Case volume and mortality in haematological patients with acute respiratory failure

High case volume is associated with improved survival in medical and surgical conditions. The present study sought to determine whether intensive care unit (ICU) case volume was associated with survival of critically ill patients with haematological malignancies and acute respiratory failure (ARF). A regional database containing data from 1,753 haematological patients with ARF admitted to 28 medical ICUs from 1997 to 2004 was used. Multivariate analysis using mixed models was performed to adjust for severity of illness and other confounding factors, including a propensity score that incorporates differences between ICUs with different case volumes. The three case volume tertiles were: low volume (<12 admissions per year), intermediate volume (12-30 admissions per year), and high volume (>30 admissions per year). In univariate analyses, ICU case volume was not associated with ICU mortality. After adjusting for prognostic factors for ICU mortality and the propensity score, patients in high-volume ICUs had lower mortality than other patients. A case volume increase of one admission per year led to a significant mortality reduction with an odds ratio of 0.98 (95% confidence limits 0.97-0.99). Mortality was independently associated with severity of organ dysfunction. In intensive care units admitting larger numbers of critically ill haematological patients with acute respiratory failure, mortality was lower than in other intensive care units. The mechanisms of the relationship between volume and outcome among haematological patients with acute respiratory deserve additional studies.