GAS-EXCHANGE AND LUNG-MECHANICS DURING PERCUTANEOUS TRANSTRACHEAL VENTILATION IN AN UNPARALYZED CANINE MODEL

Objective: To compare the efficacy of percutaneous transtracheal venti lation (PTV) in the unparalyzed state with that in the paralyzed stare using a sedated nonobstructed canine model. Methods: Eight mongrel do gs (16.8-32 kg) were anesthetized, instrumented, and placed in a volum e plethysmograph. Anesthesia was achieved with pentobarbital sodium (u p to 30 mg/kg). The spontaneous respiratory drive was kept intact. PTV was performed using a 13-ga transtracheal catheter and compressed air at 45 psi at an I:E ratio of 1:3 (15 breaths/min). Each dog was seque ntially ventilated in both the paralyzed and unparalyzed states, The p aralyzed/unparalyzed sequence was alternated among the animals to avoi d sequence bias. Paralysis was achieved with succinylcholine (0.1 mg/k g bolus and 0.01 mg/kg/min drip). Reversal of paralysis was achieved b y discontinuing the succinylcholine infusion. Key variables, including arterial blood gas, tidal volume, and pulmonary mechanics, were measu red and compared for the paralyzed and unparalyzed stales. Results: Ga s exchanges and lung mechanics were similar between the unparalyzed an d paralyzed states. There was no significant difference in mean pH, pC O(2), pO(2), tidal volume, or peak inspiratory transpulmonary pressure . There was also no significant difference in pulmonary resistance or pulmonary compliance.Conclusion: In a sedated nonobstructed canine mod el, PTV is as efficacious in the unparalyzed state as it is in the par alyzed state, The lung mechanics are also similar in the states. These data suggest that it may be unnecessary to induce paralysis when usin g PTV for emergency ventilation in the heavily sedated state.