title: Pulmonary capillary blood volume and membrane conductance in Andeans and lowlanders at high altitude: a cross-sectional study.
abstract: Lung carbon monoxide (CO) transfer and pulmonary capillary blood volume (Vc) at high altitudes have been reported as being higher in native highlanders compared to acclimatised lowlanders but large discrepancies appears between the studies. This finding raises the question of whether hypoxia induces pulmonary angiogenesis. Eighteen highlanders living in Bolivia and 16 European lowlander volunteers were studied. The latter were studied both at sea level and after acclimatisation to high altitude. Membrane conductance (Dm(CO)) and Vc, corrected for the haemoglobin concentration (Vc(cor)), were calculated using the NO/CO transfer technique. Pulmonary arterial pressure and left atrial pressures were estimated using echocardiography. Highlanders exhibited significantly higher NO and CO transfer than acclimatised lowlanders, with Vc(cor)/VA and Dm(CO)/VA being 49 and 17% greater (VA: alveolar volume) in highlanders, respectively. In acclimatised lowlanders, Dm(CO) and Dm(CO)/VA values were lower at high altitudes than at sea level. Echocardiographic estimates of cardiac output and pulmonary arterial pressure were significantly elevated at high altitudes as compared to sea level. The decrease in Dm(CO) in lowlanders might be due to altered gas transport in the airways due to the low density of air at high altitudes. The disproportionate increase in Vc in Andeans compared to the change in Dm(CO) suggests that the recruitment of capillaries is associated with a thickening of the blood capillary sheet. Since there was no correlation between the increase in Vc and the slight alterations in haemodynamics, this data suggests that chronic hypoxia might stimulate pulmonary angiogenesis in Andeans who live at high altitudes.
authors.affiliation: Laboratory of Physiologic Adaptations to Physical Activities, Poitiers University, UPRES EA 3813, 4 Allée Jean Monnet, 86000 Poitiers, France. Claire.de-Bisschop@mshs.univ-poitiers.fr
authors.forename: Claire
authors.initials: C
authors.lastname: de Bisschop
authors.forename: Laurent
authors.initials: L
authors.lastname: Kiger
authors.forename: Michael C
authors.initials: MC
authors.lastname: Marden
authors.forename: Alfredo
authors.initials: A
authors.lastname: Ajata
authors.forename: Sandrine
authors.initials: S
authors.lastname: Huez
authors.forename: Vitalie
authors.initials: V
authors.lastname: Faoro
authors.forename: Jean-Benoit
authors.initials: JB
authors.lastname: Martinot
authors.forename: Robert
authors.initials: R
authors.lastname: Naeije
authors.forename: Hervé
authors.initials: H
authors.lastname: Guénard
mesh_terms: D000328:Adult; D000531:Altitude; D000532:Altitude Sickness / Q000378:metabolism / Q000503:physiopathology; D001810:Blood Volume; D001838:Bolivia; D002196:Capillaries / Q000503:physiopathology*; D002462:Cell Membrane / Q000378:metabolism; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D008168:Lung / Q000098:blood supply / Q000503:physiopathology*; D008297:Male; D011653:Pulmonary Diffusing Capacity; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity