Apnea testing guided by continuous transcutaneous monitoring of partial pressure of carbon dioxide

Objective: To continuously monitor Pco(2) during two different protocols for apnea testing as part of the determination of brain death. Design: Prospective comparative study using continuous transcutaneous Pco(2) (tcPco(2)) monitoring in 54 apnea tests with or without artificial CO2 augmentation. Another 53 apnea tests were not continuously monitored. Setting: Intensive care wards in Northern Bavaria. Patients: Ninety-six consecutive patients with suspected brain death. Interventions: Apnea tests guided by transcutaneous monitoring during a Paco(2) of greater than or equal to 60 torr (greater than or equal to 8 kPa). Measurements and Main Results: The mean of the difference between tcPco(2) and Paco(2) was -0.26 +/- 1.16 (SEM) torr (-0.035 +/- 0.15 kPa). Seventy percent of all transcutaneous measurements were within +/-10% of the Pace(2) values. The individual differences ranged from -25.8 to 16.9 torr (-3.44 to 2.25 kPa). Conclusions: While not as precise as could be desired in individual cases, the overall agreement between tcPco(2) and Pace(2) was good. Transcutaneous monitoring aided in effectively reducing the CO2 target overshoot with artificial CO2 augmentation, reduced the necessary number of blood gas checks compared with a former study, using predetermined time locked evaluations, and prolonged only tests with artificial CO2 augmentation.