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

Objective: 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. Design: Observational study. Subjects: Eighteen healthy subjects (mean age 45 +/- 10 yrs, ten males) participating in a high-altitude trek in Nepal. Interventions: 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. Measurements and Main Results: 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). Conclusions: 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. (Crit Care Med 2010; 38:1818-1823)