CrossTalk opposing view: Barometric pressure, independent of , is not the forgotten parameter in altitude physiology and mountain medicine

Richalet, Jean‐Paul

doi:10.1113/jp279160

Cited by 37 publications

(30 citation statements)

References 17 publications

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“…In conclusion, we concur with Richalet () that prospective studies should ensure proper and exact matching of

P_{{normalO}_{2}}

between the experimental conditions. All reports should thus detail exact methodological approach employed and report all pertinent environmental variables (terrestrial altitude, P B ,

P_{{normalO}_{2}}

and

F_{normalI O_{2}}

where applicable) along with their variability.…”

supporting

confidence: 91%

“…It is a privilege to have this crosstalk debate with our opponent, Prof. Richalet, who provided a comprehensive methodological summary primarily discussing the optimal approach for exact matching of the oxygen partial pressure (

P_{{normalO}_{2}}

) under hypobaric and normobaric conditions (Richalet, 2020). We are pleased that we agree on many points such as the need for an appropriate standardization of

P_{{normalO}_{2}}

(Millet & Debevec, ).…”

mentioning

confidence: 99%

“…Nevertheless, we appreciate that exact standardization of hypoxic stimuli between normobaric and hypobaric conditions is indeed challenging. We also recognize that when modelling a certain normobaric hypoxia level to the corresponding terrestrial altitude one should employ exact

P_{normalI O_{2}}

calculations, detailed by Richalet (), and consider the geographic location (West, ). However, normobaric hypoxic testing sessions are not always performed at sea level and the consequent altitude‐related reduction of barometric pressure ( P B ) should be considered when defining the corresponding hypoxia levels.…”

mentioning

confidence: 99%

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Rebuttal from Grégoire P. Millet and Tadej Debevec

Millet

Debevec

2020

The Journal of Physiology

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“…In conclusion, we concur with Richalet () that prospective studies should ensure proper and exact matching of

P_{{normalO}_{2}}

between the experimental conditions. All reports should thus detail exact methodological approach employed and report all pertinent environmental variables (terrestrial altitude, P B ,

P_{{normalO}_{2}}

and

F_{normalI O_{2}}

where applicable) along with their variability.…”

supporting

confidence: 91%

P_{{normalO}_{2}}

) under hypobaric and normobaric conditions (Richalet, 2020). We are pleased that we agree on many points such as the need for an appropriate standardization of

P_{{normalO}_{2}}

(Millet & Debevec, ).…”

mentioning

confidence: 99%

P_{normalI O_{2}}

mentioning

confidence: 99%

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Rebuttal from Grégoire P. Millet and Tadej Debevec

Millet

Debevec

2020

The Journal of Physiology

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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%

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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“…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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CrossTalk opposing view: Barometric pressure, independent of , is not the forgotten parameter in altitude physiology and mountain medicine

Cited by 37 publications

References 17 publications

Rebuttal from Grégoire P. Millet and Tadej Debevec

Rebuttal from Grégoire P. Millet and Tadej Debevec

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

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