Sharon Eve Sonenblum

Assessing Evidence Supporting Redistribution of Pressure for Pressure Ulcer Prevention: A Review

The formation and underlying causes of pressure ulcers (PUs) are quite complex, with multiple influencing factors. However, by definition pressure ulcers cannot form without loading, or pressure, on tissue. Clinical interventions typically target the magnitude and/or duration of loading. Pressure magnitude is managed by the selection of support surfaces and postural supports as well as body posture on supporting surfaces. Duration is addressed via turning and weight shifting frequency as well as with the use of dynamic surfaces that actively redistribute pressure on the body surfaces. This article shows that preventative interventions must be targeted to both magnitude and duration and addresses the rationale behind several common clinical interventions--some with more scientific evidence than others.

Validation of an accelerometer-based method to measure the use of manual wheelchairs

The goal of this project was to develop and validate a methodology for measuring manual wheelchair movement. The ability to study wheelchair movement is necessary across a number of clinical and research topics in rehabilitation, including the outcomes of rehabilitation interventions, the long-term effects of wheelchair propulsion on shoulder health, and improved wheelchair prescription and design. This study used a wheel-mounted accelerometer to continuously measure distance wheeled, and to continuously determine if the wheelchair is moving. Validation of the system and algorithm was tested across typical mobility-related activities of daily living, which included short slow movements with frequent starts, stops, and turns, and straight, steady state propulsion. Accuracy was found to be greater than 90% across wheelchair and wheel types (spoke and mag), propulsion techniques (manual and foot), speeds, and everyday mobility-related activities of daily living. Although a number of approaches for wheelchair monitoring are currently present in the literature, many are limited in the data they provide. The methodology presented in this paper can be applied to a variety of commercially available products that record bi-axial accelerations, and used to answer many research questions in wheeled mobility.

The Participation and Activity Measurement System: An example application among people who use wheeled mobility devices

Purpose. To present the Participation and Activity Measurement System (PAMS), a system designed to examine activity and participation among people who use wheeled mobility devices. Methods. Description of PAMS’ components and an example of its application among people who use tilt-in-space wheelchairs. Results. PAMS combines objective and subjective descriptions of mobility-based activities within a persons home and community. By applying technologies such as wheel revolution counters, seat occupancy sensors and global positioning systems, PAMS captures diverse metrics of wheelchair use including destinations, wheeled distance, duration of occupancy and the use of specialised features such as tilt. These metrics also provide the basis for a prompted recall interview designed to elicit contextual data about wheelchair use within a persons home and community. A recent study among people who use tilt-in-space wheelchairs demonstrates the components and application of PAMS. Conclusions. The combination of objective and subjective data afforded by the application of PAMS reflects a complex relationship between wheelchair use and the role of mobility as people go about their daily home and community activities. PAMS can be adapted to a variety of research questions and may be used as an alternative or supplement to self-report assessments of activity and participation.

Use of power tilt systems in everyday life.

Purpose. The goal of this study was to monitor and describe the use of power tilt systems in everyday life. Additionally, tilt measurements were used to determine if participants performed regular pressure reliefs. Methods. Wheelchair occupancy and seat position of 16 fulltime power wheelchair users were monitored regularly for 1–2 weeks. Daily wheelchair occupancy, typical position, time spent at different tilt angles, tilt frequency and pressure relieving tilt (PRT) frequency were described. Results. Participants used their tilt systems in many different ways, including subjects who typically sat at small (0–14°) tilt angles and subjects who typically sat at medium (15–29°) tilt angles. Few subjects tilted past 45°. Almost all subjects tilted throughout the day, with the median subject performing >3 tilts per hour of wheelchair occupancy. Despite the regular use, few subjects performed regular PRTs (median = 0.13/h) Conclusion. Differences in tilt-use illustrated the variability in function and activity among users, as well as the diverse benefits of a tilt system for different users. Further study into why subjects did not regularly achieve PRT magnitudes would be valuable to inform improved training, education and follow-up.

