Biosensor technology in the treatment of cardiovascular disease - Biomaterials and Devices for the Circulatory System - page 297

will be of particular benefi t to an ageing population. Devolution of patient
monitoring to the community will be enabled by advancing technologies,
including communications (i.e. broadband Internet and Bluetooth®), and
sensing (i.e. biosensors). In addition, the application of nanotechnology to
the production of biosensors is already yielding interesting devices, and
may improve the prospects for permanently implantable sensors.
The involvement of biosensors in feedback loops may expand in the
future, as sensing technology and communication between devices improves.
The integration of sensors (both biosensors and others, i.e. fl ow and pres-
sure sensors) with devices that provide some form of treatment represents
a signifi cant advancement in medical devices, particularly in the area of
implanted devices. A good example of this would be the sensing of blood
glucose, and feedback to a device, such as a pump, for the automatic admin-
istration of the required quantity of insulin. 60 Medtronic has commercialised
such a device: the MiniMed Paradigm® REAL-time insulin pump and
continuous glucose monitoring system, which uses a subcutaneous needle-
type glucose sensor.
Devices which are implanted in the circulatory system, such as stents,
heart valves and grafts, may also benefi t from integration with sensing func-
tions in order to monitor the tissue-device interface. For example, stent
grafts for the repair of abdominal aortic aneurysms have been integrated
with pressure sensors to detect graft leakage. 61 Pacemakers are at the fore-
front of the combining of sensing with diagnosis and treatment functions.
For many years, sensors have been incorporated into pacemakers in order
to make them 'rate-responsive'; by detecting physiological and non-
physiological indicators the pacemaker is able to adjust the heart rate to
meet changing requirements of cardiac output, i.e. during exercise. A range
of parameters have been investigated for the purpose of controlling pacing
rate 62 and a combination of two sensors is usual; an activity sensor (piezo-
electric crystal or accelerometer) and a metabolic sensor measuring, for
example, QT interval or minute ventilation. 63 In the future more patients
with implanted devices may benefi t from continuous monitoring provided
by biosensors and other sensor types, which will allow the various complica-
tions that occur with these devices to be detected and treated early.

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11.9 References

1. WANG J. Amperometric biosensors for clinical and therapeutic drug monitoring:
a review. Journal of Pharmaceutical and Biomedical Analysis 1999;
19 :47-53.
2. SHANTILATHA P, VARMA S, MIT RA CK. Designing a simple biosensor. In Advances
in Biosensors 2003; vol. 5:1-36. Edited by Malhotra and Turner. Elsevier Science
BV.