Documents disponibles écrits par cet auteur

Effectiveness of intravenous infusion algorithms for glucose control in diabetic patients using different simulation models / Terry G. Farmer Jr. in Industrial & engineering chemistry research, Vol. 48 N° 9 (Mai 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 9 (Mai 2009) . - pp. 4402–4414 Titre : Effectiveness of intravenous infusion algorithms for glucose control in diabetic patients using different simulation models Type de document : texte imprimé Auteurs : Terry G. Farmer Jr., Auteur ; Thomas F. Edgar, Auteur ; Nicholas A. Peppas, Auteur Année de publication : 2009 Article en page(s) : pp. 4402–4414 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Insulin  infusion  algorithms  Glucose  dynamics  Diabetes  patient  Proportional  integral  derivative  control Résumé : The effectiveness of closed-loop insulin infusion algorithms is assessed for three different mathematical models describing insulin and glucose dynamics within a type I diabetes patient. Simulations are performed to assess the effectiveness of proportional plus integral plus derivative (PID) control, feedforward control, and a physiologically based control system with respect to maintaining normal glucose levels during a meal and during exercise. Control effectiveness is assessed by comparing the simulated response to a simulation of a healthy patient during both a meal and exercise and establishing maximum and minimum glucose levels and insulin infusion levels, as well as maximum duration of hyperglycemia. Controller effectiveness is assessed within the minimal model, the Sorensen model, and the Hovorka model. Results showed that no type of control was able to maintain normal conditions when simulations were performed using the minimal model. For both the Sorensen model and the Hovorka model, proportional control was sufficient to maintain normal glucose levels. Given published clinical data showing the ineffectiveness of PID control in patients, the work demonstrates that controller success based on simulation results can be misleading, and that future work should focus on addressing the model discrepancies. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800871t [article] Effectiveness of intravenous infusion algorithms for glucose control in diabetic patients using different simulation models [texte imprimé] / Terry G. Farmer Jr., Auteur ; Thomas F. Edgar, Auteur ; Nicholas A. Peppas, Auteur . - 2009 . - pp. 4402–4414. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 9 (Mai 2009) . - pp. 4402–4414 Mots-clés : Insulin  infusion  algorithms  Glucose  dynamics  Diabetes  patient  Proportional  integral  derivative  control Résumé : The effectiveness of closed-loop insulin infusion algorithms is assessed for three different mathematical models describing insulin and glucose dynamics within a type I diabetes patient. Simulations are performed to assess the effectiveness of proportional plus integral plus derivative (PID) control, feedforward control, and a physiologically based control system with respect to maintaining normal glucose levels during a meal and during exercise. Control effectiveness is assessed by comparing the simulated response to a simulation of a healthy patient during both a meal and exercise and establishing maximum and minimum glucose levels and insulin infusion levels, as well as maximum duration of hyperglycemia. Controller effectiveness is assessed within the minimal model, the Sorensen model, and the Hovorka model. Results showed that no type of control was able to maintain normal conditions when simulations were performed using the minimal model. For both the Sorensen model and the Hovorka model, proportional control was sufficient to maintain normal glucose levels. Given published clinical data showing the ineffectiveness of PID control in patients, the work demonstrates that controller success based on simulation results can be misleading, and that future work should focus on addressing the model discrepancies. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800871t

In Vivo Simulations of the Intravenous Dynamics of Submicrometer Particles of pH-Responsive Cationic Hydrogels in Diabetic Patients / Terry G. Farmer Jr. ; Thomas F. Edgar ; Nicholas A. Peppas in Industrial & engineering chemistry research, Vol. 47 n°24 (Décembre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 n°24 (Décembre 2008) . - p. 10053–10063 Titre : In Vivo Simulations of the Intravenous Dynamics of Submicrometer Particles of pH-Responsive Cationic Hydrogels in Diabetic Patients Type de document : texte imprimé Auteurs : Terry G. Farmer Jr., Auteur ; Thomas F. Edgar, Auteur ; Nicholas A. Peppas, Auteur Année de publication : 2009 Article en page(s) : p. 10053–10063 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Dynamics  Submicrometer  Simulations Résumé : A mathematical model describing glucose-dependent pH swelling and insulin release is developed for pH-sensitive cationic hydrogels in which glucose oxidase and catalase have been immobilized and insulin imbibed. Glucose-based swelling and insulin release are simulated for intravenously injected particles at various design conditions. The effects of particle size, the number of injected particles, insulin loading, enzyme loading, monomer functional group loading and pKa, and hydrogel cross-linking ratio on insulin release and glucose sensitivity are investigated to optimally design the device for use. Increased insulin infusion is shown to result from increasing the number of circulating gels, increasing the collapsed particle size, or decreasing the cross-linking ratio of the system. Release duration is shown to be dependent only upon the particle size and the achievable diffusion coefficient of the system. Glucose sensitivity, as measured by gluconic acid production and by the system pH, is a function of glucose oxidase loading and the concentration and pKa of the monomer used in the hydrogel. The necessary submicrometer particle size results in very rapid device insulin depletion. When the device is designed without considering constraints, the resulting release profile resembles that of an on/off switching mechanism. Future work will focus on simulations of swelling and release when the device is implanted in an alternative administration site. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie070957b [article] In Vivo Simulations of the Intravenous Dynamics of Submicrometer Particles of pH-Responsive Cationic Hydrogels in Diabetic Patients [texte imprimé] / Terry G. Farmer Jr., Auteur ; Thomas F. Edgar, Auteur ; Nicholas A. Peppas, Auteur . - 2009 . - p. 10053–10063. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 n°24 (Décembre 2008) . - p. 10053–10063 Mots-clés : Dynamics  Submicrometer  Simulations Résumé : A mathematical model describing glucose-dependent pH swelling and insulin release is developed for pH-sensitive cationic hydrogels in which glucose oxidase and catalase have been immobilized and insulin imbibed. Glucose-based swelling and insulin release are simulated for intravenously injected particles at various design conditions. The effects of particle size, the number of injected particles, insulin loading, enzyme loading, monomer functional group loading and pKa, and hydrogel cross-linking ratio on insulin release and glucose sensitivity are investigated to optimally design the device for use. Increased insulin infusion is shown to result from increasing the number of circulating gels, increasing the collapsed particle size, or decreasing the cross-linking ratio of the system. Release duration is shown to be dependent only upon the particle size and the achievable diffusion coefficient of the system. Glucose sensitivity, as measured by gluconic acid production and by the system pH, is a function of glucose oxidase loading and the concentration and pKa of the monomer used in the hydrogel. The necessary submicrometer particle size results in very rapid device insulin depletion. When the device is designed without considering constraints, the resulting release profile resembles that of an on/off switching mechanism. Future work will focus on simulations of swelling and release when the device is implanted in an alternative administration site. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie070957b