Swimming-Induced Pulmonary Edema: Pathophysiology and Risk Reduction With Sildenafil
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 compared to 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 6-7 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-susceptibles. Average VO2 and cardiac output (CO) in SIPE-susceptibles and controls were: VO2 2.42 L.min-1 vs. 1.95 L.min-1, P=0.2; CO 17.9 L.min-1 vs. 13.8 L.min-1, P=0.01). Accounting for differences in CO between groups, mean pulmonary artery pressure (MPAP) at CO=13.8 L.min-1 was 22.5 mmHg in controls vs. 34.0 mmHg in SIPE-susceptibles (P=0.004) and the corresponding pulmonary artery wedge pressure (PAWP) 11.0 mmHg vs. 18.8 mmHg (P=0.028). After sildenafil, there were no statistically significant differences in MPAP or PAWP between SIPE-susceptibles 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 Information—ClinicalTrials.gov. Identifier: NCT00815646.
- Received September 11, 2015.
- Revision received January 7, 2016.
- Accepted January 15, 2016.