[Experiences with high-frequency jet ventilation in operations of the larynx and trachea]

60 ENT patients were ventilated with the high frequency jet ventilation method, using endotracheal catheters during 50 cases of laryngeal and 10 cases of tracheal surgery. Ventilation was carried out with equipment of type MK 800 (Acutronic Ltd.) using the following parameters; rate: 150/min, insufflation time: 30-40%, pressure: 0.7-2.1 bar, and flow minute volume (FMV) 7-23 1. Anaesthesia was carried out with flunitrazepam or diazepam, fentanyl and succinylcholine. Surgical view was very good indeed, thanks to the thin jet catheter (4.7 mm outer diameter) in the trachea. At the low "tidal volumes" and intratracheal pressure changes when a rate of 150/min was used, no movement of the vocal cords was seen, so that microsurgery was easy to perform. There were no cases of hypoxia. The median pO2 value was 193 mm Hg. When a flow minute volume of 200 ml/kg was used for patients with normal lung function, and 250 ml/kg for those with impaired function, ventilation was quite adequate. The quality of ventilation should always be checked, and corrected as necessary, by blood gas analyses. Hypoventilation occurred when the FMV was less than 250 ml/kg in patients with decreased lung function, when the tip of the catheter was inserted into a mainstem bronchus or near to the tracheostoma, or when gas escape was obstructed. Unhampered gas escape must be present at all times, because otherwise intratracheal pressure rises and ventilation becomes insufficient. If the pressure increase is marked under these circumstances it can even lead to a pneumothorax.