A method of inhibiting a flow of a purging fluid from a tissue visualization device comprises positioning an imaging hood attached to a distal end of a flexible elongate shaft in proximity to a tissue region to be visualized The method also comprises introducing the purging fluid into an inflation member suspended within an open area of the imaging hood. The inflation member includes at least one aperture on a proximal portion of the inflation member. The method also comprises inflating the inflation member to a partially inflated state in which the inflation member is circumferentially separated from an inner surface of the hood to form an annular flow path for the purging fluid from the at least one aperture, between the inner surface of the hood and the inflation member, and into fluid communication with an environment external to the hood. The method also comprising inflating the inflation member to a blocking inflated state in which the inflation member expands into contact with the imaging hood to block the flow from the at least one aperture to the annular flow path.