Recent trends in acute lung injury mortality: 1996-2005

Abstract

Objective: Studies from single centers have suggested that mortality from acute lung injury (ALI) has declined over time. However, recent trends in ALI mortality from centers across the United States are unknown. We sought to determine whether recent advances in the treatment of ALI and related critical illnesses have resulted in decreased mortality from ALI.

Design: Retrospective cohort study of patients enrolled in the Acute Respiratory Distress Syndrome (ARDS) Network randomized controlled trials.

Setting: Adult intensive care units participating in the ARDS Network trials.

Patients: 2,451 mechanically ventilated patients with ALI enrolled in the ARDS Network randomized controlled trials between 1996 and 2005.

Measurements and main results: Crude mortality was 35% in 1996-1997 and declined during each subsequent time period to a low of 26% in 2004-2005 (test for trend p < 0.0005). After adjusting for demographic and clinical covariates, including receipt of lower tidal volume ventilation and severity of illness, the temporal trend persisted (test for trend p = 0.002). When analyzed by individual causes of lung injury, there were not any statistically significant temporal trends in 60-day mortality for the most common causes of lung injury (pneumonia, sepsis, aspiration, and trauma).

Conclusions: Over the past decade, there seems to be a clear temporal improvement in survival among patients with ALI treated at ARDS Network centers. Our findings strongly suggest that other advancements in critical care, aside from lower tidal volume ventilation, accounted for this improvement in mortality.

Figure 1. Crude 60-day Mortality Among ARDS Network Patients, 1996-2005

Test for trend p value= 0.19 for patients who received lower tidal volume ventilation.

Figure 2. Adjusted 60-day Mortality Among ARDS Network Patients, 1996-2005

Points represent adjusted 60-day mortality for the enrollment period, and error bars the 95% confidence intervals. Adjusted for age, gender, receipt of low tidal volume ventilation, Acute Physiology Score (APS), comorbid conditions (HIV/AIDS, lymphoma), trauma as the cause of lung injury and PaO₂:FiO₂. Reference period is 1996-1997 enrollment period (OR=1.0).

Figure 3. Adjusted 60-day Mortality by Cause of Lung Injury, 1996-2005

Points represent adjusted 60-day mortality for the enrollment period, and error bars the 95% confidence intervals. Adjusted for age, gender, receipt of low tidal volume ventilation, Acute Physiology Score (APS), comorbid conditions (HIV/AIDS, lymphoma), trauma as the cause of lung injury and PaO₂:FiO₂. Test for trend p≥0.05 for all causes of lung injury, except other/unknown p=0.008 Reference period is 1996-1997 enrollment period (OR=1.0).

Figure 3. Adjusted 60-day Mortality by Cause of Lung Injury, 1996-2005

Points represent adjusted 60-day mortality for the enrollment period, and error bars the 95% confidence intervals. Adjusted for age, gender, receipt of low tidal volume ventilation, Acute Physiology Score (APS), comorbid conditions (HIV/AIDS, lymphoma), trauma as the cause of lung injury and PaO₂:FiO₂. Test for trend p≥0.05 for all causes of lung injury, except other/unknown p=0.008 Reference period is 1996-1997 enrollment period (OR=1.0).