Quantitative Anaesthesia with the Help of Closed-Loop Control

  • D. R. Westenskow
  • P. J. Loughlin
Part of the Anaesthesiologie und Intensivmedizin / Anaesthesiology and Intensive Care Medicine book series (A+I, volume 204)


Closed-loop control systems have been used since the time of the Babylonians, when irrigation systems were opened and closed in closed-loop control mode [1]. Closed-loop control in anaesthesia began in 1950 when Bickford used the EEG signal to control the infusion of thiopental [2]. A syringe with thiopental was attached to a stepper motor. Each time the EEG crossed zero, a bolus of thiopental was given. As the patient became anaesthesized the infusion rate slowed because the frequency of the EEG decreased. Closed-loop control has adjusted ventilation during anaesthesia by comparing the difference between the desired and a measured end-tidal carbon dioxide concentration [3]. If the CO2 was high, the inspiratory airway pressure was incremented in 0.1-mm steps. When the end-tidal reached the desired level, the airway pressure was held constant. The most common application of closed-loop control is the maintenance of arterial blood pressure by the infusion of sodium nitroprusside [4]. Experience has shown that a desired end-tidal anaesthetic orblood pressure is maintained more consistently andmore accurately under closed-loop control than is done manually [5]. Closed-loop control can perform some very usedful and helpful tasks when it is made available in the anaesthesia machine design.


