The association between cardiac intensive care unit mechanical ventilation volumes and in-hospital mortality.

Abstract

The incidence of respiratory failure and use of invasive or non-invasive mechanical ventilation (MV) in the cardiac intensive care units (CICUs) is increasing. While institutional MV volumes are associated with reduced mortality in medical and surgical ICUs, this volume-mortality relationship has not been characterized in the CICU. National population-based data were used to identify patients admitted to CICUs (2005-2015) requiring MV in Canada. CICUs were categorized into low (≤100), intermediate (101-300), and high (>300) volume centres based on spline knots identified in the association between annual MV volume and mortality. Outcomes of interest included all-cause in-hospital mortality, the proportion of patients requiring prolonged MV (>96 h) and CICU length of stay (LOS). Among 47173 CICU admissions requiring MV, 89.5% (42200) required invasive MV. The median annual CICU MV volume was 43 (inter-hospital range 1-490). Compared to low-volume centres (35.9%), in-hospital mortality was lower in intermediate [29.2%, adjusted odds ratio (aOR) 0.84, 95% confidence interval (CI) 0.72-0.97, P = 0.019] and high-volume (18.2%; aOR 0.82, 95% CI 0.66-1.02, P = 0.076) centres. Prolonged MV was higher in low-volume (29.2%) compared to high-volume (14.8%, aOR 0.70, 95% CI 0.55-0.89, P = 0.003) and intermediate-volume (23.0%, aOR 0.85, 95% CI 0.68-1.06, P = 0.14] centres. Mortality and prolonged MV were lower in percutaneous coronary intervention (PCI)-capable and academic centres, but a shorter CICU LOS was observed only in subgroup of PCI-capable intermediate- and high-volume hospitals. In a national dataset, we observed that higher CICU MV volumes were associated with lower incidence of in-hospital mortality, prolonged MV, and CICU LOS. Our data highlight the need for minimum MV volume benchmarks for CICUs caring for patients with respiratory failure.