Seat Pressure Research Articles

Back Support Shape with Pelvic Support Belt Affects Asymmetrical Seated Posture and Pressure Points During Reaching Tasks in Post-Stroke Patients

To investigate the effect of different back support shapes on asymmetrical seated posture and pressure points during a reaching task in post-stroke hemiplegic patients.

Tractor seating for operators with paraplegia

ABSTRACTThis feasibility study explored the utility of using a pressure mapping instrument to explore the variable of pressure under subjects sitting on a commonly used tractor seat, and four other cushion interventions. The research model used single-subject with repeated measures during simulated tractor operation. In examining the graphical images and pressure mapping data available from the instrument; the contour tractor seat used in this study was not sufficient in redistributing pressure for people with paraplegia operating tractors, putting them at greater risk for acquiring a pressure ulcer. The use of pressure mapping equipment to study seated pressure within dynamic environments is achievable, and further studies need to be performed and replicated in simulated or in vivo environments. The data in this study suggest people with paraplegia operating agricultural equipment may not have acceptable pressure distribution using the manufacturer’s installed seat and must rely on adding wheelchair cushions or other materials to the seat surface to create acceptable pressure distribution. However, doing so changes other aspects of the seating micro or macro climate that can also be problematic.

Effect of seat positions on discomfort, muscle activation, pressure distribution and pedal force during cycling

The aim of this study was to measure and analyse discomfort and biomechanics of cycling, i.e., muscle activation, centre of pressure of seat pressure profiles and pedal forces as a function of seat position. Twenty-one recreationally active individuals cycled for 10min at 100W on an ergometer cycle using five different seat positions. The neutral position was considered as basic seat position and was compared with upward, downward, forward and backward seat positions. The initial bout was repeated at the end of the recording session. Discomfort increased for upward and backward condition compared with neutral (P<0.05). Normalized surface electromyography from gastrocnemius decreased in the downward and forward position but increased in the upward and backward position. The minimum force became less negative for forward position compared with neutral seat position (P<0.05). The degree of variability of centre of pressure increased in the upward and backward position and the entropy of the centre of pressure of sitting posture for backward position decreased compared with neutral seat position (P<0.05). The present study revealed that consecutive changes of seat position over time lead to increase in discomfort as well as alterations of the biomechanics of cycling.

Detecting Gilgai Relief Beneath Sealed Flexible Pavements Using Road Profile and Road Roughness Measurements

Expansive soils are those that expand and contract significantly when subjected to changes in moisture. The presence of such soils can accelerate the deterioration rate of pavements due to increased cracking and roughness, especially when Gilgai relief is allowed to manifest beneath the pavement structure. Gilgai relief is a naturally occurring topographical feature that results in a unique undulating ground surface. These undulations develop from deep seated swelling pressures within the underlying expansive soil layers. At present, current road roughness indices cannot isolate the roughness caused by Gilgai relief and the detection of Gilgai in the field can be difficult. This paper presents a new series of templates that can identify pavement sections that contain high concentrations of waveband roughness specific to Gilgai characteristics. These templates are based on the standard international roughness index and a variety of new calculated profile indices that measure waveband roughness quantities. The main outcome of this paper is that the influence of Gilgai relief can now be detected and quantified mathematically through these templates, which were developed from over 600 km of road profile data from flexible rural highway pavements located in north-west Victoria (Australia).

Working position influences the biomechanical demands on the lower back during dental hygiene

This investigation monitored the biomechanical demands on the lower back during simulated dental hygiene work. A total of 19 female, registered dental hygienists performed 30 continuous minutes of manual scaling (plaque removal) of a manikin’s teeth while seated. We monitored the working location and orientation of the dental hygienists, with respect to the manikin, along with their spine kinematics, spine extensor muscle activities and seat pressure, throughout the 30 min. A clock representation was used to express the working location. The location significantly influenced the dental hygienists’ pelvic orientation with respect to the manikin, spine posture, erector muscle activity and pressure distribution. Findings from this study suggest that the prevalence of lower back pain amongst dental hygienists may be directly related to low-level tonic activity of the spine’s extensor musculature, and the combined flexed and axially rotated spine postures.Practitioner Summary:Low back pain (LBP) is prevalent in dental hygienists, yet occupational demand on the low back has not been investigated. Posture, muscle activity and seat pressure were monitored. Combined spine rotation and flexion, and tonic activity of the extensor musculature may be related to LBP in dental hygienists.

