Microcapillary infusion technique for measurement of intramuscular pressure during exercise.

The microcapillary infusion method (MCI) is described and compared to the pump infusion (PI) and the wick catheter methods for recording pressure in the anterior tibial muscle at rest and during exercise in 34 volunteers and in 11 patients with chronic compartment syndrome (CCS). The infusion techniques offered excellent dynamic properties in recording pressure during exercise with infusion rates exceeding 0.1 ml/hour. Infusion rates below 3.0 ml/hour in normal legs and below 1.5 ml/hour in CCS legs were found not to increase the pressure at rest during 30 minutes. The wick catheter method was found to be unsuitable in recording intramuscular pressure during exercise because of its slow response time. The MCI method had a lower compliance, a higher resonance frequency, and a shorter response time than the PI method. The muscle relaxation pressure (MRP) during exercise increased to 34.6 (SD = 5.6) mmHg in the CCS patients during exercise compared to 17.3 (SD = 4.6) mmHg in the control group. The MCI technique offers a practical tool for studying equilibrium pressures during muscle contraction and relaxation in routine clinical investigations and research.