Effects of functional electrical stimulation on orthostatic challenges in spinal cord injured subjects

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Effects of functional electrical stimulation on orthostatic challenges in spinal cord injured subjects


Author: Chao, Yuet-lan
Title: Effects of functional electrical stimulation on orthostatic challenges in spinal cord injured subjects
Year: 2004
Subject: Hong Kong Polytechnic University -- Dissertations
Spinal cord -- Wounds and injuries -- Treatment
Electric stimulation
Department: Dept. of Rehabilitation Sciences
Pages: xii, 94 leaves : ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1772694
URI: http://theses.lib.polyu.edu.hk/handle/200/1217
Abstract: Background and Objective: Spinal cord injured individuals with impaired sympathetic activity and complete muscle paralysis below the level of lesions commonly experience orthostatic hypotension (OH) and intolerance during orthostatic challenges. Gradual head-up tilting is a standardized treatment procedure for managing OH. The aim of the study is to determine whether the addition of functional electrical stimulation (FES) to lower limbs muscles during postural tilting would improve the haemodynamic response and orthostatic tolerance in tetraplegic persons. Design: A cross-over design was used. Subjects were used as their own control and underwent two testing conditions of gradual orthostatic challenges through progressive postural tilting techniques at the angle of 0o, 15o, 30o, 45o, 60o, 75o and 90o continuously with and without the application of FES. FES was administered to four muscle groups including quadriceps, hamstrings, tibialis anterior and gastrocnemius muscles bilaterally to produce a muscle pumping mechanism during the tilting maneuver. The tilting maneuver lasted for one hour at most depends on subject's tolerance. Setting: Rehabilitation hospital. Participants: Sixteen tetraplegia (1 female, 15 male) with complete motor function at C3 to C7 level were recruited. Subjects with recent injuries were recruited from an inpatient spinal cord rehabilitation unit at MacLehose Medical Rehabilitation Centre and Kowloon Hospital.Subjects with long-standing injures were recruited from the community by convenience sampling. Main Outcome Measures: Systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR) and perceived presyncope score (PPS) were recorded at different angles of the two testing conditions. The overall duration of orthostatic tolerance was also noted. Results: Overall, the SBP and DBP showed a reduction trend while HR an increased trend when the angle of tilt increased in both testing conditions. In tilting alone condition, for every 15o increase in angle of tilt, the SBP dropped by 7.72+-5.44mmHg and DBP dropped by 4.50+-3.67mmHg, while HR increased by 4.34+-3.43beats/minute. In FES-augmented tilting maneuver, there was corresponding SBP dropped by 4.00+-4.35mmHg, DBP dropped by 2.16+-2.62mmHg, and HR increased by 3.31+-2.30beats/minute. Adding FES significantly reduced the degree of SBP drop by 3.72+-4.52mmHg (p=0.005), DBP drop by 2.34+-3.53mmHg (p=0.018), and the extent of HR increment by 1.03+-1.83beats/minute (p=0.039) for every 15o increment of angle of tilt. None of the subjects presented with any presyncopal symptoms below 30o angle of tilt. No significant difference (p>0.05) was found in the proportion of subjects who were classified as favor or neutral to FES-augmented tilting maneuver on orthostatic intolerance symptoms at either 30o and 45o angle of tilt. However, more subjects experienced the presyncopal symptoms at greater angle of tilt, and it more likely to occur in the tilting alone condition. On average, the mean duration of orthostatic tolerance for tilting alone condition was 31.19+-20.47minutes. Adding FES to tilting significantly increase the overall mean standing time by 14.25+-15.57minutes (p=0.003). Conclusion: Our findings suggested that the use of FES-induced leg muscle contraction is an effective adjunctive intervention to prevent orthostatic hypotension during tilting or standing in SCI individuals with high cord level lesions. As FES can delay orthostatic hypotension caused by tilting, this allows persons with SCI be able to stand more frequently and for longer duration without being subjected to the side effects of intolerance symptoms due to orthostatic hypotension.

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