High peak PaO2 values associated with adverse outcome in patients treated with noninvasive ventilation for acute cardiogenic pulmonary edema and pneumonia.

BACKGROUND: Noninvasive ventilation (NIV) has a sigificant impact on mortality in acute respiratory failure (ARF). Predictive parameters for mortality are of high interest. METHODS: We retrospectively analyzed 3759 blood gas analysis and clinical parameters of 475 patients presenting with ARF based on acute cardiogenic pulmonary edema and/or pneumonia. The influence of peak arterial oxygen partial pressure levels (PaO2) with respect to its predictive value for in-hopital and long-term mortality was investigated. RESULTS: Overall intra-hospital mortality was 24%. Peak PaO2 levels in kPa were significantly higher in non-survivors (20.01±10.11) compared to survivors (15.65±6.79, P<0.001). A univariate Cox proportional-hazards analysis for long-term mortality revealed associations with maximum PaO2 levels (overall cohort: HR= 1.02; 95% CI: 1.007-1.03; P=0.003; CPE: HR= 1.02; 95% CI: 0.99-1.04, P=0.05, pneumonia: HR= 1.02; 95% CI: 1-1.4, P=0.02). A PaO2 cut-off value of 13 kiloPascal (kPa) was calculated by means of Youden Index and remained true even after correction for APACHE 2 Score (HR= 1.50; 95% CI: 1.00-2.25; P=0.05) and for PaCO2 (HR= 1.63; 95% CI: 1.14-2.33; P=0.01). CONCLUSIONS: Peak PaO2 levels were associated with worse in-hopital and long-term mortality in patients treated with NIV due to ARF. These findings may indicate that application of high oxygen may be detrimental in such patients.