Peak Pressure Index Research Articles

How does moderate upper limb activity modify sitting forces for able-bodied persons and wheelchair users?

Introduction Most people with a spinal cord injury are concerned by pressure injuries (PrI). Since dynamic activities may involve distributions of forces over time that are different from static and given the significant impact of PrIs on healthcare costs, it is, important to study these sitting forces. We aim to investigate sitting forces (overall normal, shear forces and Peak Pressure Index (PPI)) assessed in both able-bodied and wheelchair users (WCU) under static and dynamic conditions. Our hypothesis is that wheelchair sitting forces encountered by able-bodied participants are significantly different from those of WCUs. Material and Methods An experimental seat and a pressure mapping system were used to investigate forces in two different populations, 102 able-bodied and 15 WCUs, in static conditions and during synchronised hand-cycling. The analysis includes statistical comparisons of the sitting conditions (static/dynamic) and of the populations (able-bodied/WCUs). Results and discussion Significant differences in normal forces and PPI were observed between able-bodied and WCUs; conversely, differences in shear forces were non-significant. This suggests that contrary to shear forces, no conclusion on normal forces drawn from trials with healthy participants can directly be applied to WCUs. Secondly, the present results indicate significant reduced averaged: normal force, PPI, and shear forces for able-bodied performing a dynamic activity compared to static sitting. WCUs experienced non-significant lower averaged normal force and PPI but significant lower averaged shear forces. Conclusion While the present results seem to indicate lower forces for able-bodied performing a dynamic activity compared to static sitting, due to reduced averaged forces, this conclusion is less clear-cut for WCUs.

Assessment of the pelvic and body interface pressure during different recumbent and semi-recumbent birthing positions

BackgroundChildbirth, a multifaceted physiological event, undergoes dynamic changes influenced significantly by the chosen birthing position, impacting comfort and maternal and neonatal outcomes among other factors. This study aimed to investigate the bed-body interface pressure across five commonly adopted birthing positions, particularly focusing on their influence on pelvic expansion biomechanics during labour. MethodsTwenty healthy participants, aged between 18 and 49 years, were evaluated. Interface pressure across multiple regions of interest, including the head, shoulder, pelvis, and full body, were meticulously assessed under different combinations of leg and back positioning. FindingsSignificant variations in interface pressure were observed based on chosen positions. Post hoc pairwise comparisons showed different pressure distributions for all regions of interest, with the combination of legs in stirrups and a flat back resulting in the lowest average pressure in the pelvic region. During the closed glottis pushing task, this combination exhibited lower peak pressure and peak pressure index in the pelvic region compared to other positions. InterpretationWhile upright positions are conventionally preferred, the study underscores the nuanced implications of recumbent and semi-recumbent positions. Although using stirrups with a flat back exerts less pressure, lying flat can impede blood flow and exacerbate pain, while stirrups might lead to discomfort and potential complications. Given these complexities, healthcare providers must consider multiple factors to determine optimal birthing positions. The interplay between birthing positions and obstetric outcomes awaits further exploration and refinement, marking an exciting frontier in maternal care.

Evaluation of the Effect of Gluteus Maximus Contraction by Electrical Stimulation on Interfacial Pressure in Supine Bed Positions.

This study investigated the impact of neuromuscular electrical stimulation (NMES) to the gluteus maximus in the bed flat position (F position) and 30-degree head elevation position (30 HE position) on sacral pressure. Twenty volunteers consented to participate in this study. Sacral pressure was measured in the F position and at the 30 HE position with and without NMES in the supine positions. NMES was applied to the gluteus maximus (frequency, 50 Hz; pulse width, 300 μs) with sufficient stimulus intensity to induce muscle contraction. Sacral maximum pressure was determined as peak pressure index (PPI) by averaging the values from the central nine sensors of the maximum pressure zone. The effect of NMES on pressure gradient and the influence of sex difference were also explored. Sacral PPI was significantly lower after NMES implementation in both the F position and the 30 HE position when compared with conditions without NMES (P <0.001). The pressure gradient was also significantly decreased with NMES (P <0.001). Analysis of sex difference in subjects treated with NMES revealed a significantly greater effect on maximum sacral pressure in males than in females. Application of NMES to the gluteus maximus helps to disperse sacral pressure in supine positions. NMES on the gluteus maximus can be a clinical means to manage interfacial pressure in supine positions.

