Wheelchair cushion effect on pressure and skin temperature

Eight wheelchair cushions representing five types of materials were evaluated in two population groups, able-bodied and spinal cord injured (SCI). Objective factors such as area of first light, pressure, tuberosity and thigh temperatures, and subjective factors such as cosmesis, handling ability, and purchase were studied. Twenty subjects (10 men and 10 women; 10 SCI and 10 able-bodied) from 16 to 35 years of age were chosen to participate in the study. Pressure was measured with the Pressure Evaluation Pad and skin temperature of each ischial tuberosity and posterior thigh was determined. Temperature differences were not significant among cushions but the alternating pressure and foam cushions produced consistently higher temperatures compared to other cushions for both groups of subjects. No significant differences among cushions were found for area of first light, cosmesis, handling ability, or purchase. However, three cushions were rated acceptable in cosmesis while three different cushions were rated acceptable in handling ability by all subjects. No cushion rated a perfect score by all subjects regarding purchase but all the SCI subjects said they would purchase the air-filled cushion. Overall pressure differences were not significant but large individual variations were observed. The authors believe that pressure produced by wheelchair cushions should be measured with a standard device such as the Pressure Evaluation Pad, and that, to reduce the incidence of pressure sores, cushion use in each patient should be modified on the basis of initial and periodic assessment of both objective and subjective factors.     

Functional magnetic stimulation of the colon in persons with spinal cord injury

OBJECTIVE: To evaluate the usefulness of functional magnetic stimulation (FMS) as a noninvasive method to stimulate the colon in individuals with spinal cord injury (SCI). DESIGN: A prospective before-after trial consisting of 2 protocols. SETTING: FMS laboratories of 2 SCI centers. PARTICIPANTS: Two able-bodied men and 13 men with SCI levels ranging from C3 to L1. Protocol 1 consisted of 9 subjects, 2 of whom were excluded from the analysis. Protocol 2 consisted of 4 subjects. INTERVENTION: Commercially available magnetic stimulators with round magnetic coils (MCs) were used. Protocol 1 measured the effects of FMS on rectal pressure by placing the MC on the transabdominal and lumbosacral regions. Protocol 2 consisted of a 5-week stimulation period to investigate the effects of FMS on total and segmental colonic transit times (CTTs). MAIN OUTCOME MEASURE: An increase in rectal pressure and a decrease in CTT by magnetic stimulation. RESULTS: Data were averaged and the standard error of the mean was calculated. Statistically significant changes in rectal pressure and CTT were also measured. Rectal pressures increased from 26.7 +/- 7.44cmH(2)O to 48.0 +/- 9.91cmH(2)O, p =.0037, with lumbosacral stimulation, and from 30.0 +/- 6.35cmH(2)O to 42.7 +/- 7.95cmH(2)O, p =.0015, with transabdominal stimulation. With FMS, the mean CTT decreased from 105.2 to 89.4 hours, p =.02. CONCLUSION: FMS is able to stimulate the colon and reduce CTT. FMS is a noninvasive, technological advancement for managing neurogenic bowel in patients with SCI.     

Pelvic movement and interface pressure distribution during manual wheelchair propulsion

OBJECTIVE: To investigate the movement of the ischial tuberosities and the redistribution of interface pressure during manual wheelchair propulsion. DESIGN: Measurement of ischial tuberosity positions and comparison with corresponding position of the zones of peak pressure by using independent samples t tests. Analysis of variance was used to compare peak and average pressures under static and dynamic conditions. SETTING: Human locomotion laboratory. PARTICIPANTS: Ten subjects with spinal cord injury (SCI) and 10 individuals with no disabilities. INTERVENTIONS: Manual wheelchair propulsion on a stationary wheelchair ergometer at the subject's maximum propulsion speed. MAIN OUTCOME MEASURES: Seat interface pressure and the 3-dimensional position of the pelvis were measured with a pressure mat and an optical motion analysis system. RESULTS: During wheelchair sprinting, the ischia were located at 19.2+/-11.7 mm behind the corresponding peak pressure locations. The anteroposterior rocking of the pelvis was 11.2 degrees and 5.2 degrees for the normal and SCI group, respectively. The average interface pressure over the ischial tuberosity area was lower under dynamic conditions. It was also observed in the SCI group that there was a concentration of high-pressure gradients around the peak pressure areas of the buttock during dynamic propulsion. CONCLUSION: Peak pressure locations did not concur exactly with the ischial tuberosities during propulsion. The movements of the ischial bone and the cyclic loading imposed on the tissue underneath the ischial tuberosities during dynamic conditions may have implications for the etiology of decubitus ulcers.     

