Apnea testing using the oxygen insufflation method for diagnosis of brain death may compromise pulmonary function

The aim of our study was to compare the reliability and safety of the classical I-AT with the continuous positive airway pressure apnea test (CPAP-AT).

In the group of 48 patients (group O), an I-AT was performed at the end of BD diagnostic procedures, and approximately 1-1.5h later CPAP-AT with 100% FiO₂ and CPAP of 10cm H₂O, provided by ventilator in CPAP mode. After pre‑oxygenation with 100% FiO₂ for 10min, the PaO₂/FiO₂ ratio was recorded prior to I-AT at time-point one (T1) and prior to CPAP-AT at time-point two (T2). Group O was categorized into subgroup N-H (non-hypoxemic), consisting of 41 patients with good lung function, and subgroup H (hypoxemic) consisting of 7 patients with poor lung function. Within each subgroup PaO₂/FiO₂ at T1 and T2 were compared.

In Group O, PaO₂/FiO₂ decreased from 321±128mmHg at T1 to 291±119mmHg at T2 (p=0.004). In subgroup N-H, PaO₂/FiO₂ declined from 355±103 to 321±100mmHg (p=0.008), and in subgroup H, PaO₂/FiO₂ remained almost unchanged. Additionally, in 4 patients from subgroup N-H, PaO₂/FiO₂ decreased below 200mmHg at T2.

Our study indicates that I-AT may compromise pulmonary function and this may support the recommendation of safer CPAP-AT alternative.