The effect of high frequency oscillatory ventilation on pulmonary stretch receptors in the dog

High frequency oscillatory ventilation is a form of artificial ventilation where the tidal volume is less than the anatomical dead space. The efficacy of gas exchange depends upon the oscillatory frequency, volume, bias flow and the airway pressure. The present study was undertaken to determine the influence of oscillatory frequency, oscillatory volume and mean airway pressure upon the activity of pulmonary stretch receptors and rapidly adapting receptors during high frequency oscillatory ventilation. The experiments were conducted on dogs anaesthetized with either chloralose or nembutal. In Series I (16 slowly adapting stretch receptors) the effects of changing in turn, the oscillatory frequency, oscillatory volume and mean airway pressure were examined. The bias flow was held constant. Significant changes in the frequency of discharge of slowly adapting stretch receptors occurred only with alterations in oscillatory frequency (8,16,28 Hz) and mean airway pressure (3, 6 & 9 cm H2O). No significant changes in the activity of slowly adapting stretch receptors were observed when the oscillatory volume was altered (2.5, 5.0 & 7.5 ml/kg). With each manoeuvre there were significant small increments in intrathoracic gas volume. In Series II (16 slowly adapting stretch receptors) the interaction between oscillatory frequency and mean airway pressure was studied. The effect of each was greatest at the lowest value of the other variable. In Series III the effect of changing oscillatory frequency on the discharge from rapidly adapting receptors were examined. It was found that changes in frequency at a fixed airway pressure (3 cm H2O) and oscillatory volume failed to alter the activity significantly.(ABSTRACT TRUNCATED AT 250 WORDS)