title: Determinants of ventilation and pulmonary artery pressure during early acclimatization to hypoxia in humans.
abstract: Pulmonary ventilation and pulmonary arterial pressure both rise progressively during the first few hours of human acclimatization to hypoxia. These responses are highly variable between individuals, but the origin of this variability is unknown. Here, we sought to determine whether the variabilities between different measures of response to sustained hypoxia were related, which would suggest a common source of variability. Eighty volunteers individually underwent an 8-h isocapnic exposure to hypoxia (end-tidal P(O2)=55 Torr) in a purpose-built chamber. Measurements of ventilation and pulmonary artery systolic pressure (PASP) assessed by Doppler echocardiography were made during the exposure. Before and after the exposure, measurements were made of the ventilatory sensitivities to acute isocapnic hypoxia (G(pO2)) and hyperoxic hypercapnia, the latter divided into peripheral (G(pCO2)) and central (G(cCO2)) components. Substantial acclimatization was observed in both ventilation and PASP, the latter being 40% greater in women than men. No correlation was found between the magnitudes of pulmonary ventilatory and pulmonary vascular responses. For G(pO2), G(pCO2) and G(cC O2), but not the sensitivity of PASP to acute hypoxia, the magnitude of the increase during acclimatization was proportional to the pre-acclimatization value. Additionally, the change in G(pO2) during acclimatization to hypoxia correlated well with most other measures of ventilatory acclimatization. Of the initial measurements prior to sustained hypoxia, only G(pCO2) predicted the subsequent rise in ventilation and change in G(pO2) during acclimatization. We conclude that the magnitudes of the ventilatory and pulmonary vascular responses to sustained hypoxia are predominantly determined by different factors and that the initial G(pCO2) is a modest predictor of ventilatory acclimatization.
authors.affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK.
authors.forename: Marzieh
authors.initials: M
authors.lastname: Fatemian
authors.affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK.
authors.forename: Mari
authors.initials: M
authors.lastname: Herigstad
authors.affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK.
authors.forename: Quentin P P
authors.initials: QP
authors.lastname: Croft
authors.affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK.
authors.forename: Federico
authors.initials: F
authors.lastname: Formenti
authors.affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK.
authors.forename: Rosa
authors.initials: R
authors.lastname: Cardenas
authors.affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK.
authors.forename: Carly
authors.initials: C
authors.lastname: Wheeler
authors.affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK.
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Smith
authors.affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK.
authors.forename: Maria
authors.initials: M
authors.lastname: Friedmannova
authors.affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK.
authors.forename: Keith L
authors.initials: KL
authors.lastname: Dorrington
authors.affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Robbins
mesh_terms: D000064:Acclimatization; D000293:Adolescent; D000328:Adult; D000531:Altitude; D001794:Blood Pressure; D002245:Carbon Dioxide / Q000378:metabolism; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism; D011651:Pulmonary Artery / Q000502:physiology*; D012123:Pulmonary Ventilation
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen