Stress Doppler echocardiography for identification of susceptibility to high altitude pulmonary edema

Abstract

OBJECTIVEThis prospective single-blinded study was performed to quantitate noninvasive pulmonary artery systolic pressure (PASP) responses to prolonged acute hypoxia and normoxic exercise.BACKGROUNDHypoxia-induced excessive rise in pulmonary artery pressure is a key factor in high-altitude pulmonary edema (HAPE). We hypothesized that subjects susceptible to HAPE (HAPE-S) have increased pulmonary artery pressure response not only to hypoxia but also to exercise.METHODSPASP was estimated at 45, 90 and 240 min of hypoxia (Fi02=12%) and during supine bicycle exercise in normoxia using Doppler-echocardiography in nine HAPE-S and in 11 control subjects.RESULTSIn the control group, mean PASP increased from 26 ± 2 to 37 ± 4 mm Hg (ΔPASP 10.3 ± 2 mm Hg) after 90 min of hypoxia and from 27 ± 4 to 36 ± 3 mm Hg (ΔPASP 8 ± 2 mm Hg) during exercise. In contrast, all HAPE-S subjects revealed significantly greater increases (p = 0.002 vs. controls) in mean PASP both during hypoxia (from 28 ± 4 to 57 ± 10 mm Hg, ΔPASP 28.7 ± 6 mm Hg) and during exercise (from 28 ± 4 to 55 ± 11 mm Hg, ΔPASP 27 ± 8 mm Hg) than did control subjects. Stress echocardiography allowed discrimination between groups without overlap using a cut off PASP value of 45 mm Hg at work rates less than 150 W.CONCLUSIONSThese data indicate that HAPE-S subjects may have abnormal pulmonary vascular responses not only to hypoxia but also to supine bicycle exercise under normoxic conditions. Thus, Doppler echocardiography during supine bicycle exercise or after 90 min of hypoxia may be useful noninvasive screening methods to identify subjects susceptible to HAPE.