Prospective Assessment of Swimming-Induced Pulmonary Edema in Open-Water Athletes at Moderate Elevations: Incidence and Diagnostic Utility of Point-of-Care Ultrasound

Abstract

Background

Swimming-induced pulmonary edema (SIPE) is an acute condition affecting otherwise healthy athletes during immersion. Although incidence has been studied at sea level and low elevations, little is known about SIPE at moderate elevations.

Methods

A prospective cross-sectional study was conducted among 7866 endurance athletes competing in half-ironman triathlons (St George, Utah, 771 m; Boulder, Colorado, 1665 m) and open-water swims. Symptomatic and asymptomatic athletes presenting to the medical tent underwent structured questionnaires, cardiopulmonary exams, and handheld lung ultrasound (LUS) using an adapted BLUE protocol. SIPE was defined by ≥3 B lines in >1 lung field.

Results

Of 144 athletes enrolled, 29 (0.37%) demonstrated LUS-confirmed SIPE. Female incidence (0.68%) was consistent with sea-level data, whereas male incidence (0.26%) was significantly higher than previously reported at 250 m (0.09%; P<.001). Nontraditional symptoms, including anxiety, tachycardia, and wetsuit tightness, were associated with several positive cases. Mean SpO₂ was significantly lower among LUS-positive athletes (93.8 vs 95.5%; P=0.01). Receiver operating characteristic analysis suggested a revised diagnostic threshold of ≤93% at altitude (area under the curve 0.77) compared with the standard ≤95% used at sea level. Crackles were infrequent and demonstrated low sensitivity (67%) but moderate specificity (86%).

Conclusions

SIPE incidence at moderate elevation is comparable overall to sea level but significantly higher in male athletes. Standard SpO₂ diagnostic cutoffs may overestimate SIPE at altitude; ≤93% improves accuracy. Handheld LUS is feasible in endurance race settings and should be integrated into event medical protocols.