Abstract
OBJECTIVES: This study examines the relationships between hospitals' annual acute respiratory distress syndrome case volume with hospitals' acute respiratory distress syndrome case fatality rates and individuals' odds of acute respiratory distress syndrome hospital mortality. DESIGN: Retrospective cohort study. SETTING: The U.S. Healthcare Cost and Utilization Project's Nationwide Inpatient Sample, 2002-2011. PATIENTS: Acute respiratory distress syndrome discharges defined by the presence of an acute respiratory distress syndrome International Classification of Diseases, 9th revision, Clinical Modification diagnosis code (518.82 or 518.5) and a mechanical ventilation procedure code (96.70, 96.71 or 96.72) on the discharge diagnosis and procedure lists. If the procedure code 96.71 was on the discharge record (mechanical ventilation < 96 hr duration), the patient also needed to be classified as deceased. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We analyzed 2,686 hospitals and 117,204 cases of acute respiratory distress syndrome. Average annual hospital acute respiratory distress syndrome in-hospital mortality was 47%. Acute respiratory distress syndrome case volume was categorized as low (1-9), medium (10-49), and high (50-423 cases per year). In a hospital-level Poisson regression adjusting for hospital characteristics, when compared with low-volume acute respiratory distress syndrome hospitals, high- and medium-volume acute respiratory distress syndrome hospitals had lower annual acute respiratory distress syndrome case fatality (rate ratio, 0.75; 99% CI, 0.71-0.79 and rate ratio, 0.86; 99% CI, 0.82-0.90, respectively; p ≤ 0.001 for both). In an individual-level, multivariable model adjusting for hospital and individual characteristics, high and medium acute respiratory distress syndrome volume hospitals were associated with lower odds of acute respiratory distress syndrome mortality compared with low-volume hospitals (odds ratio, 0.85 [99% CI, 0.74-0.99]; p = 0.006 and odds ratio, 0.89 [99% CI 0.79-1.00]; p = 0.01, respectively). CONCLUSIONS: In this cohort, at both an individual- and hospital-level, higher acute respiratory distress syndrome hospital case volume is associated with lower acute respiratory distress syndrome hospital mortality.