Skin Blood Content Research Articles

Development and validation of quantitative optical index of skin blood content.

.SignificanceWe present an approach to estimate with simple instrumentation the amount of red blood cells in the skin microvasculature, designated as parameter . Variations of parameter are shown to reflect local changes in the quantity of skin red blood cells during a venous occlusion challenge.AimTo validate a simple algebraic model of light transport in skin using the Monte Carlo method and to develop a measure of the red blood cell content in skin microvessels using the Monte Carlo predictions; to guide the development of an instrument to measure experimentally variations of the amount of red blood cells in the skin.ApproachMonte Carlo simulations were carried out in a multilayer model of the skin to compute remitted light intensities as a function of distance from the illumination locus for different values of the skin blood content. The simulation results were used to compute parameter and its variations with local skin blood content. An experimental setup was developed to measure parameter in human volunteers in whom skin blood content of the forearm increased during temporary interruption of the venous outflow.ResultsIn the simulations, parameter was in baseline conditions, and it increased in near proportion with the blood content of the skin layers. Measuring the diffusely reflected light intensity 0.5 to 1.2 mm away from the illumination locus was optimal to detect appreciable changes of the reflected light intensity as skin blood content was altered. Parameter measured experimentally on the human forearm was in baseline conditions it increased at a rate of when venous outflow was temporarily interrupted.ConclusionParameter derived experimentally with a two-wavelength diffuse reflectometer can be used to measure local variations of the amount of red blood cells in skin microvessels.

Volumetric quantification of skin microcirculation disturbance induced by local compression

We report on the estimation of blood content and vessel volume fraction changes in the microcirculatory bed of human skin under controlled mechanical compression using 3-dimensional optoacoustic (OA) angiography. A consecutive decrease in the fraction of blood vessels and skin blood content as a result of an increase in pressure from 0 to 72 mmHg applied to the imaged area was demonstrated by means of an acoustical-resolution OA microscope with a spatial resolution of 50 μm. Pressures below 32 mmHg were shown to weakly affect the acquired OA angiograms. The loss of OA signal from the blood vessels was observed after a further pressure increase of up to 72 mmHg. The vascular changes observed by OA microscopy were confirmed by infrared (IR) thermometry measurements which revealed similar dynamics of microcirculation interruption in the area under pressure.

Quick analysis of optical spectra to quantify epidermal melanin and papillary dermal blood content of skin.

This paper presents a practical approach for assessing the melanin and blood content of the skin from total diffuse reflectance spectra, R(λ), where λ is wavelength. A quick spectral analysis using just three wavelengths (585nm, 700 nm and 800 nm) is presented, based on the 1985 work of Kollias and Baquer who documented epidermal melanin of skin using the slope of optical density (OD) between 620 nm and 720 nm. The paper describes the non-rectilinear character of such a quick analysis, and shows that almost any choice of two wavelengths in the 600-900 range can achieve the characterization of melanin. The extrapolation of the melanin slope to 585nm serves as a baseline for subtraction from the OD (585nm) to yield a blood perfusion score. Monte Carlo simulations created spectral data for a skin model with epidermis, papillary dermis and reticular dermis to illustrate the analysis.

New closed-form approximation for skin chromophore mapping

The concentrations of blood and melanin in skin can be estimated based on the reflectance of light. Many models for this estimation have been built, such as Monte Carlo simulation, diffusion models, and the differential modified Beer-Lambert law. The optimization-based methods are too slow for chromophore mapping of high-resolution spectral images, and the differential modified Beer-Lambert is not often accurate enough. Optimal coefficients for the differential Beer-Lambert model are calculated by differentiating the diffusion model, optimized to the normal skin spectrum. The derivatives are then used in predicting the difference in chromophore concentrations from the difference in absorption spectra. The accuracy of the method is tested both computationally and experimentally using a Monte Carlo multilayer simulation model, and the data are measured from the palm of a hand during an Allen's test, which modulates the blood content of skin. The correlations of the given and predicted blood, melanin, and oxygen saturation levels are correspondingly r = 0.94, r = 0.99, and r = 0.73. The prediction of the concentrations for all pixels in a 1-megapixel image would take ∼ 20 min, which is orders of magnitude faster than the methods based on optimization during the prediction.

Optical assessment of skin blood content and oxygenation

The alteration of blood flow in the skin and subcutaneous tissue due to mechanical loading is of great importance in the prevention of decubitus ulcers. A technique is described for assessing changes in blood content optically. The results indicate that such changes occur after loading even though the deformation is maintained constant.

