Pressure Mapping Research Articles

Twelve-Week Daily Gluteal and Hamstring Electrical Stimulation Improves Vascular Structure and Function, Limb Volume, and Sitting Pressure in Spinal Cord Injury: A Pilot Feasibility Study.

We examined the long-term effects of low-intensity electrical stimulation on (micro)vasculature and sitting pressure of a home-based, wearable electrical stimulation device in a pilot feasibility study. In a cohort observation before-after trial, nine middle-aged male (n = 8) and female (n = 1) individuals (48 ± 15 yrs) with American Spinal Injury Association A-C classified chronic (1-24 yrs) spinal cord injury underwent 12 wks of self-administered daily, low-intensity gluteal and hamstring electrical stimulation (50 Hz, 6 hrs [30-min electrical stimulation, 15-min rest]). Common femoral artery diameter and blood blow were determined with ultrasound, skin vascular function during local heating was assessed using Laser-Doppler flowmetry, thigh volume was estimated using leg circumferences and skinfolds, and interface sitting pressure was measured using pressure mapping. Resting common femoral artery diameter increased (0.73 ± 0.20 to 0.79 ± 0.22 cm, P < 0.001) and baseline common femoral artery blood flow increased (0.28 ± 0.12 to 0.40 ± 0.15 l/min, P < 0.002). Gluteal cutaneous vascular conductance showed a time*temperature interaction (P = 0.01) with higher conductance at 42°C after 12 wks. Ischial peak pressure decreased (P = 0.003) by 32 ± 23 mm Hg and pressure gradient decreased (23 ± 7 to 16 ± 6 mm Hg, P = 0.007). Thigh volume increased (+19%, P = 0.01). Twelve-week daily home-based gluteal and hamstring electrical stimulation is feasible and effective to improve (micro)vasculature and sitting pressure, and electrical stimulation may have clinical implications for ameliorating pressure ulcers and (micro)vascular complications in spinal cord injury.

Highly Elastic and Fatigue-Resistant Graphene-Wrapped Lamellar Wood Sponges for High-Performance Piezoresistive Sensors

Three-dimensional (3D) conductive aerogels with structural robustness and mechanical resilience are highly attractive for sensitive and stable pressure sensing. However, the fabrication of such 3D aerogels often relies on complicated bottom-up assembly processes that involve costly raw materials or intensive energy consumption or directly coating synthetic polymer sponges (e.g., polyurethane) with conductive materials, which may pose environmental concerns for their disposal. Herein, a simple and sustainable strategy is proposed to fabricate a reduced graphene oxide-coated wood sponge (RGO@WS) with a lamellar structure for high-performance piezoresistive sensors. The introduced RGO nanosheets endow the RGO@WS not only with high conductivity but also with high elasticity and excellent fatigue resistance. These features make it an ideal piezoresistive sensor with a high sensitivity of 0.32 kPa–1 (superior to most polymeric sponge-based sensors), high working stability over 10 000 cycles, and excellent sensing reproducibility at ultralow temperatures. Thanks to its prominent sensing performance, the RGO@WS-based sensor can serve as a wearable device for detecting human motions and physiological signals and allows for spatially resolved pressure mapping via integrating the sensors into a large-area sensing array. The developed highly elastic and fatigue-resistant RGO@WS represents a promising and sustainable alternative to the synthetic polymer-based piezoresistive sensors.

Assessment of Stress in the Soil Surrounding the Axially Loaded Model Pile by Thin, Flexible Sensors.

Foundation piles transfer the applied vertical load to the surrounding soil by skin friction and base resistance. These two components induce stress in the soil. The load transfer is still not fully recognized, and some pile load tests analyses have raised many doubts. The present paper aimed to measure the stress levels during pile load tests in laboratory conditions. This research examined the possibilities of using thin, flexible sensors in measuring the stress in soil. Two sensors were used: tactile pressure sensor with mapping system and color film pressure sensors with digital analyzing. Calibration and preliminary tests of the sensors have been described. This calibration proved that this kind of sensor could measure the stress in the soil in laboratory conditions. The results of stress distribution in the soil, shown as pressure maps, have been presented. Significant stress changes were observed in pile load tests. Rough and smooth piles were compared in the analyses. Stress distribution was the result of simultaneous interaction of pile skin and base. The knowledge about stresses surrounding the pile allows us to carry out a deeper analysis of the pile–soil interaction.

Evaluation of Meniscal Load and Load Distribution in the Canine Stifle after Tibial Plateau Levelling Osteotomy with Postoperative Tibia Plateau Angles of 6 and 1 Degrees.

The aim of the study was to investigate the kinetic and kinematic changes in the stifle after a tibial plateau levelling osteotomy (TPLO) with a postoperative tibia plateau angle (TPA) of either 6 or 1 degrees. Biomechanical ex vivo study using seven unpaired canine cadaver hindlimbs from adult Retrievers.Hinge plates were applied and a sham TPLO surgery was performed. Motion sensors were fixed to the tibia and the femur for kinematic data acquisition. Pressure mapping sensors were placed between femur and both menisci. Thirty per cent bodyweight was applied to the limbs with the stifle in 135 degrees of extension. Each knee was tested with intact cranial cruciate ligament (CCL), deficient CCL, 6 degrees TPLO and 1degree TPLO. Transection of the CCL altered kinematics and kinetics. However, comparing the intact with both TPLO set-ups, no changes in kinematics were detected. After 1 degree TPLO, a significant reduction in the force acting on both menisci was detected (p = 0.006). Tibial plateau levelling osteotomy restores stifle kinematics and meniscal kinetics after transection of the CCL ex vivo. The contact force on both menisci is reduced significantly after TPLO with a TPA of 1 degree. Increased stifle flexion might lead to caudal tibial motion.

Oxidative coupling of methane over MnO2/ZrO2 catalyst in supercritical water: A parametric study

Hydrocarbons production with carbon numbers above C2 through methane coupling has been a target of many researches in the past decades. Recently we discovered that the reaction also occurs under supercritical water conditions. In this work, effects of reaction parameters such as catalyst Mn loading, charged catalyst amount, reaction time as well as reaction pressures and temperatures on the catalytic methane coupling under sub- and supercritical water environment were explored over MnO2/ZrO2 catalyst using a batch reactor. It was found within the investigated parameters that methane coupling activity was maximum at 12–35 MPa, 365–400 °C, 10 wt% Mn loading on ZrO2, reaction time 5 min and 1.0 g catalyst charging. It was conjectured from the temperature–pressure mapping of products that the reaction pathway of hydrocarbon formation over MnO2/ZrO2 is not the same with methanol formation pathway.

The thromboxane receptor antagonist NTP42 improves haemodynamics, inhibits remodelling, and restores function within the cardiopulmonary system in preclinical pulmonary arterial hypertension models

Abstract Background Pulmonary arterial hypertension (PAH) is a rare and fatal disease characterised by a progressive increase of pulmonary artery pressure leading to right heart failure. While current PAH therapies provide symptomatic relief and some improvement in quality of life, they show limited benefit in preventing disease progression and often have severe side effects. Recent studies by us reported that a novel thromboxane A2 receptor (TP) antagonist NTP42 attenuated multiple disease hallmarks of PAH in two preclinical models of the disease. Purpose The aim of this study was to assess the efficacy of a novel oral formulation of NTP42 developed for pharmaceutical use on monocrotaline (MCT)-induced PAH in rats across a range of cardiopulmonary parameters, and when compared with standard of care (SOC) PAH therapies. It also aimed to evaluate the expression of the TP, the target receptor for NTP42, in tissues from the MCT-induced PAH model and related disease models. Methods PAH was induced by subcutaneous injection of 60 mg/kg MCT. Rats were randomly assigned to 7 groups: (1) No MCT; (2) MCT Only; (3) MCT+NTP42 Formulation (1 mg/kg); (4) MCT+Sildenafil (50 mg/kg); (5) MCT+Macitentan (30 mg/kg), (6) MCT+Selexipag (1 mg/kg), and (7) MCT+Riociguat (5 mg/kg), where in all cases twice-daily oral dosing was initiated 7 days post-MCT and continued for 22 days. Results The results show that the formulated NTP42 reduced the severity of MCT-induced PAH as determined from haemodynamic measurements of mean pulmonary artery pressure (mPAP) and right ventricular systolic pressure (RVSP), Fulton's Index of cardiac hypertrophy and histological assessments of pulmonary vascular remodelling, pulmonary oedema, inflammation and fibrosis, and right ventricular fibrosis. In addition, these assessments showed that NTP42 inhibited these effects at least to a similar extent relative to the SOC drugs Sildenafil, Macitentan, Selexipag and Riociguat. Notably, unlike most of the PAH SOCs, NTP42 had no adverse effects on liver weight and or on hepatic histopathology. Importantly, NTP42 had no effects on either the systemic mean arterial pressure (mAP) or heart rate (HR). Furthermore, while abundant expression of the target TP was noted in numerous cell and tissue types of both cardiac and pulmonary tissue, there were highly significant upregulations of TP expression observed following PAH-induction (RV, &amp;gt;2-fold, p=0.0002). Conclusions Taken together, these data demonstrate that NTP42 significantly attenuates MCT-induced PAH and to a similar or greater extent relative to market leader PAH SOC drugs. Notably, we reveal that expression of the TP, the target receptor for NTP42, was shown to be highly significantly upregulated throughout the cardiopulmonary system, validating the potential importance of this largely ignored PAH target ripe for pharmaceutical intervention. Funding Acknowledgement Type of funding sources: Public grant(s) – EU funding. Main funding source(s): EU Horizon 2020 SME Instrument

