Perioperative pulmonary function in acute respiratory failure: effect of ventilator type and gas mixture

Whether maintaining pulmonary nitrogenation and/or a stable ventilatory pattern during surgery would minimize changes in perioperative pulmonary function in two groups of patients with acute respiratory failure (ARF) whose lungs were being mechanically ventilated was examined. Group 1 (n = 39 cases) (inspired oxygen fraction [FIO2] less than or equal to 0.5, minute ventilation less than or equal to 15 l/min, peak inspiratory pressure less than or equal to 50 cmH2O, positive end-expiratory pressure [PEEP] less than or equal to 10 cmH2O) were assigned randomly to one of four intraoperative ventilator-gas mixture (FIO2 approximately 0.5) combinations: 1) Siemens 900C ventilator, N2/O2; 2) Siemens 900C ventilator, N2O/O2; 3) Ohio anesthesia ventilator, N2/O2; or 4) Ohio anesthesia ventilator, N2O/O2. Group 2 (n = 15 cases) (ventilatory requirements exceeding any of those in Group 1) had their lungs ventilated intraoperatively with the Siemens 900C ventilator and a gas mixture determined by their anesthesiologist (FIO2 approximately 0.6-1.0). In patients whose lungs were ventilated with the Ohio N2O/O2 combination, PaO2/FIO2 decreased significantly (P less than 0.05) from 358 +/- 93 mmHg (mean +/- SD) preoperatively to 282 +/- 77 mmHg intraoperatively. The level of PEEP increased significantly from 5 +/- 3 cmH2O preoperatively to 9 +/- 4 cmH2O intraoperatively (P less than 0.05). In patients whose lungs were ventilated with the Ohio N2/O2 combination, PaO2/FIO2 decreased significantly from 270 +/- 86 mmHg preoperatively to 174 +/- 74 mmHg intraoperatively. These variables did not change significantly in patients ventilated with the Siemens ventilator (groups 1 and 2). Pulmonary oxygen gas exchange returned to preoperative values by the first hour postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)