[Benchmark of a high-frequency jet ventilator, the Mistral]

To test a high-frequency jet ventilator, the Mistral (Acutronic Laboratory) on a lung model.

The jet ventilator Mistral was tested with two connectors (7 and 20 ml) and four catheters. Pressure and flow measurements were performed by varying the driving pressure (1 to 3 bars), the I/T ratio (0.25, 0.35, 0.45) and the frequency (1 to 5 Hz). Recorded data were: the volume delivered by the ventilator, the pressure measured in the connecting line between the ventilator and the injector and the difference between the end expiratory pressure measured by the ventilator through the injector and the tracheal pressure.

An increase in driving pressure induced a proportional increase in minute volume whatever the injection catheter used. After insufflation, when a Seldicath catheter was used, the pressure decrease was the slowest and the time constant the longest. Increase in frequency or I/T ratio, particularly beyond 0.35, was associated with an increase of the end expiratory pressure measured by the respirator. The gradient of pressure measured by the respirator and by an external sensor was lower with the 7 ml connector whatever the catheter used, and was larger with the Seldicath catheter.

The use of a low volume connector should be preferred, because it allows the measurement of the end expiratory pressure for a larger range of driving pressure, expiratory time and catheters. The performances of the Seldicath catheter are below those of the other catheters studied.