Initial and Delayed Onset of Acute Respiratory Failure: Factors Associated with Development and Outcome

In a prospective observational study of 1038 adult admissions to a 31-bed medical/surgical intensive care unit (ICU), acute respiratory failure (ARF, defined as a Pao(2)/Fio(2) ratio <or=200 mm Hg and the need for respiratory support) occurred in 182 (58%) of the 313 admissions with an ICU stay of more than 48 h. Initial ARF (onset within 48 h of ICU admission) occurred in 133 (42%) patients, and delayed onset ARF (onset >48 h after ICU admission) in 49 (16%). On admission, the cardiovascular sequential organ failure assessment (SOFA) score was higher in initial than in delayed onset ARF (1.1 +/- 1.5 vs 0.6 +/- 1.2, P < 0.05). High admission serum C-reactive protein concentrations (OR 1.08, 95% CI 1.04-1.12, P = 0.0001) and SOFA scores (OR 1.20, 95% CI 1.08-1.33, P = 0.0007) were the factors independently associated with initial ARF, and a low Glasgow coma scale (GCS) score (OR 1.13, 95% CI 1.04-1.21, P = 0.0018) was associated with delayed onset ARF. In initial ARF, a high SOFA score (OR 1.24, 95% CI 1.12-1.38, P = 0.0001) and a low GCS score (OR 0.89, 95% CI 0.83-0.96, P = 0.0013) on admission, and in delayed onset ARF, a low GCS score at 48 h (OR 0.67, 95% CI 0.54-0.84, P = 0.0011) were independently associated with death. The mortality rate was similar for initial and delayed onset ARF.