CrossTalk proposal: Barometric pressure, independent of , is the forgotten parameter in altitude physiology and mountain medicine

Millet, Grégoire P.; Debevec, Tadej

doi:10.1113/jp278673

Cited by 64 publications

(49 citation statements)

References 32 publications

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“…Several differences between NH and HH were reported, such as minute ventilation (Savourey et al, 2003), oxydative stress (Faiss et al, 2013), sleep disturbance (Saugy et al, 2016), and cerebrovascular function (Aebi et al, 2020). Therefore, NH and HH are not interchangeable (Conkin, 2016) but the clinical significance of the difference remains highly debated (Millet and Debevec, 2020;Richalet, 2020).…”

Section: Introductionmentioning

confidence: 99%

“…Isolating the hypobaric effect from the hypoxic one would allow comparing similar normoxic conditions with different P B . A hypobaric normoxic (HN) condition (i.e., low P B and hyperoxic breathing in order to obtain a comparable P I O 2 than in normobaric normoxia, NN) is therefore of interest for evaluating the putative hypobaric effect in normoxia (Millet and Debevec, 2020). Moreover, there is a practical interest of the present study since hypobaric normoxia occurs in the context of aviation; i.e., for pilots exposed to hypobaria in cockpit using supplemental oxygen.…”

Section: Introductionmentioning

confidence: 99%

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Minimal Influence of Hypobaria on Heart Rate Variability in Hypoxia and Normoxia

et al. 2020

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Introduction: The present study evaluated the putative effect of hypobaria on resting HRV in normoxia and hypoxia. Methods: Fifteen young pilot trainees were exposed to five different conditions in a randomized order: normobaric normoxia (NN, P B = 726 ± 5 mmHg, F I O 2 = 20.9%), hypobaric normoxia (HN, P B = 380 ± 6 mmHg, F I O 2 ∼ =40%), normobaric hypoxia (NH, P B = 725 ± 4 mmHg, F I O 2 ∼ =11%); and hypobaric hypoxia (HH at 3000 and 5500 m, HH3000 and HH5500, P B = 525 ± 6 and 380 ± 8 mmHg, respectively, F I O 2 = 20.9%). HRV and pulse arterial oxygen saturation (SpO 2) were measured at rest seated during a 6 min period in each condition. HRV parameters were analyzed (Kubios HVR Standard, V 3.0) for time (RMSSD) and frequency (LF, HF, LF/HF ratio, and total power). Gas exchanges were collected at rest for 10 min following HRV recording. Results: SpO 2 decreased in HH3000 (95 ± 3) and HH5500 (81 ± 5), when compared to NN (99 ± 0). SpO 2 was higher in NH (86 ± 4) than HH5500 but similar between HN (98 ± 2) and NN. Participants showed lower RMSSD and total power values in NH and HH5500 when compared to NN. In hypoxia, LF/HF ratio was greater in HH5500 than NH, whereas in normoxia, LF/HF ratio was lower in HN than NN. Minute ventilation was higher in HH5500 than in all other conditions. Discussion: The present study reports a slight hypobaric effect either in normoxia or in hypoxia on some HRV parameters. In hypoxia, with a more prominent sympathetic activation, the hypobaric effect is likely due to the greater ventilation stimulus and larger desaturation. In normoxia, the HRV differences may come from the hyperoxic breathing and slight breathing pattern change due to hypobaria in HN.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Minimal Influence of Hypobaria on Heart Rate Variability in Hypoxia and Normoxia

et al. 2020

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“…Previous work comparing differences between cardiorespiratory responses in acute HH and NH focused primarily on resting and submaximal exercise conditions [6][7][8]11,12,40]. Results of a recent meta-analysis (primarily performed on studies investigating resting conditions) indicate differences in variables related to VE, NO, fluid retention, and acute mountain sickness (AMS) associated factors between acute HH and NH [11].…”

Section: Discussionmentioning

confidence: 99%

“…Third, we were not able to evaluate potential gender differences, as there are only very few studies including female athletes. Fourth, we must acknowledge that the validity of any comparison between acute NH and HH conditions depends on the accuracy of the calculation of the equivalent altitude, as was recently addressed in detail [40,54]. The calculation may depend on the location of the experimental site, the ambient temperature, or the degree of hygrometry and the official standard used [54].…”

Section: Limitationsmentioning

confidence: 99%

A Focused Review on the Maximal Exercise Responses in Hypo- and Normobaric Hypoxia: Divergent Oxygen Uptake and Ventilation Responses

Treml

Gatterer

Burtscher³

et al. 2020

IJERPH

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The literature suggests that acute hypobaric (HH) and normobaric (NH) hypoxia exposure elicits different physiological responses. Only limited information is available on whether maximal cardiorespiratory exercise test outcomes, performed on either the treadmill or the cycle ergometer, are affected differently by NH and HH. A focused literature review was performed to identify relevant studies reporting cardiorespiratory responses in well-trained male athletes (individuals with a maximal oxygen uptake, VO2max > 50 mL/min/kg at sea level) to cycling or treadmill running in simulated acute HH or NH. Twenty-one studies were selected. The exercise tests in these studies were performed in HH (n = 90) or NH (n = 151) conditions, on a bicycle ergometer (n = 178) or on a treadmill (n = 63). Altitudes (simulated and terrestrial) varied between 2182 and 5400 m. Analyses (based on weighted group means) revealed that the decline in VO2max per 1000 m gain in altitude was more pronounced in acute NH vs. HH (−7.0 ± 1.4% vs. −5.6 ± 0.9%). Maximal minute ventilation (VEmax) increased in acute HH but decreased in NH with increasing simulated altitude (+1.9 ± 0.9% vs. −1.4 ± 1.8% per 1000 m gain in altitude). Treadmill running in HH caused larger decreases in arterial oxygen saturation and heart rate than ergometer cycling in acute HH, which was not the case in NH. These results indicate distinct differences between maximal cardiorespiratory responses to cycling and treadmill running in acute NH or HH. Such differences should be considered when interpreting exercise test results and/or monitoring athletic training.

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“…In their proposal, Millet and Debevec consider that barometric pressure per se may exert an important influence on physiological responses to hypoxia (Millet & Debevec, 2020). Their argument is based on a number of studies exploring the potential differential effect of normobaric vs. hypobaric hypoxia.…”

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confidence: 99%

Rebuttal from Jean‐Paul Richalet

Richalet

2020

The Journal of Physiology

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CrossTalk proposal: Barometric pressure, independent of , is the forgotten parameter in altitude physiology and mountain medicine

Cited by 64 publications

References 32 publications

Minimal Influence of Hypobaria on Heart Rate Variability in Hypoxia and Normoxia

Minimal Influence of Hypobaria on Heart Rate Variability in Hypoxia and Normoxia

A Focused Review on the Maximal Exercise Responses in Hypo- and Normobaric Hypoxia: Divergent Oxygen Uptake and Ventilation Responses

Rebuttal from Jean‐Paul Richalet

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