Assessment of ear barofunction by tympanometry method

BACKGROUND: When selecting divers, pilots and caisson workers to determine ear barofunction, the subjects tolerance to compression or decompression in the hyperbaric chamber and the condition of the eardrums after leaving the chamber are evaluated. This approach to selection and annual examination is quite informative, although there are isolated cases of unreliable assessments due to concealment of complaints by the examinees, due to the desire to work in the profession. In the course of daily professional activities of these specialists, the diving or aviation doctor needs to detect timely barofunction changes caused by acute respiratory diseases, mechanical injuries, allergic reactions, vasomotor edema of nasal mucosa, etc.&#x0D; AIM: To investigate the possibility of using the tympanometry method for examination and dynamic control of ear barofunction among divers.&#x0D; MATERIALS AND METHODS: The study involved 42 people who were immersed in a flow-decompression chamber to determine barofunction. After 20 days, the subjects were re-examined by tympanometry method at normal atmospheric pressure using the Valsalva technique.&#x0D; RESULTS: The tympanometric indexes of the subjects with the I degree of barofunction had statistically insignificant changes, with IIIII degrees of barofunction there was an increase of peak pressure index and narrowing of peak curve width after diving in a hyperbaric chamber. Among persons with low barofunction (IIIII degrees), the tympanometry method revealed an increase in peak pressure index.&#x0D; CONCLUSION: The conducted research has shown promising use of tympanometry among specialists working in conditions of varying barometric pressure.

Impact of a new clinical mattress solution on interface pressure and comfort during supine lying.

Effective pressure management for individuals is critical for hospital and community-based care, to prevent the occurrence of pressure ulcers. This study explores the impact of a new mattress and topper solution on interface pressure and comfort during supine lying. In this quantitative, healthy cohort study, patient-surface interface pressures were calculated for three mattresses (a standard hospital mattress, a new mattress solution (Levitex Foams Ltd., UK) and a dynamic air flow mattress) with and without an innovative topper solution (Levitex Foams Ltd., UK). Subjective comfort, contact surface area, peak and mean pressure and peak pressure index (head, sacrum, heels) were calculated for all mattress conditions for a 21-minute period. A total of 27 healthy volunteers took part in this study. The new mattress solution decreased peak pressure significantly compared with the hospital and air mattresses (p<0.04). Lower peak pressures were observed for the hospital mattress compared with the dynamic air flow mattress. The new mattress solution improved comfort and significantly lowered (>30%; p≤0.005) heel and head pressure compared with the other surfaces. Both hospital and air mattresses significantly reduced pressure and improved comfort with the addition of the new topper solution (p<0.05). The new mattress solution used in this study offers a potentially improved pressure management solution for individuals. Implementation of the topper may also help to improve pressure management when used with existing standard or dynamic air flow mattresses.

Pressure Distribution Comparison among Standard Seating Surfaces and Strap Seating System

