COMPARISON OF MACRO-LIGHTGUIDE AND MICRO-LIGHTGUIDE SPECTROPHOTOMETRIC MEASUREMENTS OF MICROVASCULAR HEMOGLOBIN OXYGENATION IN THE TUBERCULIN REACTION IN NORMAL HUMAN SKIN

The changes in haemoglobin oxygenation (SO2) occurring in the tubercul in reaction in human skin were measured using macro- and micro-lightgu ide spectrophotometry and the results compared. A significant differen ce was found between the measurements from the respective instruments, demonstrating that the micro-lightguide technique measures only in th e most superficial capillaries. Laser Doppler flux (LDF) and transcuta neous oxygen (tcpO2) measurements were also obtained concurrently. At the height of the reaction, heating did not significantly change SO2 o r LDF, showing that the vessels in the skin were maximally vasodilated . Although SO2 was increased in the reaction, tcpO2 decreased. This su ggests that the infiltrating cells may present a diffusion barrier to oxygen between the capillaries and the tissue cells. This study has sh own that micro-lightguide spectrophotometry gives a local picture of i ntracapillary oxygen supply, which is useful in elucidating the pathop hysiological changes occurring during chronic inflammation.