Apnea Testing for Brain Death/Death by Neurologic Criteria in Adults: A Prospective Multicenter Observational Study Assessing the Relationship Between Methodology, Safety, and Duration

IMPORTANCE: Apnea testing is an integral component of brain death (BD) assessments. The optimal method of Apnea Testing is currently not known. OBJECTIVES: To describe the current use of apnea test methods, and compare the effect of the chosen apnea test method (passive oxygenation, continuous positive airway pressure [CPAP], or exogenous Co2) on safety and duration of apnea test in adult BD/death by neurologic criteria (DNC) organ donors. DESIGN: A prospective multicenter observational study. SETTING: Seventy-four ICUs in Ontario, Canada, who participate in organ donation practices. PATIENTS: All BD/DNC assessments in Ontario, Canada, from July 2023 to August 2024. INTERVENTIONS: None. MAIN OUTCOMES AND MEASURES: Outcomes included the rate of apnea test attempts, completions, and adverse events. We also measured the incidence of each method used and the duration of the apnea test. RESULTS: During the 1-year study period, a total of 368 BD/DNC assessments were performed, of which 361 (98%) attempted an apnea test. Of the 361 apnea tests attempted, 236 (65%) used passive oxygenation (tracheal insufflation), 103 (29%) used CPAP-based methods, and 22 (6%) used exogenous Co2. Nine tests were not completed: seven were terminated due to adverse events (all with passive oxygenation; five hypoxemia, two hemodynamic instability) and two due to observed respiratory effort. All adverse events occurred with the passive oxygenation method (p = 0.20). No statistically significant differences were seen in apnea test duration between methods. The median test durations were 12 minutes (interquartile range [IQR], 10-17 min), 12 minutes (IQR, 8-15 min), and 15 minutes (IQR, 11-25 min) for passive oxygenation, positive pressure, and exogenous Co2, respectively. CONCLUSIONS AND RELEVANCE: In this large multicenter study, passive oxygenation was associated with a nonsignificant increase in adverse events compared with CPAP-based and exogenous Co2 methods. Exogenous Co2 did not shorten apnea test time. These findings support further investigation of CPAP-based methods as an alternative approach to apnea testing and refinement of Co2 delivery parameters.