The Role of Shear Stress and Shear Strain in Pressure Injury Development.

ABSTRACT: Although other patient safety indicators have seen a decline, pressure injury (PI) incidence has continued to rise. In this article, the authors discuss the role of shear stress and shear strain in PI development and describe how accurate assessment and management can reduce PI risk. They provide explanations of shear stress, shear strain, friction, and tissue deformation to support a better clinical understanding of how damaging these forces are for soft tissue. Clinicians must carefully assess each patient's risk factors regarding shear forces within the contexts of activity and mobility. The authors also provide a toolbox of mitigation strategies, including support surface selection, selection of materials that contact the individual, management of immobility using positioning techniques, and the use of safe patient handling techniques. With a clear understanding of how shear forces affect PI risk and mitigation strategies, clinicians will more accurately assess PI risk and improve PI prevention care plans, ultimately reducing PI incidence to become more aligned with other patient safety indicators.

Movement and Pressure Injury Prevention Care for Nursing Home Residents: Addressing the Nescience.

OBJECTIVE: To compare movement associated with position changes among nursing home residents who remain in lying versus upright positions for more than 2 hours and among residents living with obesity, dementia, or neither condition. METHODS: The authors conducted a descriptive exploratory study using secondary data (N = 934) from the Turn Everyone And Move for Ulcer Prevention (TEAM-UP) clinical trial to examine transient movements (<60 seconds) within prolonged periods of 2 to 5 hours without repositioning. RESULTS: Nursing home residents exhibit significantly more episodic transient movements when upright than lying. Residents with obesity or dementia exhibited similar frequencies of episodic transient movements compared with residents with neither obesity nor dementia. Upright or lying movements were more frequent among residents with obesity than among those with neither obesity nor dementia selectively when prolonged events ranged from 2 to 4 hours. Pairwise comparisons of movement rates among resident subgroups (living with obesity, living with dementia, or neither group) across repositioning intervals showed episodic transient movements were significantly higher across all subgroups for repositioning intervals up to 3 hours when compared with repositioning intervals of greater than 3 hours. CONCLUSIONS: Findings challenge assumptions that nursing home residents are inactive and at risk for prolonged sitting. These preliminary findings, along with TEAM-UP findings where no pressure injuries occurred in up to 5 hours in prolonged positions, support establishing a standard 3-hour repositioning interval with use of high-density mattresses without a negative impact on pressure injury occurrence. There should be caution when considering repositioning intervals greater than 3 hours. Further research is indicated to explore protective effect of episodic transient movements of other subgroups.

Thermal measurement of erythema across skin tones: Implications for clinical identification of early pressure injury.

AIM: To assess the effectiveness of thermography, colorimetry, and oximetry at detecting temperature changes after erythema induction across diverse skin tones in healthy adults. MATERIALS AND METHODS: Erythema was induced at the forearm and ulnar head (UH) using a cupping device. Temperature via thermal image, erythema value via colorimeter, and oxygen saturation via oximeter were collected immediately and 5-10 min (delayed) after cupping at both sites. RESULTS: At the forearm, the delayed timepoint was significantly warmer than baseline. At the UH, the immediate timepoint was significantly colder than baseline. Erythema increased at both timepoints and both locations. The correlation between temperature change and erythema change was weak. Change in temperature did not differ between skin tone groups. The Intermediate Low Eumelanin skin tone group had more change in erythema compared to the Intermediate Mid (i.e., darkest) skin tone group immediately after cupping at the UH and at the delayed timepoint at the forearm. CONCLUSIONS: This study observed differences in the change of erythema across skin tones but did not observe differences in temperature across skin tones. Given high variability in results, it is premature to conclude thermal imaging works equally well across all skin tones. Further research is necessary to validate the effectiveness of thermal imaging in diverse populations. Results suggest visual erythema may be a problematic indicator as less erythema was consistently noted in participants with dark skin tones. The potential of technology to increase our ability to detect erythema warrants further investigation.