Prototype for Knee-load Relief through Ischiatic Support

Objective: The objective of this work was to develop a passive exoskeleton prototype for the relief of knee-load employing ischiatic body weight support. Methods and materials: A functional prototype was developed and tested with three volunteers to analyze its potential effectiveness and effects on gait kinematics. The performance of the prototype was assessed using motion capture and pressure mapping systems, and a testing bench for the study of ischiatic body weight. Results and discussion: The results of the tests indicate that the prototype allows reducing the load supported by the knees and does not have a significant effect on the kinematics of the hip and knee joints. The process allowed the designers to identify possibilities of improvement mainly on reducing the restrictions imposed by the prototype to the motion of the ankles, especially on the midstance of the support phase. Conclusions: The passive exoskeleton prototype developed for ischiatic body weight support allows setting different percentages of knee-load relief. The prototype does not have a significant effect on the kinematics of the hip and knee joints. Nevertheless, improvements must be performed to reduce the restrictions to the motion of the ankles.

Understanding the role of foot biomechanics on regional foot orthosis deformation in flatfoot individuals during walking

BackgroundFoot orthoses (FOs) are one of the most common interventions to restore normal foot mechanics in flatfoot individuals. New technologies have made it possible to deliver customized FOs with complex designs for potentially better functionalities. However, translating the individuals’ biomechanical needs into the design of customized FOs is not yet fully understood. Research questionOur objective was to identify whether the deformation of customized FOs is related to foot kinematics and plantar pressure during walking. MethodsThe kinematics of multi-segment foot and FOs contour were recorded together with plantar pressure in 17 flatfoot individuals while walking with customized FOs. The deformation of FOs surface was predicted from its contour kinematics using an artificial neural network. Plantar pressure map and deformation were divided into five anatomically based regions defined by the corresponding foot segments. Forward stepwise linear mixed models were built for each of the four gait phases to determine the feet-FOs interaction. ResultsIt was observed that some associations existed between foot kinematics and pressure with regional FOs deformation. From heel-strike to foot-flat, longitudinal arch angle was associated with FOs deformation in forefoot. From foot-flat to midstance, rearfoot eversion accounted for variation in the deformation of medial FOs regions, and forefoot abduction for the lateral regions. From midstance to heel-off, rearfoot eversion, longitudinal arch angle, and plantar pressure played significant role in deformation. Finally, from heel-off to toe-off, forefoot adduction affected the deformation of forefoot and midfoot. SignificanceThis study provides guidelines for designing customized FOs. Flatfoot individuals with excessive rearfoot eversion or very flexible medial arches require more support on medial FOs regions, while the ones with excessive forefoot abduction need the support on lateral regions. However, a compromise should be made between the level of support and the level of increase in plantar pressure to avoid stress on foot structures.

