Additional Protection

Regardless of how carefully you designed your instrument, absolute safety cannot be guaranteed in the real world. Despite all the safety testing and evaluation required by the FDA, medical device manufacturers still pay a premium for insurance to protect themselves from exposure against liability. For this reason, it often happens that additional or redundant hardware to ensure safety beyond the minimum requirements is cost-effective, since it will bring concomitant savings in insurance costs...

Ecg Amplifier With Pacemaker Pulse Detection And Artifact Rejection

Patients with cardiac pacemakers may have difficulties, especially just after implantation of the pacemaker and lead system, from failure of the pacing system to properly sense the heart's intrinsic signals or to evoke heartbeats (capture the myocardium). This may reflect problems in the electronics, the leads, the placement of the leads, or the myocardium itself. The most catastrophic event is failure of the pacemaker to capture the heart when the patient's intrinsic rate is slow or...

Output Voltage Into Tissue

Figure 8.12 This circuit generates pacing pulses with an amplitude of 3 or 6 V, depending on the state of the pacing amplitude selector switch. When inactive, microcontroller sets the HIGH AMPLITUDE PACING line low, charging tank capacitor C2 to VDD. To generate a 6-V pacing pulse, HIGH AMPLITUDE PACING line is set low to connect the positive terminal C2 to the battery's negative terminal. For 3-V pacing, HIGH AMPLITUDE PACING is set high, to connect the positive terminal of C2 to VDD. A pacing...

Irf9530

Figure 8.37 An isolated dc dc rated at 3 kV with a maximum 60-Hz leakage of a 2- a A converter powers the battery charger circuitry. A single-chip gel-cell charge controller IC (UC3906) charges two sealed 12-V batteries. Q4 switches power to the high-voltage power supply from the +24-V battery. This switch is tumed-on by Q5 upon receipt of the appropriate command from the shock-box microcontroller. IC9 produces 5 V to run the microcontroller and associated logic. Figure 8.37 An isolated dc dc...

Clinical Uses Of Electrical Stimulation

Clinical electrical stimulation is simply the application of electrical currents to a body, be it for function or therapy. As we just discussed, the current of electrons passing through the wires is converted into a current of ions moved within the tissue, which are in turn capable of transporting electrical charge across the membranes of excitable tissues. The purpose of these applied currents is to cause the targeted depolarization of nerve and or muscle to threshold. The most common clinical...

Electrode 2

Interferential Frequency Circuit

Figure 7.19 Circuit of a battery-powered, two-channel TENS unit. IC1 produces a pulse every time the stimulation channels need to be triggered. The trigger frequency can be varied between 3 and 100 Hz. Burst TENS is activated when SW2 connects the reset line of timer IC3 periodically to inhibit IC1 from oscillating. Modulated TENS is enabled by closing SW3, which allows a triangle wave generated by IC2 to modulate the frequency of IC1. The electrodes are driven by step-up transformer Tl....