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Summary Acute cardiogenic pulmonary edema is one of the main reasons for hospitalization of patients. The mortality rate is high and most patients require ventilatory assistance. But endotracheal intubation has specific complications and risks for the patient. Systematic reviews suggest a reduced need for artificial ventilation and likewise decreased mortality in patients with acute cardiogenic pulmonary edema when Continuous Positive Airway Pressure (CPAP) therapy is utilized. Up to now there was no systematic investigation into the preclinical use of CPAP. Question By comparing patients with acute cardiogenic pulmonary edema treated with preclinical CPAP and a historical control group, it should be cleared if there was an influence on hospital mortality and intubation rate in the CPAP-group. Material and methods CPAP-therapy was introduced in 2006 in DRK-rescue services in Mittelhessen. The data was taken from rescue service protocols, from a questionaire especially designed for this study and filled in by the emergency physician, and lastly from the health records of the Universitätsklinikum Gießen und Marburg GmbH, location Marburg. As primary study end points, intubation rate and hospital mortality for both groups should be analyzed. Secondary study end points include the duration of hospital stay, the duration of ventilatory assistance, time spent in intensive care unit, the vital signs, the frequency of myocardial ischemia, and the time of transportation in prehospital rescue service. Those parameters were analyzed and compared between the two groups. The vital signs were also analyzed within each group. The statistical analysis was performed as a matched pairs analysis. The evaluation of categorial data was done by Chi-Squared-Test. When the sample was too small the Fisher-Yates-Test was performed. Metric data was evaluated with the T-Test for paired samples when the sample was normally distributed and with Wilcoxon signed-rank test when the sample was distributed abnormally. Results In the primary study end points there was detected a significant reduction of intubation rate in the CPAP-group compared to the historical control group. Moreover, a trend could be seen with clinical relevance towards a reduced hospital mortality in the CPAP-group without statistical significance. The secondary study end points showed a significant reduction in the lenght of stay in the intensive care unit and a trend towards less hours of assisted ventilation in the CPAP-group. Interestingly there was a trend towards a shorter lenght of hospital stay in the control group. The vital signs were first compared within each group and showed a significant improvement in both groups in all vital signs after treatment. There was no significant difference in the comparison of the vital signs between CPAP-group and control group. No difference could be seen between the two groups when comparing the frequency of myocardial ischemia. Transport times to the hospital were about 5 minutes longer in the CPAP-group, but this was not statistically significant. Discussion This study demonstrates an easily executable preclinical application of CPAP, a good tolerance of the therapy in patients, and a significantly reduced intubation rate. Many studies indicate that if CPAP is applied in the emergeny care unit to patients with acute cardiogenic pulmonary edema, there is a marked reduction in the need for intubation and also decreased mortality rate. Ultimately, this results could be confirmed in this study with preclinical use of CPAP. Using CPAP en route to hospital means that, on average, the application of this therapy can begin 30 to 45 minutes earlier. In summary the preclinical use of CPAP is highly recommended.