A rapid method for pressure-mapping ultrasound fields using a moving hydrophone

Medical ultrasound transducers are commonly characterized in well-controlled water tanks using miniature pressure-calibrated hydrophones. Spatial beam dimensions of the ultrasound field can be quantified by positioning hydrophones in a 2D plane where acoustic waveforms are acquired at closely spaced locations. However, even when using automated computer-controlled positioning, this technique is time consuming if the hydrophone is repositioned and allowed to come to rest at each location where pressure measurements are desired. Here we present a novel technique where acoustic waveforms are acquired while the hydrophone is in motion. The transducer under test is pulsed at a rate which, depending on the hydrophone speed, determines the spatial resolution of the pressure map. Applying this technique results in substantial time savings and allows larger beam areas to be more accurately mapped. Limitations, such as translation stage motor noise and pulse length, are discussed and examples are presented which demonstrate the ability to rapidly characterize a variety of ultrasound transducer types.

Trends and projection of heavy snowfall in Hokkaido, Japan as an application of self-organizing map

AbstractThis paper showed the frequency of local-scale heavy winter snowfall in Hokkaido, Japan, its historical change, and its response to global warming using self-organizing map (SOM) of synoptic-scale sea-level pressure anomaly. Heavy snowfall days were here defined as days when the snowfall exceeded 10 mm in water equivalent. It was shown that the SOMs can be grouped into three categories for heavy snowfall days: 1) a passage of extratropical cyclones to the south of Hokkaido, 2) a pressure pattern between the Siberian high and the Aleutian low, and 3) a low-pressure anomaly just to the east of Hokkaido. Groups 1 and 2 were associated with heavy snowfall in Hiroo (located in southeastern Hokkaido) and in Iwamizawa (western Hokkaido), respectively, and heavy snowfall in Sapporo (western Hokkaido) was related to Group 3. The large-ensemble historical simulation reproduced the observed increasing trend in Group 2 and future projection revealed that Group 2 was related to a negative phase of the Western Pacific pattern and the frequency of this group would increase in the future. Heavy snowfall days associated with SOM Group 2 would also increase due to the increase in water vapor and preferable weather patterns in global warming climate, in contrast to the decrease of heavy snowfall days in other sites associated with SOM Group 1.

Chair design for older immobile people: Comparison of pressure mapping and manual handling outcomes

The number of older adults unable to transfer or ambulate independently is increasing. High support chairs enable people experiencing loss of mobility to be mobile, but current chair designs are associated with global functional loss and pressure ulcers. This pilot study compared the functionality of a traditional design high support chair to a new design of motorised high support chair: 1) a motion laboratory study compared joint angles and pressure at the hip, knee, ankle, elbow and spine when pushing each chair, and 2) a pressure mapping study compared the interface pressure when older people with limited mobility used the chairs. Significant reduction in joint angles for the person pushing the chair (degree difference range −3.6 to 14.2) and decreased seated pressure (w/kg difference range −0.2 to 2.1) for the seated user were identified for the motorised chair. Longitudinal investigations are required to determine if the significant differences identified in this pilot study result in less manual handling injuries and pressure areas.

Evaluating load distribution at the bearing-housing interface using thin film pressure sensors

The objective of this investigation was to utilize thin film pressure sensors to evaluate the pressure distribution between rolling element bearings and a housing. A test rig was constructed to place thin film sensors around the perimeter of a test bearing inside of a housing. High precision drive shafts were manufactured that produce a light and heavy interference fit with each of the test bearings. Pressure map results are used to evaluate the effect of internal clearance on the load distribution of different bearing types. The thin film sensor system was also used to investigate the circumferential load distribution on the housing. The presented apparatus and test method could be used to validate bearing fit selection and housing design.

A Proposal of Implementation of Sitting Posture Monitoring System for Wheelchair Utilizing Machine Learning Methods.

This paper presents a posture recognition system aimed at detecting sitting postures of a wheelchair user. The main goals of the proposed system are to identify and inform irregular and improper posture to prevent sitting-related health issues such as pressure ulcers, with the potential that it could also be used for individuals without mobility issues. In the proposed monitoring system, an array of 16 screen printed pressure sensor units was employed to obtain pressure data, which are sampled and processed in real-time using read-out electronics. The posture recognition was performed for four sitting positions: right-, left-, forward- and backward leaning based on k-nearest neighbors (k-NN), support vector machines (SVM), random forest (RF), decision tree (DT) and LightGBM machine learning algorithms. As a result, a posture classification accuracy of up to 99.03 percent can be achieved. Experimental studies illustrate that the system can provide real-time pressure distribution value in the form of a pressure map on a standard PC and also on a raspberry pi system equipped with a touchscreen monitor. The stored pressure distribution data can later be shared with healthcare professionals so that abnormalities in sitting patterns can be identified by employing a post-processing unit. The proposed system could be used for risk assessments related to pressure ulcers. It may be served as a benchmark by recording and identifying individuals’ sitting patterns and the possibility of being realized as a lightweight portable health monitoring device.

