Frequent subclinical high-altitude pulmonary edema detected by chest sonography as ultrasound lung comets in recreational climbers

Abstract

The ultrasound lung comets detected by chest sonography are a simple, noninvasive, semiquantitative sign of increased extravascular lung water. The aim of this study was to evaluate, by chest sonography, the incidence of interstitial pulmonary edema in recreational high-altitude climbers. Observational study. Eighteen healthy subjects (mean age 45 +/- 10 yrs, ten males) participating in a high-altitude trek in Nepal. Chest and cardiac sonography at sea level and at different altitudes during ascent. Ultrasound lung comets were evaluated on anterior chest at 28 predefined scanning sites. At individual patient analysis, ultrasound lung comets during ascent appeared in 15 of 18 subjects (83%) at 3440 m above sea level and in 18 of 18 subjects (100%) at 4790 m above sea level in the presence of normal left and right ventricular function and pulmonary artery systolic pressure rise (sea level = 24 +/- 5 mm Hg vs. peak ascent = 42 +/- 11 mm Hg, p < .001). Ultrasound lung comets were absent at baseline (day 2, altitude 1350 m, 1.06 +/- 1.3), increased progressively during the ascent (day 14, altitude 5130 m: 16.5 +/- 8; p < .001 vs. previous steps), and decreased at descent (day 20, altitude 1355 m: 2.9 +/- 1.7; p = nonsignificant vs. baseline). An ultrasound lung comet score showed a negative correlation with O(2) saturation (R = -.7; p < .0001). In recreational climbers, chest sonography revealed a high prevalence of clinically silent interstitial pulmonary edema mirrored by decreased O(2) saturation, whereas no statistically significant relationship with pulmonary artery systolic pressure was observed during ascent.