Impact of prehospital noninvasive mechanical ventilation in acute pulmonary edema: the NIVEMS cohort study

BACKGROUND. Acute pulmonary edema (APE) is a frequent medical event requiring out-of-hospital attendance of emergency services. Early prehospital noninvasive ventilation (NIV) can improve the clinical course of APE.
OBJECTIVES. To analyze changes in oxygen saturation measured by pulse oximetry (SpO2) and respiratory frequency (RF) in patients with APE treated with early prehospital NIV vs conventional oxygen therapy.
METHOS. Prospective double-cohort study with data recorded for 433 patients with APE attended by advanced life support units of the emergency medical system of Catalonia from January 1, 2014, to March 31, 2018. Patients were exposed to either prehospital NIV or conventional oxygen therapy. To analyze data we used the Kaplan-Meier method and Cox regression modelin and calculated of adjusted hazard ratios (aHR).
RESULTS. The NIVEMS (Noninvasive Ventilation in Emergency Services) study collected valid data to analyze for 382 patients with a mean (SD) age of 79.7 (9.58) years; 56.3% were women. Prehospital NIV was applied in 44.7% of the cohort. The median time until optimization of SpO2 to more than 94% was 10 min (95% CI, 8.37-11.63 min) with NIV vs 30 min (95% CI, 19.44-40.56 min) with conventional oxygen therapy. The median time until optimization of RF to fewer than 28 breaths/min was 31 min (95% CI, 24.56- 37.44 min) with NIV vs 50 min (95% CI, 38.61-61.39 min) with conventional therapy. NIV favored optimization of SpO2 (aHR, 4.66; 95% CI, 2.91-7.45) and RF (aHR, 3.24; 95% CI, 1.97-5.31).
CONCLUSION. Prehospital application of NIV in patients with clinically suspected APE is associated with a shorter time to optimization of SpO2 and RF.