Bedside risk stratification for mortality in patients with acute respiratory failure treated with noninvasive ventilation.

Our hypothesis was that patients managed with noninvasive ventilation (NIV) on the wards could be risk-stratified with initial pulse oximetry/fraction of inspired oxygen (SpO2/FiO2) ratios and tidal volumes (Vte). A prospective study of consecutive patients with acute respiratory failure requiring NIV on the wards was conducted. A multivariate logistic regression model and a negative binomial regression model were used. A total of 403 patients (55.8% women) had a mean age of 65.0 ± 14.9 years with a mean body mass index of 32.1 ± 11.1 kg/m2. The 28-day mortality was 14.1%, and the intubation rate was 16.1%. Pneumonia was associated with the highest 28-day mortality (22.5%) and rate of intubation (36.7%) when compared with chronic obstructive pulmonary disease (4.4% and 7.3%) or congestive heart failure (22.2% and 13.4%). The SpO2/FiO2 groups were <214 (26.6%), 214 -357 (66.0%), and ≥357 (7.4%). Those in the SpO2/FiO2 < 214 group had a higher 28-day mortality rate (odds ratio [OR] = 8.19; 95% confidence interval [CI] 1.02 -65.7), intubation rate (OR = 3.7; 95% CI 1.1 -12.1), intensive care unit admission rate (OR = 2.9; 95% CI 1.2 -7.4), and length of stay (relative risk = 2.0; 95% CI 1.3 -3.0). A Vte/predicted body weight <7.7 mL/kg was associated with increased intubations (OR = 3.1; 95% CI 1.3 -7.4), intensive care unit admissions (OR = 2.5; 95% CI 1.3 -4.6), and 30-day readmissions (OR = 2.9; 95% CI 1.2 -6.8). In conclusion, in patients without acute respiratory distress syndrome who had acute respiratory failure managed with noninvasive ventilation on the wards, severe hypoxemia as assessed by a simple SpO2/FiO2 ≤ 214 was associated with poor outcomes.