Apnea Testing on Conventional Mechanical Ventilation During Brain Death Evaluation.

Introduction: The use of continuous positive airway pressure has been shown to improve the tolerance of the apnea test, a critical component of brain death evaluation. The ability to deactivate the apnea backup setting has made apnea testing possible using several conventional mechanical ventilators. Our goal was to evaluate the safety and efficacy of apnea testing performed on mechanical ventilation, compared with the oxygen insufflation technique, for the determination of brain death.

Methods: This was a retrospective study. In 2016, our institution approved a change in policy to permit apnea testing on conventional mechanical ventilation. We examined the records of consecutive adults who underwent apnea testing as part of the brain death evaluation process between 2016 and 2022. Using an apnea test technique was decided at the discretion of the attending physician. Outcomes were successful apnea test and the occurrence of patient instability during the test. This included oxygen desaturation (SpO2) < 90%, hypotension (mean arterial pressure < 65 mm Hg despite titration of vasopressor), cardiac arrhythmia, pneumothorax, and cardiac arrest.

Results: Ninety-two adult patients underwent apnea testing during the study period: 58 (63%) with mechanical ventilation, 32 (35%) with oxygen insufflation, and 2 (2%) lacked documentation of technique. Apnea tests could not be completed successfully in 3 of 92 (3%) patients-two patients undergoing the oxygen insufflation technique (one patient with hypoxemia and one patient with hypotension) and one patient on mechanical ventilation (aborted for hemodynamic instability). Hypoxemia occurred in 4 of 32 (12.5%) patients with oxygen insufflation and in zero patients on mechanical ventilation (p = 0.01). Hypotension occurred during 3 of 58 (5%) tests with mechanical ventilation and 4 of 32 (12.5%) tests with oxygen insufflation (p = 0.24). In multivariate analysis, the use of oxygen insufflation was an independent predictor of patient instability during the apnea test (odds ratio 37.74, 95% confidence interval 2.74-520.14).

Conclusions: Apnea testing on conventional mechanical ventilation is feasible and offers several potential advantages over other techniques.