Breathing System Circuit Volume Anaesthesia Workstation Inspiratory Airway Pressure Anaesthetic Uptake 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Gadd CJ (1929) Baylonian law. In: Encyclopedia Britannica, 14th edn., vol 2. Encyclopedia Britannica, Chicago, p 863Google Scholar
  2. 2.
    Bickford RG (1950) Automatic electroencephalographic control of general anesthesia. EEG Clin Neurophysiol 2:93–96CrossRefGoogle Scholar
  3. 3.
    Frumin MJ, Lee ASJ (1957) A physiologically oriented artificial respirator which produces N2O–-O2 anesthesia in man. J Lab Clin Med 49:617PubMedGoogle Scholar
  4. 4.
    Sheppard LC (1980) Computer control of the infusion of vasoactive drugs. Ann Biomed Eng 8:431–444PubMedCrossRefGoogle Scholar
  5. 5.
    Smith NT, Quinn ML, Flick J et al (1984) Automatic control in anesthesia: a comparison in performance between the anesthetis and the machine. Anesth Analg 63:715–722PubMedGoogle Scholar
  6. 6.
    Westenskow DR, Jordan WS (1984) The Utah system: computer-controlled anesthetic delivery. Contemp Anesth Pract 8:221–233PubMedGoogle Scholar
  7. 7.
    Ritchie RG, Ernst EA, Pate BL, Pearson JD, Sheppard LC (1987) Closed-loop control of an anesthesia delivery system: development and animal testing. IEEE Trans Biomed Eng 34(6): 437–443PubMedCrossRefGoogle Scholar
  8. 8.
    Westenskow DR, Zbinden AM, Thomson DA, Kohler B (1986) Control of end-tidal halothane cncentration. Part A: anaesthesia breathing system and feedback control of gas delivery. Br J Anaesth 58:555–562PubMedCrossRefGoogle Scholar
  9. 9.
    Westenskow DR et al (1977) Instrumentation for measuring continuous oxygen consumption of surgical patients. IEEE Trans Biomed Eng 4(24): 331–337CrossRefGoogle Scholar
  10. 10.
    Westenskow DR, Jordan WS, Hayes JK (1983) Uptake of enflurane: a study of the variability between patients. Br J Anaesth 55:595PubMedCrossRefGoogle Scholar
  11. 11.
    Eveleigh VW (1972) Introduction to control systems design. McGraw-Hill, New York, pp 1–8Google Scholar
  12. 12.
    Ziegler JG, Nichols NB (1942) Optimum settings for automatic controllers. Trans ASME 64:759–768Google Scholar
  13. 13.
    Isermann R (1981) Digital control systems. Springer, Berlin Heidelberg New YorkGoogle Scholar
  14. 14.
    Westenskow DR (1986) Fundamentals of feedback control applied to microcomputer instrumentation design. Int J Clin Monit Comput 3:239–244PubMedCrossRefGoogle Scholar
  15. 15.
    Westenskow DR, Meline L, Pace NL (1987) Controlled hypotension with sodium nitroprus-side: anesthesiologist versus computer. J Clin Monit 3: (2) 80–86PubMedCrossRefGoogle Scholar
  16. 16.
    Westenskow DR (1986) Automating patient care with closed-loop control. MD Comput 3: (2) 14–20PubMedGoogle Scholar
  17. 17.
    Westenskow DR (1987) Closed-loop control of blood pressure, ventilation, and anesthesia delivery. Int J Clin Monit Comput 4:69–74PubMedCrossRefGoogle Scholar
  18. 18.
    Jaklitseh RR, Westenskow DR (1987) A model-based self-adjusting two-phase controller for vecuronium-induced muscle relaxation during anesthesia. IEEE Trans Biomed Eng 34:583–594CrossRefGoogle Scholar
  19. 19.
    De Vries JW et al (1987) Infusion of vecuronium controlled by a closed-loop system. Br J Anaes 58:1100–1103CrossRefGoogle Scholar
  20. 20.
    Ritchie G et al (1985) A microcomputer-based controller for neuromuscular block during surgery. Ann Biomed Eng 13:3–15PubMedCrossRefGoogle Scholar
  21. 21.
    Linkens DA et al (1982) Self-tuning control of muscle relaxation during anesthesia. In: Proceedings, IEEE conf appl adaptive and multivariable contr, Hull, England, July 1982, p 96–102Google Scholar
  22. 22.
    Frumin MJ, Lee ASJ (1957) A physiologically oriented artificial respirator which produces N20–02 anesthesia in man. J Lab Clin Med 49:617PubMedGoogle Scholar
  23. 23.
    Coon RL, Zuperku EJ, Kampine JP (1978) Systemic arterial blood pH servocontrol of mechanical ventilation. Anesthesiology 49:201–204PubMedCrossRefGoogle Scholar
  24. 24.
    Ohlson KB, Westenskow DR, Jordan WS (1982) A microprocessor based feedback controller for mechanical ventilation. Ann Biomed Eng 10:3548Google Scholar
  25. 25.
    East TD, Westenskow DR, Pace NL, Nelson LD (1982) A microcomputer-based differential lung ventilation system. IEEE Trans Biomed Eng 29:736–730PubMedCrossRefGoogle Scholar
  26. 26.
    Hayes JK, Westenskow DR, East TD, Jordan WS (1984) Computer-controlled anesthesia delivery system. Med Instrum 18: (4) 224–231PubMedGoogle Scholar
  27. 27.
    Ross JAS, Wloch RT, White DC et al (1983) Servo-controlled closed-circuit anaesthesia. Br J Anaesth 55:1053PubMedCrossRefGoogle Scholar
  28. 28.
    Coles JR, Brown WA, Lampard DG (1973) Computer control of respiration and anaesthesia. Med Biol Eng 11:262PubMedCrossRefGoogle Scholar
  29. 29.
    Mapleson WW, Chilcoat RT, Lunn JN et al (1980) Computer assistance in the control of depth of anaesthesia. Br J Anaesth 52:234pCrossRefGoogle Scholar
  30. 30.
    Tatnall ML, Morris P, West PG (1981) Controlled anaesthesia: an approach using patient characteristics identified during uptake. Br J Anaesth 53:1019PubMedCrossRefGoogle Scholar
  31. 31.
    Loughlin PJ, Westenskow DR(1987) A closed loop controller for end-tidal anesthetic concentration. EMBS 13–16 November, BostonGoogle Scholar
  32. 32.
    Fürst SR (1985) A computer-controlled anesthesia delivery system. Thesis, Department of Anesthesiology, Bioengineering Division, University of UtahGoogle Scholar
  33. 33.
    Zbinden AM, Frei F, Westenskow DR, Thomson DA (1986) Control of end-tidal halothane concentration. Part B: verification in dogs. Br J Anaesth 58:563–571PubMedCrossRefGoogle Scholar
  34. 34.
    Wallroth CF (1984) Technical conception for an anaesthesia system with electronic metering of gases and vapors. Acta Anaesthesiol Belg 34:279–294Google Scholar
  35. 35.
    Brunner JX, Wolff G, Cumming G et al (1985) Accurate measurement of N2 volumes during N3 washout required dynamic adjustment of delay time. J Appl Physiol 59:1008–1012PubMedGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1989

Authors and Affiliations

  • D. R. Westenskow
  • P. J. Loughlin

There are no affiliations available

Personalised recommendations