Functional magnetic stimulation facilitates gastric emptying

OBJECTIVE: To evaluate the effect of functional magnetic stimulation (FMS) on gastric emptying in able-bodied and spinal cord injury (SCI) subjects. DESIGN: A prospective, nonrandomized clinical experiment. SETTING: SCI and disorder center in a Veterans Affairs medical facility. PARTICIPANTS: Five healthy, able-bodied subjects and 4 subjects with SCI. INTERVENTION: A commercially available magnetic stimulator was used; a round magnetic coil was placed along the T9 spinous process. The intensity of the magnetic stimulation was 60%, with a frequency of 20 Hz, and a burst length of 2 seconds for the gastric emptying protocol. Man Outcome Measures: Rate of gastric emptying and time required to reach gastric emptying half-time (GE(t1/2)) with and without FMS. Data fit into linear regression curve. RESULTS: Accelerated gastric emptying was achieved in both able-bodied and SCI subjects. The mean +/- standard error of mean of the GE(t1/2) at baseline and with FMS was 36+/-2.9 minutes and 33+/-3.1 minutes, respectively, for able-bodied subjects, and 84+/-11.1 minutes and 59+/-12.7 minutes, respectively, for SCI subjects. CONCLUSION: Gastric emptying was enhanced by FMS in able-bodied subjects and was greatly enhanced in SCI subjects. FMS can be a useful noninvasive therapeutic tool to facilitate gastric emptying in humans.     

Fasting serum levels of adiponectin, ghrelin, and leptin in men with spinal cord injury

OBJECTIVES: To measure serum levels of adiponectin, ghrelin, and leptin in men with spinal cord injury (SCI) and to investigate possible correlations between these serum levels and various factors, such as body mass index (BMI), age, injury level, and duration of injury. DESIGN: Cross-sectional. SETTING: A university hospital that is a tertiary referral center. PARTICIPANTS: Eighty-nine men with traumatic neurologically complete SCI (30 with tetraplegia, 59 with paraplegia) and 37 age- and BMI-matched male controls. Subjects with SCI were injured at the mean age +/- standard error of 28.5+/-1.0 years (range, 14.7-59.1 y) and the mean injury duration was 10.8+/-0.7 years (range, 1.1-27.7 y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Serum levels of adiponectin, ghrelin, and leptin and BMI. RESULTS: Serum leptin levels in subjects with SCI (mean, 7.0+/-0.5 mg/mL) [corrected] were significantly higher than those in able-bodied controls (mean, 4.7+/-0.6 mg/mL) [corrected] (P<.01). The group with tetraplegia had higher serum leptin levels than the group with paraplegia, but this did not reach a statistically significant level (8.2+/-1.1 ng/mL vs 6.4+/-0.5 mg/mL [corrected] P=.097). There were significant differences in serum leptin levels among the 3 groups by 1-way analysis of variance (P=.008). Serum adiponectin levels in subjects with SCI (7.1+/-0.5 mg/mL) [corrected] were higher than those in able-bodied controls (5.6+/-0.5 mg/mL) [corrected] but this was not statistically significant (P=.08). In contrast, serum levels of ghrelin in subjects with SCI (302.0+/-17.5 pg/mL) were similar to those in the controls (264.0+/-27.0 pg/mL) (P=.24). Serum leptin levels correlated positively with BMI (SCI, r=.698, P<.001; controls, r=.782, P<.001), whereas serum adiponectin (SCI, r=-.527, P<.001; controls, r=-.315, P=.057) and ghrelin (SCI, r=-.368, P<.001; controls, r=-.447, P=.006) levels correlated negatively with the BMI in both subjects with SCI and controls. CONCLUSIONS: Men with SCI have significantly higher serum leptin levels than able-bodied controls, and serum leptin levels correlated with the degree of neurologic deficit. Men with SCI had a tendency toward higher serum adiponectin level than able-bodied controls. Serum levels of ghrelin in men with SCI were similar to those of controls.     

Using Reactive Hyperemia to Assess the Efficacy of Local Cooling on Reducing Sacral Skin Ischemia Under Surface Pressure in People With Spinal Cord Injury: A Preliminary Report

Objectives

To investigate the efficacy of local cooling on reducing sacral skin ischemia in a weight-bearing position, and to identify the underlying physiological mechanisms using wavelet-based spectrum analysis of reactive hyperemia in people with spinal cord injury (SCI).

