Review of: Thompson J, Petrie DA, Ackroyd-Stolarz S: "Out-of-Hospital Continuous Positive Airway Pressure Ventilation Versus Usual Care in Acute Respiratory Failure: A Randomized Controlled Trial." Annals of Emergency Medicine. Sep;52(3):232-41, 24, 1.e1, 2008. Epub 2008 Apr 3.
Paramedics in Halifax, Canada were trained in the use of continuous positive airway pressure (CPAP) ventilation for patients in respiratory distress. They were skilled in drug-facilitated (midazolam) intubation and had a success rate of 96% for cardiac arrest and 90% for non-cardiac arrest intubations.
The criteria for CPAP application was listed in a table. Along with CPAP, the patients were to be provided usual care based on the provider impression. Once the paramedics determined the patient was a candidate for CPAP, they contacted dispatch, which randomly assigned the patient to either receive CPAP plus usual care (CPAP group) or usual care only (control group).
In total, 71 patients were enrolled into the study, with one in each group lost to follow-up after refusing full consent. There were no significant differences in baseline physiologic
parameters, out-of-hospital scene times, or emergency department (ED) diagnosis between groups. In the control group, 17 of 34 (50%) patients were intubated versus seven of 35 (20%) in the CPAP group. Mortality was 12 of 34 (35.3%) in the usual care versus five of 35 (14.3%) in the CPAP group.
They concluded that paramedics can be trained to use CPAP for patients in severe respiratory failure. There was a 30% reduction in tracheal intubation rate and an absolute reduction in mortality of 21% in appropriately selected out-of-hospital patients who received CPAP instead of usual care. Larger, multicenter studies are recommended to confirm this observed benefit seen in this relatively small trial.
This is the first prospective randomized controlled study of the use of prehospital CPAP. The data from this relatively small study is compelling. The 30% reduction in intubation translates to a number needed to treat of three. That is that for every three persons treated with CPAP, you will avoid one intubation. The number needed to reduce mortality is five.
The unique thing this study showed is that the Canadian paramedics were highly accurate in their prehospital diagnosis. The prehospital diagnosis and ED diagnosis of the underlying cause agreed 98% of the time. This was unlike the Hubble study, where the medics were incorrect by confusing congestive heart failure (CHF) with chronic obstructive pulmonary disorder (COPD) half the time. Regardless of their misdiagnosis the CPAP showed improved morbidity and decreased mortality. However, I envy the diagnostic accuracy of the Halifax paramedics, because they were better able to administer additional usual care in addition to CPAP.
With the publication of this study, I will officially go on the record saying, "CPAP is the prehospital standard of care for patients in respiratory distress."