Savourey, Gustave; Launay, Jean-Claude; Besnard, Yves; Guinet, Angélique; Travers, Stéphane

doi:10.1007/s00421-002-0789-8

Cited by 176 publications

(237 citation statements)

References 11 publications

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“…Loeppky et al, 1997;Savourey et al, 2003), it could be argued that the present results might not be representative of those expected in a hypobaric hypoxic setting. However, a previous study has shown that the hand CIVD responses are similar in normobaric and hypobaric hypoxia (Meeuwsen et al, 2009).…”

Section: Methodological Considerationscontrasting

confidence: 65%

Acute Effects of Normobaric Hypoxia on Hand-Temperature Responses During and After Local Cold Stress

Keramidas

Kölegård

Mekjavic

et al. 2014

High Altitude Medicine & Biology

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Keramidas, Michail E, Roger Kölegård, Igor B. Mekjavic, and Ola Eiken. Acute effects of normobaric hypoxia on hand-temperature responses during and after local cold stress. High Alt Med Biol. 15:183-191, 2014.-The purpose was to investigate acute effects of normobaric hypoxia on hand-temperature responses during and after a cold-water hand immersion test. Fifteen males performed two right-hand immersion tests in 8°C water, during which they were inspiring either room air (Fio 2 : 0.21; AIR), or a hypoxic gas mixture (Fio 2 : 0.14; HYPO). The tests were conducted in a counterbalanced order and separated by a 1-hour interval. Throughout the 30-min cold-water immersion (CWI) and the 15-min spontaneous rewarming (RW) phases, finger-skin temperatures were measured continuously with thermocouple probes; infrared thermography was also employed during the RW phase to map all segments of the hand. During the CWI phase, the average skin temperature (Tavg) of the fingers did not differ between the conditions (AIR: 10.2 -0.5°C, HYPO: 10.0 -0.5°C; p = 0.67). However, Tavg was lower in the HYPO than the AIR RW phase (AIR: 24.5 -3.4°C; HYPO: 22.0 -3.8°C; p = 0.002); a response that was alike in all regions of the immersed hand. Accordingly, present findings suggest that acute exposure to normobaric hypoxia does not aggravate the cold-induced drop in hand temperature of normothermic males. Still, hypoxia markedly impairs the rewarming responses of the hand.

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Section: Methodological Considerationscontrasting

confidence: 65%

Acute Effects of Normobaric Hypoxia on Hand-Temperature Responses During and After Local Cold Stress

Keramidas

Kölegård

Mekjavic

et al. 2014

High Altitude Medicine & Biology

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Section: Discussionmentioning

confidence: 99%

“…Normobaric hypoxia, in comparison to hypobaric hypoxia, represents a different challenge to ventilation and cardiac autonomic control (5,27,28). For example, increased breathing frequency with a lower tidal volume, higher end-tidal O 2 and CO 2 fractions, and a higher heart rate have been shown when hypobaric hypoxia is compared to normobaric hypoxia (27). To date there are no data on whether hypobaric hypoxia affects the distribution of heart beats throughout the ventilatory cycle, or whether any changes in this distribution affects ventilatory efficiency when exposed to low ambient PO 2 .A further technical limitation was that in the present study, isocapnia may not have been maintained during the hypoxia trial.…”

