Quantitative Reflection Spectrophotometry: Spatial and Temporal Variation of Hb Oxygenation in Human Skin

Abstract

Applying a fast scanning reflection spectrophotometer and multicomponent spectra analysis, oxygen saturation (S_Hb) and relative concentration (C_Hb) of hemoglobin in the skin were determined at eight skin sites in 11 healthy persons. S_Hb was significantly higher at the tip of the index finger and big toe (90 ± 3.9 and 92 ± 4.2%, respectively) compared with the forehead, volar forearm, back of hand, abdomen, calf and forefoot where mean values varied between 52 and 67% (p < 0.001). C_Hb also was higher at acral sites (big toe: 2.04 ± 0.14 arbitrary units (AU); index finger: 2.13 ± 0.19 AU) than at the other locations (p < 0.0001) where it was between 0.56 ± 0.12 AU (abdomen) and 0.95 ± 0.28 AU (forefoot). In the course of time, rhythmical oscillations of both parameters at a frequency of 3-5/min were seen in 68% of the measurements, predominantly at the six proximal sites. Heating the measuring site to 44 °C caused a biphasic increase of C_Hb and S_Hb which was significant at the proximal sites (p < 0.0001). S_Hb values came into the range of arterial blood. Temporal and spatial variation of both parameters decreased. Reflection spectrophotometry gives the possibility to directly assess dermal hemoglobin saturation, its physiological variability and reactions to provocation stimuli. Concentration and saturation of hemoglobin in dermal vessels appear definitely different at acral compared with proximal sites.

Investigation of spatial resolution dependent variability in transcutaneous oxygen saturation using point spectroscopy system

“…This is followed by mean StO2 of 84.8 0.9%  for detection distance of 50 mm. These values are comparable to that observed in the works of previous researchers who used different analytical model namely Kubelka Munk [14] and Cumulant based forward model (CM) [15,16]. The results in Table 1 and Figure 3 also revealed small standard deviation among these subjects, indicating good repeatability of the analytical technique and the proposed experimental method when the imaged skin site is of close proximity to the detection system (<50 mm).…”

“…posterior forearm, leg). This is contributed by the presence of arteriovenous anastomoses (AVAs) which can be found in abundance in the acral skin site [14]. The AVAs provide circulatory connection between the artery and veins and also produce shunting of oxygenated arterial blood into the venous compartment during muscle relaxation.…”

Nonlinear fitting model for continuous monitoring of mean blood oxygen saturation

“…4, the mean of S m O 2 estimated for the fingertip and the back of hand of the employed human subjects at rest condition, and the heated fingertips are given by 92.6±3.7%, 39.8±6.85% and 102±3.1%, respectively. The high S m O 2 value of 92.6±3.7% observed for the fingertip of volunteers at rest agreed well with the oxygen saturation value of 92±2.6% reported by Caspary et al [11] who also conducted the similar experiment. This is due to the presence of Arteriovenous anastomoses (AVAs) that are available in abundance in acral (fingertip) than non-acral skin (back of the hand) [12].…”

Glucose, In Vivo Assay of

“…For human skin at different measuring sites, at a given skin temperature, the tip of the index finger showed the highest hemoglobin concentrations which could be related to the tissue blood volume. 8 Our own measurements showed that the human lip was an even better test location for the same reasons (see Figure 3). In Figure 3(a) the diffuse reflectance spectra of different skin tissues are presented, which are dominated by the absorption features of oxygenated hemoglobin (hemoglobin oxygenation saturation, HbSO 2 , is usually high at around 90%).…”