High-flow oxygen for apnea testing in brain death determination

Apnea testing is mandatory for brain death determination but may induce hypoxemia despite standard preoxygenation procedures. High-flow oxygen (HFO) systems may improve apneic oxygenation during the procedure, although clinical data remain limited.

We conducted a retrospective single-center cohort study including consecutive adult patients undergoing apnea testing for brain death determination between January 2023 and May 2026. Standard oxygen insufflation (6-15 L/min) was compared with HFO delivered through the Opt970® interface (Fisher & Paykel) at 50 L/min and FiO₂ 1.0. The primary outcome was longitudinal pulse oximetry saturation (SpO₂) evolution during apnea testing. Secondary outcomes included desaturation events and arterial blood gas parameters. Repeated SpO₂ measurements were analyzed using a linear mixed-effects model.

A total of 144 apnea tests were analyzed, including 78 using standard oxygen insufflation and 66 using HFO. Baseline characteristics and ventilatory parameters were comparable between groups. Lowest SpO₂ during apnea testing was significantly higher with HFO (100 [98-100] vs. 99 [95-99]; p = 0.003), while desaturation below 94% occurred less frequently (9.1% vs. 21.8%; p = 0.04). Post-test PaCO₂ was slightly higher in the HFO group (73 [67-81] vs. 70 [62-77] mmHg; p = 0.04). Longitudinal mixed-effects analysis demonstrated a significant decrease in SpO₂ over time in both groups (p < 0.0001). However, HFO was associated with overall higher SpO₂ values throughout the procedure (β=+1.38; standard error 0.69; p = 0.047), without significant group-by-time interaction (p = 0.578).

HFO delivered through the Opt970® device was associated with modestly higher oxygen saturation during apnea testing compared with standard oxygen insufflation. Further prospective studies are required to confirm these findings.