Section: Discussionmentioning

confidence: 99%

Effects of hypoxia and hypercapnia on human HRV and respiratory sinus arrhythmia

Brown¹,

Barnes²,

Mündel³

2014

Acta Physiologica Hungarica

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Purpose: Hypercapnia increases minute ventilation (V'E) with little effect on heart rate (HR), whereas hypoxia may increase HR without affecting V'E. However, the effects of hypercapnia and hypoxia on both heart rate variability (HRV) and the clustering of heart beats during spontaneous breathing (respiratory sinus arrhythmia -RSA), are not clear. Methods: In this study, 10 human volunteers breathed room air (RA), hypercapnic (5% CO 2 ) or hypoxic (10% O 2 ) gas mixtures, each for 6 min, while resting supine. ECG, mean arterial pressure (MAP), ventilatory flow, inhaled and exhaled fractions of CO 2 and O 2 , were recorded throughout. Results: Both V'E and MAP increased with 5% CO 2 , with no change in HR. Hypoxia did not change ventilation but increased HR. High frequency components of HRV, and the relative proportion of heart beats occurring during inhalation increased with 5% CO 2 , but neither changed with 10% O 2 . Conclusion: Increased RSA concomitant with increased MAP suggests RSA -vagal dissociation with hypercapnia. Elevated heart rate with acute hypoxia with no change in either frequency components of HRV or the distribution of heart beats during ventilation, suggested that clustering of heart beats may not be a mechanism to improve ventilation-perfusion matching during hypoxia.Keywords: autonomic nervous system, spectral analysis, cardiovascular control, heart rate variability, hypoxia, hypercapniaOscillations in the human heart rate at rest contribute to heart rate variability (HRV) (1, 18, 21, 23), and may indicate cardiac sympatho-vagal balance (7). Low (LF: 0-0.04 Hz), middle (MF: 0.04-0.15 Hz) and high (HF: 0.15-0.4 Hz) frequency bands form part of this variability and are often determined by spectral analysis of an R-R interval tachogram using fast Fourier transform (FFT). The influence of both hypoxia and hypercapnia on resting HRV has been studied at rest, but with equivocal results regarding changes in the frequency domain (37). Hypoxia may decrease HRV total power (TP) (6, 14, 29) and decrease both MF and HF power (3,6,21,23,24,29). However, hypoxia may decrease HF and increase MF power (14), or have no effect on HF power while increasing MF power (15). Hypercapnia stimulates ventilation and therefore increases HF power (usually with a concomitant decrease in MF power), but has little or no effect on resting heart rate. These equivocal findings emphasize the complex interaction between ambient PO 2 , PCO 2 , and autonomic nervous system function (10, 30). Hypoxia and hypercapnia may also influence respiratory sinus arrhythmia (RSA) -a measure synonymous with the HF component of HRV (31). RSA is due to the modulatory effects of pulmonary ventilation on vagal activity (2, 7) and reflects the preferential

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“…These physiological differences could be the result of an increase in dead space ventilation, probably related to reduced barometric pressure in hypobaric hypoxia. 38 Another research showed that some variables of heart rate variability were affected in …”

Section: Normobaric Versus Hypobaric Hypoxiamentioning

confidence: 99%

Can sildenafil improve physical performance at altitude? Current scientific evidence

Toro-Salinas

Torrella

Pagés

et al. 2016

Apunts. Medicina de l'Esport

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Sildenafil has proven to efficiently reduce the increase in pulmonary artery pressure provoked by hypoxic pulmonary vasoconstriction. However, its role as a possible factor in increasing exercise performance under hypoxic conditions remains to be demonstrated. The use of sildenafil has increased among mountaineers, not as a high altitude pulmonary edema preventive drug, but as a means that could help to improve performance. Several studies have attempted to address this issue, with conflicting results. Currently, despite the inconclusive data at simulated or real altitude, and with the clear evidence that, in normoxia, sildenafil does not improve performance, this drug is being used (and sometimes overused) by people who climb high peaks. However, such potential performance improvement would depend on the degree of hypoxemia (altitude) and the individual responsiveness to this drug. This paper reviews the current knowledge on this matter. © 2015 Consell Català de l'Esport. Generalitat de Catalunya. Published by Elsevier España, S.L.U. All rights reserved. PALABRAS CLAVESildenafilo; Gran altitud; Inhibidor de PDE-5; Ejercicio; Hipoxia; Normobárico; Hipobárico ¿Afecta sidenafilo a la capacidad física en altitud? Evidencias científicas en la actualidad Resumen Sildenafilo ha demostrado eficacia reduciendo la hipertensión pulmonar provocada por la vasoconstricción pulmonar hipóxica. Su papel como posible factor para aumentar el rendimiento en el ejercicio en condiciones de hipoxia está por demostrar, pero el uso de sildenafilo ha aumentado entre los montañeros, no como un fármaco preventivo del edema pulmonar de gran altitud, sino en la creencia de que podría ayudar a mejorar el rendimiento físico a gran altura geográfica. Varios estudios han tratado de abordar este tema, con resultados

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Normo- and hypobaric hypoxia: are there any physiological differences?

Cited by 176 publications

References 11 publications

Acute Effects of Normobaric Hypoxia on Hand-Temperature Responses During and After Local Cold Stress

Acute Effects of Normobaric Hypoxia on Hand-Temperature Responses During and After Local Cold Stress

Effects of hypoxia and hypercapnia on human HRV and respiratory sinus arrhythmia

Can sildenafil improve physical performance at altitude? Current scientific evidence

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