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Measurement of Heated Skin O 2 Diffusion Conductance and Po 2 Sensor Induced O 2 Gradient
Author(s) -
EBERHARD P.,
SEVERINGHAUS J. W.
Publication year - 1978
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.1978.tb01384.x
Subject(s) - electrode , conductance , analytical chemistry (journal) , cathode , membrane , diffusion , capillary action , skin conductance , permeability (electromagnetism) , composite material , electrical engineering , materials science , chromatography , thermodynamics , biomedical engineering , medicine , chemistry , physics , condensed matter physics , biochemistry , engineering
A large cathode heated transcutaneous Po 2 electrode was used to measure the resistance of skin to diffusion of O 2 from the capillary bed to the surface. With a non‐0 2 ‐consuming tcPo 2 electrode, one would read ideal tcPo 2 , P 1 , which approximates Pao 2 between 50 and 100 mmHg due to approximate cancellation of the rise by heating and the fall by skin O 2 consumption. When a large cathode tcPo 2 electrode is used, its O 2 consumption causes a Po 2 gradient across skin resistance, Rs, which depends on electrode membrane resistance, R M (with Mylar), or R T (with Teflon). Surface Po 2 will fall below P 1 , and assuming no change in capillary Po 2 : P T /Pi = R T /(R T + R s ) and P M /P 1 , = R M /(R M + R s ) (1) 12 μm Teflon is 50 times as permeable to O 2 as 6 μm Mylar. When an electrode, covered alternately with these two membranes, was mounted on the same skin site in six subjects, the mean observed P T /P M was about 0.3. Substituting in equation (1) yields R T /R s = 0.4, R m /R s = 20, and P m /P 1 = 0.95. Using the known 0 2 permeability of Teflon, we computed skin O 2 conductance to be 6.6 pmol O 2 /(cm 2 . s. kPa), or 15 nl 0 2 /(cm 2 s'atm). This method thus provides a way of determining ideal tcPo 2 and stirring effect, Ø, of other electrodes and various membranes.