The Heart is a Pump
Human circulation in its simplest analog is plumbing, with the heart as its blood pump. During the early 1980s, the project displays of the ASAIO conference (American Society of Artificial Internal Organs) made this clear. Exhibits demonstrated large mechanical pumps modeled to do the work of the human heart, submerged in tanks, pumping volumes of water that would support an adult body. The posters showed pictures from first animal trials - cows that had been implanted with the blood pumps, large enough to support the device. Obviously, all these devices required flow measurement to prove their design.
Over the past two decades, ventricular assist pump designs have evolved and devices developed with corporate backing serve as an end stage treatment for patients with failing hearts. The devices shown at ASAIO today are sophisticated, small enough to fit in a child and are no longer an engineering dream. With Transonic technology accurately and reliably measuring flow at all stages of development and implementation, the vision has become a reality.
Ventricular assist devices are first conceived and tested on the bench in tubing models that reproduce physiologic pressures and flow rates of the human circulatory system. Pulsatile and mean volume flow are important measurement parameters in determining the validity of the bench set up as well as the performance of the device in the circuit. Several different types of pump devices have been designed and tested using Transonic® technology, including total artificial heart replacements, implantable ventricular and biventricular assist devices, and extracorporeal assist devices.
In Vivo Testing
Transonic Implantable Perivascular flow probes are also important in the preclinical stage of device testing. The efficacy of the device must be tested in animal models that share the size and volume flow capacity of the human heart. Long term implant studies are performed in calves and sheep; often with multiple Transonic Perivascular flow probes implanted on the pump outlet graft, the pulmonary artery, the ascending aorta, and various peripheral vessels or a coronary artery to determine the effectiveness of the pump in maintaining whole body circulation. These studies can run from 3 months to a year and rely on the continued accuracy and performance of Transonic flow probes. Custom calibration and programming of Transonic Perivascular flow probes may apply to increase performance under specialized conditions.