Laser Doppler fluxmetry (LDF) or photopletysmography (PPG) are frequently used as non-invasive tools for the detection of the so-called “inspiratory gasp response” (IGR), a vasoconstrictive episode provoked by a voluntary deep inspiration. According to our knowledge, a rigorous comparison of both methods has not been reported in the literature. Therefore, the aim of the study was to compare the detection of IGR with LDF and PPG. We investigated 14 young and healthy volunteers. A PPG and a LDF probe were applied to adjacent fingertips of the dominant hand (thumb/index finger). After baseline measurements the subjects were asked to perform a deep inspiration with time intervals of 90 sec., 60 sec., 30 sec., and 15 sec. We found that both methods are useful to detect individual IGR. However, overall correlation of IGR amplitude detected with LDF and PPG was poor (r=0.433). Surprisingly, there was a continuous increase of the correlation coefficient from the first (r=0.105) or second (r=0.184) IGR to the fifth (r=0.727) IGR. These results imply that experimental data obtained with PPG and LDF are not equivalent and therefore one has to be cautious regarding the comparison and interpretation of results obtained with these two different methods.

Date Published: 13 October 2003
PDF: 6 pages
Proc. SPIE 5068, Saratov Fall Meeting 2002: Optical Technologies in Biophysics and Medicine IV, (13 October 2003); doi: 10.1117/12.518778

Published in SPIE Proceedings Vol. 5068:
Saratov Fall Meeting 2002: Optical Technologies in Biophysics and Medicine IV
Valery V. Tuchin, Editor(s)