The impact of tilting on blood flow and localized tissue loading

AIM OF THE STUDY The overall goal of this research was to improve the use of seated tilt to increase function, health and quality of life for people using power wheelchairs. Specifically, the objective of this study was to evaluate the biomechanical responses to seated full body tilt in persons with spinal cord injury (SCI). MATERIALS AND METHODS Laser Doppler Flowmetry and interface pressure measurement were employed to measure changes in blood flow and loading at the ischial tuberosities across different amounts of tilt. Eleven participants with SCI were studied in a laboratory setting. RESULTS Results showed that biomechanical responses to tilt were highly variable. Pressure reduction at the ischial tuberosity was not present at 15°, but did occur with tilts to 30° and greater, and could be explained by the tilt position and upright pressure. Unlike pressure, blood flow increased with all tilts from an upright position, but did not increase when tilting from 15° to 30°. Only 4 of 11 participants had increases in blood flow of ≥10% at 30° tilt, whereas 9 participants did during maximum tilt (i.e., 45°-60°). CONCLUSIONS Based on the results of this study, tilting for pressure reliefs as far as the seating system permits is suggested to maximize the potential for significant blood flow increases and pressure relief. The use of interim small tilts is also supported, as they also provide some benefit.

3D anatomy and deformation of the seated buttocks

AIM To describe the 3D anatomy and deformation of the buttocks during sitting. MATERIALS AND METHODS The buttocks of 4 able-bodied individuals and 3 individuals with spinal cord injury were scanned sitting in a FONAR Upright MRI. T1-weighted Fast Spin Echo scans were collected with the individuals seated on a custom wheelchair cushion to unload the ischial tuberosities (ITs) and seated on a 3 inch foam cushion. Multi-planar scans were analyzed, and the muscle, bone and adipose tissue was manually segmented for 3D rendering and analysis of the quantity, geometry, and location of tissues. RESULTS The gluteus maximus was positioned lateral and posterior to the IT, covering the inferior portion of the IT for only 2 able-bodied participants. Adipose thickness directly under the IT did not differ by diagnosis, nor did it have a consistent response to loading. However, the envelopment of the IT by the surrounding adipose tissue was much greater in two of the participants with spinal cord injuries. These two subjects also had the most curved skin surface as the tissue wrapped around the IT. Tissue strains around the ischium were most visible in the adipose and connective tissue. The gluteus maximus displaced and distorted upwards, posterior and lateral, away from the inferior IT. CONCLUSIONS Multi-planar imaging is necessary to investigate anatomy and deformation of the buttocks. 5 out of 7 participants did not sit directly on muscle. The tissue beneath their ITs was predominantly composed of fat and connective tissue, suggesting that these tissues might be most vulnerable to injury.

mobilityRERC state of the science conference: individualizing pressure ulcer risk and prevention strategies

Abstract Pressure ulcers (PUs) remain a costly and, often avoidable, complication of full time wheelchair use. Clinicians routinely evaluate PU risk to assist in selecting devices and interventions that may prevent PUs from occurring. Clinical assessment of risk can be evaluated in many different manners, both formally and informally and, typically, is based on combinations of demographic, disability and client-reported behavioral factors. Many of these factors add to PU risk because they impact the physiology and/or biomechanics of the skin and tissue. This article results from a presentation during the Wheeled Mobility Rehabilitation Engineering Research Center’s (RERC’s) State of the Science Conference in 2012. The presentation’s purpose was to present issues and concepts related to pressure ulcer prevention and set the stage for group discussion which followed the presentation. This article progresses through the current state of the science related to PU risk, starting with the tissue and cellular changes resulting from pressure, through the impact that external loading has on blood flow and tissue deformation, and ending with clinical assessment of risk based upon demographic and behavioral factors. Implications for Rehabilitation Factors leading to the development of PUs are numerous and varied, but the defining factor is excessive external loading or pressure on the skin. The amount of pressure needed to cause tissue damage varies widely within and across individuals- based on anatomy and the presence or absence of bony structures under the area of interest, tissue stiffness and other individual characteristics, and most importantly – the amount of tissue deformation that occurs. Clinicians routinely evaluate wheelchair users with respect to pressure ulcer risk, however, objective risk measurements that inform prescription are not readily available. A need exists to provide clinicians with objective measurements of pressure ulcer risk that can inform individualized interventions.