Design

Repeated-measures and before-after trial design.

Setting

University research laboratory.

Participants

Wheelchair users with SCI with injury level between C4 and T5 (n=10) and able-bodied controls (n=10).

Interventions

Three protocols consisting of pressure without temperature changes, pressure with local cooling (Δt=−10°C), and pressure with local heating (Δt=+10°C) were tested. Each protocol consisted of a 10-minute baseline period, a 20-minute loading period at 60mmHg, and a 20-minute recovery period (reactive hyperemia). A 30-minute washout period was allowed between protocols.

Main Outcome Measures

A compound sensor head consisting of laser Doppler and heating and cooling probes was used to measure sacral skin blood flow and control skin temperature. Reactive hyperemic response to pressure and temperature stimuli was characterized in the time and frequency (metabolic [.0095–.02Hz], neurogenic [.02–.05Hz], and myogenic [.05–.15Hz] components) domains.

Results

Pressure with local cooling resulted in a smaller reactive hyperemic response in both people with SCI and able-bodied controls as compared with pressure with local heating (P<.017) and pressure without temperature changes (P<.017), and the smaller hyperemia was attributed to reduced metabolic and neurogenic activities. People with SCI showed an attenuated response in reactive hyperemia (P<.017).

Conclusions

This study supports the concept of using local cooling to reduce skin ischemia under surface pressure in people with SCI.     

Periodically relieving ischial sitting load to decrease the risk of pressure ulcers

OBJECTIVE: To investigate the relieving effect on interface pressure of an alternate sitting protocol involving a sitting posture that reduces ischial support. DESIGN: Repeated measures in 2 protocols on 3 groups of subjects. SETTING: Laboratory. PARTICIPANTS: Twenty able-bodied persons, 20 persons with paraplegia, and 20 persons with tetraplegia. INTERVENTIONS: Two 1-hour protocols were used: alternate and normal plus pushup. In the alternate protocol, sitting posture was alternated every 10 minutes between normal (sitting upright with ischial support) and with partially removed ischial support (WO-BPS) postures; in the normal plus pushup protocol, sitting was in normal posture with pushups (lifting the subject off the seat) performed every 20 minutes. MAIN OUTCOME MEASURE: Interface pressure on seat and backrest. RESULTS: In WO-BPS posture, the concentrated interface pressure observed around the ischia in normal posture was significantly repositioned to the thighs. By cyclically repositioning the interface pressure, the alternate protocol was superior to the normal plus pushup protocol in terms of a significantly lower average interface pressure over the buttocks. CONCLUSIONS: A sitting protocol periodically reducing the ischial support helps lower the sitting load on the buttocks, especially the area close to ischial tuberosities.     

Wavelet-based spectrum analysis of sacral skin blood flow response to alternating pressure

Jan Y-K, Brienza DM, Geyer MJ, Karg P. Wavelet-based spectrum analysis of sacral skin blood flow response to alternating pressure.

Objectives

To provide insight into the physiologic mechanisms associated with alternating pressure, using wavelet analysis of skin blood flow (SBF) oscillations, and to determine whether the application of alternating pressure induces myogenic responses, thereby enhancing SBF as compared with constant loading.

Design

Repeated-measures design.

Setting

University research laboratory.

Participants

Healthy, young adults (N=10; 5 men, 5 women; mean age ± standard deviation, 30.0±3.1y).

Intervention

Alternating pressure for 20 minutes (four 5-min cycles with either 60mmHg or 3mmHg) and constant loading for 20 minutes at 30mmHg on the skin over the sacrum.

Main Outcome Measures

A laser Doppler flowmeter was used to measure sacral SBF response to both alternating pressure and constant loading. Wavelet-based spectrum analysis of SBF oscillations was used to assess underlying physiologic mechanisms including endothelium-related metabolic (.008-.02Hz), neurogenic (.02-.05Hz), and myogenic (.05-.15Hz) controls.

Results

Alternating pressure stimulated an increase in sacral SBF of compressed soft tissues as compared with constant loading (P<.01). SBF during the high-pressure phase of 4 alternating pressure cycles showed an increasing trend. An increase in power in metabolic frequency range and a decrease in power in the myogenic frequency range during alternating pressure were observed compared with SBF prior to loading. Power increased in the myogenic frequency range during the low-pressure phase of alternating pressure and decreased during the high-pressure phase.

