Ventilatory volume and pressure required for oscillatory ventilation in dogs.

Abstract

We determined the ventilatory volume and pressure required to maintain a PaCO2 of 40 mmHg in dogs at between 0.5 and 16 Hz. The ventilator used was that incorporating a powerful, specially made loudspeaker to which a sine-wave signal was introduced. A windmill-type flowmeter measured the minute volume. The tidal volume, expressed per kg of body weight, was 16.1 at 0.5 Hz, decreasing linearly with log f, and reaching a value of 6.1 ml/kg at 16 Hz. The minute volume increased 10 times from 0.5 to 16 Hz. The intratracheal pressure was 12 to 13 cmH2O between 0.5 and 2 Hz, rising to 16 at 4 Hz and finally reaching 77.2 cmH2O at 16 Hz. The PaO2 values were always above 500 mmHg when FIO2 was 1.0. The frequency-impedence data were analyzed for R, I and C values. The fitting of the data to an R-I-C series model was good, but the R values obtained were considerably higher than those reported using a smaller amplitude of oscillation.