Time course of the human pulmonary vascular response to 8 hours of isocapnic hypoxia

• Published in: The American journal of physiology Vol. 273; no. 3 Pt 2; p. H1126
• Main Authors: Dorrington, K L, Clar, C, Young, J D, Jonas, M, Tansley, J G, Robbins, P A
• Format: Journal Article
• Language: English
• Published: United States 01.09.1997
• Subjects: Adult; Blood Pressure; Carbon Dioxide - blood; Cardiac Output; Diastole; Heart Rate; Hemodynamics; Humans; Hypoxia - physiopathology; Male; Oxygen - blood; Partial Pressure; Pulmonary Alveoli - physiology; Pulmonary Alveoli - physiopathology; Pulmonary Artery - physiology; Pulmonary Artery - physiopathology; Pulmonary Circulation - physiology; Regression Analysis; Stroke Volume; Systole; Time Factors; Vascular Resistance
• ISSN: 0002-9513; 2163-5773
• DOI: 10.1152/ajpheart.1997.273.3.H1126

To examine the hypothesis that the human pulmonary vascular response to hypoxia has a component with a slow time course, we measured pulmonary vascular resistance (PVR) in six healthy adult males during 8 h of isocapnic hypoxia. A balloon-tipped pulmonary artery catheter with thermistor was introduced via a forearm vein and used to derive PVR. The subjects were seated in a chamber in which the oxygen and carbon dioxide concentrations were adjusted to maintain an end-tidal Po2 of 50 Torr and an end-tidal Pco2 equal to the subject's normal prehypoxic value. PVR was measured before and at 0.5-h intervals during 8 h of hypoxia, the following 3 h of isocapnic euoxia (end-tidal Po2 100 Torr), and a subsequent 1-h reexposure to hypoxia. PVR rose from 1.23 +/- 0.26 (SE) Torr-min.1(-1) under euoxia [time (t) = 0] to 1.77 +/- 0.21 Torr.min.1(-1) at t = 0.5 h, reached a maximum at 2 h (2.91 +/- 0.33 Torr.min.1(-1)), and remained fairly constant between 2 and 8 h. Restoration of euoxia at 8 h led to a reduction in PVR with a slow component. Reexposure to hypoxia at 11 h resulted in a greater increase in PVR than at 1 h. Systemic vascular resistance had a similar slow component to its response, falling from 18.6 +/- 1.3 Torr.min.1(-1) at t = 0 to 17.3 +/- 1.4 Torr.min.1(-1) at t = 0.5 h, 14.4 +/- 0.6 Torr.min.1(-1) at t = 4 h, and 13.8 +/- 0.8 Torr.min.1(-1) at t = 8 h. The human pulmonary and systemic vascular responses to hypoxia extend over at least several hours.