Multi-stage balloon catheter, and method of operating same in a curved passageway

A method of operating a multistage balloon catheter that includes a catheter that defines an inflation lumen and a centerline;

• a multistage balloon mounted on the catheter and having an interior fluidly connected to the inflation lumen;
• a plurality of waist hoops at respective waist locations of the multistage balloon, and each adjacent pair of waist hoops being separated by a bulb segment of the multistage balloon;
• the multistage balloon having a deflated state, a first inflation state and a second inflation state, and the method comprising the steps of:
• positioning the multistage balloon in a curved passageway with the multistage balloon in the deflated state;
• inflating the multistage balloon to the first inflation state with fluid at a first fluid pressure;
• holding the waist locations of the multistage balloon against expansion with hoop tension in the waist hoops while in the first inflation state;
• conforming the centerline to match the curved passageway responsive to an interaction of the bulb segments with a wall that defines the curved passageway, and wherein the interaction pivoting adjacent bulb segments relative to each other about a respective pivot axis that is perpendicular to the centerline and intersects the waist hoop that separates the adjacent bulb segments;
• and
• expanding the waist locations into space defined by the wall and the multistage balloon by changing the multistage balloon from the first inflation state to the second inflation state by increasing fluid pressure from the first fluid pressure to a second fluid pressure while the centerline remains conformed to match the curved passageway.