The effects of lower-extremity functional electric stimulation on the orthostatic responses of people with tetraplegia

Abstract

Objective: To determine whether application of functional electric stimulation (FES) to lower-limb muscles during postural tilting improves orthostatic tolerance in people with tetraplegia.

Design: A crossover design.

Setting: A rehabilitation hospital.

Participants: Sixteen acute and chronic subjects with tetraplegia (15 men, 1 woman) with complete motor function loss at the C3-7 levels were recruited. Time since injury ranged from 2 to 324 months (mean, 118.9+/-104.2 mo).

Intervention: Subjects were tested on a progressive head-up tilting maneuver with and without the application of FES at 0 degrees , 15 degrees , 30 degrees , 45 degrees , 60 degrees , 75 degrees , and 90 degrees continuously for up to 1 hour. FES was administered to 4 muscle groups including the quadriceps, hamstrings, tibialis anterior, and gastrocnemius muscles bilaterally at an intensity that provided a strong, visible, and palpable contraction. This was to produce a muscle pumping mechanism during the tilting maneuver.

Main outcome measures: Systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate, perceived presyncope score, and the overall duration of orthostatic tolerance, that is, the time that subjects could tolerate the tilting maneuver without developing severe hypotension or other intolerance symptoms.

Results: When the tilt angle was increased, the subjects' SBP and DBP tended to decrease, whereas the heart rate tended to increase in both testing conditions. Adding FES to tilting significantly attenuated the drop in SBP by 3.7+/-1.1 mmHg (P = .005), the drop in DBP by 2.3+/-0.9 mmHg (P = .018), and the increase in heart rate by 1.0+/-0.5 beats/min (P = .039) for every 15 degrees increment in the angle of the tilt. FES increased the overall mean standing time by 14.3+/-3.9 min (P = .003).

Conclusions: An FES-induced leg muscle contraction is an effective adjunct treatment to delay orthostatic hypotension caused by tilting; it allows people with tetraplegia to stand up more frequently and for longer durations.