Independent lung ventilation with a single ventilator using a variable resistance valve.

Independent lung ventilation using two ventilators has been attempted in the treatment of acute respiratory failure due to unilateral lung disease. However, this method has been found to be cumbersome and difficult to use. We reasoned that a bifurcated endotracheal tube with a variable resistance valve may enable us to change the inspiratory airway pressures and, hence, the inspired tidal volume to one lung using a single ventilator. We tested this hypothesis in eight anesthetized sheep and created a bronchopleural fistula in one lung as a model of unilateral lung disease. A bifurcated endotracheal tube was placed to separate the ventilation to each lung and, through a "Y" connector, both right and left lungs were ventilated simultaneously with a single ventilator. A variable resistance valve was placed between the "Y" connector and the tube ventilating the experimental lung with bronchopleural fistula. With a ventilator-generated peak inspiratory pressure of 31 +/- 2 cm H2O, the airway pressure distal to the valve was randomly changed from 31 cm H2O to 23 +/- 2, 15 +/- 1, 8 +/- 1, and 0 cm H2O. This resulted in progressive diversion of tidal volume from the experimental lung to the control lung and an increase in exhaled tidal volume due to a decrease in air leak from the bronchopleural fistula. These data suggest that a variable resistance valve may be used for independent lung ventilation using a single ventilator.