Modification of the effects of immobilization upon metabolic and physiologic functions of normal men by the use of an oscillating bed

Abstract

A study was made of the influence of an oscillating bed on the metabolic and physiologic disturbances associated with immobilization. The subjects were three normal healthy young men. The investigation was carried out on a metabolism ward during control (four to five weeks), immobilization (five weeks) and recovery (five to six weeks) periods. The dietary intake was constant. During the immobilization periods the subjects were in bivalved plaster casts extending from umbilicus to toes. One year previously the three subjects studied had participated in an experiment identical with the present study except that they had been immobilized in standard (fixed) hospital beds. During immobilization in the oscillating bed: 1. 1. Nitrogen excretion increased in the same general pattern as in the fixed bed experiment; but in two of the subjects nitrogen loss was approximately half as great as during an equal period of immobilization in the fixed bed. 2. 2. The loss of calcium, chiefly in the urine, was, on the average, half as great as during the same period in the fixed bed. 3. 3. The loss of phosphorus was significantly less in two of the subjects than during the same period in the fixed bed. 4. 4. Although urinary citric acid, pH and urine volume did not appreciably change, the significant reduction in urinary calcium and phosphorus losses would render the precipitation of calcium phosphate in the urinary tract less likely than during immobilization in a fixed bed. 5. 5. There was good correlation between the excretion of urinary total sulfur and nitrogen on the basis of the ratio in which they exist in muscle. The correlation between nitrogen and phosphorus on the same basis was less good, between nitrogen and potassium poor. 6. 6. Creatine tolerance tests indicated that creatine metabolism was significantly less impaired than during immobilization in the fixed bed. The decrease in muscle mass and strength of the immobilized limbs was also less than during an equal period in the fixed bed. 7. 7. Changes in basal oxygen consumption were not significant. 8. 8. The deterioration produced by fixed bed immobilization in the mechanisms essential for adequate circulation in the erect position (as measured by tilt table tests) was largely prevented. 9. 9. Measurements of venous pressure in the foot veins during oscillation revealed an average change in pressure of 140 mm. of water with each change in position of the bed. A rhythmical shift was observed in the average level of the diaphragm with each change in position of the bed, without significant alteration in the pulmonary minute ventilation. 10. 10. Changes in urinary 17-ketosteroid excretion and in serum calcium levels were not significant. 11. 11. As in the fixed bed experiment, there were no significant alterations in blood coagulation studies, circulation time, heart size or electrocardiograms. During the recovery phase most metabolic and physiologic functions returned to control levels or became re-stabilized more rapidly than following immobilization in the fixed bed. Following recovery from the oscillating bed experiment, one subject was re-immobilized in a fixed bed for two weeks. The results duplicated closely the changes observed during the first two weeks of his first immobilization in a fixed bed a year previously.