Bulk diffusion apnea test in the diagnosis of brain death.

OBJECTIVE: To assess the efficacy of bulk diffusion in maintaining oxygenation during apnea testing for brain death.

DESIGN: Case series.

SETTING: ICU in a primary care hospital.

PATIENTS: Twenty-four consecutive patients with suspected brain death. Most patients suffered cerebral trauma from vehicular accidents.

INTERVENTION: Patients were preoxygenated with an FIO2 of 1.0 and were maintained during apnea testing with bulk flow of an FIO2 of 1.0 at 40 to 60 L/min in adults and 15 L/min in children. The pre-apnea PaCO2 was between 35 to 45 torr (4.7 to 6.0 kPa) in all patients.

MAIN OUTCOME MEASURES: Twenty-three patients completed the test. Five patients had a PaO2 < 100 torr (< 13 kPa) during the 10-min ventilator withdrawal time period.

MAIN RESULTS: No patient breathed spontaneously during the apnea test. Twenty-two patients achieved a PaCO2 > 60 torr (> 8 kPa). One patient had a postapnea PaCO2 of 59 torr (7.8 kPa). The test was stopped in one patient who became hypotensive.

CONCLUSIONS: The bulk diffusion technique has several advantages, including ease of performance over other methods of supplying oxygen during apnea testing, but this method does not prevent hypoxemia in patients with lung disease.