Changes in ventilation and perfusion in anesthetized dogs following lobar lavage with saline solution

The therapeutic application of endobronchial lavage has been inhibited by concern regarding alterations in the exchange of gases, particularly hypoxemia, and by the technical complexity of the procedure. Using a cuffed fiberoptic bronchoscope with which lavage could be restricted to one lobe, we studied the sequence of alterations in the exchange of gases after lavage and the attendant disturbances in ventilation and perfusion in ten mongrel dogs following lobar lavage with 1,850 ml of physiologic saline solution. Sequential scintiphotographs of ventilation and perfusion and sequential measurements of arterial blood gas levels were obtained. Linkage of the computer to the scintillation camera allowed quantification of data on ventilation and perfusion from the lobar area of interest. Lavage induced a reduction in regional ventilation and perfusion in all dogs. The decline in ventilation preceded that in perfusion, and the computed ratio of ventilation over perfusion reached its lowest point during the first 30 minutes after lavage. The arterial oxygen pressure (PaO2) declined in all dogs from a mean baseline value of 87 mm Hg to a mean value of 76 mm Hg at 30 minutes after lavage and gradually returned to a mean of 85 mm Hg by six hours after lavage. The lowest value for PaO2 occurred after balloon occlusion prior to lavage. Calculations of shunt showed a minimal increment in the intrapulmonary shunt (Qs/Qt). In the normal dog, lobar lavage induces mild hypoxemia due to an imbalance of ventilation and perfusion that resolves within six hours.