Abstract Rationale The PREOXI trial (NEJM 2024) demonstrated that preoxygenation with noninvasive ventilation (NIV) decreased the incidence of hypoxemia during emergency tracheal intubation compared to oxygen mask in critically ill adults. In patients with acute pulmonary insults (API), including pneumonia, shunting and increased dead space may limit the effectiveness of NIV. In contrast, NIV is well-supported for treatment of acute hypercapnic respiratory failure due to obstructive lung disease (OLD). The effectiveness of NIV as a preoxygenation strategy in patients with API or OLD remains uncertain. Methods We conducted two effect modification (subgroup) analyses of the PREOXI randomized controlled trial evaluating whether (1) the presence of API (defined as pneumonia, aspiration, COVID-19, or ARDS) or (2) chronic OLD (defined as COPD or asthma) modified the effect of preoxygenation with NIV versus oxygen mask. The primary outcome was incidence of hypoxemia during intubation, defined as peripheral oxygen saturation 85% between induction and two minutes after intubation. The secondary outcome was the lowest SpO2 during intubation. Effect modification was assessed by estimating risk differences for the primary outcome within each subgroup and testing interaction terms in generalized linear models. Results are reported as median (IQR) unless otherwise specified. Results Among the 1,301 patients enrolled in the PREOXI trial, 316 (24.3%) had an API, and 253 (19.4%) had chronic OLD. In patients with API, the baseline S/F ratio was 158 (82) compared to 303 (284) in patients without API. Among patients with API, hypoxemia during intubation occurred in 17 patients in the NIV group and 42 in the oxygen mask group (absolute risk difference -16.7%, 95% CI: -25.8% to -7.6%). The lowest SpO2 was 97% (10) in the NIV group and 94% (15) in the oxygen mask group (p = 0.0006). Among patients with OLD, hypoxemia during intubation occurred in 16 patients in the NIV group and 26 in the oxygen mask group (absolute risk difference -8.3%. 95% CI: -18.4% to 1.9%). Interaction p-values were 0.077 for API and 0.759 for OLD for the pre-specified effect direction. Similar trends were observed in other secondary outcomes. Conclusion Among patients with API and chronic OLD, hypoxemia during intubation was less common in patients randomized to preoxygenation with NIV compared to patients preoxygenated with face mask, without evidence of effect modification by either condition. These results support using NIV for preoxygenation in patients with these respiratory comorbidities, particularly in those with API who face elevated risk of hypoxemia during intubation. This abstract is funded by: None
Figg et al. (Fri,) studied this question.