Best-practices for preventing skin injury beneath personal protective equipment during the COVID-19 pandemic: A position paper from the National Pressure Injury Advisory Panel.

COVID-19 has infected millions of patients and impacted healthcare workers worldwide. Personal Protective Equipment (PPE) is a key component of protecting frontline clinicians against infection. The benefits of PPE far outweigh the risks, nonetheless, many clinicians are exhibiting skin injury caused by PPE worn incorrectly. These skin injuries, ranging from lesions to open wounds are concerning because they increase the susceptibility of viral infection and transmission to other individuals. Early into the COVID-19 pandemic (April 2020), the U. S. National Pressure Injury Advisory Panel (NPIAP) developed a series of position statements to improve wear-ability of PPE and protect healthcare professionals and their patients as safe from harm as possible under the circumstances. The NPIAP positions, which were formed by conducting a systematic review of what was known at the time, include: (a) Prepare skin before and after wearing PPE with skin sealants, barrier creams and moisturisers; (b) Frequent PPE offloading to relieve pressure and shear applied to skin; (c) treat visible skin injuries immediately caused by PPE to minimise future infection; (d) non-porous dressings may provide additional skin protection, but lack evidence; (e) health systems should take care to educate clinicians about placement and personal hygiene related to handling PPE. Throughout all of these practices, handwashing remains a top priority to handle PPE. These NPIAP positions provided early guidance to reduce the risk of skin injury caused by PPE based on available research regarding PPE injuries, a cautious application of evidence-based recommendations on prevention of device-related pressure injuries in patients and the expert opinion of the NPIAP Board of Directors. Clinicians who adhere to these recommendations reduce the prospects of skin damage and long-term effects (e.g. scarring). These simple steps to minimise the risk of skin injury and reduce the risk of coronavirus infection from PPE can help.

Using Technology to Detect Erythema Across Skin Tones.

OBJECTIVE: To examine the effectiveness of the ColorMeter DSM III (ColorMeter; Cortex Technology) at grouping individuals by skin tone and measuring erythema/skin discoloration after erythema induction across skin tones. METHODS: This pre/post experimental study induced erythema on a convenience sample of 61 healthy adults. Skin tone at baseline was measured using the ColorMeter, Munsell Soil Color Chart 5YR (Munsell), and Pantone SkinTone Guide (Pantone) and compared with the Eumelanin Human Skin Colour Scale (Eumelanin Scale) groupings. Erythema and melanin values on the arm immediately and after recovery time were compared with baseline values. Melanin was measured at five body regions on the face and arm. RESULTS: Participants were predominantly women (64% [n = 39] women, 36% [n = 22] men) and young (mean, 28.8 ± 14.3 years); 5% (n = 3) were Hispanic, 26% (n = 16) Asian, 29% (n = 18) Black, 38% (n = 23) White, and 7% (n = 4) identified with more than one race. ColorMeter lightness (L*) and melanin measures were strongly correlated with both Munsell and Pantone values. Munsell skin tone groups were not aligned with Eumelanin Scale groupings. Most participants were in the Eumelanin intermediate-low group, and this changed depending on which body location melanin value was used. The change in erythema from baseline did not differ significantly across skin tone groups at the ulnar head, but on the forearm at the delayed time point, significant differences existed between light and both medium and dark skin tone groups (P = .001; 95% CI, 0.04-0.37). CONCLUSIONS: The ColorMeter provides an effective objective measure of skin tone and erythema/discoloration across various skin tones and may improve on current standards for detection. The proposed Eumelanin Scale-Modified provides additional sensitivity for persons with medium skin tones.

Necessary Products for the Prevention and Treatment of Pressure Injuries: Lessons Learned That Translate Beyond the COVID-19 Pandemic.

