We present a novel implantable multi-wavelength reflectance sensor for the measurement of blood pressure with
pulse transit time (PTT). Continuous long-term monitoring of blood pressure and arterial oxygen saturation is
vital for medical diagnostics and the ensuing therapy of cardiovascular diseases. Conventional cuff-based blood
pressure monitors do not provide continuous data and put severe constraints on the patients' daily lives. An
implantable sensor would eliminate such problems. The new biocompatible sensor is placed subcutaneously on
blood perfused tissue. The PTT is calculated by photoplethysmograms and the ECG-signal, that is recorded with
intracorporal electrodes. In addition, the sensor detects the arterial oxygen saturation. An ensuing spectralphotometric
analysis of the light intensity changes delivers data on the concentration of dysfunctional hemoglobin
derivatives. Experimental measurements showed a clear correlation between the estimated PTT and the systolic
blood pressure reference. These initial results demonstrate the potential of the sensor as part of an fully
implantable sensor system for the longterm-monitoring of cardiovascular parameters.
A miniaturized photoplethysmographic sensor system which utilizes the principle of pulse oximetry is presented.
The sensor is designed to be implantable and will permit continuous monitoring of important human vital
parameters such as arterial blood oxygen saturation as well as pulse rate and shape over a long-term period
in vivo. The system employs light emitting diodes and a photo transistor embedded in a transparent elastic
cu. which is directly wrapped around an arterial vessel. This paper highlights the specific challenges in design,
instrumentation, and electronics associated with that sensor location. <i>In vitro</i> measurements were performed
using an artificial circulation system which allows for regulation of the oxygen saturation and pulsatile pumping of
whole blood through a section of a domestic pig's arterial vessel. We discuss our experimental results compared to
reference CO-oximeter measurements and determine the empirical calibration curve. These results demonstrate
the capabilities of the pulse oximeter implant for measurement of a wide range of oxygen saturation levels and
pave the way for a continuous and mobile monitoring of high-risk cardiovascular patients.