Objective: To evaluate the impact of noninvasive positive pressure mechanical ventilation (NPPV) on ventilator-associated pneumonia (VAP).
Design: Prospective observational study.
Setting: Medical intensive care unit (ICU) of a university teaching hospital.
Patients: Cohort of 320 consecutive patients staying in the ICU more than 2 days and mechanically ventilated for > or = 1 day.
Measurements and results: VAP was diagnosed when, satisfying classical clinical and radiological criteria, fiberoptic bronchoalveolar lavage and/or protected specimen brush grew > or = 10(4) and > or = 10(3) CFU/ml, respectively, of at least one microorganism. Patients were classified into four subgroups according to the way in which mechanical ventilation was delivered: NPPV then tracheal intubation (TI) (n = 38), TI then NPPV (n = 23), TI only (n = 199), and NPPV only (n = 60). Occurrence of VAP was estimated by incidence rate and density of incidence. Risk factors for VAP were assessed by logistic regression analysis. Twenty-seven patients had 28 episodes of VAP. The incidence rates for patients with VAP were 18% in NPPV-TI, 22% in TI-NPPV, 8% in TI, and 0% in NPPV (p < 0.0001). The density of incidence of VAP was 0.85 per 100 days of TI and 0.16 per 100 days of NPPV (p = 0.04). Logistic regression showed that length of ICU stay and ventilatory support were associated with VAP.
Conclusions: There is a significantly lower incidence of VAP associated with NPPV compared to tracheal intubation. This is mainly explained by differences in patient severity and risk exposure.