Volume compensation chambers have long been proposed as a means to vent the rigid housing of an implanted ventricular assist device, in order to permit free filling and emptying of the pump while avoiding percutaneous vent lines. As part of the first clinical trials of our completely implanted, intact-skin ventricular assist system, we have assessed the function of the volume compensation chamber. The chamber is circular in cross-section, 12 cm in diameter and 1 cm thick. The chamber body is constructed of dip-cast segmented polyurethane. An interior tubing skeleton helps maintain chamber shape when implanted. A velour covering provides the necessary texture to keep the chamber flexible over the long term. A self-sealing percutaneous infusion port is used to replenish gas that leaves the chamber by diffusion into surrounding tissues. Chambers were implanted in two patients as part of the clinical trial of the overall system. Chambers were placed in the left chest between the lung and the pleura. Chamber volume was set in the perioperative period, then replenished every four weeks. A pressure monitor and non-coring needle are the only special equipment needed for the replenishment procedure. A simpler procedure, intended for use in a primary care office, is being developed. Chamber implantation was well-tolerated. There was sufficient capacity to x rays to verify chamber location, without interfering with other diagnostic needs. The infusion port was readily located, and the replenishment procedure easily completed. Early results indicate that in humans the chambers may be more compliant, and capable of operating over a wider volume range, than they are in calves. Thus, further extension of the time between gas replenishments may be possible. New materials under development may more significantly increase the time between chamber refills.
All Science Journal Classification (ASJC) codes
- Biomedical Engineering