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

Abstract

Study design: This study was a repeated measures study. Objectives: The objective was to systematically measure the relative reduction in interface pressure (IP) at the ischial tuberosities (IT) and sacrum through 101 increments of tilt in a manual wheelchair among individuals with motor complete spinal cord injury (SCI). Setting: This study was carried out in Manitoba, Canada. Methods: 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 101 increments between 01 and 501, 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. Results: Tilt angle had a highly significant effect on pressure reduction at the IT (P ¼ 0.000) and the cosine relationship between these variables was expressed as quadratic. Reduction in sacral pressure did not occur until 301 tilt, with increased loading at smaller tilt angles. Pressure reduction at the IT and sacrum was not significantly different for tetraplegic and paraplegic participants. Conclusion: Small tilt angles are more suitable for postural control than pressure management. A minimum tilt of 301 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.

Review of the Current Management of Pressure Ulcers

“…22 These technologies were also used in determining that 30 degrees of wheelchair tilt is needed to relieve pressure from the ischial and sacral areas. 23 Their use in bed-bound patients has been limited but has great potential for determining pressure points at risk for ulceration and in determining the effect of pressure-relieving positions on established wounds.…”

Effect of interpolation on parameters extracted from seating interface pressure arrays

“…Once positioned in the wheelchair, participants were instructed to sit as still as possible for 6 min to allow for appropriate settling time and to allow for sensor creep [4,29]. Interface pressure data were recorded at 1 Hz for 2 min, yielding a total of approximately 120 samples per participant.…”

“…For example, expression of the interface pressure via the dispersion index allows for objective measure of the evenness of load distribution and has been used to inform clinical recommendations [3]. Features extracted from pressure maps have been useful in a wide variety of clinical applications relevant to wheelchair use, particularly in pressure ulcer prevention and management [4][5][6]. Indeed, objective measures derived from pressure array data are lately considered sufficiently robust as to be utilized as primary outcome measures in randomized clinical trials [7][8].…”

Wheelchair Tilt-in-Space and Recline Functions: Influence on Sitting Interface Pressure and Ischial Blood Flow in an Elderly Population

“…For users who are not able to independently perform such manoeuvres, wheelchairs with incorporated tilt (inclination of complete seat pan and backrest unit) and recline (additional leaning of only the backrest) functions offer the ability to temporarily redistribute weight and reduce sitting pressure [9]. Several wheelchair studies have reported a decrease in sitting interface pressure [17–26] as well as an increase in ischial blood flow [18, 27, 28] when tilted and/or reclined, compared to upright sitting. However, all of these studies were performed in cohorts of spinal cord injured patients with only one exception, where healthy young subjects were analysed [20].…”