How and to what degree do the slight differences in the attachment positions of the sensors influence the values of photoplethysmographic measures? To address this question, we measured pulse rate (PR) and alternating current-to-direct current ratio (AC/DC) from the tips of the index fingers of 12 subjects under rest condition, using a sensor geometry having one light source and three photo detectors. The analysis revealed that the values of the intraclass correlation coefficient, an index of internal consistency, for PR and AC/DC across geometries were 1.00 and 0.90, respectively. The mean values of PR from the three photo detectors remained the same whereas those of AC/DC did not. These findings indicate that the internal consistency of PR and AC/DC across geometries are high, which implies that they can be used irrespective of the slight differences in the sensor attachment positions.
