Analysis of Initial Emergency Department Ventilator Settings in Accordance with Ability to Oxygenate

In most emergency department (ED) patients, mechanical ventilation is initiated with limited data. Ability to oxygenate is usually available and could indicate acute respiratory distress syndrome (ARDS).

To determine if patients' ability to oxygenate is associated with initial ventilator settings. We hypothesize that severely hypoxemic patients were exposed to similar initial settings compared to those oxygenating normally.

Retrospective chart review of adults intubated in nine EDs in 2019. Partial pressure of arterial oxygen (PaO₂₎:fraction of inspired oxygen (FiO₂₎ (P:F) was calculated based on postintubation arterial blood gas (ABG) and concurrent ventilator settings. Patients were grouped into severe hypoxemia = P:F ≤ 100 and normal oxygenation = P:F > 300. The primary outcome was the association of oxygenation group with initial Tidal Volume (V_T), FiO₂ and positive end-expiratory pressure (PEEP). Group differences were analyzed using chi-square for categorical variables and Wilcoxon rank sum for continuous data, following normality testing with Shapiro Wilk.

Of 1995 adults intubated, 175 were severely hypoxemic and 578 had normal oxygenation yielding a cohort of 753. Severely hypoxemic patients were more likely white, female, and had a higher body mass index (BMI). They were initiated on similar V_T (7.0 [6.3-7.9] vs. 7.0 [6.4-7.8] mL/kg/ideal body weight [IBW]; p = 0.94), higher PEEP (5 [5-8] vs. 5 [5-5] cm H₂O; p < 0.0001), and more likely to be placed on 100% FiO₂ (81% vs. 53%; p < 0.0001).

Initial PEEP and FiO₂, but not V_T differ based on a patient's ability to oxygenate. Most severely hypoxemic patients were started on a PEEP of 5 and most normally oxygenating patients were started on 100% FiO₂.