title: VESTPD as a measure of ventilatory acclimatization to hypobaric hypoxia.
abstract: This study compared the ventilation response to an incremental ergometer exercise at two altitudes: 633 mmHg (resident altitude = 1,600 m) and following acute decompression to 455 mmHg (≈4,350 m altitude) in eight male cyclists and runners. At 455 mmHg, the VESTPD at RER <1.0 was significantly lower and the VEBTPS was higher because of higher breathing frequency; at VO2max, both VESTPD and VEBTPS were not significantly different. As percent of VO2max, the VEBTPS was nearly identical and VESTPD was 30% lower throughout the exercise at 455 mmHg. The lower VESTPD at lower pressure differs from two classical studies of acclimatized subjects (Silver Hut and OEII), where VESTPD at submaximal workloads was maintained or increased above that at sea level. The lower VESTPD at 455 mmHg in unacclimatized subjects at submaximal workloads results from acute respiratory alkalosis due to the initial fall in HbO2(≈0.17 pHa units), reduction in PACO2(≈5 mmHg) and higher PAO2throughout the exercise, which are partially pre-established during acclimatization. Regression equations from these studies predict VESTPD from VO2and PBin unacclimatized and acclimatized subjects. The attainment of ventilatory acclimatization to altitude can be estimated from the measured vs. predicted difference in VESTPD at low workloads after arrival at altitude.
authors.affiliation: 1 Research Section: VA Medical Center , Albuquerque, NM, USA (retired) and Adjunct Faculty: Department of Health, Exercise and Sports Sciences, The University of New Mexico , Albuquerque, NM, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Loeppky
authors.affiliation: 2 School of Kinesiology and Nutritional Science, California State University , Los Angeles, CA, USA.
authors.forename: A C
authors.initials: AC
authors.lastname: Sheard
authors.affiliation: 3 Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine , Natick, MA, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Salgado
authors.affiliation: 4 Department of Health, Exercise and Sports Sciences, The University of New Mexico , Albuquerque, NM, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Mermier
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000328:Adult; D000472:Alkalosis, Respiratory / Q000503:physiopathology; D000531:Altitude; D001274:Atmospheric Pressure; D015415:Biomarkers; D015444:Exercise / Q000502:physiology; D018869:Heat-Shock Response / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D000072277:Maximal Respiratory Pressures; D012123:Pulmonary Ventilation / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology; D055815:Young Adult
chemical_list: D015415:Biomarkers
keywords: Haldane effect; acclimatization; acid–base balance; breathing frequency; hyperventilation; hypobaric hypoxia; hypocapnia; tidal volume