Bilevel positive airway pressure (BiPAP) is a form of non-invasive ventilation (NIV) that is used to help and facilitate breathing. Our objective is to evaluate the impact of BiPAP application timeonthelength of emergency room (ER)stay in pulmonary edema patients. This is a retrospective cohort study that included patients whopresented to theERat King Abdullah Medical City (KAMC) from June2019 toJune2021. The eligibility criteriaforBiPAPapplication were congestive heart failure(CHF) and type 1 and type 2 respiratory failure, The data were collected from theTrack Caresystem.We defined early BiPAP as BiPAP application time within one hour from admission, and late BiPAP more than one hourand we calculated the percentage of discharge within four hours in each group. Out of 147 fulfilling study eligibility,64% had CHF, 23%had type 2 respiratory failure and 13%had type 1 respiratory failure.For patients discharged withinfour hours,85%wereintheearlyBiPAPand 15% were in the late BiPAP groups(p=0.001as compared to the late discharge group).Discharge within four hours was observed with the following percentages in the study subgroups:CHF early BiPAP(84%), late BiPAP (16%)(p = 0.004),type1 respiratory failure earlyBiPAP(79%),lateBiPAP(21%) (p = 0.71) and type 2 respiratory failure earlyBiPAP(94%), lateBiPAP(6%)(p = 0.89). Our results show that there is a significant outcome in earlyBiPAPapplication in decreasing the length of ER stay only in patients with pulmonary edema.