New Sensor Design Made to Discriminate between Tissue Blood Flow at Different Tissue Depths at the Sacral Area

Evaluation of antidecubitus mattresses is to a large extent based on interface pressure and pressure distribution measurements. These measurements do not give an answer to the effect on the tissue microcirculation cause by the external loading. A better and more direct parameter on the properties’ of the mattress would be to measure blood flow in the tissue under loading. This paper presents a new optical sensor probe for blood flow measurement that combines the two methods laser Doppler and photoplethysmography, PPG. With use of two methods, multiple light wavelengths and combinations of the distances between light sources and photodetector in the PPG, the blood flow at several different tissue depths can be assessed. However, interference problems between the two methods occurred with the present sensor design. The preliminary result presented in this paper, shows differences in blood flow response at the different measurement depths.