Influence of the Hand Position and the Pulse Oximeter Sensor Position on the Pulse Blood Filling Signal

In the article the influence of the hand position and the pulse oximeter sensor position on the measured pulse blood filling signal was examined. The photoplethysmography method was used to register pulse waves. This method was implemented on the basis of the ARDUINO UNO board and the Pulse Sensor photoplethysmographic sensor. To study the influence of the hand position, signals were recorded from the phalanx of the finger and the radial artery of the right hand in three positions: the hand lies on the table, the hand is lowered down and the hand is raised up. The influence of the position of the sensor, in its turn, was examined on the basis of pulse waves recorded from the artery and at some distance to the left and right of it. All signals were processed in Matlab with the use of the previously developed algorithm for analyzing the contour characteristics of the wave. The processing results show that the higher the hand is positioned, the smaller the amplitude of the measured wave for both vessels. A sensor shift of 1 centimeter does not have a significant effect on the shape of the recorded signal, however, a shift to a greater distance can lead to incorrect diagnostic results.