Diffuse alveolar damage associated mortality in selected acute respiratory distress syndrome patients with open lung biopsy

Introduction: Diffuse alveolar damage (DAD) is the pathological hallmark of acute respiratory distress syndrome (ARDS), however, the presence of DAD in the clinical criteria of ARDS patients by Berlin definition is little known. This study is designed to investigate the role of DAD in ARDS patients who underwent open lung biopsy. Methods: We retrospectively reviewed all ARDS patients who met the Berlin definition and underwent open lung biopsy from January 1999 to January 2014 in a referred medical center. DAD is characterized by hyaline membrane formation, lung edema, inflammation, hemorrhage and alveolar epithelial cell injury. Clinical data including baseline characteristics, severity of ARDS, clinical and pathological diagnoses, and survival outcomes were analyzed. Results: A total of 1838 patients with ARDS were identified and open lung biopsies were performed on 101 patients (5.5%) during the study period. Of these 101 patients, the severity of ARDS on diagnosis was mild of 16.8%, moderate of 56.5% and severe of 26.7%. The hospital mortality rate was not significant difference between the three groups (64.7% vs 61.4% vs 55.6%, p = 0.81). Of the 101 clinical ARDS patients with open lung biopsies, 56.4% (57/101) patients had DAD according to biopsy results. The proportion of DAD were 76.5% (13/17) in mild, 56.1% (32/57) in moderate and 44.4% (12/27) in severe ARDS and there is no significant difference between the three groups (p = 0.113). Pathological findings of DAD patients had a higher hospital mortality rate than non-DAD patients (71.9% vs 45.5%, p = 0.007). Pathological findings of DAD (odds ratio: 3.554, 95% CI, 1.385-9.12; p = 0.008) and Sequential Organ Failure Assessment score on the biopsy day (odds ratio: 1.424, 95% CI, 1.187-1.707; p<0.001) were significantly and independently associated with hospital mortality. The baseline demographics and clinical characteristics were not significantly different between DAD and non-DAD patients. Conclusions: The correlation of pathological findings of DAD and ARDS diagnosed by Berlin definition is modest. A pathological finding of DAD in ARDS patients is associated with hospital mortality and there are no clinical characteristics that could identify DAD patients before open lung biopsy.