OBJECTIVE: To identify the challenges encountered in obtaining the required support surfaces and products to meet pressure injury (PrI) prevention and treatment needs during COVID-19. METHODS: The authors used SurveyMonkey to gather data on healthcare perceptions and the challenges experienced regarding specific product categories deemed necessary for PrI prevention and treatment in US acute care settings during the pandemic. They created three anonymous surveys for the target populations of supply chain personnel and healthcare workers. The surveys addressed healthcare workers' perceptions, product requests, and the ability to fulfill product requests and meet facility protocols without substitution in the categories of support surfaces and skin and wound care supplies. RESULTS: Respondents answered one of the three surveys for a total sample of 174 respondents. Despite specific instructions, nurses responded to the surveys designed for supply chain personnel. Their responses and comments were interesting and capture their perspectives and insights. Three themes emerged from the responses and general comments: (1) expectations differed between supply chain staff and nurses for what was required for PrI prevention and treatment; (2) inappropriate substitution with or without proper staff education occurred; and (3) preparedness. CONCLUSIONS: It is important to identify experiences and challenges in the acquisition and availability of appropriate equipment and products for PrI prevention and treatment. To foster ideal PrI prevention and treatment outcomes, a proactive approach is required to face daily issues or the next crisis.

Movement Patterns of Transient and Prolonged Positioning Events in Nursing Home Residents: Results from the TEAM-UP Trial.

OBJECTIVE: To characterize transient and prolonged body position patterns in a large sample of nursing home (NH) residents and describe the variability in movement patterns based on time of occurrence. METHODS: This study is a descriptive, exploratory analysis of up to 28 days of longitudinal accelerometer data for 1,100 NH residents from the TEAM-UP (Turn Everyone and Move for Ulcer Prevention) clinical trial. Investigators analyzed rates of transient events (TEs; less than 60 seconds) and prolonged events (PEs; 60 seconds or longer) and their interrelationships by nursing shift. RESULTS: Residents' positions changed for at least 1 minute (PEs) nearly three times per hour. Shorter-duration movements (TEs) occurred almost eight times per hour. Residents' PE rates were highest in shift 2 (3 pm to 11 pm ), when the median duration and maximum lengths of PEs were lowest; the least active time of day was shift 3 (11 pm to 7 am ). Three-quarters of all PEs lasted less than 15 minutes. The rate of TEs within PEs decreased significantly as the duration of PEs increased. CONCLUSIONS: The NH residents demonstrate complex patterns of movements of both short and prolonged duration while lying and sitting. Findings represent how NH residents naturally move in real-world conditions and provide a new set of metrics to study tissue offloading and its role in pressure injury prevention.

Pressure Ulcer Risk Factors in Persons with Mobility-Related Disabilities.

OBJECTIVE: To assess pressure ulcer (PU) risk in persons with mobility impairments using a large data set to identify demographic, laboratory, hemodynamic, and pharmacologic risk factors. METHODS: The cohort of interest was persons with disabilities who have mobility impairments and are diagnostically at risk of PUs. To define this cohort, diagnoses that qualify patients for skin protection wheelchair cushions were used. Data were obtained from the Cerner Health Facts data warehouse. Two cohorts were defined: persons with and without a history of PUs. Analysis included descriptive statistics and multivariate logistic regression modeling. Variables retained in the model were identified using LASSO, gradient boosting, and Bayesian model averaging. MAIN RESULTS: The resulting cohorts included more than 87,000 persons with a history of PUs and more than 1.1 million persons who did not have a PU. The data revealed seven disability groups with the greatest prevalence of PUs: those with Alzheimer disease, cerebral palsy, hemiplegia, multiple sclerosis, paraplegia/quadriplegia, Parkinson disease, and spina bifida. Ulcers in the pelvic region accounted for 82% of PUs. Persons with disabilities who were male or black had a greater prevalence of PUs. Physiologic risk factors included the presence of kidney or renal disease, decreased serum albumin, and increased serum C-reactive protein. CONCLUSIONS: The results indicate that, although persons with disabilities can exhibit a wide functional range, they remain at risk of PUs and should be evaluated for proper preventive measures, including support surfaces and wheelchair cushions.

