DIAGNOSIS OF DEFECTS IN OXIDATIVE MUSCLE METABOLISM BY NONINVASIVE TISSUE OXIMETRY

The dynamics of oxygen delivery and utilization are examined in a vari ety of mitochondrial disorders during rest, exercise and post exercise . We used a non-invasive optical technique to measure the oxygen consu mption in the exercising limb in normal subjects and 5 patients with c ytochrome c oxidase deficiency. We also examined 6 patients with MELAS and MERRF syndrome. We measured near-infrared spectra of hemoglobin i n the gastrocnemius muscle during treadmill exercise. Normal subjects demonstrated a sustained deoxygenation during exercise, indicating an efficient utilization of delivered oxygen. Patients with cytochrome c oxidase deficiency demonstrated consistent oxygenation during exercise indicating an under utilization of delivered oxygen. Patients with ME LAS and MERRF syndrome showed similar under utilization of oxygen duri ng exercise. Non-invasive tissue oximetry during exercise demonstrates specific abnormalities in a variety of mitochondrial disorders, indic ating abnormal oxygen utilization, and will be a useful addition to th e clinical investigation of such disorders.