A technique based on laser Doppler flowmetry and photoplethysmography for simultaneously monitoring blood flow at different tissue depths

Abstract

The aim of this study was to validate a non-invasive optical probe for simultaneous blood flow measurement at different vascular depths combining three photoplethysmography (PPG) channels and laser Doppler flowmeter (LDF). Wavelengths of the PPG were near-infrared 810 nm with source-to-detector separation of 10 and 25 mm, and green 560 nm with source-to-detector separation of 4 mm. The probe is intended for clinical studies of pressure ulcer aetiology. The probe was placed over the trapezius muscle, and depths from the skin to the trapezius muscle were measured using ultrasound and varied between 3.8 and 23 mm in the 11 subjects included. A provocation procedure inducing a local enhancement of blood flow in the trapezius muscle was used. Blood flows at rest and post-exercise were compared. It can be concluded that this probe is useful as a tool for discriminating between blood flows at different vascular tissue depths. The vascular depths reached for the different channels in this study were at least 23 mm for the near-infrared PPG channel (source-to-detector separation 25 mm), 10-15 mm for the near-infrared PPG channel (separation 10 mm), and shallower than 4 mm for both the green PPG channel (separation 4 mm) and LDF.

Influence of skin type and wavelength on light wave reflectance

“…By normalizing the modulation, and using wavelengths that have been found to better determine pulsatile blood flow, our present study demonstrated the practical application of a PPG device may be a promising technique as a heart rate monitor. 9,16,20,26,32 To our knowledge this is the first study to examine light wavelength reflectance and skin type influence during both rest and exercise.…”

“…6,16,49,50 The main concern with PPG technology for detection of pulse rate is related to the melanin concentration of the skin and its related pigmenting of skin. 3,20,50 Melanin is known to be highly absorbent to light, and thereby attenuating the incident light wavelength.…”

“…It is therefore critical that the device penetrate deep enough to provide detection of arterial vessels in order to determine the pulsatile changes in associated volume between systole and diastole. 3,6,8,9,16,20,23,25,26 In the present study, the interaction between various light wavelengths and skin type was investigated at rest and during exercise. We hypothesized that certain wavelengths of light would provide better light reflectance across skin types represented by a greater peak in modulation.…”

Measuring of Microcirculation Blood Flow in Capillaries with a Laser-Doppler Flowmetry

“…Повышение величины σ, как и значение величины Р М , может зависеть от раз-ных факторов. По мнению различных исследователей [7][8][9][10], рост значения σ может быть связан с более ин-тенсивным функционированием механизмов активно-го контроля. Кроме этого, большое влияние оказывает изменение сердечных и дыхательных ритмов в слу-чае патологии органов.…”

Fifty years of publishing in biomedical engineering: reflections after 7-year editorship

“…To give some insight onto the best-cited original papers, we selected the top ten from the periods 2008-2009 and 2010-2011. Out of these 20 papers, 7 are in the area of the circulation [8,9,15,20,24,25,27], 7 in the area of rehabilitation including brain computer interface [6,7,11,14,16,17,28], 2 related to sleep [19,35], 2 to tissue engineering and nanotechnology and 2 to electroporation [4,21]. Obviously the distribution of these subjects of publications are somewhat influenced by the special issues we had over this period [2,5,12,18,26,31,32].…”