The impact of tilting on blood flow and localized tissue loading (original) (raw)

Measuring the effect of incremental angles of wheelchair tilt on interface pressure among individuals with spinal cord injury

Spinal Cord, 2011

This study was a repeated measures study. The objective was to systematically measure the relative reduction in interface pressure (IP) at the ischial tuberosities (IT) and sacrum through 10° increments of tilt in a manual wheelchair among individuals with motor complete spinal cord injury (SCI). This study was carried out in Manitoba, Canada. A total of 18 adults with ASIA A or B level of injury were recruited through an out-patient SCI clinic. Using a standardized protocol, participants were tilted in 10° increments between 0° and 50°, and IP readings were obtained at the IT and sacrum using pressure mapping technology. Relative pressure reduction from baseline was calculated and compared between tilt angles. Tilt angle had a highly significant effect on pressure reduction at the IT (P=0.000) and the cosine relationship between these variables was expressed as quadratic. Reduction in sacral pressure did not occur until 30° tilt, with increased loading at smaller tilt angles. Pressure reduction at the IT and sacrum was not significantly different for tetraplegic and paraplegic participants. Small tilt angles are more suitable for postural control than pressure management. A minimum tilt of 30° is required to initiate unloading the sacrum and to achieve a clinically important reduction in pressure at the IT. Larger tilt angles resulted in more substantial pressure reduction than previously reported. Tilt-in-space appears to have similar benefits for individuals with paraplegia and tetraplegia.

Dynamic changes in seating pressure gradient in wheelchair users with spinal cord injury

Assistive Technology, 2019

Pressure ulcer interventions are commonly assessed with measures of seating interface pressure, such as peak pressure gradients (PPGs). Decreases in PPG magnitudes may reduce pressure ulcer risk by decreasing tissue deformation and increasing tissue perfusion of at-risk weight-bearing tissues. Changes in PPG directions, which have previously been overlooked in the seating pressure literature, may provide a transient increase in blood flow to at-risk tissues, even if the PPG magnitude and location remain the same. The purpose of this study was to assess both PPG components in response to combinations of wheelchair tilt and recline angles. Thirteen power wheelchair users were recruited into the study. Six combinations of wheelchair tilt (15°, 25°, and 35°) and recline (10° and 30°) were tested in random order. Each combination was tested with 5min upright sitting, 5-min tilt and recline, and 5-min maximal pressure relief recovery. Changes in PPG magnitudes and PPG directions under the left ischial tuberosity were computed for the six angle combinations. The findings in this study suggested that when combining wheelchair tilt and recline, the recline function may be particularly useful in reducing PPG magnitudes, while the tilt function may be particularly useful in manipulating PPG directions.

Investigation of peak pressure index parameters for people with spinal cord injury using wheelchair tilt-in-space and recline: Methodology and preliminary report

2014

The purpose of this study was to determine the effect of the sensel window's location and size when calculating the peak pressure index (PPI) of pressure mapping with varying degrees of wheelchair tilt-in-space (tilt) and recline in people with spinal cord injury (SCI). Thirteen power wheelchair users were recruited into this study. Six combinations of wheelchair tilt (15 ∘ , 25 ∘ , and 35 ∘ ) and recline (10 ∘ and 30 ∘ ) were used by the participants in random order. Displacements of peak pressure and center of pressure were extracted from the left side of the mapping system. Normalized PPI was computed for three sensel window dimensions (3 sensels × 3 sensels, 5 × 5, and 7 × 7). At least 3.33 cm of Euclidean displacement of peak pressures was observed in the tilt and recline. For every tilt angle, peak pressure displacement was not significantly different between 10 ∘ and 30 ∘ recline, while center of pressure displacement was significantly different ( < .05). For each recline angle, peak pressure displacement was not significantly different between pairs of 15 ∘ , 25 ∘ , and 35 ∘ tilt, while center of pressure displacement was significantly different between 15 ∘ versus 35 ∘ and 25 ∘ versus 35 ∘ . Our study showed that peak pressure displacement occurs in response to wheelchair tilt and recline, suggesting that the selected sensel window locations used to calculate PPI should be adjusted during changes in wheelchair configuration.

Effect of seat inclination on seated pressures of individuals with spinal cord injury

Physical therapy, 2004

Manual wheelchair configurations commonly include "squeezing" the wheelchair frame to improve balance for users with spinal cord injuries. This squeezing is achieved by lowering the rear portion of the seat relative to the front of the seat while maintaining the same back angle. The study's purpose was to examine the effect of increasing posterior seat inclination on buttock interface pressures. Nine male and 5 female subjects (mean age=37 years, SD=11.2, range=19-55) with complete thoracic or lumbar spinal cord injury were tested. Subjects sat on a pressure mat placed over a foam cushion. Pressure readings were taken at seat angles reflecting seat height decreases of 0, 5.1, 7.6, and 10.2 cm (0, 2, 3, and 4 in) of the rear of the seat relative to the front of the seat. An analysis of variance and a Duncan multiple range test were used for data analysis. No meaningful differences were found in measurements of interface pressure (dispersion index, contact area, and seat...

