Gas exchange during high-frequency ventilation of the chicken

Recent studies have shown that high-frequency ventilation (HFV) at 1-30 Hz is capable of maintaining adequate gas exchange in humans and dogs even when tidal volumes are substantially less than dead space. We evaluated the effectiveness of HFV in roosters by comparing CO2 elimination during various frequencies and tidal volumes of HFV with CO2 elimination during conventional mechanical ventilation. Sinusoidal oscillations were applied at the tracheal cannula. A bias flow provided fresh gas at the top of the tracheal cannula. Three conclusions emerge from the data. 1) HFV enhances gas transport in the chicken as it does in mammals. 2) At low oscillatory flows (amplitude X frequency) CO2 elimination depends on both frequency and tidal volume, whereas at higher flows CO2 elimination depends more strongly on tidal volume. The flow at which this transition occurs is relatively lower than in humans and much lower than in dogs. 3) HFV at volumes below dead space is usually not capable of maintaining adequate gas exchange in the chicken in contrast to results in dogs and humans.