Effect of Electrode Placement on Controlling Orthostatic Hypotension in People with Cervical Spinal Cord Injury
Effect of Electrode Placement on Controlling Orthostatic Hypotension in People with Cervical Spinal Cord Injury
A common therapeutic intervention after spinal cord injury (SCI) is prolonged standing in a standing frame. For people with SCI, standing for 40 minutes or more, three to four times weekly improves several health-related issues including well-being, circulation, skin integrity, reflex activity, bowel and bladder function, digestion, sleep, pain, and fatigue. However, a person who experiences orthostatic hypotension (OH)-defined as a decrease of 20mm hg in systolic blood pressure or a decrease of 10mm hg in diastolic pressure within 3 minutes of standing from a sitting or supine position-secondary to SCI may not tolerate positioning in a standing frame, thus resulting in a loss of access to these health benefits.
OH is common for people with SCI. It results from central nervous system dysregulation causing pooling of blood in the lower extremities that can lead to dizziness, light-headedness, blurred vision, weakness, fatigue, nausea, palpitations, headache, and/or syncope. Although an array of physical and pharmacologic interventions are available to people in the general population for managing OH, few such interventions have been evaluated for use by people with SCI, especially when the level of injury is C5 or above.
One possible intervention that may be effective for people with OH secondary to SCI is functional electrical stimulation (FES) because its application results in a dose-dependent increase in blood pressure. An unanswered question is whether the placement of FES electrodes on various parts of the body has differential effects. Therefore, the purpose of this study is to evaluate blood pressure responses among people with OH secondary to cervical SCI when receiving FES intervention involving the placement of electrodes in three different positions as well as when receiving no FES intervention during tilt table sessions. The selected positions for electrode placement are: (a) the calves, (b) the quads and abdominals, and (c) the quads, abdominals, and calves. The researchers hypothesize that FES intervention, regardless of placement, will result in better control of OH than no FES intervention and that no significant blood pressure difference will occur across the three FES placements.
Participants will engage in three initial heads-up tilt table sessions with no FES intervention to confirm the presence and consistency of OH. During these sessions, the participant will lie supine on a tilt table at 0°, and, using a blood pressure cuff secured around the arm, the researchers will measure and record supine blood pressure. The researchers will then adjust the tilt table to 30° for three minutes and take and record another blood pressure measurement. If the participant reports no OH symptoms and the researchers observe no changes in appearance or signs of distress at that time, the researchers will query the participant about willingness to adjust the table to an additional 10° of tilt. Following three minutes at this level, the researchers will again measure and record the participant's blood pressure. These procedures will continue with increments of 10° of increased tilt every three minutes to a maximum of 90° tilt until the session time (maximum of 60 minutes) has elapsed or the participant expresses discomfort, measured blood pressure drops relative to the supine recording, or the researchers observe behaviors indicative of OH (e.g., sweating, change in skin color, change in breathing pattern, grimacing). If any of these OH symptoms occur, the researchers will adjust the tilt table to lower levels of incline until the participant's blood pressure stabilizes to the supine position measurement, and the session will be terminated.
Intervention sessions will begin after three days of baseline measurements. Intervention sessions will follow the same procedures except that the conditions will alternate randomly among the three FES placement and the no FES conditions. All sessions will be held at Quality Living, Inc., in Omaha, Nebraska.
Inclusion Criteria:
Exclusion Criteria: