ANTERIOR COMPARTMENT MUSCLE PO2 MEASUREMENT DURING ELEVATION

The aim of this study was to establish the ability of an invasive fibre-optic probe to measure intra-muscular pH, pCO 2 , pO 2 , HCO 3 - − , ambient temperature, base excess and O 2 saturation. The secondary aim was to determine the effect of elevation of the limb on these parameters. Fibre-optic probes were introduced into the anterior compartment muscle of the leg in five volunteers via 16G cannulae. After equilibration the limb was monitored for 11min with the volunteer supine on an examination couch. The limb was elevated to 22cm (Braun frame) and then 44cm for the same time. Subsequently the leg was returned to 22cm and supine. All volunteers followed this set protocol. Continuous recording of all indices was made throughout. Data was stored to a personal computer for analysis. Similar trends were observed across all subjects for all parameters. The mean pO 2 when lying flat was 27mmHg (S.D.7.4). Elevation to 22cm increased muscle pO 2 to 33 mmHg (S.D. 5.8). Further elevation to 44 cm resulted in a reduction in muscle pO 2 to a level below that measured when supine. When the limb was returned to 22cm the pO2 trend reversed, the level improving. Returning to the supine position the pO 2 returned to the level seen at the start of monitoring. This novel probe gives reproducible measures of pH, pCO 2 , pO 2 , HCO 3 − , ambient temperature, base excess and O 2 saturation. Results indicate that elevation to 22cm improves muscle oxygenation; a height of 44cm seems detrimental. This technique may be applicable in surveillance for compartment syndromes and muscle ischaemia.