Lumbar postures, seat interface pressures and discomfort responses to a novel thoracic support for police officers during prolonged simulated driving exposures

A high prevalence of low back pain has been reported among professional drivers, including mobile police officers. The purpose of this investigation was to develop and evaluate a novel thoracic support designed for mobile police officers. Fourteen participants (7 male, 7 female) attended two 120-min driving simulations using a Crown Victoria Interceptor seat and the same seat equipped with a surface mounted thoracic support. Time-varying spine postures, seat pressures and ratings of discomfort were measured. Averaged discomfort values were low (less than 10 mm of a possible 100 mm) for both seating conditions. The postures in the thoracic support condition were more similar to non-occupational driving without occupational equipment than the Crown Victoria seating condition. The reduction in pressure area at the low back with the thoracic support has the potential to reduce discomfort reporting in officers compared to a standard vehicle package.

Blood pressure-lowering effect of the sodium glucose co-transporter-2 inhibitor ertugliflozin, assessed via ambulatory blood pressure monitoring in patients with type 2 diabetes and hypertension.

This study compared the blood pressure-lowering effect of ertugliflozin (1, 5, 25 mg), hydrochlorothiazide (HCTZ; 12.5 mg) and placebo in 194 patients with type 2 diabetes mellitus and hypertension for 4 weeks using ambulatory blood pressure monitoring. Endpoints (change from baseline to week 4) were: 24-h mean systolic blood pressure (SBP; primary); daytime, night-time, seated predose SBP, 24-h, daytime, night-time, seated predose diastolic blood pressure, 24-h urinary glucose excretion and fasting plasma glucose (FPG; secondary). Safety and tolerability were monitored. Significant decreases in placebo-corrected 24-h mean SBP (-3.0 to -4.0 mmHg) were recorded for all doses of ertugliflozin (for HCTZ, this was -3.2 mmHg). Daytime, but not night-time SBP was consistently reduced. Ertugliflozin produced dose-dependent significant decreases in FPG and increases in urinary glucose excretion. No notable changes in plasma renin activity or urinary aldosterone were seen. The most common adverse events were urinary tract infection, genital fungal infection, upper respiratory tract infection and musculoskeletal pain.

Relationship between serum levels of endogenous secretory RAGE and blood pressure in male nondiabetic patients with obstructive sleep apnea.

The interaction of advanced glycation end products (AGE) and their specific cell-surface receptor (RAGE) has an important role in the pathogenesis of cardiovascular disease and diabetic complications. Two isoforms of C-truncated RAGE, soluble RAGE (sRAGE) and endogenous secretory RAGE (esRAGE), may prevent activation of RAGE signaling by acting as decoys. This study investigated whether serum esRAGE and sRAGE levels are associated with blood pressure in nondiabetic patients with obstructive sleep apnea (OSA). Male nondiabetic patients (n=139) with OSA were enrolled. Serum esRAGE and sRAGE levels were examined using enzyme-linked immunosorbent assay. Three consecutive seated systolic blood pressure (SBP) and diastolic blood pressure (DBP) measurements were obtained at 5-min intervals in the morning. In univariate analysis, there was a significant correlation between serum esRAGE and SBP or DBP, but not between serum sRAGE and SBP or DBP. Multiple regression analysis showed that SBP was independently associated with waist circumference, HbA1c, minimum SaO2 and serum esRAGE, and that DBP was independently associated with low-density lipoprotein cholesterol, apnea-hypopnea index, serum AGE and body mass index, but not with serum esRAGE. These results indicated that serum esRAGE levels were inversely associated with blood pressure, especially SBP, in male nondiabetic patients with OSA. esRAGE may have a protective role against hypertension in patients with OSA, and it may be a novel biomarker for OSA patients at high risk of developing cardiovascular diseases.

Lifestyle risk factors for pressure ulcers in community-based patients with spinal cord injuries in Japan.

Case-control study. To identify daily living-related risk factors for pressure ulcer (PU) occurrence in community-living patients with spinal cord injury (SCI). To determine whether seat pressure influences PU occurrence, and how often patients with SCI perform pressure relief activities while living in the community. Kanagawa Rehabilitation Hospital, Kanagawa, Japan. Thirty-one patients admitted to this hospital for PU treatment were included in the case (PU) group. Thirty outpatients who did not have PUs at the time of the study, and had lived without PUs for at least a year, were included in the control (No PU) group. Patients were interviewed about lifestyle-related PU risk factors and a pressure-mapping system was used to measure interface pressure (IP) on their wheelchair seat. The No PU group patients recorded their daily activities and pressure relief maneuvers for 1 week. Eight lifestyle factors and one risk assessment scale significantly differed between groups. Three factors showed significant odds ratios by logistic regression. IP did not significantly differ between groups. The self-counted number of pressure relief maneuvers (median (25th-75th percentile)) performed per hour in the No PU group was 2.5 (0.7-4.3) and including transfer and urination was 3.5 (2.0-5.3). We identified potential PU risk factors related to lifestyle. The scores of one risk assessment scale were also associated with PU risk. Our results did not suggest an IP damage threshold. Patients in the No PU group performed pressure relief maneuvers, including related activities, approximately once every 17 min.

Influence of wheelchair footrest height on ischial tuberosity pressure in individuals with paraplegia.

To describe the effect of wheelchair footrest height on sitting pressures in persons with paraplegia. Seventeen manual wheelchair users with paraplegia underwent a seat pressure examination while footrests were elevated from the initial position with the thighs parallel to the seat (p0), by 10% (position p10) and by 20% of the fibula length (position p20). We analyzed average pressure (AP), the contact surface of the body with the seat (CS), pressures on the ischial tuberosities-left (LIP) and right (RIP)--and average pressure on both ischial tuberosities (AIP). A gradual increase in footrest elevation was accompanied by significant increases in AP (p0: 57.24±14.31; p10: 60.65±14.85; p20: 62±15.3 mm Hg; Kendall coefficient of concordance W=0.962), AIP (p0: 159.35±54.95; p10: 176.35±53.3; p20: 184.26±54.09 mm Hg; W=0.896), LIP (p0: 165.24±54.05; p10: 183±52.08; p20: 193.18±56.32 mm Hg; W=0.751) and RIP (p0: 153.71±71.23; p10: 167.35±72.19; p20: 175.35±70.84 mm Hg; W=0.524) and a significant decrease in CS (p0: 1218.2±100.8; p10: 1131.8±134.6; p20: 1065±142.6 cm(2); W=0.985). There was a moderate correlation between the relative increase in LIP and RIP between p0 and p10, and between p10 and p20 (Pearson's correlation coefficient for LIP r=0.66; P=0.04, for RIP r=0.77; P=0.003), and a high correlation between relative changes in AIP (r=0.87; P<0.0001). Wheelchair footrest elevation caused a steady rise in AIP; however, left to right side pressure differences changed variably, suggesting that the risk of pressure ulcers may increase disproportionately with footrest elevation.

Backrest Shape Affects Head-Neck Alignment and Seated Pressure.

Unstable back support against gravity results in a forward head posture and contributes to buttocks pressure ulcers. However, the association between these health problems and a wheelchair backrest is unclear. Our newly developed wheelchair (N-WC) supports the back of the pelvis and thorax from obliquely underneath. The purpose of this study was to investigate the effect of different backrest shapes on head-neck alignment and seated pressure. Data from 28 healthy subjects were analyzed. Outcome measures were head-neck alignment angles, support angles of the backrest, and pressure distributions on the supporting surfaces. Compared with a typical wheelchair that has a flat backrest, the seat pressure decreased and the center of pressure was located in the middle of both the seat and backrest in the N-WC. Moreover, the head-neck alignment when seated in the N-WC was upright. These results highlight the importance of the shape of the wheelchair backrest.

The Effects of Sitting on a Mechanical Lift Sling on Interface Seat Pressure

The Effects of Sitting on a Mechanical Lift Sling on Interface Seat Pressure

Cardiovascular control, autonomic function, and elite endurance performance in spinal cord injury.

We aimed to determine the relationship between level of injury, completeness of injury, resting as well as exercise hemodynamics, and endurance performance in athletes with spinal cord injury (SCI). Twenty-three elite male paracycling athletes (C3-T8) were assessed for neurological level/completeness of injury, autonomic completeness of injury, resting cardiovascular function, and time to complete a 17.3-km World Championship time-trial test. A subset were also fitted with heart rate (HR) monitors and their cycles were fitted with a global positioning systems device (n = 15). Thoracic SCI exhibited higher seated systolic blood pressure along with superior time-trial performance compared with cervical SCI (all P < 0.01). When further stratified by autonomic completeness of injury, the four athletes with cervical autonomic incomplete SCI exhibited a faster time-trial time and a higher average speed compared with cervical autonomic complete SCI (all P < 0.042). Maximum and average HR also tended to be higher in cervical autonomic incomplete vs autonomic complete. There were no differences in time-trial time, HR, or speed between thoracic autonomic complete vs incomplete SCI. In conclusion, autonomic completeness of injury and the consequent ability of the cardiovascular system to respond to exercise appear to be a critical determinant of endurance performance in elite athletes with cervical SCI.

