The purpose of this study was first to evaluate the near infrared spectroscopy (NIRS) device, INVOS 4100 as a method of measuring exercise and arterial occlusion induced muscle ischemia in human leg, by comparison with InSpectra tissue spectrometer Model 325, and secondly to determine the influence of skin and subcutaneous thickness on the NIRS measurements. Twenty healthy subjects (43 ± 8 years) volunteered for the study. Tissue oxygen saturation (StO2) in the anterior tibial muscle was measured simultaneously with InSpectra Model 325 in one leg and INVOS 4100 in the contralateral leg during an exercise test until muscle exhaustion and arterial occlusion with and without exercise. The skin and subcutaneous thickness was identified by ultrasound imaging. Baseline StO2 was 87 ± 8 % detected by InSpectra and 76 ± 6 % by INVOS. Both devices detected an immediate decrease of StO2 (p < 0.001) during exercise, arterial occlusion with and without exercise, and a significant post ischemic hyperaemia (p < 0.001) during recovery. There was a significant inverse correlation between skin and subcutaneous thickness and baseline StO2 (r = -0.78, p < 0.01) as well as change in StO2 during exercise (r = -0.65, p = 0.002) for InSpectra, which was not apparent for INVOS. The results demonstrate that the cerebral/somatic oxygenation monitor (INVOS) is able to detect experimentally induced skeletal muscle ischemia in the human leg as well as the peripheral tissue spectrometer (InSpectra). Muscle oxygen saturation measurement by INVOS is less affected by skin and subcutaneous thickness than measured by InSpectra.

Changes in muscle oxygen saturation during and after an exercise test that elicits leg pain cannot be used to distinguish between patients with CACS and patients with other causes of exercise-induced leg pain.

We measured intramuscular oxygenation in the anterior tibial muscle of 176 patients with exercise-induced leg pain by noninvasive near-infrared spectroscopy before, during, and after an exercise test that elicited the symptoms. Clinical investigation was performed after each test. Intramuscular pressure was measured in patients with nonconclusive findings. Chronic anterior compartment syndrome (CACS) was diagnosed in 47 patients, and other causes for the leg pain were diagnosed in 129 patients by clinical means. The mean level of oxygenation decreased to 33 ± 19% in patients with CACS and to 34 ± 19% in patients without CACS compared with baseline level (100%) at rest before exercise. The level of oxygenation was below 20% during the exercise test in 12 of 47 (26%) patients with CACS and in 30 of 129 (23%) patients without CACS. The time required for reoxygenation after the cessation of exercise was 61 ± 34 s in patients with CACS and 46 ± 20 s in patients without CACS (P < 0.05). We conclude that the magnitude of intramuscular deoxygenation during exercise is an unreliable measure to diagnose CACS. However, the time for reoxygenation returning to baseline level following an exercise test is a valuable adjunct in diagnosing CACS.

Purpose To investigate distributions and identify possible differences in intramuscular pressure (IMP) values at 1 min post-exercise between the four muscle compartments of the lower leg, in patients with exertional leg pain with or without chronic exertional compartment syndrome (CECS). Methods A consecutive series of patients seeking orthopaedic consultation for exertional leg pain underwent IMP measurements between 2009 and 2018. The diagnosis of CECS was confirmed (n = 442) or ruled out (n = 422), based on the patient’s history, clinical examination, and IMP measurements. Results The median (range) 1 min post-exercise IMP values in affected compartments in the patients diagnosed with CECS were 33 (25–53) mmHg (deep posterior), 35 (27–54) mmHg (superficial posterior), 40 (26–106) mmHg (lateral), and 47 (24–120) mmHg (anterior). In patients with no CECS, the median (range) 1 min post-exercise IMP values in the compartments were 12 (2–28) mmHg (deep posterior), 12 (2–27) mmHg (superficial posterior), 14 (2–26) mmHg (lateral), and 18 (4–34) mmHg (anterior). The IMP was significantly lower in the lateral and both posterior compartments than in the anterior compartment in both patients diagnosed with CECS and patients without CECS. Conclusion The study demonstrates significantly lower IMP values in the posterior and lateral compartments compared to the anterior compartments. These findings suggest a lowering of the IMP 1 min post-exercise cut-off value for diagnosing CECS in the lateral and both posterior compartments, which may lead to improved treatment of patients with suspected CECS in the lower leg. Level of evidence Level II.