Caution, Not Causality: The Limitations of Risk Factor & Outcome Research on Ventilator-Associated Events

The VAE definition is significantly more objective due to relying upon distinct measures of oxygenation (fraction of inspired oxygen [Fi02] and positive end-expiratory pressure [PEEP]), as opposed to previously utilized clinical definitions but now encompasses a much broader group of disorders beyond pneumonia, including pulmonary edema, atelectasis, mucus plugging, abdominal disorders and sepsis, which may impact lung function, pulmonary embolism, and transfusion-related lung injury.1,2 Discordance between clinical VAP and VAE has been well described in which VAE surveillance has not correlated with traditionally defined VAP cases.2,3 Additionally, recommended prevention strategies for VAP may not necessarily impact VAE, and compliance with VAP bundles has not correlated with improvement in VAE rates.4 These reports have raised questions regarding the value of VAE as a metric for patient care or outcomes. Trials utilizing spontaneous awakening and breathing trials have demonstrated decreased time on the ventilator and decreased VAE rates.2,6−8 These strategies, coupled with minimization of sedation, early mobility, use of low tidal ventilation, and conservative fluid and blood product, have all shown some success in decreasing the conditions associated with VAE (eg, pneumonia, atelectasis, acute respiratory distress syndrome (ARDS), pulmonary edema, and more).1,7,8 We suggest focusing on PVAPs rather than the entire VAE umbrella. Because severity of illness was only assessed on ICU admission, these may simply be markers of level of illness.