Tissue oxygen measurement and 31P magnetic resonance spectroscopy in patients with muscle tension and fibromyalgia.

Muscle tissue oxygen tension was measured by a polarographic oxygen fine-needle probe, and inorganic phosphate and creatine phosphate spectra were recorded using magnetic resonance spectroscopy in patients with chronic low back pain and in patients with fibromyalgia. Results were compared with healthy controls. The tissue oxygen tension was markedly higher in those with tense muscles than in normal subjects. Magnetic resonance spectra for inorganic phosphate were higher in patients demonstrating muscle contraction, and intracellular pH was shifted in the alkaline direction in cases with increased muscle tension. Results show that hypoxia is not the result of increased muscle tension, as was thought previously, but results from oversupply of oxygen demanded by the muscle, leading to increased capillary perfusion and rising oxygen tension.