AIMS: Pressure injuries (PIs) are common issues that can be minimized through the use of pressure-redistributing support surfaces. Cushions that provide immersion and contour are considered the most effective for pressure relief; however, others are readily available on the market. The aim of this study is to determine how a wheelchair equipped with Comfort Tension Seating&amp;reg;(CTS) compares to standard sling seating, foam, and a high-end pressure redistributing contoured cushion. &#x0D; &#x0D; MATERIALS &amp;amp; METHODS: Pressure redistribution qualities as measured through peak pressure index (PPI) using pressure mapping technology were gathered on four different seating surfaces -standard sling seat, CTS, and two cushion types flat cross-section foam, contoured-cushion, and CTS. Twenty non-disabled participants trialed each cushion for five minutes each. The methods of this study are described and outcomes analyzed by comparing the PPI and comfort of the four cushions.&#x0D; &#x0D; RESULTS: A Wilcoxon signed-rank test, and related samples Friedman&amp;rsquo;s two-way analysis of variance by ranks (ANOVA) was calculated. The results show that there is a significant difference between each of the cushions in comfort and pressure redistribution. There was a statistically significant difference in mean PPI between the three groups in which the CTS performed better than the sling and flat cross-section foam, but not quite as good as the high-end contoured cushion (p &amp;lt;.001). &#x0D; &#x0D; CONCLUSION: While not as optimal as the contoured M2 foam cushion, the CTS seating surface appears to provide superior pressure-redistributing performance compared to sling and flat cross-section foam. This suggests that the CTS could be used as a support surface for many applications, except for individuals with high-level PI risk, without using tilt and recline features.

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 REHABILITATION A 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.

Upright vs. supine shape-capturing comparison for custom-contoured cushions

AimsThis study aims to explore best practices of shape capturing methods for creating custom-contoured wheelchair cushions for the purpose of reducing pressure injury risk. Materials and methodsPressure redistribution qualities were measured by peak pressure index (PPI) and compared between custom-contoured seating systems molded in supine vs. upright shape-capturing positions. Subjects consisted of 14 able-bodied participants in a within-subjects comparison. ResultsA Wilcoxon signed-rank test and paired t-test were calculated to compare the mean differences of the PPI between shape-capturing positions. Supine shape-capturing resulted in a statistically significant lower PPI compared to upright (z = 2.040, p < . 05) (t = −2.28, p < .05). ConclusionShape-capturing in the supine position provided greater pressure distribution as opposed to an upright position. Creating custom-contoured cushions molded in a supine position can reduce the risk of pressure injury to the patient.

Custom-contoured seating from unloaded shape capture: A pilot study

AimsTraditional methods of shape-capture for creating custom-contoured seating have commonly consisted of capturing the buttocks in a loaded position. This study seeks to compare an innovative unloaded shape capture method to off-the-shelf pressure relieving cushions. Materials and methodsThe pressure redistribution and support characteristics of a cushion designed using an unloaded shape-capture method was compared to off-the-shelf pressure redistributing cushions. The methods of this pilot trial are described, and the outcomes are analyzed and summarized through descriptive statistics, including peak pressure index, average pressure, surface contact, quadrant distribution and perception of postural support. ResultsA Wilcoxon signed-rank test was calculated to compare the mean difference in PPI between the unloaded shape-capture cushion among the other cushions. Differences in peak pressure between the unloaded shape capture cushion and off-the-shelf pressure relieving cushions were not significant, however there was a significant reduction in pressure between the unloaded shape-capture cushion and both sling seat and baseline non-contoured foam cushion (z = 2.673, p = .008). ConclusionThe unloaded shape-capture method results in a cushion with pressure redistribution characteristics similar to off-the-shelf pressure redistributing cushions while providing superior postural support. The unloaded shape-capture method appears to be a feasible alternative to traditional loaded methods and is worthy of further research.

