Clinical Application of Bionic Baroreflex System

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Background : We developed a bionic technology for the treatment of central baroreflex failure, and tested its efficacy in restoration of arterial pressure(AP) against a clinical model of orthostatic hypotension during surgery.Methods and Results : The bionic baroreflex system(BBS) was a negative feedback system controlled by a computer, which sensed AP and automatically computed the frequency (STM) of a pulse train to stimulate sympathetic nerves through an epidural catheter placed at the level of lower thoracic spinal cord. According to a classical feedback control theory, i.e., feedback correction with proportional and integral gain factors, we designed an operational rule for the BBS. We first identified the transfer function from STM to AP by a white-noise system-identification method in 12 sevoflurane-anesthetized patients who underwent an orthopedic surgery of cervical vertebrae, and then determined the feedback correction factors with a numerical simulation to enable the BBS to quickly and stably attenuate an external disturbance on AP. The performance of the designed BBS was examined in a clinical model of orthostatic hypotension (n=21). Without the implementation of the BBS, a sudden deflation of the thigh tourniquet dropped AP by 17±3 mmHg in 10 sec and by 25±2 mmHg in 50 sec. During real-time execution of the BBS, on the other hand, the fall in AP was 9±2 mmHg at 10 sec and 1±2 mmHg at 50 sec, and 0±1 mmHg at 100 sec after the deflation.Conclusions : The bionic technology for the artificial baroreflex system would be applicable to humans.