Conclusions

SBF control mechanisms, as assessed by the characteristic frequencies embedded in SBF oscillations, show different responses to 2 loading pressures with the same average pressure but different patterns. Our study suggests that optimization of operating parameters and configurations of alternating pressure support surfaces to compensate for impaired SBF control mechanisms in pathologic populations may be possible using wavelet analysis of blood flow oscillations.     

Improved efficiency with a wheelchair propelled by the legs using voluntary activity or electric stimulation

OBJECTIVE: To determine whether a new leg-propelled wheelchair provides enhanced efficiency and mobility to wheelchair users. DESIGN: Observational; subjects were tested while wheeling with the arms and legs and while walking (where possible) for 4-minute periods in random order with approximately 10-minute rest periods between exercise sets. SETTING: Tests were done on an indoor 200-meter track. PATIENTS: Group 1, 13 controls; group 2, 9 persons with complete spinal cord injury (SCI); group 3, 13 persons with other motor disorders (retaining some voluntary control of the legs). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Physiological Cost Index (PCI), (computed as change in heart rate divided by velocity of movement) and oxygen consumption (VO(2)) RESULTS: Arm wheeling took significantly more effort (mean PCI =.52 beats/m) than walking (.33 beats/m) in control subjects. Leg wheeling was most efficient (.23), requiring less than half the effort of arm wheeling and 30% less effort than walking. For SCI subjects, leg wheeling with functional electric stimulation (FES) required less than half the effort (.18) of arm wheeling (.40). The FES group could not walk. Subjects in group 3 could walk, but with substantial effort (1.81) compared with arm (.76) or leg wheeling (.64). Results for VO(2) were similar. CONCLUSIONS: Better wheelchair efficiency can be obtained for many disabled individuals, by moving the leg muscles voluntarily or with FES.     

Different risk factor patterns for metabolic syndrome in men with spinal cord injury compared with able-bodied men despite similar prevalence rates

OBJECTIVE: To determine if the prevalence of metabolic syndrome and risk factors differs between age- and race-matched men with spinal cord injury (SCI) and able-bodied men. DESIGN: Cross-sectional. SETTING: Urban university. PARTICIPANTS: Men with SCI (n=185), ages 20 to 59 years, were matched 1 to 1 with able-bodied men from the 1999-2002 National Health and Nutrition Examination Surveys. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Waist circumference, blood pressure, glucose, triglyceride (TG), total (TC), and low- (LDL) and high-density lipoprotein (HDL) cholesterol. RESULTS: Despite similar prevalence for metabolic syndrome, different risk factor patterns were found between groups. Men with SCI had a significantly lower mean HDL, TG, and glucose in addition to lower TC and LDL. After adjusting for smoking, education, and household income by using conditional logistic regression, men with SCI had a higher risk for abdominal obesity (odd ratio [OR]=1.78; 95% confidence interval [CI], 1.07-2.96) and reduced HDL (OR=1.76; 95% CI, 1.06-2.94) but lower risks for elevated glucose (OR=0.55; 95% CI, 0.33-0.94) than their able-bodied counterparts. By using linear regression and controlling for waist circumference, men with SCI had lower TC, LDL, TG, and glucose concentrations but lower HDL. Racial differences in risks were found in both SCI and able-bodied men; however, among the SCI men, prevalence for low HDL and elevated glucose was similar between whites and African Americans. CONCLUSIONS: Men with SCI do not appear to have an increased prevalence of metabolic syndrome compared with able-bodied counterparts, suggesting that other nontraditional risks may contribute to their increased mortality from cardiovascular disease and diabetes.     

Using multifractal detrended fluctuation analysis to assess sacral skin blood flow oscillations in people with spinal cord injury

The purpose of this study was to investigate whether the multifractal detrended fluctuation analysis (MDFA) of skin blood flow oscillations (BFO) differed between nondisabled controls and people with spinal cord injury (SCI). The study of skin BFO has shown promise for assessing blood flow control mechanisms and risk for pressure ulcers. We recruited 23 subjects, including 11 people with SCI and 12 nondisabled controls. Thermally induced maximal sacral skin BFO were measured by laser Doppler flowmetry. MDFA was used to characterize nonlinear complexity of metabolic (0.0095 to 0.02 Hz), neurogenic (0.02 to 0.05 Hz), and myogenic (0.05 to 0.15 Hz) BFO. We found that maximal vasodilation was significantly smaller in people with SCI than in nondisabled controls (p < 0.05). MDFA showed that metabolic BFO exhibited less complexity in people with SCI (p < 0.05), neurogenic BFO exhibited less complexity in people with complete SCI (p < 0.05), and myogenic BFO did not show significant differences between people with SCI and nondisabled controls. This study demonstrated the feasibility of using the MDFA to characterize nonlinear complexity of BFO, which is related to vasodilatory functions in people with SCI.     