Evaluation of interface pressure and temperature management in five wheelchair seat cushions and their effects on user satisfaction

BackgroundFactors such as the manufacturing materials, shape or even the mechanical and thermal response of sitting Pressure Redistribution Support Surfaces (PRSS) can be potential contributors to pressure ulcers. However, few studies have compared a number of characteristics of the most frequently used devices. ObjectiveTo compare three potential contributors to pressure ulcers in five commercial PRSS: pressure redistribution, temperature and perceived comfort. Method: Study with a cross-over randomized design in healthy volunteer participants. Data was collected in a temperature and relative humidity controlled environment. To assess thermal response, the temperature (Flir-E60) of the region of interest was captured before and after use of each PRSS for further analysis. The region of interest was the gluteal zone. To assess the pressure redistribution a pressure mat (XSensor®) was used between the 5 cushion and each study participant using a standardized method. Finally, a subjective perception questionnaire recorded comfort, adaptability and thermal sensation parameters. Data analysis levels of significance were set at 0.05. ResultsA total of 22 participants completed the assessments. There were no statistically significant differences in baseline temperatures between PRSS (>0.05). Pressure redistribution analysis showed significant differences between all PRSS in all variables evaluated except in the maximum and peak pressure index al sacrum. The subjective assessment suggested no major user-perceived differences between PRSS. ConclusionSeat cushions made of open cell polyurethane foam blocks of variable hardness and the horseshoe cushion (also open cell polyurethane foam) seem to provide a more effective pressure relief characteristic than those injected with polyurethane foam and gel in most of the studied pressure variables. However, the cushions provide similar thermal response and perceived comfort.

A comparison of air-cell and gel surgical table pads and an evaluation of the influence of pressure distribution and other factors on pressure injury prevention

Guidelines for pressure injury prevention consider the use of pressure-redistributing pads to prevent tissue deformation. However, limited research exists to assess the pressure distribution provided by the operating tables and the effectiveness of pressure-redistributing pads in preventing pressure injuries. In this study, we compared the pressure distribution properties of two surgical table pads and identified parameters influencing pressure injury outcomes after a lengthy surgical procedure. Twenty-seven patients undergoing left ventricular assist device implantation surgery participated in the study. Participants were randomly assigned to use either an air cell-based pad or a gel pad. Interface pressure was recorded during the surgery. We analyzed the effect of surgical table pad type, interface pressure distribution and pressure injury outcomes and analyzed what characteristics of the patients and the interface pressure are most influential for the development of pressure injuries. Comparing the interface pressure parameters between the air-cell group and the gel group, only the peak pressure index x time was significantly different (p < 0.05). We used univariate logistic regression analysis to identify significant predictors for the pressure injury outcome. The support surface was not significant. And, among patient characteristics, only age and BMI were significant (p ≤ 0.05). Among the interface pressure parameters, pressure density maxima, peak pressure index x time, and coefficient of variation were significant for pressure injury outcome (p ≤ 0.05). Peak pressure index, average pressure, and the surgery length were not statistically significant for pressure injury outcomes.

An Experimental Intervention Study Assessing the Impact of a Thin Silicone Gel Surface Overlay on Interface Pressure.

Introduction The incidence of pressure ulcers (PUs) presents a substantial threat to patients, especially geriatric patients, those with restricted mobility, and patients suffering from chronic diseases such as cancer. PUs creates a huge financial burden on healthcare authorities and patients, costing billions to treat and manage. Radiography and radiotherapy patients may experience medical device related (MDR) PUs and studies have shown that high interface pressure (IP) values exist for the head when placed on an X-ray table without a mattress. These high IP values pose a PU risk to patients, especially those accessing prolonged radiography/radiology and radiotherapy procedures. The current study assessed the impact on IP values for the head from using a thin silicone gel surface overlay during radiographic procedures and identified whether this reduced the risk of PUs. Materials and Methods A calibrated XSENSOR pressure mat was used to measure IP for the head on an X-ray table with and without a thin silicone gel surface overlay. Prior to pressure mapping, the silicone gel surface overlay was assessed for its impact on radiation attenuation and image quality. Results Study participants were 14 males (70%) and six females (30%), with an age range of 25–53 years (mean = 34.4 ± 7.0). Paired-samples t-test results indicated that there was a statistically significant decrease in the mean IP for the head on the X-ray table without the silicone gel surface overlay (mean = 83.9 ± 8.2 in mmHg) and the X-ray table with the gel surface overlay (mean = 62.4 ± 6.1 in mmHg), p ≤ 0.001. Paired-samples t-test results indicated that there was a statistically significant decrease in the mean peak pressure index (PPI) for the head on the X-ray table without the silicone gel surface overlay (mean = 205.1 ± 28.2 in mmHg) and the X-ray table with the gel surface overlay (mean = 159.8 ± 26.8 in mmHg), p ≤ 0.001. Conclusions The use of a thin silicone gel surface overlay could reduce IP risk for the head by approximately 25%. The reduction in IP risk could have a significant impact in reducing the risk of developing a PU. To ensure maximum benefit, the silicone gel surface overlay should be evaluated to address the specific needs within radiography and radiotherapy planning and treatment settings.

