Matemática e Estatística | Capítulos/artigos em livros internacionais / Book chapters/papers in international books
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Browsing Matemática e Estatística | Capítulos/artigos em livros internacionais / Book chapters/papers in international books by Author "Amorim, Pedro"
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- Garch models for drug effects on patient heart rate, during general anaesthesiaPublication . Brás, Susana; Nunes, Catarina S.; Amorim, PedroA model that can describe the effect of anaesthetic drugs on patient’s heart rate (HR) is of great importance when considering haemodynamic stability under surgery. A Generalized Autoregressive Conditional Heteroscedasticity (GARCH) model was used to model HR considering the effect concentrations of the anaesthetic propofol and the analgesic remifentanil, using the clinical data of 16 patients. The model was able to capture the HR trend in all 16 patients with very small errors throughout the surgical time. A correlation was found between the GARCH parameters and patient baseline characteristics, leading to the possibility a patient adjusted adaptive model.
- Modelling drugs' pharmacodynamic interaction during general anaesthesia: the choice of pharmacokinetic modelPublication . Nunes, Catarina S.; Mendonça, Teresa F.; Antunes, Luís; Ferreira, David A.; Lobo, Francisco; Amorim, PedroThe effect of drugs’ interaction on the brain signal Bispectral Index (BIS) is of great importance for an anaesthesia control drug infusion system. In this study, two renowned pharmacokinetic (PK) models for propofol are compared, in order to evaluate its influence on the performance/predictably of a drug interaction model for BIS, considering data of 45 patients. The model was fitted per patient during anaesthesia induction, and tested for prediction under surgery. The results showed that the choice of PK model had influence on the overall performance. In the prediction phase, only one PK model presented good results with small errors.
- Predictive adaptive control of the bispectral Index of the EEG (BIS): using the intravenous anaesthetic drug propofolPublication . Nunes, Catarina S.; Mendonça, Teresa F.; Magalhães, Hugo; Lemos, João M.; Amorim, PedroThe problem of controlling the level of unconsciousness measured by the Bispectral Index of the EEG (BIS) of patients under anaesthesia, is considered. It is assumed that the manipulated variable is the infusion rate of the hypnotic drug propofol, while the drug remifentanil is also administered for analgesia. Since these two drugs interact, the administration rate of remifentanil is considered as an accessible disturbance. In order to tackle the high uncertain present on the system, the predictive adaptive controller MUSMAR is used. The performance of the controller is illustrated by means of simulation with 45 patient individual adjusted models, which incorporate the effect of the drugs interaction on BIS. This controller structure proved to be robust to the remifentanil disturbance, different reference values and noise. A reduction of propofol consumption was also observed when comparing to the real clinical dose used for a similar BIS trend.
- The influence of two different drug infusion profiles on the pharmacodynamics model performancePublication . Ferreira, Ana Isabel Leitão; Nunes, Catarina S.; Gabriel, J.; Amorim, PedroTo model the effect of anesthetic drugs on the Bispectral Index (BIS) of the EEG is of great importance for a reliable predictive response model during surgery. In this study, the impact of using two different drug infusion profiles in a pharmacodynamics interaction model was studied and the methods were compared with respect to their performance. Clinical data of 22 patients were considered. The interaction model was optimized per patient using nonlinear least squares during the induction of anesthesia, and tested for prediction abilities of test patients. In the optimization phase, all models could follow the BIS trend with errors not significantly differ- ent from zero. In the test data the choice of drug infusion pro- file proved to have a significant impact, showing that the per- formance is greatly influenced by the interaction. Results also show a time delay between the BIS signal and the Modeled BIS in both groups. This delay corresponds to a delay in the dy- namics of the patient and could be related to the delay in BIS processing time. This work is an important step to predict the effect of anesthetic drugs.