High arterial pulse wave velocity is a risk factor for falls in community-dwelling older people.

To examine whether arterial stiffness is a risk factor for falls in community-dwelling older people. Prospective cohort study. Community population, Sydney, Australia. Community-dwelling older adults (mean age 79.8±4.4, 52.2% female; N=481). Carotid-femoral pulse wave velocity (PWV) was measured in the supine position after lying for 10 minutes. Demographic, medical, and medication characteristics and levels of physical activity were obtained in clinical interviews and questionnaires, and falls were recorded with monthly falls diaries for 12 months. Participants in the top quintile of PWV (high PWV) were more likely to have higher seated systolic blood pressure (SBP) and heart rate, unsatisfactory control of blood pressure, diabetes mellitus, and lower physical activity levels. These participants were also more likely to be male and taking cardiovascular medications. Of the 473 participants available for follow-up, 212 (44.8%) reported one or more falls. In modified Poisson regression analyses, high PWV was a risk factor for falls (relative risk=1.37, 95% confidence interval=1.06-1.78) after adjusting for use of psychotropic and cardiovascular medications, age, sex, body mass index, seated SBP, heart rate, and diabetes status. In community-dwelling older people, high PWV (as a measure of arterial stiffness) was a risk factor for falls after adjusting for potential demographic, anthropometric, disease, and medication confounders. Further research is required to investigate mediators for this association and the effect of lowering arterial stiffness on falls in older people.

Measuring static seated pressure distributions and risk for skin pressure ulceration in ice sledge hockey players

Purpose: To determine whether sledge hockey players with physical disability have higher average seated pressures compared to non-disabled controls. Method: Fifteen age-matched controls without physical disability and 15 experimental participants with physical disability were studied using a pressure mapping device to determine risk for skin pressure ulceration and the impact of cushioning and knee angle positioning on seated pressure distributions. Results: Regardless of participant group, cushioning, or knee angle, average seated pressures exceeded clinically acceptable seated pressures. Controls had significantly higher average seated pressures than the disability group when knees were flexed, both with the cushion (p = 0.013) and without (p = 0.015). Knee extension showed significantly lower average pressures in controls, both with the cushion (p < 0.001) and without (p < 0.001). Placement of the cushion resulted in significantly lower average pressure in controls when knees were extended (p = 0.024) but not when flexed (p = 0.248). Placement of the cushion resulted in no difference in pressure (p = 0.443) in the disability group. Conclusions: Pressures recorded indicate high risk for skin ulceration. Cushioning was effective only in the control group with knees extended. That knee extension significantly lowered average seated pressures is important, as many sledge hockey players utilize positioning with larger knee flexion angles.Implications for RehabilitationIce sledge hockey is a fast growing adaptive sport.Adaptive sports have been associated with several positive improvements in overall health and quality of life, though may be putting players at risk for skin ulceration.Measured static seated pressure in sledges greatly exceeds current clinically accepted clinical guidelines.With modern improvements in wheelchair pressure relief/cushioning there are potential methods for improvement of elevated seated pressure in ice hockey sledges.

Authentication Based on Seating Pressure Distribution using the MT System

This paper proposes a system for authentication based on seating pressure distribution, using the MT system as a new method of biometric authentication that is difficult to forge and does not inconvenience users. The main characteristic is that the only action required of the user is to sit down. Feature values were extracted based on the pressure distribution when individuals seat, and individual users were distinguished from other persons by means of the Mahalanobis-Taguchi (MT) system used in quality engineering. The result of the experiment was a False Rejection Rate of 2.2% and a False Acceptance Rate of 1.1%.

The Effect of Wallet Thickness on Spine Posture, Seat Interface Pressure, and Perceived Discomfort During Sitting

