Continuous monitoring of oxygen tension in human gastrocnemius muscle during exercise

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Abstract
Summary. A technique for continuous monitoring of the intramuscular oxygen tension (i.m. PO2) in human skeletal muscle at rest and during exercise was evaluated. A commercially available oxygen transducer mounted in the tip of a flexible catheter was slightly modified and its characteristics in terms of linearity, response time etc. were investigated in vitro.The oxygen probe was introduced through a cannula into the gastrocnemius muscle often normal subjects and ten patients with peripheral arterial insufficiency. The i.m. PO2 was continuously monitored at rest as well as during fatiguing leg exercise performed on a foot ergometer. The resting i.m. PO2 was 3.83 ± 0.45 kPa in normal subjects and 3.67 ±0.53 kPa in patients with peripheral arterial insufficiency. During exercise a decrease in the i.m. Po2 was found in both patients and normal subjects. At a work load of 8 kg normal subjects exercised for 8.1 ±0.6 min and the i.m. PO2 decreased to 2.45±0.39 kPa. At the same work load (8 kg) the i.m. PO2 decreased to I ‐22±0–4 kPa in the patients although their exercise time was considerably shorter (2.5 ±0.3 min) because of the development of claudication pain. An increase of the work load to 12 kg in the normals reduced the exercise time to 2.2 ± 0.1 min and provoked a more pronounced decrease in the i.m. PO2 (0.99 ±0.01 kPa). The limitations and advantages of the present technique are discussed in relation to other techniques. The results demonstrate that this technique is suitable for measurements of i.m. PO2 in human skeletal muscle tissue during exercise.