Approaches to Mechanical Ventilation in Patients With and Without Acute Brain Injury: A Registry-Based Cohort Study.

Abstract

Differences in mechanical ventilation strategies between patients with and without acute brain injury (ABI) remain incompletely characterized. We aimed to compare ventilation approaches in patients with and without ABI over a 10-year period and to investigate impacts of practice changes on Pa o2 and Pa co2 . Retrospective registry-based cohort study involving prospectively collected data from nine ICUs across Toronto, Ontario, Canada. Adult patients (≥ 18 yr) receiving invasive ventilation for at least 48 hours from 2014 to 2023 were included. Patients were classified as having ABI (exposure) or non-ABI (comparator) conditions. Between-group differences in tidal volume (V t ), positive end-expiratory pressure (PEEP), Pa co2 , and Pa o2 were summarized using adjusted linear mixed-effects regression. Six additional ventilation and gas exchange variables were evaluated in unadjusted analyses. None. Thirteen thousand nine hundred twenty-five patients were included. Mean age ( sd ) was 59.1 years (17.5 yr), 38.1% of patients ( n = 5305) were female, and 25.2% had ABI ( n = 3503). Over the first 7 ventilation days, V t was comparable between groups, with a daily median close to 6 mL/kg (interquartile range, 6-7 mL/kg) predicted body weight. PEEP was significantly lower in patients with ABI (median 5 vs. 8 cm H 2 O in non-ABI patients; p < 0.001). Among patients with hypoxemic respiratory failure, PEEP remained significantly lower in the ABI subset. From 2014 to 2023, V t decreased slightly in both groups, while PEEP remained unchanged. Pa co2 was largely maintained within 35-45 mm Hg in ABI patients and Pa o2 remained largely within 80-120 mm Hg. Differences in six additional ventilation parameters between groups were minimal. Both ABI and non-ABI patients received comparable V t that trended downwards over time. Pa co2 and Pa o2 remained largely within guideline-recommended ranges. However, PEEP was significantly lower in ABI patients, including among those with hypoxemic respiratory failure, highlighting potential opportunities to improve PEEP application in relevant subsets.