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 steno sis in dogs and plastic models. Design: Prospective, randomized trial in dogs, and multitrial tests in tracheal stenosis models. Setting: An imal laboratory in a university setting. Interventions: Tracheal steno sis was surgically created around the middle of the trachea, Conventio nal mechanical ventilation and jet ventilation were compared at the sa me value of Pace, in dogs and at the same tidal volume in tracheal ste nosis models, Subjects: Twelve mongrel dogs and four types of plastic models with combinations of short or long stenosis and fluid or nonflu id stenosis. Measurements and Main Results: Canine Studies. Mean peak airway pressure values at the distal and proximal portion of the steno sis, and the end-expiratory pressure at the distal portion of the sten osis, were significantly higher during conventional mechanical ventila tion than during jet ventilation. The mean values of arterial pressure , pulmonary arterial pressure, central venous pressure, and cardiac ou tput did not change significantly between conventional mechanical vent ilation and jet ventilation, except for the pulmonary artery occlusion pressure value. Plastic Mold Studies. Peak airway pressure and end-ex piratory airway pressure at the poststenotic trachea during jet ventil ation with the model lung were significantly lower than during convent ional mechanical ventilation. The difference in peak airway pressure a nd end-expiratory airway pressure values between jet ventilation and c onventional mechanical ventilation increased more in short stenosis an d 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 mor e by the reversed flow than by the expiration during conventional mech anical ventilation. This reversed flow may provide lower end expirator y airway pressure at the poststenotic portion with jet ventilation tha n with conventional mechanical ventilation. We conclude that jet venti lation was a useful method of ventilation in cases with tracheal steno sis, especially nonfluid and short stenosis.