Efficacy of capnometry in ventilatory management of cardiac patients

The ability of capnometry to prevent hypercarbia and to safely help in weaning post-cardiac surgery patients was investigated. The first group, 60 patients, had arterial blood gases (ABG) determined after each new ventilator setting. The corresponding end-tidal CO2 (PETCO2) was recorded and PaCO2-PETCO2 gradients were established at each ABG determination. The initial gradient was maintained during ventilation in the patient. A later gradient, determined when the patient was waking, was used to wean. The next 50 patients, the second group, had responses to ventilator changes determined solely by capnometry. ABG were routinely drawn only to establish the maintenance and weaning PaCO2-PETCO2 gradients. The initial gradients of 8.43 +/- 3.45 (mean +/- SD) and 7.65 +/- 2.24 mmHg, in the first and second groups, narrowed to 1.27 +/- 3.79 and 2.21 +/- 3.96 mmHg, respectively, when the patients were ready to wean. All patients in both groups were safely weaned. Patients in the second group had fewer ABG determinations, 3.78 +/- 1.30 v 5.40 +/- 1.97, a decrease of 1.62 (95% confidence interval 1.54 to 1.70). No patient was hypercarbic. The study shows that capnometry can be used to safely wean patients, decrease the number of ABG, and prevent hypercarbia.