title: Pulmonary capillary recruitment in response to hypoxia in healthy humans: a possible role for hypoxic pulmonary venoconstriction?
abstract: We examined mechanisms by which hypoxia may elicit pulmonary capillary recruitment in humans. On separate occasions, twenty-five healthy adults underwent exposure to intravenous saline infusion (30 ml/kg ∼ 15 min) or 17-h normobaric hypoxia ( [FIO2 = 12.5%). Cardiac output (Q) and pulmonary capillary blood volume (Vc) were measured before and after saline infusion and hypoxic-exposure by a rebreathing method. Pulmonary artery systolic pressure (sPpa) and left ventricular (LV) diastolic function were assessed before and after hypoxic-exposure via echocardiography. Saline infusion increased Q and Vc (P < 0.05) with no change in Vc/Q (P = 0.97). Hypoxic-exposure increased Vc (P < 0.01) despite no change in Q (P = 0.25), increased sPpa (P < 0.01), and impaired LV relaxation. Multiple regression suggested that ∼ 37% of the hypoxia-mediated increase in Vc was attributable to alterations in Q, sPpa and LV diastolic function. In conclusion, hypoxia-induced pulmonary capillary recruitment in humans is only partly accounted for by changes in Q, sPpa and LV diastolic function. We speculate that hypoxic pulmonary venoconstriction may play a role in such recruitment.
authors.affiliation: Division of Cardiovascular Diseases, Department of Internal Medicine, Mayo Clinic & Foundation, Rochester, MN 55902, USA. taylor.bryan@mayo.edu
authors.forename: Bryan J
authors.initials: BJ
authors.lastname: Taylor
authors.forename: Jesper
authors.initials: J
authors.lastname: Kjaergaard
authors.forename: Eric M
authors.initials: EM
authors.lastname: Snyder
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Olson
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Johnson
mesh_terms: D000328:Adult; D002196:Capillaries / Q000502:physiology; D004452:Echocardiography; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008168:Lung / Q000098:blood supply* / Q000502:physiology; D008297:Male; D008875:Middle Aged; D012129:Respiratory Function Tests; D014661:Vasoconstriction / Q000502:physiology; D055815:Young Adult