Heterogeneous nature of hypoxic pulmonary vasoconstriction in humans, demonstrated with contrast-enhanced magnetic resonance imaging in a healthy subject (A) who is supine and breathing 12% oxygen (Sao2 73–77%). The colors indicate peak signal intensity (PSI) after intravenous injection of magnetic resonance contrast and represent perfusion of parenchymal lung tissue from 0 (black) to maximal (white). Heterogeneity of pulmonary blood flow is quantified as the coefficient of variation of the peak signal intensity (B) which increases more in subjects susceptible to high-altitude pulmonary edema (HAPE-S). Sao2 = arterial oxygen saturation. Reprinted, with permission of the American Thoracic Society. Copyright © 2014 American Thoracic Society. Dehnert C et al. Magnetic resonance imaging of uneven pulmonary perfusion in hypoxia in humans. Am J Respir Crit Care Med 2006; 174:1132–8. Official Journal of the American Thoracic Society.
