Normo or hypobaric hypoxic tests: propositions for the determination of the individual susceptibility to altitude illnesses

Savourey, Gustave; Launay, Jean-Claude; Besnard, Yves; Guinet-Lebreton, Angélique; Alonso, Antonia; Sauvet, Fabien; Bourrilhon, Cyprien

doi:10.1007/s00421-007-0417-8

Cited by 49 publications

(87 citation statements)

References 25 publications

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“…This was already described by Paul Bert 140 years ago and confirmed later by others [16,17]. But these differences do not have any consequences for the tactics of acclimatization, neither in isobaric conditions nor in the mountains [18,19].…”

Section: Which Group May Benefit From Pre-acclimatization?supporting

confidence: 64%

Pre-Acclimatization for High Altitude Sojourns in Hypoxic Chambers

Küpper¹,

Schoeffl²

2012

Med Sport

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More and more people go to high altitude without enough time for proper acclimatization. If there is a lack of time for any reason hypoxic chambers may be used for pre-acclimatization to avoid altitude diseases. Since there are different protocols and the data differ, there is no general consensus about the standard how to perform pre-acclimatization by simulated altitude. We review different types of exposure and focus target groups which may get benefit from pre-acclimatization. We suggest to perform pre-acclimatization by sleeping some nights at a simulated altitude which follows the altitude profile of the "Gold Standard" for high altitude acclimatization. Until there are more detailed data about intermittent hypoxia this method should provide the best effect.

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Section: Which Group May Benefit From Pre-acclimatization?supporting

confidence: 64%

Pre-Acclimatization for High Altitude Sojourns in Hypoxic Chambers

Küpper¹,

Schoeffl²

2012

Med Sport

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“…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).…”

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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“…There is a suggestion that the initial responses of oxygen saturation and symptoms of hypoxia are infl uenced by the protocol employed, but these differences were lost after 5 min [ 98 ]. Also, Savourey et al [ 99 ] observed initially higher respiratory frequencies and lower tidal volumes in hypobaric hypoxia than in the equivalent normobaric hypoxia, with lower end tidal oxygen and carbon dioxide levels, and lower oxygen saturations after 5 min of exposure. These differences were lost after 30 min of exposure.…”

Section: Differences Between Hypobaric and Normobaric Hypoxiamentioning

confidence: 95%