Effect of conventional mechanical ventilation and jet ventilation on airway pressure in dogs and plastic models with tracheal stenosis.

OBJECTIVE

To evaluate the effect of jet ventilation on tracheal stenosis in dogs and plastic models.

DESIGN

Prospective, randomized trial in dogs, and multitrial tests in tracheal stenosis models.

SETTING

Animal laboratory in a university setting.

INTERVENTIONS

Tracheal stenosis was surgically created around the middle of the trachea. Conventional mechanical ventilation and jet ventilation were compared at the same value of Paco2 in dogs and at the same tidal volume in tracheal stenosis models.

SUBJECTS

Twelve mongrel dogs and four types of plastic models with combinations of short or long stenosis and fluid or nonfluid stenosis.

MEASUREMENTS AND MAIN RESULTS

Canine Studies. Mean peak peak airway pressure values at the distal and proximal portion of the stenosis, and the end-expiratory pressure at the distal portion of the stenosis, were significantly higher during conventional mechanical ventilation than during jet ventilation. The mean values of arterial pressure, pulmonary arterial pressure, central venous pressure, and cardiac output did not change significantly between conventional mechanical ventilation and jet ventilation, except for the pulmonary artery occlusion pressure valve. Plastic Mold Studies. peak airway pressure and end-expiratory airway pressure at the poststenotic trachea during jet ventilation with the model lung were significantly lower than during conventional mechanical ventilation. The difference in peak airway pressure, and end-expiratory airway pressure values between jet ventilation and conventional mechanical ventilation increased more in short stenosis and nonfluid stenosis.

CONCLUSIONS

The jet flow that struck the portion of the stenosed wall reversed direction, even during early expiration. Therefore, the expiration during jet ventilation was facilitated more by the reversed flow than by the expiration during conventional mechanical ventilation. This reversed flow may provide lower end-expiratory airway pressure at the poststenotic portion with jet ventilation than with conventional mechanical ventilation. We conclude that jet ventilation was a useful method of ventilation in cases with tracheal stenosis, especially nonfluid and short stenosis.