[High-frequency jet ventilation with the HFV 970 prototype in laryngeal microsurgery: comparison of 2 injection...

To describe the results obtained with the use of a high frequency jet ventilation system with the HFV 970 prototype through two types of injector, an intratracheal cannula and an endotracheal tube, in 12 patients undergoing laryngoscopic microsurgery.

After anesthetic induction with propofol and succinylcholine, an intratracheal cannula was placed in the patients in group A by way of cricothyroid membrane puncture. The tracheas of group B patients were intubated with a number 7 tube, through which was inserted the same type of cannula as had been used with group A patients. A prototype Servo HFV 970 respirator was used with the following protocol: minute volume 120 ml/min, inspiratory time 30%, respiratory rate 120 cycles/min and a FiO2 of 1. Anesthesia was maintained with propofol in continuous perfusion. The parameters studied were peak airway pressure, PCO2, PO2 and pH. Data were recorded at baseline and every 5 min thereafter until the end of surgery.

During high frequency jet ventilation there were no statistically significant differences between groups A and B with respect to peak airway pressure. PCO2 in group A increased significantly during surgery, while in group B it decreased significantly. Oxygenation was excellent in both groups, being significantly higher than baseline values at all times studied, with no statistically significant differences between the 2 groups.

Our results for the efficacy of ventilation and oxygenation with the prototype HFV 970 are similar to those published for conventional high frequency jet ventilation. Using a tracheal tube assures adequate ventilation, but supposes a tendency to entrapment, whereas use of an intratracheal cannula is associated with lower ventilatory efficacy and less entrapment. Oxygenation is excellent with both systems.