How is the apnea test performed?
Adjust vasopressors to a systolic blood pressure ≥100 mm Hg.
Preoxygenate for at least 10 minutes with 100% oxygen to a PaO 2 ≥200 mm Hg. Reduce ventilation frequency to 10 breaths per minute to eucapnia.
Reduce PEEP to 5 cm H 2 O (oxygen desaturation with decreasing PEEP may suggest difficulty with apnea testing).
If pulse oximetry oxygen saturation remains >95%, obtain a baseline blood gas (PaO 2 , PaCO 2 , pH, bicarbonate, base excess).
Disconnect the patient from the ventilator.
Preserve oxygenation (e.g., place an insufflation catheter through the endotracheal tube and close to the level of the carina and deliver 100% O 2 at 6 L/min).
Look closely for respiratory movements for 8 to 10 minutes.
Respiration is defined as abdominal or chest excursions and may include a brief gasp.
Abort if systolic blood pressure decreases to <90 mm Hg. Abort if oxygen saturation measured by pulse oximetry is <85% for >30 seconds.
Retry procedure with T-piece, CPAP 10 cm H 2 O, and 100% O 2 12 L/min.
If no respiratory drive is observed, repeat blood gas (PaO 2 , PaCO 2 , pH, bicarbonate, base excess) after approximately 8 minutes.
If respiratory movements are absent and arterial PCO 2 is ≥60 mm Hg (or 20-mm Hg increase in arterial PCO 2 over a baseline normal arterial PCO 2 ), the apnea test result is positive (i.e., supports the clinical diagnosis of brain death).
If the test is inconclusive but the patient is hemodynamically stable during the procedure, it may be repeated for a longer period of time (10 to 15 minutes) after the patient is again adequately preoxygenated.
