The Independent Patient

Photo: Sensor on a fingertip

Monitoring of blood pressure with
a tiny implant; © Fraunhofer IMS

Little video cameras and hidden lenses observe supermarket, tram and cash point around the clock. Constant observation is an ever-present trend, not only on public places, but also in medicine. Especially people with chronic diseases can benefit from this development because they can get back a piece of freedom.

Researchers from Fraunhofer Institute of Microelectronic Circuits and Systems (IMS) in Duisburg, Germany, have developed a tiny implantable sensor for example. “The sensor is suitable for patients who have difficulties to regulate their blood pressure and who develop high peaks of their blood pressure especially at night”, explains Hoc Khiem Trieu, head of department of the IMS. Patients who have to observe their blood pressure in the long-term have to wear a blood pressure cuff around the arm up to now. This cuff inflates every 30 minutes, also at night. That is uncomfortable because it interrupts the sleep of many people. The new sensor should change this. It is only one millimetre, but measures the blood pressure 30 times per second. The patient does not notice anything.

At the moment the sensor is used in animal testing. The implant is inserted into the groin artery by a catheter under radiation control so that the tip of the sensor sticks in the artery. The tip of the sensor has little wires which deform if the blood in the groin artery flows around it. The blood pressure can be calculated. With an external device the data are called up and the doctor can interpret them.

More flexibility for the patient

Patients who have to observe their blood coagulation can also benefit from constant monitoring thanks to modern technology. With a little device they can determine their INR value at home. The INR value gives information about the consistency of the blood. “The target group are people who must take drugs to thin their blood lifelong”, says Christian Dücker, physician at the institute of hemostaseology and transfusion medicine at the University Hospital Dusseldorf. These are people with atrial fibrillation or a high risk of developing thrombosis. Without such a device, these patients have to go to a doctor every two to four weeks in order to give a blood sample. The doctor sends the blood test to a lab and at the next day the patient gets his INR value.

The consultation of a doctor is necessary less often with this device. The advantage for the patient is that he can react faster if the values of his blood coagulation differ from the target value. The patient can change himself the dose of the drugs. Doctors suggest making the test once a week because the effect of many drugs for anticoagulation depends on nutrition. A drop of blood out of the fingertip is given on a test strip and is introduced into the device. The time until the blood coagulates is measured and a software calculates the INR value.

Since three years Dücker trains patients in the handling with such devices. A special training programme was developed an evaluated. “Every patient can deal with such a device, except dement people for example”, he says. And with this constant blood monitoring they can make life easier.

Simone Heimann