Assessment of prognosis in patients with community-acquired pneumonia who require mechanical ventilation

Study objectives: Knowing that mortality is high in patients who require me chanical ventilation patients with community-acquired pneumonia (CAP), we h ypothesized that the severity of acute lung injury could be used along with nonpulmonary factors to identify patients with the highest risk of death. We formulated a prediction model to quantitate the risk of hospital mortali ty in this population of patients, Design: Historical prospective study using data collected over the first 24 h of mechanical ventilation. We utilized a hypoxemia index-(1 - lowest [Pa o(2)/PAo(2)) x (minimum fraction of inspired oxygen to maintain Pao(2) at > 60 mm Hg) x 100], where PAo(2) is the alveolar partial pressure of oxygen- to grade the severity of acute lung injury on a scale from 0 to 100. Setting: Tertiary care university hospital ICU. Patients: One hundred forty-four adult patients mechanically ventilated for respiratory failure caused by CAP. Measurements and results: Hospital mortality was 46% (n = 66). Multivariate logistic regression analysis revealed five independent predictors of hospi tal mortality: (1) the extent of lung injury assessed by the hypoxemia inde x; (2) the number of nonpulmonary organs that failed; (3) immunosuppression ; (4) age > 80 years; and (5) medical comorbidity with a prognosis for surv ival < 5 years, At a 50% mortality threshold, the prediction model correctl y classified outcome in 88% of cases. All patients with > 95% predicted pro bability of death died in hospital. Conclusions: Based on clinical parameters measured over the first 24 h of m echanical, ventilation, this model accurately identified critically ill, me chanically ventilated patients with CAP for whom prolonged intensive care m ay not be of benefit.