Higher oscillatory shear index is related to aneurysm recanalization after coil embolization in posterior communicating artery aneurysms.

The recurrence rate of posterior communicating artery (Pcom) aneurysms after endovascular treatment (EVT) is higher than that for aneurysms located in other sites. However, it is still unclear what mechanisms are responsible for the recanalization of cerebral aneurysms. In this investigation, we compared hemodynamic factors related with recanalization of Pcom aneurysms treated by endoluminal coiling using computational fluid dynamics (CFD) with high-resolution three-dimensional digital subtraction angiography images. Twenty patients were enrolled. A double-sinogram acquisition was performed with and without contrast injection after coil embolization to get true blood vessel lumen by relatively complementing the first sinogram with the second. Adaptive Cartesian meshing was performed to produce vascular wall objects for CFD simulation. The boundary condition for inlet (ICA) was set for dynamic velocity according to the cardiac cycle (0.8s). Hemodynamic parameters were recorded at two specific points (branching point of Pcom and residual sac). The peak pressure, peak WSS, and oscillatory shear index (OSI) were recorded and analyzed. The median age was 61.0years, and 18 patients (90%) were female. During a median follow-up of 12months, seven (35%) treated aneurysms showed recanalization. The median aneurysm volume was significantly higher, and aneurysm height and neck sizes were significantly longer in the recanalization group than those in the stable group. At the branching point of the Pcom, the peak pressure, peak WSS, or OSI did not significantly differ between the two groups. The only statistically significant hemodynamic parameter related with recanalization was the OSI at the aneurysm point. Multivariate logistic regression showed that with an increase of 0.01 OSI at the aneurysm point, the odds ratio for the aneurysm recanalization was 1.19. A higher OSI is related with recanalization after coil embolization for a Pcom aneurysm.

Quality Prediction for Injection Molding by Using a Multilayer Perceptron Neural Network.

Injection molding has been widely used in the mass production of high-precision products. The finished products obtained through injection molding must have a high quality. Machine parameters do not accurately reflect the molding conditions of the polymer melt; thus, the use of machine parameters leads to erroneous quality judgments. Moreover, the cost of mass inspections of finished products has led to strict restrictions on comprehensive quality testing. Therefore, an automatic quality inspection that provides effective and accurate quality judgment for each injection-molded part is required. This study proposes a multilayer perceptron (MLP) neural network model combined with quality indices for performing fast and automatic prediction of the geometry of finished products. The pressure curves detected by the in-mold pressure sensor, which reflect the flow state of the melt, changes in various indicators and molding quality, were considered in this study. Furthermore, the quality indices extracted from pressure curves with a strong correlation with the part quality were input into the MLP model for learning and prediction. The results indicate that the training and testing of the first-stage holding pressure index, pressure integral index, residual pressure drop index and peak pressure index with respect to the geometric widths were accurate (accuracy rate exceeded 92%), which demonstrates the feasibility of the proposed method.

Wheelchair Seated Posture and Health Outcomes of Older Veterans in Community Living Centers.