Tool interface pressure during the forming of model composite corners

A new experimental technique is proposed to measure the pressure gradient in corner laminates with the aim of guiding manufacturing practices that can produce composites laminates to the desired thickness. A pressure mapping sensor was placed between a metal mould tool and a silicone sheet that acts as an idealised composite part. The compaction pressure loss in internal corners and rise in external corners is reported for the first time, covering a part thickness to radius ratio of 0.2 to 0.8 in the corner. A conclusive trend was observed in internal corners, where the pressure drop increases proportionally with the thickness to radius ratio. The sensor thickness, bulk, and contact with the tool created difficulties in measuring the true extent of the pressure rise for external corners. Stretchable thin film sensors might provide better alternatives for future studies looking to investigate pressure gradients in doubly curved geometries.

Biomechanical Analysis of Segmental Medial Meniscal Transplantation in a Human Cadaveric Model

Background: Meniscal deficiency has been reported to increase contact pressures in the affected tibiofemoral joint, possibly leading to degenerative changes. Current surgical options include meniscal allograft transplantation and insertion of segmental meniscal scaffolds. Little is known about segmental meniscal allograft transplantation. Purpose: To evaluate the effectiveness of segmental medial meniscal allograft transplantation in the setting of partial medial meniscectomy in restoring native knee loading characteristics. Study Design: Controlled laboratory study. Methods: Ten fresh-frozen human cadaveric knees underwent central midbody medial meniscectomy and subsequent segmental medial meniscal allograft transplantation. Knees were loaded in a dynamic tensile testing machine to 1000 N for 20 seconds at 0°, 30°, 60°, and 90° of flexion. Four conditions were tested: (1) intact medial meniscus, (2) deficient medial meniscus, (3) segmental medial meniscal transplant fixed with 7 meniscocapsular sutures, and (4) segmental medial meniscal transplant fixed with 7 meniscocapsular sutures and 1 suture fixed through 2 bone tunnels. Submeniscal medial and lateral pressure-mapping sensors assessed mean contact pressure, peak contact pressure, mean contact area, and pressure mapping. Two-factor random-intercepts linear mixed effects models compared pressure and contact area measurements among experimental conditions. Results: The meniscal-deficient state demonstrated a significantly higher mean contact pressure than all other testing conditions (mean difference, ≥0.35 MPa; P < .001 for all comparisons) and a significantly smaller total contact area as compared with all other testing conditions (mean difference, ≤140 mm2; P < .001 for all comparisons). There were no significant differences in mean contact pressure or total contact area among the intact, transplant, or transplant-with-tunnel groups or in any outcome measure across all comparisons in the lateral compartment. No significant differences existed in center of pressure and relative pressure distribution across testing conditions. Conclusion: Segmental medial meniscal allograft transplantation restored the medial compartment mean contact pressure and mean contact area to values measured in the intact medial compartment. Clinical Relevance: Segmental medial meniscal transplantation may provide an alternative to full meniscal transplantation by addressing only the deficient portion of the meniscus with transplanted tissue. Additional work is required to validate long-term fixation strength and biologic integration.

A tight-binding atomistic approach for point defects and surfaces applied to the o-Al[formula omitted]Co[formula omitted] quasicrystalline approximant

We implemented an N-body potential for the Al–Co interactions and applied it to the o-Al13Co4 quasicrystalline approximant. We show its ability to model this complex compound in the presence of point and extended defects (atomic vacancies and surfaces). The importance of stress relaxation in vacancy formation is highlighted through the mapping of local pressures in the bulk compound. Thanks to the many body character of the potential, the surfaces could be investigated which was not done before in atomistic studies of this complex phase. Our classical simulations point up the competition between preserving the cohesion by minimizing the number of broken bonds and avoiding the presence of Co atoms at the surface. This study opens the way to large scale simulations of phenomena involving complex metallic alloys in particular at their surfaces.

