Transcutaneous optical telemetry system with infrared laser diode.

A transcutaneous telemetry system is indispensable when monitoring and controlling the operation of an artificial heart totally implanted inside the body. A telemetry system using light is more useful than radio waves from the viewpoint of electromagnetic interference and power consumption. In this report, a transcutaneous optical coupler consisting of an infrared laser diode (LD) and a PIN photodiode (PINPD) was evaluated, and the transcutaneous optical coupling and information transmission characteristics were evaluated in in vitro experiments. The wavelength and directional angle of the LD used were 830 nm and 9.5 degrees, respectively. With regard to the directional angle of PINPD, the authors found that a PINPD with a larger directional angle allowed for more deviation between the axes optical axes of the LD and the PINPD. It was also found that the transcutaneous coupler had an optimum distance for the permissible deviation to be maximized. The information signals modulated by the phase shift keying (PSK) were transmitted at a rate of 9,600 bps through goat skin 4 mm thick, and demodulated by the phase locked loop (PLL) on the receiving side. As a result, the information signals were demodulated without any errors in deviation within 10.5 mm at a distance of 11 mm. In conclusion, the transcutaneous optical telemetry system using an infrared LD has sufficient characteristics to monitor and control the operation of an artificial heart totally implanted inside the body.

An electrohydraulic ventricular assist system with a linear actuator.

An electrohydraulic ventricular assist system with a linear actuator was developed, and in vitro and in vivo evaluations were performed. During in vitro evaluations this system could yield 5.6 L/min of pump flow against a mean afterload of 100 mmHg. Durability tests were performed for more than 4 months. The system was implanted in three goats and a maximum pump flow of 4.2 L/min was obtained against a mean afterload of 100 mmHg, and 3.2 L/min against 130 mmHg. These evaluations have proven that the system can maintain stable hemodynamics under various conditions.