Some people move it, move it… for pressure injury prevention

Objective: To describe differences in in-seat behavior observed between individuals with a spinal cord injury (SCI) with and without a history of recurrent pressure injuries. Design: Cross-sectional cohort study. Setting: General community. Participants: Twenty-nine adults more than 2 years post SCI, who used a wheelchair as their primary mobility device and had the ability to independently perform weight shift maneuvers. Participants were grouped according to whether or not they had a history of recurrent pressure injuries (PrIs), with 12 subjects having had two or more pressure injuries in the pelvic area (PrI Group). Interventions: Not applicable. Main Outcome Measures: Daily time in wheelchair, number of transfers, and frequency of pressure reliefs (full unloading), weight shifts (30% load reduction), and in-seat movements (transient center of pressure movements or unloading). Results: The median participant spent 10.3 hours in his wheelchair and performed 16 transfers to or from the wheelchair daily. Pressure reliefs were performed less than once every 3 hours in both groups. Weight shifts were performed significantly more often by the No PrI Group (median (interquartile range) 2.5 (1.0–3.6) per hour) than the PrI Group (1.0 (0.4–1.9), with P = 0.037 and effect size r = 0.39). In-seat movements were performed 46.5 (28.7–76.7) times per hour by the No PrI group and 39.6 (24.3–49.7) times per hour for the PrI group (P = 0.352, effect size r = 0.17). Conclusion: Weight shifts that can be produced by functional activities and that partially unload the buttocks should be considered as an important addition to individuals’ PrI prevention regimen.

Wheelchair use in ultra-lightweight wheelchair users

Abstract Purpose: The goal of this study was to describe how ultra-lightweight wheelchair users use their wheelchairs during everyday mobility. Method: We instrumented a convenience sample of 69 ultra-lightweight wheelchair users with a seat switch to measure their occupancy, and an accelerometer on their wheel to measure distance wheeled, time spent wheeling and daily bouts of mobility. Results: On the median day, subjects wheeled 83 bouts and 1.4 km over 45 min. A typical bout of mobility was 8.3 m in length, lasting 20 s and occurring at a speed of 0.44 m/s. Fast (>1 m/s) and long (>2 min) bouts represented less than 4% of bouts and were more common among younger participants and those who were employed or a student. Conclusions: Highly functional manual wheelchair users present with a significant mobility disability, moving far less than their ambulating peers despite moving with similar mobility characteristics. The typical bout characteristics – short and slow bouts – are consistent with indoor mobility and transitions between functional activities. For wheelchair users, it highlights the importance of manoeuverability and the need for prescription and training to emphasize manoeuverability. Implications for Rehabilitation Measurement of wheelchair use, both how and how much, might provide unique insight to what equipment would be most appropriate for an individual. Participants who used an ultralight wheelchair presented with a significant mobility disability, wheeling only 1.7 km/day on average. Fast (>1 m/s) and long (>2 min) bouts are uncommon, representing less than 4% of bouts. Younger participants and those who were employed or a student were more likely to wheel one fast and long bout per day. Because wheelchair mobility was dominated by short, slow bouts, prescription and training need to emphasize maneuverability.

Buttock tissue response to loading in men with spinal cord injury

Objective/Background Despite the fact that most people with a spinal cord injury who use a wheelchair for mobility are considered at-risk for pressure ulcer (PrU) development, there still exists a spectrum of risk amongst this group. Efforts to differentiate risk level would benefit from clinical tools that can measure or predict the buttocks response to loading. Therefore, the goal of this study was to identify how tissue compliance and blood flow were impacted by clinically-measurable risk factors in young men with SCI. Methods Blood flow at the ischial tuberosity was measured using laser Doppler flowmetry while the seated buttock was unloaded, and loaded at lower (40–60 mmHg) and high (>200 mmHg) loads. Tissue compliance of the buttock was measured using the Myotonometer while subject were lifted in a Guldmann Net. Results Across 28 participants, blood flow was significantly reduced at high loads, while no consistent, significant changes were found at lower loads. At 40–60 mmHg, blood flow decreased in participants with a pressure ulcer history and lower BMI, but stayed the same or increased in most other participants. The buttock displaced an average of 9.3 mm (2.7 mm) at 4.2 N, which represented 82% (7%) of maximum displacement. BMI was related to the amount of buttock tissue displacement while smoking status explained some of the variation in the percent of max displacement. Conclusion Wide variability in tissue compliance and blood flow responses across a relatively homogeneous population indicate that differences in biomechanical risk may provide an explanation for the spectrum of PrU risk among persons with SCI.