In an effort to improve efficiency and quality of care, regionalization of adult critical care services, similar to trauma and neonatal intensive care, has been suggested. However, there is little research to understand if hospitals with higher patient volumes have better outcomes. The objective of this project was to determine whether hospital volume is associated with improved survival for medical or surgical patients receiving mechanical ventilation.
This population-based retrospective cohort study tracked 13,846 medical and 6,373 surgical patients receiving mechanical ventilation for greater than two consecutive days between 1998 and 2000 in Ontario, Canada. Within these groups, the odds ratio for death within 30 days of initiation of mechanical ventilation was calculated in relation to hospital volume of ventilation. Estimates were adjusted for patient demographics, diagnoses, and urgency status; hospital region and rural location; and accounted for clustering within hospitals.
There was no effect of volume on mortality for surgical patients. After adjustment for clustering, among medical patients, the lowest-volume category (<100 episodes/yr) had a non-significant increase in mortality, with an odds ratio (95% confidence interval) of 1.13 (0.87–1.47) compared with the highest-volume category (>700 episodes/yr). A post hoc analysis revealed that within the lowest-volume category, the proportion of patients transferred to larger hospitals was 81% for hospitals with <20 episodes/yr and only 32% for hospitals with 20–99 episodes/yr, with odds ratios (95% confidence interval) for mortality of 0.74 (0.49 –1.12) and 1.18 (0.90 –1.54), respectively, compared with the highest-volume category.
For surgical patients requiring mechanical ventilation for more than two days, hospital volume had no effect on mortality. For medical patients, higher mortality may occur in a subgroup of low-volume hospitals that do not routinely transfer their patients to larger-volume facilities. This finding needs further investigation in a larger-sized study.