SWIMMING INDUCED PULMONARY EDEMA (SIPE)

Most commonly presents in individuals conducting sustained strenuous surface swimming in cold water (e.g., Marine combat swimmers, special operators, scuba divers, and triathletes).26,27 Studies have shown a variable incidence of SIPE among different populations. Symptom severity can range from full recovery within 24 hours to death.28-33 While severe outcomes are possible, most otherwise healthy individuals will recover within 24-48 hours. Recurrence of SIPE is not uncommon.34

RISK FACTORS

- Pre-existing cardiovascular disease
- Female sex
- Prior history of SIPE
- Overhydration
- Prone horizontal position during swimming
- Tight-fitting wetsuits
- Concurrent respiratory infection.35-40

DIAGNOSTIC CRITERIA

During or immediately after exertional water immersion/swimming:

- Dyspnea or cough
- Hypoxemia
- +/- Frank hemoptysis or expectoration of pink-frothy sputum
- Findings on chest radiograph suggestive of pulmonary edema. These include air space opacification, perifissural thickening, increased septal and interstitial lines, widened azygos vein diameter, and enlarged cardiac silhouette. Findings typically resolve within 48 hours.36
- The presence of B-line artifacts on ultrasound may assist in the diagnosis of SIPE when chest x-ray capabilities are unavailable. 37
- Pulmonary infection or water aspiration is considered less likely to be the underlying causes of clinical presentation.

PATHOPHYSIOLOGY

Incompletely understood and thought to be due to:

- Peripheral vasoconstriction in the setting of exertional water immersion leads to shunting of blood from the periphery to the central venous system. This engorges central veins and leads to an increase in cardiac preload and pulmonary artery pressures. Increased pressure in the pulmonary vessels results in ‘fracturing’ of pulmonary capillaries that lead to interstitial and alveolar edema.
- Diastolic dysfunction and stroke volume mismatch between the left and right ventricles may contribute to SIPE pathophysiology. 38

Management:

- Typically, self-limiting and resolves with rest within 24-48 hours.39
- Diuretics, → , ß 2-agonists, and supplemental oxygen may be given for persistent SIPE-related symptoms or severe cases of SIPE.40
- CPAP and PEP device have proved feasible and safe for pre-hospital treatment of SIPE. 39