We investigated the value of surface electromyography (EMG) as an aid to diagnosing the chronic compartment syndrome (CCS) by detecting elevated intramuscular pressure (IMP) at rest after an exercise test that was caused by remaining muscle contraction. IMP and EMG were measured in the anterior tibial muscle in 37 patients who were suspected to have CCS after an exercise test. At rest after the test, the EMG signal was positive in five of 37 (14%) patients, indicating that patients had remaining muscle contractions that elevated IMP. IMP exceeded 30 mmHg in 16 of 37 patients (43%). In 13 of these 16 patients, the EMG signal was silent, confirming that they had CCS. In the remaining three patients, the EMG signal was initially positive (5-34% of maximal voluntary contraction), and then became silent after communicating with the patients to relax their legs. Only one of the three patients was proven to have CCS. Other reasons for leg pain were diagnosed in 23 patients. The results demonstrated that simultaneous measurements of IMP and EMG differentiate elevated IMP at rest after exercise due to the volumetric load of the compartment muscles seen in patients with CCS and due to the remaining muscle contraction, thereby preventing a false diagnosis of CCS.
We used photoplethysmography (PPG) to measure the relative changes in the anterior tibial muscle blood flow (MBF) in response to exercise when intramuscular pressure (IMP) was elevated (the test leg) or when IMP was normal (the control leg). The elevated IMP was induced by applying venous obstruction of 40 mmHg or 65 mmHg (thigh tourniquet) of a casted leg in eight healthy subjects. Subjects performed dorsiflexion of both feet in sitting position with or without venous obstruction. IMP at rest after exercise increased to 39.4±7.9 mmHg or to 58.3±8.4 mmHg, respectively. MBF at rest before exercise was 100%. At rest after exercise, it increased to 184±52.6% in the test leg when IMP was 39.4 mmHg, and to 279±108.3% in the control leg. MBF at rest after exercise was 156±58.2% in the test leg when IMP was 58.3 mmHg and 303±95.3% in the control leg. The abnormally elevated IMP induced by venous obstruction of a casted leg reduced MBF at rest after exercise. PPG seems to be a suitable method to measure changes in MBF in response to exercise and in experimental conditions with abnormally elevated IMP.
Venous insufficiency is associated with decreases in muscle blood flow (MBF) and oxygenation of the leg. We hypothesize that mild external compression of the leg increases microvascular MBF and oxygenation in a leg experiencing venous hypertension. Thigh compression was used as a model for venous hypertension in five healthy subjects (3 males, 2 females). MBF was measured using photoplethysmography (PPG) and relative muscle oxygenation was measured using near‐infrared spectroscopy (NIRS). Both PPG and NIRS probes were placed on the anterior compartment of the leg. An inflatable tourniquet was placed on the thigh and inflated to 65 mmHg. An inflatable cuff covered the entire leg including the probes and was inflated to 40 mmHg. After establishing a baseline, MBF and oxygenation were measured during 12 min of venous occlusion along with a 4‐min interval of superimposed leg cuff compression. Baseline of MBF was normalized to 100%; all subsequent data (see table) were divided by this reference value (means ± SE). Baseline muscle oxygenation was established after 6 min of venous occlusion and is reported as ΔmV.
In a model of venous hypertension, mild external compression increases leg muscle blood flow and oxygenation. These findings may explain the beneficial effects of compression therapy on healing of venous stasis ulcers.
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