Respiration maintained by externally applied vibration and tracheal insufflation in the cat

It was reported recently that adequate gas exchange could be maintained in patients and experimental animals by applying very high-frequency (15 Hz), low-volume oscillations at the upper airways. This report deals with a new mode of high-frequency ventilation, in which gas exchange is achieved in paralyzed casts by externally vibrating the chest wall. These vibrations, which alone caused very small-volume (<0.5 ml) oscillations at the tracheal opening, maintained gas exchange at normal PaCO₂ for hours when coupled with tracheal air insufflation. PaCO₂ values as low as 15 torr could be achieved by increasing the insufflation rate. Vibration frequencies in the range of 20-45 Hz were equally effective. The method required little or no continuous positive airway pressure, caused little elevation of mean tracheal pressure, and no consistent changes in arterial and central venous pressures during ventilation. In addition to the potential merits of this method of ventilation, the described vibrations seem to considerably reduce the anatomic dead space and as such may assist conventional methods of artificial ventilation or even spontaneous breathing when rapid and shallow.