The influence of epidermal thickness on transcutaneous oxygen pressure measurements in normal persons

Abstract

Transcutaneous oxygen pressure measurements (TcPO2) were performed in ten healthy men (age 30.6 years, range 28-35) in six regions: anterolaterally 10 cm below and above the knee on both legs, 5 cm laterally to umbilicus and on the inside of the left humerus, which was subsequently biopsied for measurements of epidermal thickness from the basal lamina to the uppermost layer of stratum granulosum. Transcutaneous oxygen pressure was on average 70 mmHg (range 42-88 mmHg), and that of epidermal thickness 70 microns (range 43-120 microns). Epidermis was thinnest on the inside of the humerus (mean +/- SD) 61.3 mu +/- 11.0 and about 25% thicker (NS) in the regions above and below the knees. The relationship between TcPO2 (y) and epidermal thickness (x) could be described by the regression equation y = alpha i - 0.26x where the intercept alpha i differed between subjects, the mean value being 88 mmHg (range 77-103). The common regression coefficient of -0.26 was significantly different from zero (p less than 0.01, r2 = 0.49). Although the oxygen gradient across the total epidermis can not be estimated from skin biopsies, correction for the thickness of the living part of the skin may prove beneficial when TcPO2 measurements are used as an indicator of wound healing. The results suggests that the change of oxygen tension across the living part of epidermis is 0.26 mmHg/micron at various skin locations in different subjects.

Improving the reach of vaccines to low-resource regions, with a needle-free vaccine delivery device and long-term thermostabilization

“…However, the human skin is much thicker than mouse skin (e.g. mouse ear epidermis is 17.5±2.1 µm [37]; the human forearm dorsal epidermis is 61.3±11.0 µm [39]), so it is necessary to test if the densely packed microprojections can penetrate human skin. In order to test this, we tested the NP penetration into pig skin, because pig is considered as a good model for human skin penetration studies, because pig skin is physiologically similar to human skin both in skin thicknesses and mechanical properties [40].…”

Preamputation evaluation of limb perfusion with laser Doppler imaging and transcutaneous gases

“…Although TcPO 2 has been extensively used over the years to estimate viability of ischemic tissue, it is a technique that assesses skin perfusion only indirectly and is prone to complications from limited oxygen diffusion because of local edema and skin thickness [11][12][13]. Edema is prevalent in PVD complicated by infection, and skin thickness severely limits the usefulness of TcPO 2 in the plantar surface of the foot.…”

“…Later, clinicians used this phenomenon to estimate the degree of local perfusion deficit by measuring the level of skin PO 2 reached after enhancing local blood flow by topical heating [9][10]. However, many factors can affect the TcPO 2 measurements, including local edema [11], anatomical localization [8], thickness of the epidermal stratum corneum [12][13], and leg dependency [14].…”

Selection of lower limb amputation level not aided by transcutaneous pO2 measurements

“…However, our results show that this was not the case: healing took place even at very low transcutaneous oxygen pressures, and amputations failed to heal in 14 cases with normal transcutaneous oxygen pressures. The best measure of the tissue viability is the capillary oxygen pressure, butthereisalackofacloserelationship to the transcutaneous oxygen pressure due to the interindividual variation in the gradient across the epidermal layer (Jaszczak 1988, Falstie-Jensen et al 1988) and due to variation in the diffusibility ofoxygen in the skin. Also different handling of the skin previous to measurement of the transcutaneous oxygen pressure plays a role (Jaszczak 1988).…”