System for identifying patient response to anesthesia infusion
First Claim
1. A method of assisting a human expert in reducing predictable variations in the depth of anesthesia during the administration of a medical anesthesia drug to a patient, the method comprising the step of solving:
- where the coefficients C1, C2, C3, as well as the time periods τ
p (initial time delay after drug infusion) and Tp (time constant representing speed of response) are initiated by assessment of a human expert.
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Abstract
A generic model structure captures basic characteristics in BIS-based patients'"'"' responses to anesthesia and surgical stimulation, the model being used in combination with the insight of an anesthesiologist. The model structure represents the patient response with a time delay, a time constant for response speed, and a nonlinear function for drug sensitivity. Clinical data confirms the model structure and is used to establish parameters and function forms for individual patients. A feedback and predictive control strategy for anesthesia drug infusion is then introduced on the basis of the patient model. Feedback control alone cannot avoid large fluctuations in BIS values when significant surgical stimulation is imposed, as a result of time delays in a patient'"'"'s response to drug infusion. Predictive control attenuates fluctuations of BIS levels from surgical stimulation.
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Citations
10 Claims
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1. A method of assisting a human expert in reducing predictable variations in the depth of anesthesia during the administration of a medical anesthesia drug to a patient, the method comprising the step of solving:
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where the coefficients C1, C2, C3, as well as the time periods τ
p (initial time delay after drug infusion) and Tp (time constant representing speed of response) are initiated by assessment of a human expert.- View Dependent Claims (2, 3)
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4. A method of determining a model that corresponds to a predicted response of a patient to anesthesia drug delivery, the method comprising the steps of:
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first determining an initial time delay τ
p after drug infusion for the patient;
second determining a time constant Tp representing speed of response of the patient; and
third determining a nonlinear static function ƒ
p representing the sensitivity of the patient to a dosage of the anesthesia drug at steady state. - View Dependent Claims (5, 6)
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7. A system for determining a predicted response of a patient to the administration of an anesthesia drug, the system comprising:
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a first memory for storing patient dynamics information relating to the infusion of a bolus dosage of anesthesia drug, said first memory having a first output for producing a first output signal corresponding to a first anesthesia level;
a second memory for storing patient dynamics information relating to the infusion of a titrated dosage of anesthesia drug, said second memory having a second output for producing a second output signal corresponding to a second anesthesia level;
a third memory for storing patient dynamics information relating to the patient'"'"'s predicted response to events of surgical stimulation, said third memory having a third output for producing a third output signal corresponding to an anesthesia effect level;
a signal combiner arrangement for receiving the first and second output signals and the anesthesia effect level, and producing at an output thereof a combined anesthesia effect signal;
a limiter coupled to the output of said signal combiner for establishing maximum and minimum values of the combined anesthesia signal; and
a virtual anesthesia monitor for producing an anesthesia value responsive to the combined anesthesia signal. - View Dependent Claims (8, 9, 10)
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Specification