High-frequency ventilation by bilateral phrenic nerve stimulation in dogs

We succeeded in achieving good gas exchange by oscillatory phrenic nerve stimulation (PNS) in dogs. In 7 out of 14 dogs, adequate gas exchange was attained by PNS at 3, 4 and 5 pulses per sec (pps). VE increased with stimulation frequency up to 4 or 5 pps, but decreased above 6 pps. We also applied sinusoidal oscillation using a piston pump at the trachea in the same dogs to analyze the mechanical properties of the respiratory system. The V/P ratio, oscillatory volume divided by driving pressure, decreased markedly at 6 Hz while the pleural pressure remained constant up to 10 Hz. These facts indicate that the fall in VE is due to mechanical properties of the airway and lung, and not due to failure of the ventilatory pump system. We conclude that frequencies of 3-5 pps in high-frequency ventilation are optimal for maintaining effective gas transport when the diaphragma is used as the oscillatory generator.