Effect of oxygen therapy on the risk of mechanical ventilation in emergency acute pulmonary edema patients.

Abstract

We investigated the effects of hyperoxemia on morbidity and mortality in acute cardiogenic pulmonary edema (ACPE). We conducted a retrospective cohort study of patients in our emergency department (ED) with ACPE who received arterial blood gases. Patients were classified based on the first PaO2 as hypoxemic (<75 mmHg), normoxemic (75-100 mmHg) and hyperoxemic (>100 mmHg). The primary outcome was the rates of mechanical ventilation (MV). We also reported adjusted odds ratios (AOR) and their 95% confidence intervals (CI) of the primary outcome after adjusting for predictors of MV determined a priori. Secondary outcomes were median hospital length of stay (LOS) and in-hospital mortality. We recruited 335 patients; 34.0% had hyperoxemia. The rates of normoxemia and hypoxemia were 27.5% and 38.5%, respectively. The rates of MV were: hypoxemic 60/129 (46.5%) vs. normoxemic 41/92 (44.6%) vs. hyperoxemic 50/114 (43.9%); P = 0.62. The AORs for MV for the hyperoxemic and hypoxemic groups (reference: normoxemic group) were 0.98 (95% CI: 0.53-1.79) and 1.38 (95% CI: 0.77-2.48), respectively. Intubation rates for the groups were: hypoxemic 15/129 (11.6%) vs. normoxemic 6/92 (6.5%) vs. hyperoxemic 12/114 (10.6%); P = 0.43. The secondary outcomes were comparable among the groups. In-hospital mortality rates were: hypoxemic 6/129 (4.7%) vs. 6/92 (6.5%) vs. 10/114 (8.8%); P = 0.42. Our exploratory study did not report effects on mechanical ventilation, median hospital LOS and in-hospital mortality from hyperoxemia compared to hypoxemic and normoxemic ED patients with ACPE. Further studies are warranted to prove or disprove our findings.