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

Abstract

Introduction: 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).

Material and methods: 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.

Results: 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.

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

Keywords: Apnea test; Brain death; Brain death diagnosis; Oxygen insufflation; Pulmonary ventilator.