Influence of passive leg movements on blood circulation on the tilt table in healthy adults

Abstract

BACKGROUND: One problem in the mobilization of patients with neurological diseases, such as spinal cord injury, is the circulatory collapse that occurs while changing from supine to vertical position because of the missing venous pump due to paralyzed leg muscles. Therefore, a tilt table with integrated stepping device (tilt stepper) was developed, which allows passive stepping movements for performing locomotion training in an early state of rehabilitation. The aim of this pilot study was to investigate if passive stepping and cycling movements of the legs during tilt table training could stabilize blood circulation and prevent neurally-mediated syncope in healthy young adults. METHODS: In the first experiment, healthy subjects were tested on a traditional tilt table. Subjects who had a syncope or near-syncope in this condition underwent a second trial on the tilt stepper. In the second experiment, a group of healthy subjects was investigated on a traditional tilt table, the second group on the tilt ergometer, a device that allows cycling movements during tilt table training. We used the chi-square test to compare the occurrence of near-syncope/syncope in both groups (tilt table/tilt stepper and tilt table/tilt ergometer) and ANOVA to compare the blood pressure and heart rate between the groups at the four time intervals (supine, at 2 minutes, at 6 minutes and end of head-up tilt). RESULTS: Separate chi-square tests performed for each experiment showed significant differences in the occurrence of near syncope or syncope based on the device used. Comparison of the two groups (tilt stepper/ tilt table) in experiment one (ANOVA) showed that blood pressure was significantly higher at the end of head-up tilt on the tilt stepper and on the tilt table there was a greater increase in heart rate (2 minutes after head-up tilt). Comparison of the two groups (tilt ergometer/tilt table) in experiment 2 (ANOVA) showed that blood pressure was significantly higher on the tilt ergometer at the end of head-up tilt and on the tilt table the increase in heart rate was significantly larger (at 6 min and end of head-up tilt). CONCLUSIONS: Stabilization of blood circulation and prevention of benign syncope can be achieved by passive leg movement during a tilt table test in healthy adults.

Figure 1

The tilt table with stepping device (tilt stepper)

Figure 3

The tilt table with ergometer device (tilt ergometer)

Figure 2

The tilt stepper: generation of leg movements

Figure 4

Blood pressure +/- SE during 75° the tilt table and tilt stepper test

Figure 5

Blood pressure +/- SE during 75° the tilt table and tilt ergometer test

Figure 6

Typical recordings illustrating a subject with syncope. RF = M. rectus femoris, BF = M. biceps femoris, TA = M. tibialis anterior, GM = M. gastrocnemius

Figure 7

Typical recordings illustrating a subject without syncope. RF = M. rectus femoris, BF = M. biceps femoris, TA = M. tibialis anterior, GM = M. gastrocnemius

Figure 8

Muscle activity during the tilt table and tilt stepper test

Figure 9

Muscle activity during the tilt table and tilt stepper test