title: Artificial baroreflex: clinical application of a bionic baroreflex system.
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.
  
  
  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 (n=21). Without the implementation of the BBS, a sudden deflation of a thigh tourniquet resulted in a 17+/-3 mm Hg decrease in AP within 10 seconds and a 25+/-2 mm Hg decrease in AP within 50 seconds. By contrast, during real-time execution of the BBS, the decrease in AP was 9+/-2 mm Hg at 10 seconds and 1+/-2 mm Hg at 50 seconds after the deflation.
  
  
  CONCLUSIONS
  These results suggest the feasibility of a BBS approach for central baroreflex failure.
authors.affiliation: Department of Cardiovascular Control, Kochi Medical School, Nankoku 783-8505, Japan. yamasakf@med.kochi-u.ac.jp
authors.forename: Fumiyasu
authors.initials: F
authors.lastname: Yamasaki
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ushida
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yokoyama
authors.forename: Motonori
authors.initials: M
authors.lastname: Ando
authors.forename: Koichi
authors.initials: K
authors.lastname: Yamashita
authors.forename: Takayuki
authors.initials: T
authors.lastname: Sato
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D017704:Baroreflex; D001701:Bionics / Q000379:methods*; D005240:Feasibility Studies; D005246:Feedback; D005260:Female; D006339:Heart Rate; D006801:Humans; D007024:Hypotension, Orthostatic; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D019637:Orthopedic Procedures; D011674:Pulse; D014666:Vasomotor System