Artificial Baroreflex

Abstract

Background-We proposed a novel therapeutic strategy against central baroreflex failure: implementation of an artificial baroreflex system to automatically regulate sympathetic vasomotor tone, ie, a bionic baroreflex system (BBS), and we tested its efficacy in a model of sudden hypotension during surgery. Methods and Results-The BBS consisted of a computer-controlled negative-feedback circuit that sensed arterial pressure (AP) and automatically computed the frequency (STM) of a pulse train required to stimulate sympathetic nerves via an epidural catheter placed at the level of the lower thoracic spinal cord. An operation rule was subsequently designed for the BBS using a feedback correction with proportional and integral gain factors. The transfer function from STM to AP was identified by a white noise system identification method in 12 sevoflurane-anesthetized patients undergoing orthopedic surgery involving the cervical vertebrae, and the feedback correction factors were determined 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 then examined in a model of orthostatic hypotension during knee joint surgery (nϭ21). Without the implementation of the BBS, a sudden deflation of a thigh tourniquet resulted in a 17Ϯ3 mm Hg decrease in AP within 10 seconds and a 25Ϯ2 mm Hg decrease in AP within 50 seconds. By contrast, during real-time execution of the BBS, the decrease in AP was 9Ϯ2 mm Hg at 10 seconds and 1Ϯ2 mm Hg at 50 seconds after the deflation. Conclusions-These

Servo-Controlled Hind-Limb Electrical Stimulation for Short-Term Arterial Pressure Control

“…29 The bionic system to control AP has also been applied in human subjects. 13 Although the aforementioned bionic systems aimed to maintain AP against acute hypotension by increasing sympathetic nerve activity, [10][11][12][13]29 sympathoinhibition might also be required for the treatment of cardiovascular diseases accompanying sympathetic overactivity. Baroreceptor activation is one of the potential sympathoinhibitory neural modulation.…”

“…9 A framework of electrical neural intervention is also effective to elevate arterial pressure (AP) against hypotensive events. [10][11][12][13] Aside from direct neural stimulation, electroacupuncture can modify autonomic balance, thereby treating cardiovascular diseases. [14][15][16] Although one feature of the electroacupuncture might be its long-lasting effects, immediate cardiovascular responses to acupuncture-like stimulation are also observed in several experimental settings.…”

Cardiovascular control and time domain Granger causality: insights from selective autonomic blockade

“…Examples of applications of the perturbational method to assess causal relations include electrical stimulation of vagal and sympathetic efferent activity directed to the heart to drive heart rate modifications [3,4], electrical stimulation of sympathetic nerves directed to vascular smooth muscles to evoke skin blood flow changes [5] and perturbations of the carotid sinuses with random binary pressure pulses to evoke sympathetic responses and peripheral vasoconstriction [6]. This traditional approach led to important theoretical advances [7] and had relevant practical applications [8] but left completely unsolved the issue of assessing causal relations during spontaneous activity. Indeed, knowledge of the causal interactions when the system is under an external perturbation does not necessarily imply mastering the system functioning under spontaneous conditions.…”

Open-loop static and dynamic characteristics of the arterial baroreflex system in rabbits and rats

“…However, considering the fact that the ultimate goal of the arterial baroreflex system is to stabilize AP, an artificial controller may be designed without knowing exactly the transfer function of the total reflex arc. As an example, Yamasaki et al [ 96 ], using a classic controller with proportional and integral gain factors, demonstrated the successful application of epidural spinal cord stimulation to maintain AP against a model of sudden hypotension during knee surgery in humans. Gotoh et al [ 83 ], using a proportional–integral–differential controller, also demonstrated the ability of RVLM stimulation to control AP in conscious rats.…”