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Financing: Research Foundation - Flanders (FWO)
Project reference Nr.: G.0491.03 3E020185
Start: 2003-01-01
End: 2006-12-31
Description:
Glycemia is the concentration of glucose in the blood. Glycemia control
is a complex system in which a lot of factors may play a significant
role.
This human control system may be interrupted by an absolute or
relative shortage of insulin that may result in an elevated glycemia
level (hyperglycemia).
Recently, an article in The New England Journal of Medicine appeared in which the results of a clinical study about the intensive insulin therapy in critically ill patients were described. Those patients typically need ?intensive care?. It is known insulin resistance and the resulting hyperglycemia frequently
appear in these patients, even if they have not had diabetes before. In
this clinical study with 1548 patients it is mentioned that
normalization
of glycemia, by means of intensive administration of insulin, decreased
the mortality and morbidity rate by 50 % (!) for patients
who stayed for more than 5 days in ICU (Intensive Care Unit).
At
present, insulin administration is controlled by a labor-intensive and
empirical manual protocol in which glycemia is measured every 4 hours
or
even more frequently in case of complications or during the initial
phase. This protocol should result in getting a normal glycemia level,
i.e.,
a glycemia level between 80 and 110 mg/dl. Glycemia levels under 70
mg/dl, the so-called hypoglycemias, should be avoided because of their
possible
baleful influences. The efficiency of the protocol is complicated due
to factors such as supply of calories and drugs, patient profile, etc.
In
the near future, glycemia sample frequency will probably be increased
(e.g., glycemia measurements every 3 minutes) by applying other sensor
techniques.
In this project, a control system that
(semi-)automatically normalizes glycemia of critically ill patients
will be developed. It will determine
the insulin rate that a certain
patient will probably need at each time step. Many different dynamical
changes (such as administered calories or drugs)
will influence the condition of the patient. Consequently, the control system should be robust to overcome these disturbances.
The
control system will consist of two parts. On the one hand, a patient
model will be constructed. This model will represent
a ?mathematical? patient.
It will make it possible to predict
glycemia of a specific patient after administering a certain amount of
insulin, calories, drugs, etc. Factors
such as insulin resistance,
BMI, etc. will also be important to develop an accurate model. On the
other hand, the control system will include the
controller itself.
The latter will determine the insulin rate that will be administered to
the patient for the next time steps. The patient model
and
controller will both consist of certain structures and parameters that
are patient specific. The initial structures and parameter values will
be defined using input-output-data, which have been gathered before.
The
control system should be adaptive in order to account for different
types of specific patient behavior. Depending on initial patient
features
(e.g., BMI) a new patient who is admitted to ICU will
belong to a certain patient cluster that will be correlated with a
specific control system
(e.g., a specific patient model structure,
specific model parameter values, specific controller parameter values).
During the patient?s stay in ICU
this initial control system will be adapted in order to render it more patient-specific, and as a result, more accurate.
The
final implementation of this control system in hospitals will
significantly reduce the workload for nurses and doctors. Consequently,
the
introduction of a (semi-)automatic glycemia control system will also be
feasible in ICU-divisions of hospitals in which staff are less
motivated
nowadays to apply the manual intensive insulin therapy. Generally, this
control system will also optimize glycemia of patients in a more
stable
way. Subjective manual control will be avoided. The application of this
control system in divisions other than ICU might be an opportunity,
as
well. Finally, there is also the possibility the mortality and/or
morbidity rate will decrease further due to the stricter glycemia
control.
Probably, this will be the case in hospitals where the manual intensive insulin therapy is currently not used.
SMC people involved in the project:
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