Synchronous versus asynchronous differential lung ventilation with PEEP after unilateral acid aspiration in the dog.

Differential lung ventilation (DLV) with PEEP has been used to oxygenate patients with severe unilateral or asymmetrical lung disease. Many different ventilator systems have been used to deliver DLV, but the question of whether or not to synchronize the ventilation of the 2 lungs has not been answered. Twelve mongrel dogs were given a unilateral hydrochloric acid (HCl) injury and divided into 2 groups, one receiving synchronous and the other receiving asynchronous DLV. The assignment of synchronization and side of injury was allocated randomly. A computer-controlled DLV system was used to ventilate the dogs with equal tidal volumes to each lung. The respiratory rate was feedback controlled to maintain PaCO2 at 35 torr. After injury, 10 cm H2O of PEEP was applied to the injured lung and the dogs were ventilated with FIO2 = 0.40 for 4 h. There was no statistically significant difference in gas exchange ([PaO2, Qva/Qt, PaCO2, P(A-a)O2] or hemodynamics [mean arterial pressure (MAP), CVP, mean pulmonary arterial pressure (MPAP), mean pulmonary arterial wedge pressure (WP), cardiac output in triplicate (Q), heart rate (HR)] between the 2 groups. With this particular model, there is no need to synchronize the 2 ventilators when using DLV with unilateral PEEP.