The apnea test, which involves disconnection from the mechanical ventilator, 
presents risks during the determination of brain death, especially in hypoxemic 
patients. We describe the performance of the apnea test without disconnection 
from the mechanical ventilator in two patients. The first case involved an 
8-year-old boy admitted with severe hypoxemia due to pneumonia. He presented 
with cardiorespiratory arrest, followed by unresponsive coma due to 
hypoxic-ischemic encephalopathy. Two clinical exams revealed the absence of 
brainstem reflexes, and transcranial Doppler ultrasound revealed brain 
circulatory arrest. Three attempts were made to perform the apnea test, which 
were interrupted by hypoxemia; therefore, the apnea test was performed without 
disconnection from the mechanical ventilator, adjusting the continuous airway 
pressure to 10cmH2O and the inspired fraction of oxygen to 100%. The oxygen 
saturation was maintained at 100% for 10 minutes. Posttest blood gas analysis 
results were as follows: pH, 6.90; partial pressure of oxygen, 284.0mmHg; 
partial pressure of carbon dioxide, 94.0mmHg; and oxygen saturation, 100%. The 
second case involved a 43-year-old woman admitted with subarachnoid hemorrhage 
(Hunt-Hess V and Fisher IV). Two clinical exams revealed unresponsive coma and 
absence of all brainstem reflexes. Brain scintigraphy showed no radioisotope 
uptake into the brain parenchyma. The first attempt at the apnea test was 
stopped after 5 minutes due to hypothermia (34.9°C). After rewarming, the apnea 
test was repeated without disconnection from the mechanical ventilator, showing 
maintenance of the functional residual volume with electrical bioimpedance. 
Posttest blood gas analysis results were as follows: pH, 7.01; partial pressure 
of oxygen, 232.0mmHg; partial pressure of carbon dioxide, 66.9mmHg; and oxygen 
saturation, 99.0%. The apnea test without disconnection from the mechanical 
ventilator allowed the preservation of oxygenation in both cases. The use of 
continuous airway pressure during the apnea test seems to be a safe alternative 
in order to maintain alveolar recruitment and oxygenation during brain death 
determination.