Implantable sensor for blood pressure determination via pulse transit time

High blood pressure (BP), also known as hypertension, is the most common cardiovascular disease and one of the leading causes of death in industrial countries. Clinical research is looking for a possibility to monitor blood pressure continuously. Standard non-invasive cuff-based BP measurement devices have proven ill-suited for a continuous long-term monitoring as they severely restrain the patients mobility. With conventional intravascular sensors, patients run a very high risk of developing thrombosis. The implantable sensor system for continuous BP measurement presented here avoids this risk since it is positioned at the arterys exterior. This paper shows that BP can be determined by measuring the pulse transit time (PTT) entirely inside the body. In vivo measurements with the sensor attached to a domestic pigs carotid artery have clearly shown that the systolic blood pressure and the estimated PTT correlate. This was verified in the physiological BP range of 94-144 mmHg.