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A system model for closed-circuit inhalation anesthesia. II. Clinical validation
J G Lerou1, R Dirksen, H H Beneken Kolmer
1Institute for Anesthesiology, University of Nijmegen, The Netherlands.
Anesthesiology
|August 1, 1991
Summary
A new model accurately predicts isoflurane levels during anesthesia. Version A, with a 0% peripheral shunt, demonstrated superior prediction accuracy compared to Version B (16% shunt).
Area of Science:
- Anesthesiology
- Pharmacokinetics
- Mathematical Modeling
Background:
- Closed-circuit anesthesia requires precise control of inhalational anesthetic concentrations.
- Existing models for predicting anesthetic uptake and distribution need clinical validation.
Purpose of the Study:
- To clinically validate a 14-compartment model for predicting isoflurane alveolar concentrations during closed-circuit anesthesia.
- To compare the predictive performance of two model variants differing in peripheral shunt size.
Main Methods:
- Quantitative comparison of predicted versus measured alveolar isoflurane concentrations in 50 patients.
- Utilized mass spectrometry to measure alveolar isoflurane concentrations over time.
- Employed computer simulations of two model versions (A: 0% shunt, B: 16% shunt) to predict concentrations.
Main Results:
- Model version A (0% shunt) showed significantly lower bias (2.25%) and scatter (12.51%) than version B (12.00% bias, 14.12% scatter).
- Both bias (P=0.008) and scatter (P<0.0001) were significantly better for version A.
- For version A, prediction scatter increased with patient age (P=0.002), but bias was unaffected.
Conclusions:
- The 14-compartment model, particularly version A (0% peripheral shunt), provides accurate predictions of isoflurane alveolar concentrations in a clinical setting.
- Model performance is influenced by patient age, specifically the scatter of prediction errors.
- This validated model can aid in optimizing anesthetic delivery during closed-circuit anesthesia.