Bone mineral density after spinal cord injury: a reliable method for knee measurement

OBJECTIVES: To test the interrater reliability of a standardized method to analyze knee bone mineral density (BMD) using dual-energy x-ray absorptiometry (DXA); to compare spine, hip, and knee BMD of people with spinal cord injury (SCI) with able-bodied controls; and to determine the relation between hip BMD and knee BMD in SCI and able-bodied subjects. DESIGN: Criterion standard and masked comparison. SETTING: Primary care university hospital. PARTICIPANTS: A convenience sample of 11 subjects with complete SCI was age and sex matched with 11 able-bodied control subjects. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Four raters analyzed regions of interest according to operational definitions recently developed to standardize the analysis of BMD of the knee. Subjects with chronic SCI and matched controls underwent conventional DXA scans of the spine and hips and "less conventional" scans of the distal femurs and proximal tibias. The relation between hip and knee BMD was analyzed. RESULTS: The knee measurements were highly reliable (femur intraclass correlation coefficient model 2,1 [ICC(2,1)]=.98; tibia ICC(2,1)=.89). Subjects with SCI had lower BMD values than controls at all hip and knee sites (P<.05). Lumbar spine BMD did not differ between groups. Hip BMD was moderately predictive of distal femur BMD (R2=.67), but less correlated with the proximal tibia (R2=.38). CONCLUSIONS: Knee BMD can be reliably analyzed using DXA with this protocol. Subjects with SCI have diminished knee and hip BMD. Low hip BMD is associated with low distal femur BMD.     

Electrical muscle stimulation for pressure variation at the seating interface

A new method is proposed for pressure sore prevention using electrical muscle stimulation (EMS). Potential mechanisms through which EMS may act for this purpose are discussed, including both short-term/dynamic and chronic effects. Measurements of maximum pressure variation in three able-bodied subjects using low levels of stimulation were performed. Pressure distribution changes were also measured. Fatigue effects on pressure redistribution were studied for four able-bodied subjects as well as for one C4, complete spinal cord injured individual. The results indicate that EMS produces sizeable pressure reduction under the ischial tuberosity, with redistribution occurring over other parts of the seating surface in able-bodied subjects. Fatigue effects were not observed in the four able-bodied subjects even after prolonged stimulation. Fatigue was observed with the spinal cord injured subject, but only after extensive stimulation. These studies demonstrate the feasibility of using EMS at relatively low intensity to vary seating interface pressure. The results warrant continued investigation of EMS to assist in pressure sore prevention.     

Internal consistency, stability, and validity of the spinal cord injury version of the multidimensional pain inventory

OBJECTIVE: To evaluate the internal consistency, stability, and construct validity of a spinal cord injury (SCI) version of the Multidimensional Pain Inventory (MPI-SCI). DESIGN: Interview. SETTING: Veterans Affairs medical center and university-based institute. PARTICIPANTS: Community sample of persons with SCI and chronic pain (N=161). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: The MPI-SCI. RESULTS: The internal consistency of the MPI-SCI subscales ranged from fair (.60) for affective distress to substantial (.94) for pain interference with activities. The subscales of the MPI-SCI (ie, life interference [r=.81], affective distress [r=.71], solicitous responses [r=.86], distracting responses [r=.85], general activity [r=.69], pain interference with activities [r=.78], pain severity [r=.69], negative responses [r=.69]) showed adequate stability. In contrast, the stability of the support (r=.59) and the life control subscales (r=.31) was unacceptably low. All MPI-SCI subscales with the exception of the perceived responses by significant others subscales showed good convergent, discriminant, and concurrent validity. CONCLUSIONS: The MPI-SCI appears to be a reasonable measure for evaluating chronic pain impact after SCI. In clinical trials, however, supplementary instruments should be included to assess changes in affect, social support, and perceptions of life control.     

