Setting and monitoring of high-frequency jet ventilation in severe respiratory distress syndrome.

High-frequency jet ventilation (HFJV) is used in respiratory distress syndrome (RDS) to avoid high airway pressures and barotrauma. This study was designed to find rational strategies to regulate oxygenation and alveolar ventilation at HFJV and to determine appropriate monitoring methods. Seven dogs were subjected to total lung lavage with saline to induce RDS. PEEP was increased at conventional intermittent positive-pressure ventilation until re-expansion was indicated by a PaO2 of 300 torr at an FIO2 of 1.0 HFJV at 4 and 15 Hz was each tried at 0 and 10 cm H2O PEEP. Intermittent low-frequency inflations were also added to HFJV at 0 PEEP. Lung expansion was maintained without circulatory depression by adjustment of minute ventilation (VE) delivered by the HFJ ventilator; external PEEP was a useful complement. PaCO2 was controlled by frequency adjustment. HFJV at 4 Hz resulted in hypocapnia; intermittent low-frequency inflations had no effect. VE monitoring, CO2 elimination monitoring, and PEEP adjustment was done with a standard ventilator during HFJV. This study illustrates that HFJV is efficient in RDS; VE and external PEEP strongly influence oxygenation and may be used to regulate this factor, and frequency affects CO2 elimination, thus suggesting a method of PaCO2 control.