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The Modified Apnea Test During Brain Death Determination: An Alternative in Patients With Hypoxia. INTRODUCTION: Conventional apnea testing in patients with severe hypoxemia or hemodynamic instability with removal from the ventilator support is unsafe. We describe an alternative approach to apnea testing, which may be used in patients with hypoxia unable to undergo conventional apnea testing. METHODS: Case Report. A 42-year-old man had a severe traumatic brain injury resulting in diffuse cerebral edema and subarachnoid hemorrhage with herniation. His presentation was complicated by hypoxic respiratory failure from pulmonary contusions and hemorrhagic shock. On hospital day 2, the patient lost brain stem reflexes. Brain death testing with conventional apnea testing was attempted but aborted due to hypoxia. RESULTS: A modified apnea test was applied, which had been approved by appropriate hospital committees including critical care operations, ethics, and the brain death protocol council. Minute ventilation was gradually decreased by ≥50% to attain a PaCo2 level ≥20 mm Hg above baseline. The ventilation mode was then switched from volume control to continuous positive airway pressure while observing the patient for signs of respiration for a duration of 60 seconds. CONCLUSION: The modified apnea test does not require circuit disconnection and can be successfully applied to determine brain death without compromising safety in high-risk patients having severe hypoxia.