Correlates of life satisfaction among persons with spinal cord injury.

OBJECTIVE: To analyze the correlates of life satisfaction for individuals with spinal cord injury (SCI). STUDY DESIGN: Survey; follow-up of subjects studied prospectively since onset of injury. PARTICIPANTS: A total of 2,183 persons with SCI, from 1 to 20 years postinjury, self-selected for annual research (and clinical) follow-up by one of 18 model systems of SCI care. RESULTS: Life satisfaction, as measured with the Satisfaction With Life Scale (SWLS), is associated with several demographic, social, functional, and clinical characteristics. Stepwise linear regression analysis resulted in a predictor model that included the following: sex (beta weight: .07; p < .001); number of rehospitalizations in the last year (-.05; p < .05); years since injury (.13; p < .0001); sociocognitive disability as measured with the Functional Independence Measure (.06; p < .01); and three handicap components, as measured with the modified Craig Handicap Assessment and Reporting Technique: mobility (.26; p < .0001); occupation (.10; p < .001); and social integration (.11; p < .0001). Impairment (level of injury) contributed indirectly, through its impact on motor disability. Racial/ethnic group membership, motor disability, and education contributed indirectly, through their effects on handicap. CONCLUSIONS: Life satisfaction after SCI can be reliably measured by means of the SWLS. Correlates of subjective well-being parallel those suggested by earlier studies and those for the population at large. The effects of life satisfaction on social participation, health, and other aspects of life need further study.     

Static exercise-induced increase in blood pressure in individuals with cervical spinal cord injury

OBJECTIVE: To compare the pressor response to static exercise in subjects with cervical spinal cord injury (SCI) at the C6 to C8 level with that in able-bodied control subjects. In these SCI subjects, the descending supraspinal sympathetic neurons and afferent pathways from the contracting muscles to peripheral vessels via the medullary cardiovascular center are damaged. DESIGN: Mean arterial blood pressure, heart rate, and plasma concentrations of norepinephrine, epinephrine, renin activity, vasopressin, aldosterone, and human atrial natriuretic peptide were measured during a 2-minute period of sustained contraction of elbow flexor group muscle in 7 SCI subjects and 7 age-matched able-bodied control subjects. RESULTS: Static exercise resulted in a significant increase in mean blood pressure (p<.05) in both SCI subjects (pre-exercise. 74.7+/-2.2 mm Hg; static exercise, 81.9+/-4.1 mm Hg) and control subjects (pre-exercise, 101.0+/-4.2 mm Hg; static exercise, 117.0+/-4.9 mm Hg). In SCI subjects, there was no change in heart rate during exercise, whereas in control subjects heart rate increased during exercise (p<.05) (pre-exercise, 8.7+/-3.8 beats/min: static exercise, 76.0+/-3.1 beats/min). There were no significant changes in the hormone levels in the SCI subjects throughout the experiment. CONCLUSION: The significant increase in mean blood pressure observed in the present study indicates the presence of peripheral control from muscle receptors and evoked pressor response during static exercise in SCI subjects.     

Pressure distribution and skin temperature effect of the ROHO wheelchair balloon cushion.

This study evaluated the effectiveness of the ROHO Balloon Wheelchair Cushion in distributing pressure on the skin over the ischial tuberosities in healthy subjects. Surface skin temperatures over the ischial tuberosities and thighs of the subjects were also measured. Pressure recordings were obtained by placing a pressure sensor between the wheelchair cushion and the skin overlying the ischial tuberosities. For comparison, pressures were recorded while the same subjects sat on a 4-inch foam cushion supported on a plywood board. Skin surface temperatures on the 2 cushions were recorded on separate occasions under the ischial tuberosity and the posterior thigh during a 30-minute test period. The results indicate no important difference in resting pressures when the subjects sat on either the 4-inch foam cushion or the balloon cushion. Neither was there an important difference in pressure when the cushion was inflated to greater than the manufacturer's recommendations or when it was covered with a commercially designed cover. The average increase in skin temperature over the tuberosity was 1.9C and over the thigh, 2.6C.     

