Why do patients with interstitial lung diseases fail in the ICU? a 2-center cohort study

Admitting patients with interstitial lung disease (ILD) to the ICU is controversial, due to their associated high mortality when they require invasive mechanical ventilation. We aimed to determine the risk factors for mortality in ILD patients requiring ICU support due to acute respiratory failure. An observational cohort study was performed in 2 chest diseases teaching hospitals. We included all ILD patients with acute respiratory failure admitted between 2008 and 2010. Subject demographics, noninvasive ventilation (NIV) and invasive ventilation use, and mortality were obtained from medical records. Subjects receiving NIV were divided based on their continuous or non-continuous demand for NIV. NIV failure was defined as intubation for invasive ventilation, or death during NIV. Cox regression analysis was used to determine the hazard ratio for NIV failure. We enrolled 120 subjects: 71 male, median age 66 years. The types of ILD were idiopathic pulmonary fibrosis (n = 96), collagen vascular disease (n = 10), silicosis (n = 9), drug induced (n = 3), and eosinophilic pneumonia (n = 2). The median (IQR) Acute Physiology and Chronic Health Evaluation (APACHE II) score was 24 (19-31), and 75 (62.5%) subjects received NIV on ICU admission, 47 (62.7%) of whom needed continuous NIV. The NIV failure rate was 49.3% (n = 37). The mortality rates of continuous NIV, non-continuous NIV, invasive ventilation, and total ICU were 61.7% (29/47), 10.7% (3/28), 89.7% (61/68), 60% (72/120), respectively. APACHE II > 20 and continuous NIV demand indicated significant risk for NIV failure: hazard ratio 2.77 (95% CI 1.19-6.45), P < .02, and 5.12, (1.44-18.19), P < .01, respectively. Because of higher mortality, physicians should consider invasive ventilation cautiously in the ICU management of ILD patients with acute respiratory failure. NIV may be an option in less severely ill patients with APACHE II score < 20.