Study objectives: Knowing that mortality is high in
patients who require mechanical ventilation patients with
community-acquired pneumonia (CAP), we hypothesized 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 mortality 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[
Pao2/PAo2]) × (minimum
fraction of inspired oxygen to maintain Pao2 at>
60 mm Hg) × 100], where PAo2 is the
alveolar partial pressure of oxygen—to grade the severity of acute
lung injury on a scale from 0 to 100.
Tertiary care university hospital ICU.
hundred forty-four adult patients mechanically ventilated for
respiratory failure caused by CAP.
results: Hospital mortality was 46% (n = 66). Multivariate
logistic regression analysis revealed five independent predictors of
hospital mortality: (1) the extent of lung injury assessed by the
hypoxemia index; (2) the number of nonpulmonary organs that failed; (3)
immunosuppression; (4) age > 80 years; and (5) medical comorbidity
with a prognosis for survival < 5 years. At a 50% mortality
threshold, the prediction model correctly classified outcome in 88% of
cases. All patients with > 95% predicted probability of death died
Conclusions: Based on clinical parameters
measured over the first 24 h of mechanical ventilation, this model
accurately identified critically ill, mechanically ventilated patients
with CAP for whom prolonged intensive care may not be of