Association Between Ventilator-Associated Events and Mortality
- In ICU
- Wed, 10 Sep 2025
In 2013, the Centers for Disease Control and Prevention (CDC)/National Healthcare Safety Network (NHSN) introduced ventilator-associated events (VAEs) as a surveillance-based quality indicator for monitoring respiratory complications in mechanically ventilated patients. VAEs are defined by sustained increases in PEEP or FiO₂, regardless of underlying pathology, and can be detected objectively. However, adoption has been limited, as their prognostic value is debated. Evidence shows patients with VAEs often have worse outcomes, but previous studies largely assessed illness severity only at baseline, raising concerns about residual confounding.
Since VAEs may reflect underlying severity rather than cause mortality, a recent study reassessed the VAE–mortality relationship using analyses that account for time-dependent changes in patient severity.
The study included patients ≥12 years old who underwent mechanical ventilation for at least 3 days in 18 Japanese ICUs (May 2020–December 2022). VAEs were identified using CDC criteria, and their association with 30-day in-hospital mortality was analysed using an inverse probability weighted proportional hazards model that accounted for time-dependent changes in patient severity.
Among 1,094 patients, 106 VAEs (9.7%) occurred, with an incidence of 10.0 per 1,000 ventilation days. VAEs were associated with higher 30-day hospital and ICU mortality, longer hospital and ICU stays, and accounted for ~8–9% of attributable mortality.
The study found that VAEs were significantly associated with increased mortality and prolonged ICU/hospital stays in mechanically ventilated patients, even after adjusting for time-dependent confounders. The results align with previous studies showing similar hazard ratios, but this is the first analysis to continuously incorporate changes in disease severity and clinical management during ICU stay.
The robustness of the VAE–mortality relationship may reflect the CDC definition itself, which captures sustained oxygenation impairment, a known predictor of poor outcomes. While VAEs may sometimes represent progression of underlying disease (e.g., ARDS), their occurrence after a period of stability suggests they are more than mere markers of illness. The findings remained significant after adjusting for multiple confounders, though causality cannot be proven, and interventional studies are needed to determine preventability.
The association persisted in Japan despite differences in ICU staffing and respiratory care compared to the U.S., suggesting generalisability. The population attributable risk of VAE-related mortality was 8.8%, lower than ARDS but higher than VAP in prior reports.
In subgroup analysis, the mortality association disappeared in patients receiving futile or end-of-life care, though VAEs were still linked to worse discharge survival and delayed ventilator weaning. This highlights that VAEs in terminally ill patients may reflect inevitable decline rather than preventable complications, limiting their utility as universal quality indicators.
Overall, these findings demonstrate that VAEs remained significantly associated with mortality even after adjusting for severity as a time-dependent confounder.
Source: Intensive Care Medicine
Image Credit: iStock
