AUTOMATIC-CONTROL IN ANESTHESIA - A COMPARISON IN PERFORMANCE BETWEEN THE ANESTHETIST AND THE MACHINE

  • 1 January 1984
    • journal article
    • research article
    • Vol. 63  (8) , 715-722
Abstract
Two new servo control systems were developed by modifying an existing one. The original system was designed to control inspired halothane concentration using mean arterial pressure; the 2 new systems were designed to control inspired halothane concentration using end-tidal concentration or to control mean arterial pressure using the automated infusion of nitroprusside. The performance of each of the 3 systems was compared to the performance of experienced physician and nurse anesthetists (9, 6 and 6 experiments, respectively). The experiments incorporated a standardized testing sequence of 2 changes in desired blood pressure (set point) and 2 pharmacologically induced disturbances in blood pressure (perturbations). The scoring was designed to examine how fast blood pressure changed (90% response time), how far past the set point it went (overshoot), how long it took to eliminate most of the fluctuations in blood pressure (settling time) and the degree of fluctuation of blood pressure after settling (stability). Given 3 systems to be tested, there were (3 .times. 14) 42 possible mean scores for the machine and 42 for the anesthetists. The machine scored better than the anesthetists in 38 out of 42 of the mean scores; the differences were statistically significant in 19 out of 42 scores. The wide scatter in performances of the anesthetists prevented the achievement of significance in 9 cases with large differences between means. Thus when the scores from the 3 systems were combined to achieve a larger n value, the machine outperformed the anesthetist in 12 of 14 scores. Evidently systems such as these could assume certain discrete tasks of the anesthetist, much as the mechanical ventilator has, and possibly perform better than anesthetists in these tasks.

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