Preoxygenation of patients for coronary artery bypass grafting: vital capacity versus tidal breathing.

Arterial oxygenation, as measured by serial arterial blood gases (ABGs) and in vivo polarographic PaO2 during the rapid sequence induction of general endotracheal anesthesia, was evaluated in 20 ASA physical class IV subjects undergoing elective coronary artery bypass grafting (CABG). Subjects received a narcotic premedication 30-60 minutes prior to arrival in the operating room. Subjects in Group I (n = 10) were preoxygenated with 3 minutes of tidal breathing, while Group II (n = 10) subjects took four vital capacity breaths (VCB) within 30 seconds. Manual ventilation was withheld after the period of preoxygenation (the mean duration of apnea was 121.25 seconds). The mean PaO2 rose from 69.40 mmHg to 323.80 mmHg after preoxygenation in Group I and from 73.70 mmHg to 359.10 mmHg in Group II. After tracheal intubation, the mean PaO2 fell to 275.70 mmHg in Group I compared with 277.20 mmHg in Group II. There was no significant difference (p greater than 0.05) between the two methods of preoxygenation in their ability to increase arterial oxygen. In conclusion, vital capacity breathing is as effective as 3 minutes of tidal breathing in elevating the PaO2 in subjects with significant coronary artery disease prior to a rapid sequence induction.