Interface pressure and cutaneous hemoglobin and oxygenation changes under ischial tuberosities during sacral nerve root stimulation in spinal cord injury

Noninvasive functional magnetic stimulation (FMS) of the sacral nerve roots can activate gluteal muscles. We propose the use of sacral anterior root stimulator (SARS) implants to prevent ischial pressure ulcers in the spinal cord injury (SCI) population. In this study, we (1) investigated the acute effects of sacral FMS on ischial pressure, skin blood content, and oxygenation changes in people with SCI and demonstrated the utility of FMS as an assessment tool, and (2) showed that similar effects are possible with electrical stimulation via a SARS implant. Results indicated that sacral nerve root stimulation, either by FMS or implanted electrical stimulation, induced sufficient gluteus maximus contraction to significantly change subjects' ischial pressures and cutaneous hemoglobin and oxygenation during sitting. In addition to these beneficial acute effects, chronic stimulation via a SARS implant may build gluteal muscle bulk and prevent or reduce pressure ulcers in the SCI population.

Reactive Hyperemia Response to Pressure-Induced Localized Ischemia in Patients with Multiple Sclerosis

Multiple sclerosis (MS) causes severe disability in adults. One of the secondary complications during the course of their illness is the development of pressure sores. This study sought to determine the postischemic response in the skin microcirculation of patients with MS, compared with able-bodied (AB) subjects, with the view to identifying differences that could be linked to their increased risk for pressure sores.The reactive hyperemia response following five minutes of indentation with a pressure of 150 mmHg was monitored in nine MS patients (EDSS > 7.0) and nine age-and sex-matched AB subjects. The skin blood content and oxygenation during the reactive hyperemia response was measured using reflectance spectrophotometry. This technique is noninvasive, quantifiable for skin redness, and effective for pigmented skin.A slower rate of increase in blood content following load release, a faster decay in blood content after the peak response, a smaller total reactive hyperemia response and slower rate of re...

Effect of chronic hypercapnia on body temperature regulation

Guinea pigs and rats exposed to 15% CO2 for 7 days showed a parallel time course of changes in pH, body temperature (TB), and oxygen consumption (VO2). Between 1 and 6 h of exposure the maximal drop in actual pH occurred in guinea pigs simultaneously with the maximal fall in TB and VO2. During the subsequent period pH TB, VO2 rose again. Skin blood content (heat loss) also exhibited a biphasic pH-dependent time course. Animals showing no partial compensation of respiratory acidosis during 3 days exposure also failed in raising their TB back to normal in this time. The behavior of TB was found to be a good indicator of the acid-base status and adaptive potential of the animals to hypercapnia. Similar results were obtained in rats. Thermo-regulatory processes in the hypothalamus were affected during exposure to 15% CO2. Both guinea pigs and rats showed a decrease in norepinephrine content of the hypothalamus during the first part of exposure reaching a maximal fall at the end of 24 h. The serotonin content increased slightly during this period. During prolonged exposure to 3% CO2 for 7 days, TB showed a transient rise, and VO2 was slightly elevated.

Measurement of the cutaneous circulation.

Relationships between four commonly used indirect methods for study of the cutaneous circulation in intact, unanesthetized man were examined. Skin temperature, thermal conductance, volume plethysmography and the light absorption of the skin (as related to hemoglobin content) were simultaneously recorded on the upper extremities of normal young men as blood flow and blood content of the skin were changed by circulatory arrest, venous occlusion, indirect heating and cooling, and changes in position. Skin temperature and thermal conductance changed along parallel courses as blood flow was changed, while finger volume and reflectance of the skin to light of wavelength 550 mμ both changed in expected directions although along different courses, following passive congestion and de-congestion and changes in level of the hand relative to the heart. The advantages, disadvantages, and limitations of each of the methods in the study of cutaneous circulation in man are discussed and compared. measurement of circulation of skin; methods for measurement of cutaneous circulation; blood flow through skin; blood content of skin; skin Submitted on March 12, 1964

Spectral reflectance of the skin of Chester White pigs in the ranges 235-700 m mu and 0.707-2.6 mu.

The spectral reflectance of the intact skin of the Chester White pig was measured and compared with that of other experimental animals and of the human. From 235 to 1300 mμ the shape of the reflectance curves of the Chester White pig, rat, rabbit and human is similar. The carotene absorption band appears noticeably only on the human and faintly on the rabbit. Above 1.3 μ all reflectance curves, including the one of the hairless mouse, practically coincide. The low reflectance values above 1.8 μ, probably caused by Fresnel reflection, indicate high absorption independent of the thickness of the skin but do not yet permit identification of the absorber. Earlier results that showed spectral reflectance differences to be caused by differences in pigmentation, in skin blood content and in other skin components, and that manifested themselves only between 300 and 1200 mμ have been found valid also for the skin of the Chester White pig. Submitted on January 30, 1956

A critical assessment of the use of blood cells labelled with radioactive phosphorus for the quantitative study of skin blood content.

A critical assessment of the use of blood cells labelled with radioactive phosphorus for the quantitative study of skin blood content.