Nursing home residents sit in wheelchairs (WCs) for extended periods, often with slumped posture. They often experience pneumonia, pressure ulcers, and pain. This study described WC seated posture with its selected predictors and outcomes in the nursing home environment, throughout the daytime hours of 1 day. This observational study (n = 45) in two Veterans Administration Community Living Centers introduced a new measure of WC fit and described WC seated posture of older Veterans, with selected predictors and outcomes. Wheelchair seated posture was predicted by cognitive status, WC fit, WC skills, and duration of sitting, but not by level of sitting ability. Poor posture measured by the Seated Posture Scale was associated with pain. Highest interface pressures measurable were seen in peak pressure index (PPI = 200 mm Hg), indicating risk of pressure injury. Veterans often denied discomfort, possibly lowering overall pain scores, while reporting severe pain in specific body parts. Wheelchair seated posture was predicted by cognitive status, WC fit, WC skills, and duration of sitting. Poor posture was associated with pain, and poor posture was an outcome of poor WC fit. Poor WC fit in this study supported earlier findings in non-Veterans Administration nursing homes.

Exploring the Influence of Wheelchair-User Interface and Personal Characteristics on Ischial Tuberosity Peak Pressure Index and Gradient in Elite Wheelchair Basketball Players.

This pilot study investigated the relationship between personal and wheelchair factors on skin pressures at the ischial tuberosity in wheelchair basketball players. Seventeen wheelchair basketball players (7 male and 10 female) were evaluated during static and dynamic propulsive conditions while peak pressure index and peak pressure gradient were recorded with an interface pressure mat. The results showed that greater seat dump angles and backrest heights were negatively associated with the peak pressure index. Therapeutic cushion use was moderately associated with a reduced peak pressure gradient. Higher-class players used chair configurations associated with augmented pressure; however, classification status alone was not associated with pressure magnitude. Body mass index was negatively correlated with the static peak pressure gradient at levels approaching significance (p < .10). In conclusion, greater seat dump angles and backrest heights may provide pressure relief, whereas greater body mass index and therapeutic cushion use may reduce pressure gradients.

Demonstration of pressure reduction in a new proof of concept spine board

ABSTRACT Pressure injuries are a significant problem following spinal cord injury (SCI). High interface pressures while lying on a spine board during emergency transport appear to play a major role in their formation. The aim of the present study was to assess the interface pressures and sensing area between the body and the standard spine board (SSB) and a proof of concept spine board prototype (P-5). Twenty-one able-bodied subjects were assessed on each board. Interface pressures and sensing area were recorded every minute over 15 min. The mean peak pressure was higher on the SSB at the head, scapulothoracic (S-T), sacroiliac (S-I), and heels (227.6 mmHg, 148.9 mmHg, 360.3 mmHg, and 179.3 mmHg) compared to P-5 (51.9 mmHg, 60.1 mmHg, 66.8 mmHg, and 60.2 mmHg). The peak pressure index (PPI) at the head, S-T and S-I was higher on the SSB (100.2 mmHg, 101.6 mmHg, and 270.6 mmHg) compared to P-5 (41.6 mmHg, 51.9 mmHg and 58.7 mmHg). An analysis using pairwise comparisons for repeated measures showed that interface pressures (p < .05) and PPI (p < .001) were reduced at all locations. Modifications of a spine board incorporated in P-5 can dramatically reduce interface pressures and reduce pressure injury formation.

