The SynCardia Total Artificial Heart is connected to two tubes in Stan Larkin’s chest. They snake out from under his ribs and connect to a 13-pound compressor carried in his backpack.

It’s an apparatus that provides Larkin a sort of sound track of his life right now — an ever-present, rhythmic gallop as pulses of precisely calibrated, compressed oxygen are forced into the pneumatic ticker.

“I guess I tuned it out after about three days,” he said, chuckling.