Combining laser-doppler flowmetry and photoplethysmography to explore in vivo vascular physiology

Abstract

Biomedical and Biopharmaceutical Research J o r n a l d e I n v e s t i g a ç ã o B i o m é d i c a e B i o f a r m a c ê u t i c aCombining laser-Doppler flowmetry and photoplethysmography to explore in vivo vascular physiology AbstractLaser Doppler flowmetry (LDF) and photoplethysmography (PPG) are two well-known optical techniques, allowing sensible real-time in vivo recording of blood flow. Only a few studies have used simultaneous perfusion recordings with both techniques, meaning that not much is known regarding the utility of their combined use. Our aim was to assess the vascular response of healthy individuals to a challenge maneuver with both techniques. Twelve subjects (both sexes, 26.0 ± 5.0 years old), were selected after informed written consent. The chosen maneuver was the leg pending maneuver, with LDF and PPG being assessed in both feet, and with transcutaneous O2 (tc) pressure obtained by gasimetry, and pulse rate (PR) calculated from the PPG signal, being also registered. The Wilcoxon signed-rank test was used for phase comparisons (p<0.05). Leg pending significantly reduced perfusion on both feet, although more clearly on the pending foot. The venoarterial reflex explains this vasoconstriction while, in the unmoved foot, a centrally-mediated reflex might be involved. tcpO2 increased significantly during leg lowering, suggesting that the heat from the probe cancelled the venoarteriolar reflex (VAR) on the measurement region. No changes were seen in HR. This study seems to confirm that the combined use of LDF and PPG might help to look deeper into peripheral microcirculation mechanisms.

Impact of the isometric contraction of the calf on the local microcirculation

“…While the LDF signal showed a significant increase (p=0.027), PPG showed a significant decrease (p=0.028). Although at a first glance, these results seem to be contradictory, this has been reported in previous studies [17][18] and are likely related to the differences in the measurement depth of these techniques. PPG is a technique that registers changes in blood volume synchronous with cardiac activity.…”

Comparing the effects of human hind limb massage by analysis of Laser Doppler Flowmetry and Photoplethysmography signal components using the wavelet transform

“…with reference technologies such as LDF 4,7,6 . This new generation of PPG instrumentation and software have greatly improved the signal acquisition and readability by enhanced filtering, using separating sensor, acquisition and transmission power supplies, reducing main sources of noise such as wires 25 .…”

“…Several optical non-invasive techniques have been developed to access in vivo microcirculation, a main component of circulatory physiology 1,2 . LDF and PPG are among the most popular technologies, sharing the same optical principles, although with different operation requirements [3][4][5] . These have been extensively applied in human studies, with different purposes 2, 4, 6 .…”

“…These have been extensively applied in human studies, with different purposes 2, 4, 6 . However, these technologies provide complex pulsatile signals, difficult to analyze, due to the contribution of different organs and systems 4,7,8 . The need to obtain a deeper analysis of such types of biological signals motivated the development of other mathematical strategies for signal processing, from which the Morlet Wavelet Transform emerged 9 .…”

“…A fluxometria por laser Doppler (FLD) e a fotopletismografia (FPG) estão entre as tecnologias mais populares, compartilhando os mesmos princípios biofisicos, embora com diferentes frequências e exigências de operação 3,5 . Estas tecnologias têm sido extensivamente usadas em humanos, com diferentes finalidades 2,4,6 , contudo, fornecem em ambos os casos, sinais pulsáteis complexos, difíceis de analisar, devido à influência de diferentes órgãos e sistemas sobre a sua aquisição e registo 4,7,8 . A necessidade de se obter uma análise mais profunda de tais sinais biológicos, motivou o desenvolvimento de outras estratégias matemáticas para o processamento de sinais, a partir das quais a Transformada de Ondeleta de Morlet emergiu 9 .…”