Bronchoscopic measurement of collateral ventilation in a sheep model of emphysema.

BACKGROUND The development of bronchoscopic therapies for emphysema has renewed interest in collateral ventilation. The success or failure of bronchoscopically placed valves or biologic glues may be determined by collateral ventilation, which is exaggerated in emphysema. Furthermore, the validity of various animal models of emphysema for testing such techniques must be understood in the context of their species-specific collateral ventilation. OBJECTIVES To quantify collateral ventilation in a sheep model of emphysema using a simple in vivo bronchoscopic method. METHODS Collateral ventilation was measured in 8 anesthetized sheep using a simple method which measured pressure and flow through the working channel of a bronchoscope wedged in a segmental lung orifice. Animals then underwent nebulized papain treatments to generate emphysema, followed by repeat bronchoscopic measurements. RESULTS There was a 33% decrease in resistance to collateral ventilation following papain treatment. Changes in collateral resistance were closely correlated with disease severity as measured by changes in segmental compliance, which increased 267%. CONCLUSIONS Collateral ventilation is significantly increased in sheep following nebulized papain. Bronchoscopic measurement of collateral ventilation may be useful for evaluating other animal models of emphysema and for predicting the response to bronchoscopic therapies in human emphysema patients.