Swimming-Induced Pulmonary Edema: Pathophysiology and Risk Reduction With Sildenafil

Abstract

Background: Swimming-induced pulmonary edema (SIPE) occurs during swimming or scuba diving, often in young individuals with no predisposing conditions, and its pathophysiology is poorly understood. This study tested the hypothesis that pulmonary artery and pulmonary artery wedge pressures are higher in SIPE-susceptible individuals during submerged exercise than in the general population and are reduced by sildenafil.

Methods and results: Ten study subjects with a history of SIPE (mean age, 41.6 years) and 20 control subjects (mean age, 36.2 years) were instrumented with radial artery and pulmonary artery catheters and performed moderate cycle ergometer exercise for 6 to 7 minutes while submersed in 20°C water. SIPE-susceptible subjects repeated the exercise 150 minutes after oral administration of 50 mg sildenafil. Work rate and mean arterial pressure during exercise were similar in controls and SIPE-susceptible subjects. Average o2 and cardiac output in controls and SIPE-susceptible subjects were: o2 2.42 L·min(-1) versus 1.95 L·min(-1), P=0.2; and cardiac output 17.9 L·min(-1) versus 13.8 L·min(-1), P=0.01. Accounting for differences in cardiac output between groups, mean pulmonary artery pressure at cardiac output=13.8 L·min(-1) was 22.5 mm Hg in controls versus 34.0 mm Hg in SIPE-susceptible subjects (P=0.004), and the corresponding pulmonary artery wedge pressure was 11.0 mm Hg versus 18.8 mm Hg (P=0.028). After sildenafil, there were no statistically significant differences in mean pulmonary artery pressure or pulmonary artery wedge pressure between SIPE-susceptible subjects and controls.

Conclusions: These observations confirm that SIPE is a form of hemodynamic pulmonary edema. The reduction in pulmonary vascular pressures after sildenafil with no adverse effect on exercise hemodynamics suggests that it may be useful in SIPE prevention.

Clinical trial registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00815646.

Keywords: diving; hemodynamics; immersion; pulmonary circulation; pulmonary edema; swimming.

© 2016 American Heart Association, Inc.

Figures

Figure 1

Mean PAP and PAWP vs cardiac output. Control subjects were studied at rest and during exercise, while SIPE-susceptible subjects were studied only during exercise. Accounting for differences in cardiac output, mean PAP and PAWP were significantly higher in the SIPE-susceptible group compared to controls (P=0.004 and P=0.028, respectively). After sildenafil, mean PAP was significantly reduced (P=0.025). During the post-sildenafil exercise, neither mean PAP nor PAWP was significantly different from controls. PAP, pulmonary artery pressure; PAWP, pulmonary artery wedge pressure.