Unilateral Lung Disease and Positional Ventilation

Michael A. Gropper, MD, PhD


March 15, 2001


I have always thought that if a patient had unilateral lung disease, ie, unilateral pulmonary edema, lobar pneumonia, or pneumothorax, that to improve oxygenation urgently, the patient could be placed with the "good" lung down to maximize V/Q matching. Some recent lectures I've heard seem to contradict that. Any comments?

Response from Michael A. Gropper, MD, PhD

In general, the "good" lung should indeed be placed down to optimize V/Q matching. In this position, the majority of blood flow will go to this lung and result in the best oxygenation. Exceptions to this strategy include the circumstance in which secretions or hemorrhage from the "bad" lung might flow into the good lung if it is placed in a gravity-dependent position. In addition, the dependent portions of the lung tend to develop atelectasis, particularly in sedated or anesthetized patients. Therefore, some centers will intermittently place patients with severe hypoxemic respiratory failure in the prone position. This benefit tends to be short-lived, with the dependent portions of the now prone lung tending to become atelectatic. An alternative approach is the use of rotating beds, which minimize the formation of atelectasis.

In patients with unilateral pulmonary processes, caution should be exercised in the selection of the mode of mechanical ventilation. Because of differing compliance between the 2 lungs, very little ventilation may go to the "bad" lung. In general, ventilation with a low respiratory rate and/or an inspiratory pause will result in some recruitment of alveoli in the "bad" lung and might improve oxygenation.