The Relationship Between Hypoxic Pulmonary Vasoconstriction (HPV) (Vertical Axis) and Time in Hours (H) (Horizontal Axis) in Humans Exposed to Isocapnic Hypoxia (Approximate Inspired Po2 60 Mmhg), Beginning at 0h With a Return to Normoxia at 8h HPV Response Was Measured As the Increase in Echocardiographic Right Ventricular Systolic Pressure. Note the Two-Phase, Rapid and Slow, Onset of HPV. Also Note that after Prolonged HPV, the Pulmonary Pressures Do Not Return to Baseline for Several Hours.

(Based on data from Talbot NP, Balanos GM, Dorrington KL, et al. Two temporal components within the human pulmonary vascular response to 2 h of isocapnic hypoxia. J Appl Physiol. 2005;98:1125-1139.)

The relationship between hypoxic pulmonary vasoconstriction (HPV) (vertical axis) and time in hours (h) (horizontal axis) in humans exposed to isocapnic hypoxia (approximate inspired PO2 60 mmHg), beginning at 0h with a return to normoxia at 8h. HPV response was measured as the increase in echocardiographic right ventricular systolic pressure. Note the two-phase, rapid and slow, onset of HPV. Also note that after prolonged HPV, the pulmonary pressures do not return to baseline for several hours.