Review of: Michael H, Michael R, Roger J, et al: “Effectiveness of prehospital continuous positive airway pressure in the management of acute pulmonary edema.” Prehospital Emergency Care. 10(4):430-439, 2006
The Science
This non-randomized control group study compared the outcomes of patients in respiratory distress from presumed pulmonary edema treated by two county-based ALS EMS systems in North Carolina. One service (control group) treated the patients with furosemide, morphine, and nitroglycerin (standard therapy) and the other service (treatment group) provided non-invasive continuous positive airway pressure (CPAP) in conjunction with standard therapy. The primary outcomes were intubation rates, mortality, and the length of stay in the hospital.
Of the 215 patients enrolled, 55.8% received CPAP. From the control group, 25.26% required intubation, compared to only 8.92% from the treatment group. The percentage of patients intubated in the field was 7.36% for the control group and 4.2% for the treatment group. The overall mortality rate was 5.35% in the CPAP group, which was significantly lower than the 23.15% rate observed in the control group (p=0.000). While length of stay was on average two days shorter for the treatment group, the difference did not meet statistical significance due to low patient numbers.
The Street
This study is consistent with a growing body of research that supports the use of CPAP for respiratory distress. While this study was designed to specifically address the value of CPAP for the treatment of acute pulmonary edema, further investigation by the authors discovered that almost 25% did not have acute pulmonary edema as their final hospital diagnosis. The most common underlying conditions misdiagnosed by EMS as pulmonary edema were COPD and pneumonia. We have all been misled by our assessment and heard rales, when in fact the patient had crackles, wheezes, and rhonchi.
Another interesting thing in this study is that the CPAP patients appear to have been sicker as demonstrated by higher respiratory rates, blood pressures, and subjective complaints of dsypnea. Another difference between the two groups was that the control group was significantly more likely to receive furosemide and morphine, while the CPAP group received significantly greater doses of nitro.
Despite these dissimilarities and the inclusion of CPAP use in patients not in acute pulmonary edema, the CPAP patients still did better in all three outcomes compared to standard therapy.
Though not statistically significant due to low numbers, the patients in the control group who were placed on CPAP after hospitalization also had a lower mortality rate and need for intubation when compared to those who did not receive CPAP.
CPAP lessens the work of breathing in patients in respiratory distress from all causes and results in fewer intubations and lower mortality. This has huge ramifications on healthcare costs, as those not intubated are less likely to require ICU admission. Prehospital CPAP reduces the need for intubation and places the patient into the continuum of care that can be continued after admission. The role of furosemide and morphine has been previously evaluated with some studies showing that the inappropriate administration of these drugs to patients who don t have pulmonary edema increases their length of stay and mortality rates.
Bottom line? CPAP for everyone!
