Immersion Pulmonary Oedema

Immersion pulmonary oedema is acute non-cardiogenic-appearing pulmonary oedema that develops during swimming, snorkelling or scuba diving, and resolves within 24 to 48 hours of leaving the water. It is also called swimming induced pulmonary oedema.

Epidemiology. It affects a minority of open water swimmers, divers and military trainees, with women and older participants affected more often. Recurrence is common, at about 20 to 30% on re-exposure.

Risk factors. Cold water, exertion, over hydration before the event, tight wetsuits, high intensity swimming, hypertension, left ventricular hypertrophy, cardiomyopathy and valvular disease (mitral and aortic), and use of non-steroidal drugs.

Pathophysiology. Immersion shifts blood from the periphery to the chest, cold causes vasoconstriction and raised afterload, and exertion increases cardiac output. Together these raise pulmonary capillary pressure, resulting in stress failure of the alveolar capillary membrane and leakage of fluid and red cells. Negative pressure from breathing through a snorkel or regulator adds.

Presentation is breathlessness out of proportion to effort, cough, frothy or blood tinged sputum, chest tightness, crackles and hypoxia, starting in the water. Symptoms are often mild to moderate, but severe cases cause respiratory failure and drowning.

Red flags.

• Haemoptysis, hypoxia or chest pain.
• Loss of consciousness or arrhythmia.
• Failure to improve within 24 hours.

Clinical diagnosis from the history. Chest radiograph (bilateral perihilar opacities, normalising in 24 to 48 hours), ECG, troponin and natriuretic peptide (usually normal or mildly raised), arterial gas and echocardiography for structural heart disease. Do stress testing, cardiac MRI or coronary evaluation in those with recurrent episodes or risk factors.

Differential diagnosis. Cardiogenic pulmonary oedema, aspiration, pulmonary embolism, decompression illness, pneumonia, negative pressure oedema and barotrauma.

Immediate. Leave the water at once and sit upright. Give oxygen to keep saturation over 94%. Keep warm.

Respiratory support. CPAP at 5 to 10 cmH2O or high flow oxygen for hypoxia. Intubation is rarely needed.

Medicines. Furosemide 20 to 40 mg IV may be given when there is volume overload, with caution since the condition is not caused by total volume excess and diuresis may cause hypovolaemia. Salbutamol 2.5 to 5 mg nebulised may relieve wheeze.

Investigate and prevent. Assess for cardiac disease and hypertension. Advise slower pace, avoiding over hydration, wearing a looser wetsuit, avoiding non-steroidal drugs before exertion, and stopping at first symptoms. Treat hypertension. No preventive drug has proven value.

Return to water. Not for at least 1 to 4 weeks after full recovery and a normal cardiac assessment, and repeated episodes should lead to a decision to stop diving or open water swimming.

Monitoring. Oxygen saturation, respiratory rate and repeat radiograph.

Referral and escalation. Cardiology for recurrence, structural disease or abnormal tests, and diving medicine specialists for divers.

Special groups. In divers, take a dive history and exclude decompression illness. In older adults, exclude coronary disease.