GB1385954A - Implantable body tissue stimulating device having adjustable oper ating parameters - Google Patents

Abstract

1385954 Stimulators CORDIS CORP 26 April 1972 [10 May 1971] 19303/72 Heading A5B An implantable body tissue stimulator, such as a bladder phrenic nerve, carotid sinus or cardiac stimulator, comprises means for detecting pulse signals applied externally of the patient, a counter 43 interconnected with said detector for counting detected pulses, a stimulating pulse generator 11 having at least one adjustable pulse output parameter, and a decoder interconnected with the counter for controlling said parameter in dependence on the count held in the counter. A cardiac pacer has a pulse generator 11 comprising an output transistor Q3 driven by a relaxation oscillator Q1, Q2, the pulse repetition rate being controlled by resistor chain R4 to R8 and the output pulse current being adjustable by opening or closing a switch 17. A switching block 15 selectively shuts resistors R4 to R7 according to the state of counter 43 which also controls switch 17 to provide 16 pulse rates at each of two output currents. A magnetic read switch 21 senses external magnetic pulses and passes pulses to a pulse shaping one-shot multivibrator, comprising NOR gates 23, 25, which meshes bounce in switch 21. If the detector pulse rate is above a minimum determined by the time constant of R3, C2 an inverting gate 27 removes a reset signal from decade counter/decoder 31 which then counts the detected signals. After circuit 31 has counted six pulses it resets binary counter 43 and when circuit 31 reaches its seventh state it stops counting and counter 43 starts counting, the switches 15 and 17 staying in the state corresponding to the count in counter 43 when the external magnetic pulse brain stops.The count threshold of circuit 31 provides a high degree of noise immunity. Integrated circuit techniques may be used to form the components of the detector, counter and decoder as a plurality of integrated circuit clips or as one large clip. The binary counter 43 may be expanded to also control a pacer generator to operate in a synchronous or non- synchronous mode or in a standby or continuous mode. A semiconductor magnetic sensor may be used instead of switch 21, and instead of external magnetic pulses bursts of acoustic energy may be transmitted through body tissue or electromagnetic pulses, e.g. at 15-150 kH 2 , may be utilised. The control circuitry may also be used with a digitally tined cardiac pacer such as that described in Specification No. 1,267,493. Reference has been directed by the comptroller to Specification 1,331,967.