Differential lung ventilation: a review and 2 case reports

The respiratory parameters of some of the patients with acute respiratory failure deteriorates while using conventional ventilation. These patients suffer unilateral lung disease and the failure to respond favourably to therapy is due to increased intrapulmonary shunt. There is a reflex vasodilation in the injured lung. Functional residual capacity is reduced in the injured lung and the compliance decreases. Gas flow is then deviated to the other lung, thus increases alveolar collapse and decreases regional compliance in the injured lung. These events cause severe hypoxemia. We present here two cases with unilateral lung disease that failed to respond to conventional mechanical ventilation. Asynchronized differential lung ventilation was found to be the therapeutic answer to the problem. We discuss the pathophysiology of unilateral lung injury and the physiology of differential lung ventilation.