Seated buttocks anatomy and its impact on biomechanical risk.

AIM: The objective of this study was to describe the amount, types, and shapes of tissue present in the buttocks during sitting (i.e., seated buttocks soft tissue anatomy), and the impact of seated buttocks soft tissue anatomy on biomechanical risk. MATERIALS AND METHODS: The buttocks of 35 people, including 29 full-time wheelchair users with and without a history of pelvic pressure ulcers were scanned sitting upright on 3" of flat HR45 foam in a FONAR Upright MRI. Multi-planar scans were analyzed to calculate bulk tissue thickness, tissue composition, gluteus maximus coverage at the ischium, the contour of the skin, and pelvic tilt. RESULTS: Bulk tissue thickness varied from 5.6 to 32.1 mm, was composed mostly of adipose tissue, and was greatest in the able-bodied cohort. Skin contours varied significantly across status group, with wheelchair users with a history of pressure ulcers having tissue with a peaked contour with a radius of curvature of 65.9 mm that wrapped more closely to the ischium (thickness at the apex = 8.2 mm) as compared to wheelchair users with no pressure ulcer history (radius of curvature = 91.5 mm and apex thickness = 14.5 mm). Finally, the majority of participants presented with little to no gluteus coverage over their ischial tuberosity, regardless of status group. CONCLUSIONS: This study provides quantitative evidence that Biomechanical Risk, or the intrinsic characteristic of an individual's soft tissues to deform in response to extrinsic applied forces, is greater in individuals at greater risk for pressure ulcers.

Visualizing Tissue Strain Under the Sacrum and Coccyx in Different Supine Postures: A Case Series.

OBJECTIVE: To visually assess and report the influence of supine positioning and sacrum and coccyx anatomy on tissue deformation. METHODS: A convenience sample of three participants was scanned using MRI. All participants were scanned in a supine position with a rig oriented in a flat or horizontal position and with the torso portion of the rig elevated to 30° to simulate head-of-bed elevation. Representative images were identified to visualize and depict (1) the differences in tissue thickness and deformation in response to changes in supine positioning (0° and 30°), (2) the relative displacement of the skeleton relative to the skin during 30° incline, and (3) differences in sacrococcygeal morphology. RESULTS: The tissue thickness under the sacrum stayed the same or increased when torsos were elevated. Skeletons were displaced relative to the skin when the rig was elevated regardless of the pelvis location. Further, in the elevated position, coccyges flexed when pelvises were placed on the elevated segment but did not flex when pelvises were placed on the horizontal segment. CONCLUSIONS: This case series is useful in defining new areas of research that can (1) identify the deformation induced by normal and frictional forces resulting from different positions of the bed chassis, (2) assess the impact of positioning the pelvis on elevated versus horizontal segments of the bed chassis, and (3) define the association between sacral and coccyx morphology and pressure ulcer occurrence in hospitalized patients.

Measuring the impact of cushion design on buttocks tissue deformation: An MRI approach.

AIM: To establish a research approach for describing how different wheelchair cushion designs impact buttocks tissue deformation during sitting. MATERIALS AND METHODS: The buttocks of 4 individuals with spinal cord injury and significant atrophy were scanned sitting in a FONAR Upright MRI. Scans were collected with the individuals' buttocks fully suspended without pelvic support, and seated on 3 different commercially available wheelchair cushions. Multi-planar scans were analyzed to provide 3D renderings and measurements of tissue thickness and shape. RESULTS: Bulk tissue thicknesses at the ischium, which rarely included muscle, were reduced by more than 60% on enveloping cushion designs studied (i.e., Roho HP and Matrx Vi), and more variably (23-60%) on an orthotic off-loading design (i.e., Java). Adipose was typically displaced posterior and superior from the unloaded condition, with more lateral displacement on the Roho HP and Matrx Vi and more medial displacement present on the Java. Large changes in angle at the sacro-coccygeal joint indicated significant loading on the region. Deformation at the greater trochanter was more consistent across surfaces. Greater interface pressures tended to be associated with greater deformation, but the relationship varied by individuals and was highly non-linear. CONCLUSIONS: The buttocks in this study all deformed significantly, but at different locations and in different manners across all 3 surfaces. Attention needs to be paid to the regions of greatest deformation. A future metric of shape compliance should consider cushion performance at all high risk regions, and changes to the amount and shape of tissue in the regions of interest.

