Both continuous positive airway pressure (CPAP) and noninvasive intermittent positive-pressure ventilation (NIPPV) yield earlier resolution of dyspnea, respiratory distress, and metabolic abnormalities than does standard oxygen therapy in patients hospitalized with acute cardiogenic pulmonary edema, according to a report.
However, those treatments did not affect short-term mortality, the primary objective of the Cardiogenic Pulmonary Oedema (3CPO) trial.
Nonetheless, because of the clinical improvements, “We recommend that CPAP or NIPPV be considered as adjunctive therapy in patients with acute cardiogenic pulmonary edema who have severe respiratory distress or whose condition does not improve with pharmacologic therapy,” said Dr. Alasdair Gray of the Royal Infirmary of Edinburgh and his associates.
CPAP maintains the same positive airway pressure support throughout the respiratory cycle; NIPPV raises airway pressure more during inspiration than expiration. Both methods, which deliver oxygen through a face mask, have shown benefit in case series or small trials that have been conducted primarily at single centers. “Therefore, it is uncertain whether these results are either generalizable or robust,” Dr. Gray and his colleagues noted.
3CPO was a large, randomized, controlled trial in 26 emergency departments throughout the United Kingdom that compared the two techniques against standard oxygen therapy and against each other. A total of 367 patients were randomly assigned to standard oxygen therapy, 346 to CPAP, and 356 to NIPPV.
The mean patient age was 78 years, and subjects had marked tachycardia, tachypnea, hypertension, acidosis, and hypercapnia.
Both CPAP and NIPPV yielded greater reductions in dyspnea, heart rate, acidosis, and hypercapnia than did standard oxygen therapy, and the two methods performed similarly, the investigators said (N. Engl. J. Med. 2008;359:142-51).
Standard oxygen therapy was associated with a greater rate of failure due to respiratory distress, while both CPAP and NIPPV were associated with higher rates of noncompletion due to patient discomfort.
There were similar rates of tracheal intubation, admission to the critical care unit, and myocardial infarction among the three groups.
Unfortunately, there were no significant differences among the three groups in the primary end point of 7-day mortality, which was 9.5% with CPAP and NIPPV and 9.8% with standard oxygen therapy. The rates of 30-day mortality also were not significantly different (16.4% with CPAP and NIPPV vs 15.2% with oxygen).
Thus, early improvements in symptoms and surrogate measures of disease severity did not translate into improved short-term or long-term mortality for the two new techniques.
Previous trials have indicated that the physiologic improvements seen with noninvasive ventilation caused a reduced use of tracheal intubation, but this benefit was not observed in this study, Dr. Gray and his associates said.