&lt;title&gt;Near-infrared spectroscopy and the tilting table protocol: a novel method to study the blood flow and the oxygen consumption in tissues&lt;/title&gt;

Casavola, Claudia; Paunescu, Lelia Adelina; Franceschini, Maria Angela; Fantini, Sergio; Winter, Lew; Kim, Jin; Wood, D. A.; Gratton, Enrico

doi:10.1117/12.356789

Cited by 4 publications

(2 citation statements)

References 13 publications

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“…It is well documented that haemoglobin concentrations changes measured by NIRS can reveal changes in perfusion induced by changes in posture such as the Trendelenburg position [21,22,23]. Therefore, this study assessed whether PPG could be used to detect the same posture-dependent changes.…”

Section: Discussionmentioning

confidence: 99%

Perfusion Changes at the Forehead Measured by Photoplethysmography during a Head-Down Tilt Protocol

2019

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Photoplethysmography (PPG) signals from the forehead can be used in pulse oximetry as they are less affected by vasoconstriction compared to fingers. However, the increase in venous blood caused by the positioning of the patient can deteriorate the signals and cause erroneous estimations of the arterial oxygen saturation. To date, there is no method to measure this venous presence under the PPG sensor. This study investigates the feasibility of using PPG signals from the forehead in an effort to estimate relative changes in haemoglobin concentrations that could reveal these posture-induced changes. Two identical reflectance PPG sensors were placed on two different positions on the forehead (above the eyebrow and on top of a large vein) in 16 healthy volunteers during a head-down tilt protocol. Relative changes in oxygenated ( Δ HbO 2 ), reduced ( Δ HHb) and total ( Δ tHb) haemoglobin were estimated from the PPG signals and the trends were compared with reference Near Infrared Spectroscopy (NIRS) measurements. Also, the signals from the two PPG sensors were analysed in order to reveal any difference due to the positioning of the sensor. Δ HbO 2 , Δ HHb and Δ tHb estimated from the forehead PPGs trended well with the same parameters from the reference NIRS. However, placing the sensor over a large vasculature reduces trending against NIRS, introduces biases as well as increases the variability of the changes in Δ HHb. Forehead PPG signals can be used to measure perfusion changes to reveal venous pooling induced by the positioning of the subject. Placing the sensor above the eyebrow and away from large vasculature avoids biases and large variability in the measurements.

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Section: Discussionmentioning

confidence: 99%

Perfusion Changes at the Forehead Measured by Photoplethysmography during a Head-Down Tilt Protocol

2019

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“…NIRS measures tissue blood flow using different protocols such as the modulation of the fraction of inspired oxygen (FiO 2 ), 4 the venous occlusion, [4][5][6][7] and the tilting table. [8][9][10][11] These protocols are noninvasive, cause no discomfort, and allow simultaneous measurements of local blood flow and oxygen consumption in skeletal muscles. Moreover, the modulation of the fraction of inspired oxygen and tilting table protocols can be used for brain investigation.…”

Section: Introductionmentioning

confidence: 99%

Blood flow and oxygen consumption with near-infrared spectroscopy and venous occlusion: spatial maps and the effect of time and pressure of inflation

et al. 2000

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Abstract. We have measured the local blood flow (BF) and oxygen consumption (OC) in the human calf muscle using near-infrared spectroscopy during venous occlusion. Venous occlusion was achieved by inflating a pneumatic cuff around the thigh of the subject. We have investigated the influence of the inflation time and cuff pressure on the recovered values of BF and OC. We have found that if the cuff pressure is increased from a threshold pressure (ϳ30 mm Hg) to a critical pressure (ϳ45 mm Hg) in less than about 6 s, one measures the same values of BF and OC independent of the total inflation time and final cuff pressure. We also report nine-pixel spatial maps of BF and OC to show that this technique can lead to spatially resolved measurements of blood flow and oxygen consumption in tissues.

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<title>Calf muscle blood flow and oxygen consumption measured with near-infrared spectroscopy during venous occlusion</title>

et al. 1999

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We present non-invasive measurements of the calf muscle blood flow (BF) and oxygen consumption (OC) by near-infrared spectroscopy. We used a frequency domain tissue oximeter (modulation frequency: 1 10 MHz, wavelengths: 758 and 830 nm) to measure in real time (acquisition time: 0.64 s) the hemoglobin concentration and saturation. After 1-mm of baseline acquisition, we achieved venous occlusion by inflating a pneumatic cuff on the subject's thigh to a pressure of 60 mmHg. The cuffwas released after 1 mm. The baseline/inflation/release procedure was repeated 3 times to verify reproducibility. We calculated the BF and OC from the initial rate of increase of the total hemoglobin and deoxy-hemoglobin concentration immediately after the onset of venous occlusion. We examined 8 healthy subjects and 18 patients affected by peripheral vascular disease (PVD) in 1 or 2 legs to investigate whether muscle BF and OC at rest can be useful indicators of vascular insufficiency. In healthy legs, we obtained average values of BF=O.73 ml/(lOOml)/min and OC=O.1O ml/(lOOg)/min. The corresponding average values found in legs affected by PVD are BF=1 .39 ml/(lOOml)/min and 0C0. 16 ml/(lOOg)/min. The ranges of values of BF and OC measured in the healthy legs broadly overlap with the corresponding ranges measured in the PVD legs.

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<title>Near-infrared spectroscopy and the tilting table protocol: a novel method to study the blood flow and the oxygen consumption in tissues</title>

Cited by 4 publications

References 13 publications

Perfusion Changes at the Forehead Measured by Photoplethysmography during a Head-Down Tilt Protocol

Perfusion Changes at the Forehead Measured by Photoplethysmography during a Head-Down Tilt Protocol

Blood flow and oxygen consumption with near-infrared spectroscopy and venous occlusion: spatial maps and the effect of time and pressure of inflation

<title>Calf muscle blood flow and oxygen consumption measured with near-infrared spectroscopy during venous occlusion</title>

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