Earth Pressures Mobilised in Dry Sand with Active Rigid Retaining Wall Movement

A series of centrifuge tests was conducted to explore the earth pressures mobilised in loose and dense sand for a complete set of active movement modes of a rigid retaining wall: rotation about the base, translation and rotation about the top. Earth pressures behind the wall were measured by a Tekscan pressure mapping system. This paper reveals that earth pressures at all depths decrease simultaneously with active wall rotation about the base, while those in shallow layers can increase with active wall translation and rotation about the top. A linkage between earth pressures and shear strains was built as a simplified constitutive law, together with deformation mechanisms, allowing designers to predict flexible wall deflections during construction as well as ultimate collapse.

Earth pressures mobilised in dry sand with active rigid retaining wall movement

A series of centrifuge tests was conducted to explore the earth pressures mobilised in loose and dense sand for a complete set of active movement modes of a rigid retaining wall: rotation about the base, translation and rotation about the top. Earth pressures behind the wall were measured by a Tekscan pressure mapping system. This paper reveals that earth pressures at all depths decrease simultaneously with active wall rotation about the base, while those in shallow layers can increase with active wall translation and rotation about the top. A linkage between earth pressures and shear strains was built as a simplified constitutive law, together with deformation mechanisms, allowing designers to predict flexible wall deflections during construction as well as ultimate collapse.

The Effect of a Short Foot Eccentric Endurance Exercise on Foot Center of Pressure: A Pilot study

PURPOSE: This study aimed to investigate the effect of a 5-week short foot eccentric endurance training program on the foot center of pressure measures in healthy university graduate students.METHODS: Eleven healthy students between the ages of 18 and 35 years (n=11, 3 males, 8 females; mean age 26.5±2.5 years; BMI 23.9±2.6 kg/m&lt;sup&gt;2&lt;/sup&gt;) were included in the study. The participants volunteered in a 5-week progressive eccentric contraction short foot exercise program performed three times per week. The main outcome pressure measurements pre- and post-intervention in static double leg stance were measured using a MatScan&lt;sup&gt;®&lt;/sup&gt; Pressure Mapping System.RESULTS: Statistically significant differences were found in the base of support (&lt;i&gt;p&lt;/i&gt;=.002, ES=2.59), time to boundary (&lt;i&gt;p&lt;/i&gt;=.024, ES=1.63), and overall minima measures (&lt;i&gt;p&lt;/i&gt;=.05, ES=1.36) pre- and post-intervention.CONCLUSIONS: A 5-week progressive eccentric contraction short foot exercise program significantly decreased the center of pressure excursion measures, demonstrating improved postural control.

Noninvasive quantification of cerebrovascular pressure changes using 4D Flow MRI.

Hemodynamic alterations are indicative of cerebrovascular disease. However, the narrow and tortuous cerebrovasculature complicates image-based assessment, especially when quantifying relative pressure. Here, we present a systematic evaluation of image-based cerebrovascular relative pressure mapping, investigating the accuracy of the routinely used reduced Bernoulli (RB), the extended unsteady Bernoulli (UB), and the full-field virtual work-energy relative pressure ( WERP) method. Patient-specific in silico models were used to generate synthetic cerebrovascular 4D Flow MRI, with RB, UB, and WERP performance quantified as a function of spatiotemporal sampling and image noise. Cerebrovascular relative pressures were also derived in 4D Flow MRI from healthy volunteers ( ), acquired at two spatial resolutions (dx = 1.1 and 0.8 mm). The in silico analysis indicate that accurate relative pressure estimations are inherently coupled to spatial sampling: at dx = 1.0 mm high errors are reported for all methods; at dx = 0.5 mm WERP recovers relative pressures at a mean error of 0.02 ± 0.25 mm Hg, while errors remain higher for RB and UB (mean error of -2.18 ± 1.91 and -2.18 ± 1.87 mm Hg, respectively). The dependence on spatial sampling is also indicated in vivo, albeit with higher correlative dependence between resolutions using WERP (k = 0.64, R2 = 0.81 for dx = 1.1 vs. 0.8 mm) than with RB or UB (k = 0.04, R2 = 0.03, and k = 0.07, R2 = 0.07, respectively). Image-based full-field methods such as WERP enable cerebrovascular relative pressure mapping; however, accuracy is directly dependent on utilized spatial resolution.