Interstitial Pulmonary Edema Assessed by Lung Ultrasound on Ascent to High Altitude and Slight Association with Acute Mountain Sickness: A Prospective Observational Study.

Background: Acute mountain sickness (AMS) is a common disease that may have a pulmonary component, as suggested by interstitial pulmonary edema quantified by the B-line score (BLS) on ultrasound (US). This subclinical pulmonary edema has been shown to increase with ascent to high altitude and AMS severity, but has not been prospectively associated with AMS incidence in a large prospective study. Materials and Methods: This prospective observational study was part of a randomized controlled trial enrolling healthy adults over four weekends ascending White Mountain, California. Subjects were assessed by lung US and the Lake Louise Questionnaire at 4110 ft (1240 m), upon ascent to 12,500 ft (3810 m), and the next morning at 12,500 ft (3810 m). Results: Three hundred five USs in total were completed on 103 participants, with 73% total incidence of AMS. The mean (±standard deviation) BLS increased from baseline (1.15 ± 1.80) to high altitude (2.56 ± 2.86), a difference of 1.37 (±2.48) (p = 0.04). Overall BLS was found, on average, to be higher among those diagnosed with AMS than without (2.97 vs. 2.0, p = 0.04, 95% confidence interval [CI] -∞ to -0.04). The change in BLS (ΔBLS) from low altitude baseline was significantly associated with AMS (0.88 vs. 1.72, r² = 0.023, 95% CI -∞ to -0.01, p = 0.048). Conclusions: Interstitial subclinical pulmonary edema by lung US was found to have a small but significant association with AMS.