Effect of Wheelchair Tilt-in-Space and Recline Angles on Skin Perfusion Over the Ischial Tuberosity in People With Spinal Cord Injury

Archives of Physical Medicine and Rehabilitation, 2010

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-11 wheelchair users with SCI (9 men, 2 women; mean age ± standard deviation, 37.7±14.2 years; body mass index 24.7±2.6 kg/m 2 ; and duration of injury 8.1±7.5 years). Interventions-6 protocols of various wheelchair tilt-in-space and recline angles were randomly assigned to the participants. Each protocol consisted of a 5-min sitting-induced ischemic period and a 5-min wheelchair tilt-in-space and recline pressure relieving period. A participant sat in a position without tilt or recline for 5 minutes and then sat in one of 6 wheelchair tiled 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-min washout period (at 35° tilt-inspace 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 the changes of 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-When combined with 100° recline, wheelchair tilt-in-space at 35° resulted in a significant increase in skin perfusion as compared with upright seated position (no tilt/recline)

Load Redistribution in Variable Position Wheelchairs in People With Spinal Cord Injury

The Journal of Spinal Cord Medicine, 2010

Background/Objective: Tilt and recline variable position seating systems are most commonly used for pressure relief to decrease potential for skin breakdown. This study provides quantitative information on the magnitudes of loading on the seat and back during phases of tilt, recline, and standing. The objective of this study was to show that the amount of force reduction at the seat would differ across these 3 methods within their respective clinical ranges. Participants: Six able-bodied (AB) subjects (2 men, 4 women) with a median age of 25 years, and 10 subjects (8 men, 2 women) with spinal cord injury (SCI) with a median age of 35.5 years. Methods: Subjects sat on a power wheelchair with Tekscan pressure mats placed underneath a foam backrest and cushion. Data were collected at 5 positions for each method. Order of position and method tested were randomized. Linear regressions were used to calculate the relationships of normalized seat and backrest forces to seat and backrest angles for each chair configuration. Results: Normalized seat loads had strong linear relationships with the angles of change in tilt, recline, and standing for both groups. Maximum decreases in seat load occurred at full standing and full recline in the SCI subjects and in full standing in the AB subjects. Loads linearly increased on the back during tilt and recline and linearly decreased during standing for both groups. Conclusions: Standing and recline offered similar seat load reductions at their respective terminal positions. Standing also reduced loading on the backrest. Recognizing that each method had clinical benefits and drawbacks, the results of this study indicate that tilt, recline, and standing systems should be considered as a means of weight shifting for wheelchair users.

Measuring seating pressure, area, and asymmetry in persons with spinal cord injury

European Spine Journal, 2003

Spinal cord injury (SCI) occurs in a substantial proportion of trauma. A study from major trauma centers in the United States reports that SCI occurred in 2.6% of trauma patients, or approximately 1 in 40 patients, reported between 1982 and 1989, of whom 79% were male [4]. Wheelchair-ambulating patients with SCI are often susceptible to joint pain, spine deformity, or pressure sores [5, 6, 9, 10, 13]. Pressure on the seating area alters dramatically after SCI. The muscle atrophy that often results from SCI, combined with the loss of other soft tissues, reduces the area of the surface and the distribution of pressure to the underlying structures. Pressure, defined as force per unit area, increases rapidly with decreasing contact area. High pressures on the seating surface lead to pressure sores, a major concern of persons with SCI for both health and quality-of-life reasons. Asymmetry of static sitting in SCI has been little studied in the literature. Complications such as spine deformity, a common secondary effect of muscle imbalance, and loss of sensory ability and perception may lead to an asymmetry in loading. This asymmetry will further exacerbate the consequences of high pressures on the loading area [13].

Effects of conventional and alternating cushion weight-shifting in persons with spinal cord injury

Journal of rehabilitation research and development, 2014

A repeated-measures study of 13 adult full-time wheelchair users with spinal cord injury (SCI) was carried out to determine whether alternating-pressure air cushion (APAC) use compared with independent pressure relief (IPR) provides reliable, effective pressure relief for individuals with SCI. Bilateral mean ischial interface pressure (IP), transcutaneous oxygen tension (TcPO2), and unilateral laser Doppler blood flow were evaluated. Blood flow component contributions were determined using short-time Fourier transform (STFT)-based spectral analysis. IPR assessment was carried out at recruitment. Study participants then used an APAC for 2 wk every 3 mo for 18 mo. IPR weight-shifting decreased mean ischial IP (p < 0.05) and increased mean TcPO2 (p < 0.05). All variables rapidly returned to preintervention levels following weight-shifting except for the cardiac component of blood flow. APAC-induced weight-shifting decreased mean ischial IP (p < 0.05). Mean TcPO2 increased and ...

Use of tilt-in-space in seating systems for adults with physical disabilities

Physical Therapy Reviews, 2013

Aims: Clinicians increasingly recommend tilt-in-space (TIS) within wheelchair and seating prescriptions to reportedly prevent pressure ulcers; however, it is often unclear what the optimum tilt angle should be. This review aims to determine the use and effectiveness of TIS in seating systems. Methodology: A search of eight electronic databases was completed, namely, Medline, CINAHL, BNI, EMBASE, ASSIA, PubMed, OTDBase, and ISI Web of Science Conference Proceedings; using the keywords TIS, seating, wheelchairs, pressure ulcer, and pressure sores. Databases were searched for articles written in English between 2000 and the end of August 2012. Articles included primary research; TIS as the intervention; and had adult participants. Results: After removal of duplicates and application of inclusion criteria, 12 studies were eligible for this review. Findings show that TIS was used to manage pressure and fatigue, prevent sliding, aid skin perfusion, and facilitate user comfort. Conclusions: Reasons for using TIS will influence the degree of tilt required for the chair occupant; nonetheless, it remains difficult to specify either the optimum degree of tilt or the duration for use in TIS seating systems. In order to build an evidence base, clinicians need to be very explicit on their reasons for prescribing TIS.