Effect of seat cushion on dynamic stability in sitting during a reaching task in wheelchair users with paraplegia

OBJECTIVES: To examine the effects of seat cushions on dynamic stability in sitting during a controlled reaching task by wheelchair users with paraplegia. DESIGN: A randomized, controlled test. SETTING: Rehabilitation center. PARTICIPANTS: Nine wheelchair users with paraplegia. INTERVENTIONS: Three types of cushions--an air flotation, a generic contoured, and a flat polyurethane foam--were tested during a controlled reaching task in ipsilateral and contralateral directions, at 45 degrees from the sagittal plane in the anterolateral direction. Center of pressure (COP) coordinates were monitored by using a pressure measurement system as well as a force platform under seat. MAIN OUTCOME MEASURES: Trajectory of COP, maximal distance covered by COP, maximal velocity of COP; and the index of asymmetry between right and left maximal pressure under ischial tuberosities. RESULTS: The generic contoured cushion allowed the COP to cover significantly (p <.02) a larger distance (81 +/- 28mm) when compared with the air flotation (63 +/- 25mm) or the flat foam (61 +/- 29mm) cushions. The COP velocity was significant (p <.05) for the generic contoured cushion (.14 +/-.05m/s) versus the air flotation (.10 +/-.04m/s) or the flat-foam (.10 +/-.03m/s) cushions. The index of asymmetry was higher for the generic contoured and the flat foam cushions. During reaching, maximal pressure under ipsilateral ischial tuberosity was significantly higher for the flat foam (275 +/- 70mmHg) and the generic contoured (235 +/- 81mmHg) cushions, when compared with the air flotation cushion (143 +/- 51mmHg). CONCLUSION: Seat cushions can significantly affect sitting balance during reaching tasks. This study provided an objective method to assess the dynamic stability of wheelchair users when they perform activities of daily living requiring reaching. These findings have implications for wheelchair seating recommendations, especially seat cushion selection.     

Effect of wheelchair tilt-in-space and recline angles on skin perfusion over the ischial tuberosity in people with spinal cord injury

Jan Y-K, Jones MA, Rabadi MH, Foreman RD, Thiessen A. Effect of wheelchair tilt-in-space and recline angles on skin perfusion over the ischial tuberosity in people with spinal cord injury.

Objective

To investigate the efficacy of wheelchair tilt-in-space and recline on enhancing skin perfusion over the ischial tuberosity in wheelchair users with spinal cord injury (SCI).

Design

Repeated-measures, intervention, and outcomes-measure design.

Setting

A university research laboratory.

Participants

Wheelchair users with SCI (N=11; 9 men, 2 women; mean ± SD age, 37.7±14.2y; body mass index, 24.7±2.6kg/m²; duration of injury, 8.1±7.5y).

Interventions

Protocols (N=6) of various wheelchair tilt-in-space and recline angles were randomly assigned to participants. Each protocol consisted of a 5-minute sitting-induced ischemic period and a 5-minute wheelchair tilt-in-space and recline pressure-relieving period. Participants sat in a position without tilt or recline for 5 minutes and then sat in 1 of 6 wheelchair tilted and reclined positions, including (1) 15° tilt-in-space and 100° recline, (2) 25° tilt-in-space and 100° recline, (3) 35° tilt-in-space and 100° recline, (4) 15° tilt-in-space and 120° recline, (5) 25° tilt-in-space and 120° recline, and (6) 35° tilt-in-space and 120° recline. A 5-minute washout period (at 35° tilt-in-space and 120° recline) was allowed between protocols.

Main Outcome Measures

Laser Doppler flowmetry was used to measure skin perfusion over the ischial tuberosity in response to changes in body positions caused by performing wheelchair tilt-in-space and recline. Skin perfusion response to wheelchair tilt-in-space and recline was normalized to skin perfusion of the upright seated position (no tilt/recline).

Results

Combined with 100° recline, wheelchair tilt-in-space at 35° resulted in a significant increase in skin perfusion compared with the upright seated position (no tilt/recline; P<.05), whereas there was no significant increase in skin perfusion at 15° and 25° tilt-in-space (not significant). Combined with 120° recline, wheelchair tilt-in-space at 15°, 25°, and 35° showed a significant increase in skin perfusion compared with the upright seated position (P<.05).

Conclusions

Our results indicate that wheelchair tilt-in-space should be at least 35° for enhancing skin perfusion over the ischial tuberosity when combined with recline at 100° and should be at least 25° when combined with recline at 120°. Although smaller angles of wheelchair tilt-in-space and recline are preferred by wheelchair users for functional purposes, wheelchair tilt-in-space less than 25° and recline less than 100° may not be sufficient for effective pressure reduction for enhancing skin perfusion over the ischial tuberosity in people with SCI.