MEASUREMENTS OF OXYGENATION AND PERFUSION IN SKELETAL-MUSCLE USING MULTIPLE MICROELECTRODES

This paper describes an apparatus to measure tissue oxygenation and pe rfusion (as measured by the wash-in rate of gaseous hydrogen) simultan eously at multiple points in muscle using needle microelectrodes. The development of suitable electrodes and apparatus is described, as well as the development of the method and its validation. In particular, t he potential for tissue damage secondary to electrode insertion, the n eed for in vivo voltammetric determination of the operating potential and the extent of any electrode-tissue and of electrode-electrode inte ractions are explored, and are shown to be insufficient in magnitude t o affect the technique. Its subsequent use to characterise oxygenation and perfusion in rabbit skeletal muscle at rest is also described. In resting tibialis anterior muscle of the rabbit the mean pO(2) was 18 +/- 13.3 mm Hg and the mean perfusion was 4.4 +/- 1.3 ml s(-1) 100 g(- 1). There was a heterogeneity in simultaneously-measured values of pO( 2) and perfusion at different points within muscle, and also a tempora l variation at the same site. The spans between the highest and lowest simultaneously-measured values of pO? in muscle ranged from 14 to 80 mmHg, and for perfusion, from 1 to 12 ml s(-1) 100 g(-1). No significa nt correlation was evident from histological examination between eithe r pO(2) or perfusion and surrounding fibre type or capillary density.