OCCUPATIONAL APPLICATIONS Occupational sitting has been associated with an increased risk for developing low back pain. The present investigation examined the effects of asymmetrical sitting surfaces induced by a wallet on acute changes in spine/pelvis posture, interface pressure, and discomfort. Compared to level sitting, sitting on a wallet resulted in greater sagittal and lateral spine flexion, a smaller total contact area with the seat pan, and greater gluteal discomfort. At wallet thicknesses of 22 mm and thicker, seat pan contact pressure area decreased and thoracic spine and pelvic angles deviated laterally compared to the no-wallet condition. At a 32-mm wallet thickness, gluteal discomfort increased. These results indicate that sitting for brief periods (15 minutes) on an uneven seating surface greater than 32 mm in thickness causes postural deviations from neutral spine positions and increases gluteal discomfort. This study supports the removal of rear pocket items, especially larger ones, during sitting.TECHNICAL ABSTRACT Background: Occupations in mobile or office settings can involve prolonged seated exposures, increasing the likelihood of low back pain development. The seat-occupant interface can be impeded by wallets or other objects (cell phones, paper documents, etc.) placed in the rear pocket, potentially increasing the risk of developing low back pain directly (nerve compression) or indirectly (altered kinematics). However, there are no published studies that have examined the effect of an uneven seating surface. Purpose: This study aimed to quantify the outcomes of a non-level sitting surface on trunk kinematics, seat pan pressure distribution, and discomfort. Gender differences in responses were also examined. Methods: Twelve males and 12 females sat for 15 minutes each on 4 wallet thicknesses (0, 12, 22, and 32 mm). Sagittal and frontal plane angles of the thoracic, lumbar spine and the pelvis were measured. Seat pressure distribution (total pressure area) and discomfort using a 100-mm visual analogue scale were also collected for each thickness. Results: In the 22- and 32-mm conditions, there was greater pelvic posterior rotation, pelvic left lateral bending, thoracic flexion, and thoracic right lateral bending compared to the 0-mm condition. Males and females showed differences in the magnitude of lateral bend angles at all spine levels; however, both genders demonstrated the same directions of postural compensation. Total pressure area decreased and gluteal discomfort increased with thicker wallets, reaching significance in the 22- and 32-mm conditions, respectively. Conclusions: Sitting on wallets greater than 32 mm in thickness increased gluteal discomfort reporting after short duration exposures. Asymmetrical sitting promotes non-neutral spine postures and reduces seat pan contact area. Asymmetrical sitting is therefore not recommended, even for short duration exposures.

Dynamic pressure effect on horse and horse rider during riding

Horse riding predisposes to degenerative spinal injury to both rider and horse. This study evaluated the dynamic pressure exerted on horse and horse rider. The main comparison investigated was how the flocking (cushioning) material of a saddle affected the pressure exerted on both. Six horse riders and one horse were used to conduct this study. The Pliance® horse saddle and seat pressure testing systems, designed by NovelGmBH, were used for this study. Pressure recordings were carried out from a saddle fitted with wool then again following its conversion to air flocking. Both flocking materials were tested during a variety of different gait settings using two pressure mats to record the pressures firstly being exerted onto the horse and secondly onto the rider. This study was the first carried out to examine the pressure exerted on horse and rider. Results found that both the mean peak pressure (MPP) and mean pressure–time integral (PTI) exerted on the rider increased by as much as 21.9 and 22 %, respectively, following conversion to air flocking. In contrast, the air flocking saddle exerted a lower MPP and PTI on the horse by as much as 25.3 and 26.6 %, respectively. This study has shown that air flocking reduces the pressure exerted on the horse; however, it has also indicated that it increased the pressures exerted on the rider. As a result of our study, further research needs to be conducted to determine the most appropriate material to flock a saddle with.

Statististical Performance Evaluation of Soft Seat Pressure Relief Valves

Risk-based inspection methods enable estimation of the probability of failure on demand (PFD) for spring-operated pressure relief valves at the United States Department of Energy's Savannah River Site in Aiken, South Carolina. This paper presents a statistical performance evaluation of soft seat elastomer spring operated pressure relief valves. These pressure relief valves are typically smaller and of lower cost than hard seat (metal to metal) pressure relief valves. They can provide substantial cost savings in certain fluid service applications providing that PFD is at least as good as that for hard seat valves. PFD is the probability that a pressure relief valve fails to perform its intended safety function during a potentially dangerous over pressurization. The research in this paper shows that the proportion of soft seat spring operated pressure relief valves failing is the same or less than that of hard seat valves, and that for failed valves, soft seat valves typically have failure ratios of proof test pressure to set pressure much less than that of hard seat valves.

Research on Experimental Method for the Working Force between Packer Rubber and Casing Tube

On application of BDI STS-WIFI testing system and Dasylab software, the testing process for strain of the casing tube with the packer rubber being seated is carried out. From the process the different friction force and normal pressure of specified seating pressure are achieved, by which the empirical formula is matched. Setting the experimental result as the boundary condition, the calculation result of the practical location of the five-stage packer on basis of oil and gas wells rod string mechanics is obtained, the maximum deviation of which is 0.1m compared with the magnetic location data. The research process on the experiment method proves its accuracy in laboratory while promoting the precision of the block location of the multistage packer in practical well casing tube.