INTRODUCTION: Skepticism exists about whether normobaric and hypobaric hypoxic exposures are equivalent. We have evaluated if physiological differences between the two environments would translate into actual differences in hypoxia symptoms. METHODS: We exposed 20 subjects to 5-min 25,000-ft (7620-m) equivalent environments in an altitude chami ber and then in a ground-level portable reduced-oxygen training enclosure (PROTE). Heart rate and hemoglobin oxygen saturation (SaO2) were continuously monitored. Alveolar gas samples were collected at 1, 3, and 4 min elapsed time. Subjects completed hypoxia symptom questionnaires at the same time points. RESULTS: Mean fourth minute alveolar oxygen tension (PaO2), alveolar carbon dioxide tension (PaCO2), and respiratory quotient (RQ) differed significantly between the chamber and PROTE. Declines in SaO2 appeared biphasic, with steepest declines seen in the first minute. Rates of SaO2 decline over the 5-min exposure were significantly different. Heart rate was not different, even when indexed to body surface area. Mean number of hypoxia symptoms between hypobaric and normobaric environments after 1 min were significant. However, the temporal pattern of symptom frequencies across subjects between the chamber and PROTE were similar. CONCLUSIONS: Alveolar gas composition and arterial hemoglobin oxygen desaturation patterns differed between a ground level and hypobaric exposure. Differences in mean number of hypoxia symptoms between hypobaric and normobaric environments after 1 min, but not at 3 and 4 min, coupled with similar patterns in symptom frequencies, suggest that ground-level hypoxia training may be a sufficiently faithful surrogate for altitude chamber training.
INTRODUCTION: Skepticism exists about whether normobaric and hypobaric hypoxic exposures are equivalent. We have evaluated if physiological differences between the two environments would translate into actual differences in hypoxia symptoms. METHODS: We exposed 20 subjects to 5-min 25,000-ft (7620-m) equivalent environments in an altitude chami ber and then in a ground-level portable reduced-oxygen training enclosure (PROTE). Heart rate and hemoglobin oxygen saturation (SaO2) were continuously monitored. Alveolar gas samples were collected at 1, 3, and 4 min elapsed time. Subjects completed hypoxia symptom questionnaires at the same time points. RESULTS: Mean fourth minute alveolar oxygen tension (PaO2), alveolar carbon dioxide tension (PaCO2), and respiratory quotient (RQ) differed significantly between the chamber and PROTE. Declines in SaO2 appeared biphasic, with steepest declines seen in the first minute. Rates of SaO2 decline over the 5-min exposure were significantly different. Heart rate was not different, even when indexed to body surface area. Mean number of hypoxia symptoms between hypobaric and normobaric environments after 1 min were significant. However, the temporal pattern of symptom frequencies across subjects between the chamber and PROTE were similar. CONCLUSIONS: Alveolar gas composition and arterial hemoglobin oxygen desaturation patterns differed between a ground level and hypobaric exposure. Differences in mean number of hypoxia symptoms between hypobaric and normobaric environments after 1 min, but not at 3 and 4 min, coupled with similar patterns in symptom frequencies, suggest that ground-level hypoxia training may be a sufficiently faithful surrogate for altitude chamber training.
Authors: Nikolaus C Netzer; Linda Rausch; Arn H Eliasson; Hannes Gatterer; Matthias Friess; Martin Burtscher; Stephan Pramsohler Journal: Front Physiol Date: 2017-02-13 Impact factor: 4.566
Authors: Jonas J Saugy; Laurent Schmitt; Anna Hauser; Guillaume Constantin; Roberto Cejuela; Raphael Faiss; Jon P Wehrlin; Jérémie Rosset; Neil Robinson; Grégoire P Millet Journal: Front Physiol Date: 2016-04-19 Impact factor: 4.566
Authors: Rafael Timon; Guillermo Olcina; Paulino Padial; Juan Bonitch-Góngora; Ismael Martínez-Guardado; Cristina Benavente; Blanca de la Fuente; Belen Feriche Journal: Int J Environ Res Public Health Date: 2022-03-14 Impact factor: 3.390