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.

Effects of wheelchair cushions and pressure relief maneuvers on ischial interface pressure and blood flow in people with spinal cord injury.

OBJECTIVE: To investigate the effectiveness and interactions of 2 methods of pressure ulcer prevention, wheelchair cushions and pressure relief maneuvers, on interface pressure (IP) and blood flow of the buttocks. DESIGN: Within-subject repeated measures. SETTING: Rehabilitation center. PARTICIPANTS: Wheelchair users with a spinal cord injury or disorder (N=17). INTERVENTIONS: Participants performed 3 forward leans and 2 sideward leans with different degrees of lean while seated on each of 3 different wheelchair cushions. MAIN OUTCOME MEASURES: IP measured with a custom sensor and blood flow measured with laser Doppler flowmetry were collected at the ischial tuberosity. RESULTS: Pressure relief maneuvers had a significant main effect on the ischial IP (P<.001); all maneuvers except for the small frontward lean resulted in a significant reduction in IP compared with upright sitting. Blood flow significantly varied across postures (P<.001) with flow during upright sitting and small forward leans being significantly lower than during the full and intermediate leans in both the forward and sideward directions. CONCLUSIONS: The results of the study highlight the importance of positioning wheelchair users in a manner that facilitates in-seat movement. Regardless of the cushion being used, the pressure relief maneuvers resulted in very large reductions in IPs and significant increases in buttock blood flow. Only the small frontward lean was shown to be ineffective in reducing pressure or increasing blood flow. Because these pressure relief maneuvers involved postural changes that can occur during functional activities, these pressure relief maneuvers can become a part of volitional pressure relief and functional weight shifts. Therefore, clinical instruction should cover both as a means to impart sitting behaviors that may lead to better tissue health.

3-dimensional buttocks response to sitting: a case report.

AIM OF THE STUDY: The aim of this study was to describe an individual's 3-dimensional buttocks response to sitting. Within that exploration, we specifically considered tissue (i.e., fat and muscle) deformations, including tissue displacements that have not been identified by research published to date. MATERIALS AND METHODS: The buttocks anatomy of an able-bodied female during sitting was collected in a FONAR Upright MRI. T1-weighted Fast Spin Echo scans were collected with the individual seated on a custom wheelchair cushion with a cutout beneath the pelvis ("unloaded"), and seated on a 3″ foam cushion ("loaded"). 2D slices of the MRI were analyzed, and bone and muscle were segmented to permit 3D rendering and analyses. RESULTS: MRIs indicated a marked decrease in muscle thickness under the ischial tuberosity during loaded sitting. This change in thickness resulted from a combination of muscle displacement and distortion. The gluteus and hamstrings overlapped beneath the pelvis in an unloaded condition, enveloping the ischial tuberosity. But the overlap was removed under load. The hamstrings moved anteriorly, while the gluteus moved posterior-laterally. Under load, neither muscle was directly beneath the apex of the ischial tuberosity. Furthermore, there was a change in muscle shape, particularly posterior to the peak of the ischial tuberosity. CONCLUSION: The complex deformation of buttocks tissue seen in this case study may help explain the inconsistent results reported in finite element models. 3D imaging of the seated buttocks provides a unique opportunity to study the actual buttocks response to sitting.

The usability of two mobile health assistive technologies for wheelchair-related in-seat movement and pressure.

