Long-term transtracheal high frequency ventilation in dogs.

Long-term effects of high frequency percutaneous transtracheal ventilation (HFTV) have not been studied. The purpose of this study is to evaluate the cardiopulmonary effects of 24 h transtracheal ventilation in dogs at a respiratory rate of 100/min. Four dogs were anesthetized with intermittent pentobarbital and paralyzed with pancuronium. Ventilation in the supine position was through a 14-gauge Angiocath introduced into the trachea through the cricothyroid membrane. A respiratory rate of 100/min was used at an FIO2 of 0.4 using a fluidic logic controlled ventilator. The inspiratory-expiratory ratio was 1:2 and tidal volume 70 ml. The driving pressure of the air-oxygen mixture was 50 psi. After 24 h, residual muscle relaxant was reversed and the animal allowed to recover. There was no significant change in the following parameters over 24 h compared to starting values: PaO2, PaCO2, pH, aortic, central venous, pulmonary artery and pulmonary artery wedge pressures, heart rate, cardiac index (CI), stroke index (SI), left ventricular stroke work (LVSW), systemic vascular resistance (SVR), pulmonary vascular resistance (PVR), C(a-V)O2, oxygen consumption (VO2), pulmonary shunt (Qs/Qt). A PEEP effect of 2.9 - 5.0 torr was maintained. All dogs recovered uneventfully. Three days after the experiment, blood gases of 2 dogs were normal. One dog was killed after 3 days; macroscopic and microscopic examinations of the upper and lower airway and pulmonary parenchyma were normal. Dogs can be ventilated for as long as 24 h using HFTV transtracheally at rates of 100/min without adverse cardiopulmonary effects.