A medical system includes a flexible catheter, an imaging probe, a working catheter, and a positioning system. The flexible catheter includes a plurality of first lumens and a sealing device having one or more balloons to seal the anatomic passageways at a sealing location and one or more flaps or valves to remove air from the anatomic passageways. The imaging probe and working catheter are receivable within the plurality of first lumens and extend through the sealing device. The working catheter includes one or more second lumens to receive a medical instrument. The positioning system is configured to determine a position of a distal portion of the flexible catheter, the imaging probe, or the working catheter. The medical system is configured to collapse a portion of the anatomic passageways distal of the sealing location by removing air from the anatomic passageways to facilitate ultrasound imaging using the imaging probe.