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Acute cardiogenic pulmonary oedema (ACPO) is a relatively common cause for emergency presentation with acute dyspnoea. Current standard therapy involves treatment with oxygen and nitrates, and possibly diuretics or inotropic support.

Continuous positive airway pressure (CPAP) and non invasive ventilation (NIV) are two techniques used to provide respiratory support for patients with ACPO. Oxygen-enriched air is provided via a tight-fitting mask and ventilation assisted by either continuous pressure (CPAP) or pressure that varies with respiration (NIV).

A number of small randomised controlled trials have been carried out in patients with ACPO, predominantly using CPAP. These have shown reduced need for endotracheal intubation in patients receiving CPAP and non-significant trends towards reduced mortality. Despite theoretical advantages for NIV, one small study has shown an increased risk of myocardial infarction. A large trial is now required to determine whether CPAP or NIV produce meaningful improvements for patients with ACPO and, if so, whether the theoretical advantages of NIV produce genuine improvements in outcome. The 3CPO Trial is a multicentre, randomised controlled trial of CPAP versus NIV versus standard therapy for patients presenting to the emergency department with ACPO. Patients will be recruited from fifteen hospital around the United Kingdom and randomised in equal numbers to CPAP, NIV or standard therapy. Research staff will follow patients up in hospital and by postal questionnaire at one month, three months and six months.

The primary outcome will be survival to seven days. Secondary outcomes include: intubation rate, myocardial infarction, treatment failure, breathlessness, patient satisfaction, and health utility (EQ-5D). An economic evaluation will measure health and social care costs and quality-adjusted life-years (QALYs) gained to estimate the incremental cost per QALY gained of each intervention compared to the next most effective.

It is planned that 1200 patients will be recruited over two years. As a result of this study we will be able to determine whether CPAP and/or NIV should become standard therapy for patients presenting with ACPO in the National Health Service.