Pulmonary gas exchange after tracheal extubation was evaluated in 25 patients to determine the effect of 50% oxygen administered during mechanical ventilation following aortocoronary bypass grafting. Twenty-five patients postoperative mechanical ventilation for 16-24 hr, 13 with an inspired oxygen fraction (FIO2) of no more than 0.30 and 12 with an FIO2 of 0.50. After tracheal extubation, all patients spontaneously breathed room air (FIO2 0.21). Postextubation the calculated venous admixture of patients who had received 50% oxygen (0.20 ± 0.03 [SD]) was significantly (p < .01) greater than that calculated for patients who received lower oxygen concentrations (0.13 ± 0.04). Consequently, the PaO2 of patients who had received 50% oxygen (60 ± 5 torr) was significantly (p < .03) lower than the PaO2 of patients who had received no more than 30% oxygen (66 ± 7 torr). Thus, administration of 50% oxygen, supposedly nontoxic, to mechanically ventilated patients may cause impairment of pulmonary gas exchange after tracheal extubation. Although high concentrations of supplemental oxygen are sometimes required, unnecessary elevation of FIO2 is not likely to significantly increase oxygen delivery and may contribute to postextubation pulmonary dysfunction.
ASJC Scopus subject areas
- Critical Care and Intensive Care Medicine