Introduction: This study aimed to understand the degree to which two different mobile health assistive technologies, AW-Shift© and Sensoria® Mat, addressed seven constructs for managing wheelchair-related in-seat movement and pressure. Methods: After using each intervention system, participants answered questions regarding the general usability and usefulness of the systems. Results: System Usability Survey scores ranged from 5 (Poor) to 97.5 (Excellent), with a median response of 60.0 (Okay) for AW-Shift© and 76.3 (Good) for Sensoria® Mat. Participants reported using AW-Shift© to check areas of high pressure on their cushion, the quality of their weight shifts, and their posture significantly more often than to check the condition of their cushion or to track their movement goals. Participants reported using Sensoria® Mat to check the quality and number of weight shifts, and their posture significantly more often than to check the condition of their cushion. Conclusions: The findings of this study highlight that there is no one-size-fits-all solution and that different subpopulations of wheelchair users may have different needs and preferences. Optimizing the design for specific cohorts or constructs can result in an effective product that consistently provides meaningful and accurate information about behavior and performance.

Reducing pressure with the goal of improving outcomes: a retrospective chart review of cushion evaluations and recommendations at one seating clinic.

PURPOSE: To describe the current seating recommendations made by a seating clinic for wheelchair users who presented with a Pressure Injury (PrI) or history of PrI. METHODS: Retrospective review of electronic medical records of 133 adults who used a wheelchair as their primary means of mobility who had a cushion evaluation during which interface pressure mapping data was documented. RESULTS: Clinicians adjusted 71% of participants' wheelchair cushions, including 49% who received a new cushion, and 37% of participants' wheelchairs. The most common adjustments besides receiving a new cushion were: addition of an underlay, adjusting the inflation of a cushion, and adjustments to the foot or back support of the wheelchair. Forty-five participants only received adjustments (i.e. no new cushion), while 23 participants only received education and feedback rather than equipment modifications. Those 23 participants had significantly lower Peak Pressure Index (PPI) than those who received equipment modifications (mean [95% CI] 76.7 [59.1, 94.3] versus 111.6 [102.1, 121.2] respectively, p = 0.001). The PPI was reduced by an average of 22.5 mmHg from the initial to final seating system amongst those who received modifications ([13.9-31.0], p<.001). CONCLUSIONS: The seating clinicians considered interface pressure mapping in their decision-making and effectively reduced interface pressures with their interventions. Cushion replacement is important when someone presents with a PrI. However, adjusting an existing wheelchair cushion and/or seating system provides important additions and alternatives to consider for reducing interface pressure. There is also a role for education about proper use of equipment, weight shifts, and alternate seating surfaces.IMPLICATIONS FOR REHABILITATIONA cushion evaluation may involve evaluating more than one cushion configuration and using pressure mapping to compare the best options.To address perceived wheelchair cushion issues, posture and positioning should be evaluated and adjusted as necessary, in addition to evaluating the cushion itself.Common positioning modifications include: modifying/adding cushion underlays or inflation and foot and back supports in response to clients' changing postural needs and wheelchair components coming out of optimal position due to wear and tear.Adjustments to the wheelchair and cushion aim to distribute body weight over a larger surface area, reduce pressure at high-risk locations, improve posture, and increase function. These adjustments should consider individual's specific needs and goals, while also being mindful of funding barriers.

Does the setting matter? Observing wheelchair transfers across different environmental conditions.

The setting in which wheelchair transfers are performed can affect the difficulty and the risks associated with completion. This article presents results from an observational study involving 13 wheelchair users performing independent transfers across four settings. The aim is to understand how the environment affects how different types of independent transfers are performed. Descriptive analysis was performed alongside an objective assessment using the Transfer Assessment Instrument (TAI). The perceived difficulty reported after each transfer was also collected. Two participants exhibited radically different transferring techniques in different scenarios. Additionally, the transferring scenario was found to significantly affect the perceived difficulty of sitting transfers (toilet 2.17 ±.88; bed 1.47 ±.65, p =.001; car 1.63 ±.82, p =.012) and standing transfers (car 3.5 ±.71; bed 1 ± 0, p =.03; toilet 1 ± 0, p =.03), and the TAI score attributed to sitting pivot with use of a transfer board (couch 4.3 ±.88; bed 6.93 ± 1.29, p =.022; car 7.13 ± 1.32, p =.018). Overall, environmental constraints can lead to major technique changes and, more often, to different positioning of hands and feet which could impact the transfer's biomechanics.

