Biomedical subjects

Marco Orsini Federici

Publications and source records attributed to Marco Orsini Federici.

5 recordsLinked to original sources

PubMed2006

Control oriented model of insulin and glucose dynamics in type 1 diabetics.

The aim of the study was to realize a mathematical model of insulin-glucose relationship in type I diabetes and test its effectiveness for the design of control algorithms in external artificial pancreas. A new mathematical model, divided into glucose and insulin sub-models, was developed from the so-called "minimal model". The key feature is the representation of insulin sensitivity so as to permit the personalisation of the parameters. Real-time applications are based on an insulin standardised model. Clinical data were used to estimate model parameters. Root mean square error between simulated and real blood glucose profiles (G(rms)) was used to evaluate system efficacy. Results from parameter estimation and insulin standardisation showed a good capability of the model to identify individual characteristics. Simulation results with a G(rms) 1.30 mmol/l in the worst case testified the capacity of the model to accurately represent glucose-insulin relationship in type 1 diabetes allowing self tuning in real time.

Algorithms↗

PubMed2006

National survey on the execution of the oral glucose tolerance test (OGTT) in a representative cohort of Italian laboratories.

BACKGROUND: Recently revised diagnostic criteria for diabetes mellitus and the lack of universal agreement on the methodology for the screening and diagnosis of gestational diabetes mellitus (GDM) still generate inconsistency in execution of the oral glucose tolerance test (OGTT). The aim of the present survey was to evaluate the adherence of Italian laboratories to the internationally accepted guidelines in carrying out the OGTT for the diagnosis of diabetes in the general population and for the screening of GDM. METHODS: A questionnaire was designed to investigate the following issues related to the OGTT: 1) the relationship between laboratories and diabetes centres for the definition of standard protocols; 2) the amount of glucose administered; 3) the number and timing of blood samples; 4) the procedures used for the screening and diagnosis of GDM; and 5) reference to WHO guidelines for the interpretation of the results. The questionnaire was administered to 400 specialists in laboratory medicine working in public or private laboratories nationwide participating in the "Italian External Evaluation of Quality in Laboratory Medicine" Study Group. RESULTS: The survey was completed in the period from June to September 2003. In the observation period, 241 questionnaires were returned by specialists working in laboratories scattered throughout 15 out of the 20 Italian regions. Only 50% of the laboratories performed the OGTT according to protocols defined in agreement with local reference diabetes centres. OGTT using 75 g of glucose in adults and 1.75 g/kg for children as recommended by WHO was performed by 87.1% of the laboratories. WHO indications to collect samples at baseline and at 120 min were followed by 33.2% of the centres. Higher variability was highlighted with respect to the methodology for GDM screening: 49.8% of the laboratories always adopted the two-step procedure consisting of a glucose challenge test (GCT) and subsequent OGTT in positive cases; 4.9% performed the 100-g OGTT with four blood samples; 1.6% the 75-g OGTT with two blood samples; and 2.7% the 75-g OGTT with four blood samples. More than 30% of the centres referred to different diagnostic schemes, 62% of which used individually chosen procedures amongst those reported above, 19% used only the GCT and no subsequent OGTT in positive cases, and 18.4% used a variety of completely different, arbitrarily chosen methods. Finally, only 25.6% of the laboratories referred to the WHO limits for interpretation of the results. CONCLUSIONS: For the Italian laboratories investigated, relevant variability was highlighted for performance of the OGTT in general and GDM screening in particular. A variable relationship between laboratories and diabetes centres was also detected, which might represent a relevant indicator for the need for rationalisation or standardisation of the method for performing an OGTT. These data highlight the need for greater collaboration between these different bodies. We suggest that other similar investigations should be carried out in other countries within the framework of the IFCC Global Campaign on Diabetes Mellitus.

Blood Glucose↗

PubMed2004

Nonlinear model predictive control of glucose concentration in subjects with type 1 diabetes.

A nonlinear model predictive controller has been developed to maintain normoglycemia in subjects with type 1 diabetes during fasting conditions such as during overnight fast. The controller employs a compartment model, which represents the glucoregulatory system and includes submodels representing absorption of subcutaneously administered short-acting insulin Lispro and gut absorption. The controller uses Bayesian parameter estimation to determine time-varying model parameters. Moving target trajectory facilitates slow, controlled normalization of elevated glucose levels and faster normalization of low glucose values. The predictive capabilities of the model have been evaluated using data from 15 clinical experiments in subjects with type 1 diabetes. The experiments employed intravenous glucose sampling (every 15 min) and subcutaneous infusion of insulin Lispro by insulin pump (modified also every 15 min). The model gave glucose predictions with a mean square error proportionally related to the prediction horizon with the value of 0.2 mmol L(-1) per 15 min. The assessment of clinical utility of model-based glucose predictions using Clarke error grid analysis gave 95% of values in zone A and the remaining 5% of values in zone B for glucose predictions up to 60 min (n = 1674). In conclusion, adaptive nonlinear model predictive control is promising for the control of glucose concentration during fasting conditions in subjects with type 1 diabetes.

Blood Glucose↗

PubMed2004

Closing the loop: the adicol experience.

The objective of the project Advanced Insulin Infusion using a Control Loop (ADICOL) was to develop a treatment system that continuously measures and controls the glucose concentration in subjects with type 1 diabetes. The modular concept of the ADICOL's extracorporeal artificial pancreas consisted of a minimally invasive subcutaneous glucose system, a handheld PocketPC computer, and an insulin pump (D-Tron, Disetronic, Burgdorf, Switzerland) delivering subcutaneously insulin lispro. The present paper describes a subset of ADICOL activities focusing on the development of a glucose controller for semi-closed-loop control, an in silico testing environment, clinical testing, and system integration. An incremental approach was adopted to evaluate experimentally a model predictive glucose controller. A feasibility study was followed by efficacy studies of increasing complexity. The ADICOL project demonstrated feasibility of a semi-closed-loop glucose control during fasting and fed conditions with a wearable, modular extracorporeal artificial pancreas.

Blood Glucose↗

PubMed2003

The artificial pancreas.

In type 1 diabetes an absolute deficiency of insulin secretion requires exogenous insulin supply to guarantee the patient's life avoiding ketoacidotic coma and to prevent the chronic complications of diabetes. In order to obtain a more physiological replacement therapy different approaches have been pursued since the early 70s to create an artificial wearable pancreas able to deliver insulin according to the blood glucose values as determined by continuous monitoring. Four components are considered essential for the realisation of an artificial pancreas: the sampling system, the glucose sensor, the mathematical models and the related algorithms for the calculation of the insulin doses and the infusion system for the insulin delivery. At present the still unsolved issues are mainly represented by the availability of reliable continuous glucose monitor and control algorithms, while the new technologies allow for the miniaturisation of the system.

Algorithms↗