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Am J Respir Crit Care Med. 2005 Jan 1;171(1):83-7. Epub 2004 Oct 14.

Pulmonary blood flow heterogeneity during hypoxia and high-altitude pulmonary edema.

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Department of Medicine, Division of Physiology 0623A, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.


Uneven hypoxic pulmonary vasoconstriction has been proposed to expose parts of the pulmonary capillary bed to high pressure and vascular injury in high-altitude pulmonary edema (HAPE). We hypothesized that subjects with a history of HAPE would demonstrate increased heterogeneity of pulmonary blood flow during hypoxia. A functional magnetic resonance imaging technique (arterial spin labeling) was used to quantify spatial pulmonary blood flow heterogeneity in three subject groups: (1) HAPE-susceptible (n = 5), individuals with a history of physician-documented HAPE; (2) HAPE-resistant (n = 6), individuals with repeated high-altitude exposure without illness; and (3) unselected (n = 6), individuals with a minimal history of altitude exposure. Data were collected in normoxia and after 5, 10, 20, and 30 minutes of normobaric hypoxia FI(O(2)) = 0.125. Relative dispersion (SD/mean) of the signal intensity was used as an index of perfusion heterogeneity. Oxygen saturation was not different between groups during hypoxia. Relative dispersion was not different between groups (HAPE-susceptible 0.94 +/- 0.05, HAPE-resistant 0.94 +/- 0.05, unselected 0.87 +/- 0.06; means +/- SEM) during normoxia, but it was increased by hypoxia in HAPE-susceptible (to 1.10 +/- 0.05 after 30 minutes, p < 0.0001) but not in HAPE-resistant (0.91 +/- 0.05) or unselected subjects (0.87 +/- 0.05). HAPE-susceptible individuals have increased pulmonary blood flow heterogeneity in acute hypoxia, consistent with uneven hypoxic pulmonary vasoconstriction.

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