Studies on ballistic parameters of di-butyl phthalate-coated triple base propellant used in large caliber artillery gun ammunition

ABSTRACTTriple base propellant (TBP) containing mainly nitrocellulose, nitroglycerine, and nitroguanidine has been manufactured and coated with plasticizer in the present work. The aim was to study ballistics of di-butyl phthalate (DBP)-coated TBP. DBP solution in ethanol containing nitrocellulose dope was used for coating onto the propellant grains. DBP-deterred propellant showed inhibition to burning, resulting in lowering the values of ballistic parameters namely peak pressure (Pmax), dPmax, pressure index (α), and burning rate coefficient (β) during closed vessel firing. Increase in percentage of DBP in coating solution led to further decrease in ballistic parameters. Dynamic evaluation of the surface-moderated propellant showed comparatively lower muzzle velocity and chamber pressure for deterred propellant batches without leaving any unburnt particles in gun chamber at subzero temperatures with the lowest possible charge mass. The DBP-coated propellant can be useful in 155-mm artillery gun to achieve higher loading density as it has lower flame temperature and chamber pressure as compared to uncoated propellant which will result in increasing barrel life due to reduction in the barrel erosion.

Monitoring the biomechanical and physiological effects of postural changes during leisure chair sitting

BackgroundIndividuals with limited mobility can spend prolonged periods in leisure chairs, increasing their risk of developing a seated acquired pressure ulcer. The present study aims to use objective measures of posture and tissue viability to identify the associated risks of leisure chair related pressure ulcers. MethodsHealthy participants (n = 13) were recruited to sit on a leisure chair with either a viscoelastic foam or air cushion. Participants were asked to adopt four different postures for a period of 10 min followed by a 10 min refractory period. Measurements at the leisure chair-participant interface included interface pressure, transcutaneous tissue gas tensions at the ischial tuberosities, accelerometer data collected from the sternum and subjective comfort levels. ResultsResults indicated that interface pressures remained consistent, with peak pressure index values of less than 60 mmHg across all conditions. A proportion of participants exhibited decreased oxygen tensions associated with increased carbon dioxide tensions during one or more test condition. This was particularly prevalent during the right lean posture on the air cushion (46%). In all cases, normal tissue viability was restored during standing. The accelerometer was able to detect significant changes (p < 0.05) in relative trunk angles during slump and right lean when compared to optimal sitting posture. ConclusionCommercially available leisure chairs have little evidence to support their pressure relieving properties. This study revealed that a proportion of healthy individuals demonstrated a compromised tissue viability in specific postures. Further research is required to assess the impact of these sitting conditions in vulnerable individuals.

Exploring pressures, tissue reperfusion and body positioning: a pilot evaluation.

To assess the relationship in healthy adults and critically ill patients between: patient position, body mass index (BMI), patient body temperature, interface pressure (IP) and tissue reperfusion (TR). Also to determine the relationship in critically ill patients between: Sequential Organ Failure Assessment (SOFA) score, Braden Scale score for predicting pressure injury risk, Acute Physiology and Chronic Health Evaluation II (APACHE II) severity of disease classification score, IP and TR. This study took place in a 27-bed intensive care unit (ICU) of an Australian tertiary hospital. IP and TR outcomes were measured at the sacrum and greater trochanter. Repeated measures analyses of variance (ANOVAs) and doubly multivariate repeated measures ANOVAs were conducted using peak pressure index (PPI), peak time (PT), settled time constant (STC) and normalised hyperaemic area (NHA) measures of TR as outcomes. Participant type, body mass index (BMI), Braden and APACHE II scores and patient body temperature were considered as between-groups factors and covariates. We recruited 23 low- and high-acuity ICU patients and nine healthy adult volunteers. Not all IP readings could be obtained from ICU patients. TR readings were collected from all recruited patients, but not all TR measurements were mutually uncorrelated. Controlling for age, PPI readings differed between participant types (p=0.093), with the highest values associated with high-acuity patients and the lowest with healthy adults; the association was not substantive when controlling for age and BMI. Age was a significant variable (p=0.008), with older participants having higher scores than younger ones. No statistically significant associations between any measured parameter and TR variables were observed. However, temperature was revealed to be related to TR (p=0.091). Although not powered to detect significant effects, this pilot analysis has determined several associations of importance, with differences in outcomes observed between low- and high-acuity ICU patients; and between ICU patients and healthy volunteers.