Method for measuring long-term function of muscle-powered implants via radiotelemetry

Abstract

Long-term remote monitoring of muscle-powered implants has been made possible with development of an adjustable workload that can be remotely monitored to assess device function. This technique obviates the need for percutaneous access lines and allows test animals to remain untethered, eliminating deleterious effects caused by infection, sedation, or animal stress. Hardware components include a latex bladder fixed within a hermetically sealed canister, multichannel implantable telemetry unit, and subcutaneous access port (for pressure charge adjustment). To validate this method, in vitro tests were performed by using a third-generation muscle energy converter designed to function as an implantable hydraulic pump. Two channels of telemetered pressure data were collected and used to calculate six indexes of device function. Calculated parameters were then compared with measured values to determine accuracy. Correlation between measured and calculated parameters was high in all instances, with most estimates yielding errors of <3%. These results demonstrate the utility of this approach and support its use as a means to monitor muscle-powered devices during long-term animal trials.

Improved Mechanism for Capturing Muscle Power for Circulatory Support

“…In animal experiments, radio telemetry implants (model TL11M3‐D70‐PCP, Data Sciences International, St. Paul, MN, U.S.A.) were used to monitor pressure swings inside the bellows and the space between the bellows and housing (17). Remote pressure readings were then used to calculate volume changes and actuator displacement as described below.…”

“…Each was designed to operate as a linear piston‐in‐cylinder type pump with an eye toward keeping device complexity to a minimum. Despite numerous design improvements, however, stroke length demands raised concerns over long‐term bellows performance, and the piston‐in‐cylinder design proved difficult to reconcile with certain anatomic constraints (15–17). Based on these findings, a radical design change was implemented in an effort to reduce bellows flexion stresses, lower the housing profile, and minimize the risk of tissue encumbrance to actuator motion (18).…”

“…At Allegheny, lessons learned through four previous design iterations (15–19) have now been incorporated into a fifth‐generation device (MEC5) with significantly enhanced energy transfer capacity and tissue interface characteristics. This report details current improvements in the MEC design and summarizes results from in vitro mechanical tests.…”

Improved Mechanism for Capturing Muscle Power for Circulatory Support

“…Each was designed to operate as a linear piston-in-cylinder type pump with an eye toward keeping device complexity to a minimum. Despite numerous design improvements, however, stroke length demands raised concerns over long-term bellows performance, and the piston-in-cylinder design proved difficult to reconcile with certain anatomic constraints (15)(16)(17). Based on these findings, a radical design change was implemented in an effort to reduce bellows flexion stresses, lower the housing profile, and minimize the risk of tissue encumbrance to actuator motion (18).…”

“…At Allegheny, lessons learned through four previous design iterations (15)(16)(17)(18)(19) have now been incorporated into a fifth-generation device (MEC5) with significantly enhanced energy transfer capacity and tissue interface characteristics. This report details current improvements in the MEC design and summarizes results from in vitro mechanical tests.…”