The relationship between in-seat movement and pressure ulcers in wheelchair users with SCI/D.

OBJECTIVE: To identify parameters that are associated with time at pressure, are most related to pressure ulcer outcomes, and that may be used to influence pressure ulcer (PrU) outcomes in future intervention studies. DESIGN: Analysis used datasets from cross-sectional and longitudinal observational studies. Wheelchair-usage and in-seat metrics thresholds were optimized to differentiate individuals in PrU or No PrU groups. Logistic regression identified the demographics and in-seat activity metrics that impacted PrU outcomes. SETTING: General Community. PARTICIPANTS: Fifty individuals with spinal cord injuries and/or disorders (SCI/D) who use a wheelchair as their primary mobility device. 22 subjects were within the first year following injury and 28 had been using a wheelchair for over 2 years. Twenty-one participants reported PrU outcomes. INTERVENTIONS: Not applicable. OUTCOME MEASURES: Time in chair, pressure relief frequency, weight shift frequency, percentage of seated time that the subject is active (CoP Percent Active), frequency of in-seat movement, unloading event frequency, maximum time between events, and number of transfers. RESULTS: Optimal cutoff thresholds for the most significant in-seat movement metrics included: unloading event frequency of 3.1 times per hour (OR 0.353, 95% CI [0.110, 1.137]), maximum time between events of 155.4 min (OR 2.888, 95% CI [0.886, 9.413]), and CoP Percent Active of 2.6% (OR 0.221, 95% CI [0.063, 0.767]). When individuals were more active than these cutoffs, significantly more individuals were in the no pressure ulcer group. In predictive modeling, CoP Percent Active was the in-seat movement metric that significantly predicted PrU outcomes. The model was improved by adding age, occupation, and injury completeness. CONCLUSION: Of the 4 significant predictors in the model, only CoP Percent Active was modifiable. Therefore, an opportunity exists to design approaches to modify behavior. However, the results illustrate that the key to preventative movement may be through functional movement as opposed to scheduled, routine pressure reliefs.

Validating a wheelchair in-seat activity tracker.

Wheelchair users often experience prolonged periods of stationary sitting. Such periods are accompanied with increased loading of the ischial tuberosities. This can lead to the development of pressure ulcers which can cause complications such as sepsis. Periodic pressure offloading is recommended to reduce the onset of pressure ulcers. Experts recommend the periodic execution of different movements to provide the needed pressure offloading. Wheelchair users, however, might not remember to perform these recommended movements in terms of both quality and quantity. A system that can detect such movements could provide valuable feedback to both wheelchair users as well as clinicians. The objective of this study was to present and validate the WiSAT - a system for characterizing in-seat activity for wheelchair users. WiSAT is designed to detect two kinds of movements - weight shifts and in-seat movements. Weight shifts are movements that offload pressure on ischial tuberosities by 30% as compared to upright sitting and are maintained for 15 seconds. In-seat movements are shorter transient movements that involve either a change in the center of pressure on the sitting buttocks or a transient reduction in total load by 30%. This study validates the use of WiSAT in manual wheelchairs. WiSAT has a sensor mat which was inserted beneath a wheelchair cushion. Readings from these sensors were used by WiSAT algorithms to predict weight shifts and in-seat movements. These weight shifts and in-seat movements were validated against a high-resolution interface pressure mat in a dataset that resembles real-world usage. The proposed system achieved weight shift precision and recall scores of 81% and 80%, respectively, while in-seat movement scores were predicted with a mean absolute error of 22%. Results showed that WiSAT provides sufficient accuracy in characterizing in-seat activity in terms of weight shifts and in-seat movement.

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.