Pressure Spikes Research Articles

Surgical repair of large cyclodialysis clefts.

To describe a new surgical technique to effectively close large (>180 degrees) cyclodialysis clefts. Our method involves the use of procedures commonly associated with repair of retinal detachment and complex cataract extraction: phacoemulsification with placement of a capsular tension ring followed by pars plana vitrectomy and gas tamponade with light cryotherapy. We also used anterior segment optical coherence tomography (OCT) as a noninvasive mechanism to determine the extent of the clefts and compared those results with ultrasound biomicroscopy (UBM) and gonioscopy. This technique was used to repair large cyclodialysis clefts in 4 eyes. All 4 eyes had resolution of hypotony and improvement of visual acuity. One patient had an intraocular pressure spike requiring further surgical intervention. Anterior segment OCT imaging in all 4 patients showed a more extensive cleft than UBM or gonioscopy. This technique is effective in repairing large cyclodialysis clefts. Anterior segment OCT more accurately predicted the extent of each cleft, while UBM and gonioscopy both underestimated the size of the cleft.

Stratified effect of continuous bi-Gaussian rough surface on lubrication and asperity contact

Continuous bi-Gaussian reconstruction approach is applied to two simulated pure bi-Gaussian and four real worn surfaces. It is compared with segmented bi-Gaussian, ISO 13565-3 bi-Gaussian and Johnson reconstruction approaches in terms of surface property, lubrication and asperity contact. The results show that the continuous approach reproduces a surface in good agreement with the original in terms of maximum fluid pressure, cavitation ratio and lift load, because it serves as a concise way to achieve the high resemblance of surface property with the original surface as similar to the ISO approach. The segmented approach sometimes loses efficiency, and the Johnson approach generates a single-stratum surface with steep valleys, inducing large pressure spikes, large cavitation zone and large lift load. The superiority of the continuous approach can be drawn from the contact mechanics study on contact pressure and real contact area.

Clinical evaluation of a trabecular microbypass stent with phacoemulsification in patients with open-angle glaucoma and cataract.

PurposeTo evaluate the safety and efficacy of the iStent trabecular microbypass stent in combination with cataract surgery in patients with open-angle glaucoma (OAG).MethodsRetrospective, consecutive case series from October 2012 to December 2015 with no exclusion criteria. The series comprised of 350 eyes with OAG and cataract. Data were collected both preoperatively and postoperatively at day 1 week 1, months 1, 3, 6, 12, 18, and 24. Data included intraocular pressure (IOP), number of glaucoma medications, visual acuity, the incidence of postoperative IOP pressure spikes of greater than ≥15 mmHg at any time point, and need for additional surgery.ResultsThe mean preoperative IOP was 19.13±6.34 mmHg. At 2 years postoperation, mean IOP was 15.17±3.53 mmHg (P<0.0001). The mean number of glaucoma medications was 1.19±1.00 preoperatively and 0.61±0.96 (P<0.0001) at 2 years postoperation. At 1 day postoperatively, 31 eyes (12.4%) experienced an IOP increase of 15 mmHg above their baseline IOP that responded to topical therapy. Two patients required additional tube shunt surgery.ConclusionThe insertion of the iStent trabecular microbypass stent in combination with cataract surgery effectively lowers IOP in OAG patients. The magnitude of IOP reduction was more significant in patients with higher preoperative pressure. Medication use was also significantly reduced postoperatively. The safety profile appears favorable with a low rate of IOP spikes and only two eyes (<1%) requiring additional surgery.

Material point methods applied to one-dimensional shock waves and dual domain material point method with sub-points

Using a simple one-dimensional shock problem as an example, the present paper investigates numerical properties of the original material point method (MPM), the generalized interpolation material point (GIMP) method, the convected particle domain interpolation (CPDI) method, and the dual domain material point (DDMP) method.For a weak isothermal shock of ideal gas, the MPM cannot be used with accuracy. With a small number of particles per cell, GIMP and CPDI produce reasonable results. However, as the number of particles increases the methods fail to converge and produce pressure spikes. The DDMP method behaves in an opposite way. With a small number of particles per cell, DDMP results are unsatisfactory. As the number of particles increases, the DDMP results converge to correct solutions, but the large number of particles needed for convergence makes the method very expensive to use in these types of shock wave problems in two- or three-dimensional cases.The cause for producing the unsatisfactory DDMP results is identified. A simple improvement to the method is introduced by using sub-points. With this improvement, the DDMP method produces high quality numerical solutions with a very small number of particles.Although in the present paper, the numerical examples are one-dimensional, all derivations are for multidimensional problems. With the technique of approximately tracking particle domains of CPDI, the extension of this sub-point method to multidimensional problems is straightforward. This new method preserves the conservation properties of the DDMP method, which conserves mass and momentum exactly and conserves energy to the second order in both spatial and temporal discretizations.

Multigrid method for the solution of EHL line contact with bio-based oils as lubricants

Abstract The paper presents Elastohydrodynamic lubrication line contact problem with bio-based oil as lubricants for an isothermal case. The fast convergence method for the solution of Elastohydrodynamic lubrication line contact problem with seed oil as lubricant is analyzed using Multigrid, Multilevel Multi-Integration with the influence of different load and speed. The result shows that the use of these oils has the potential to substitute the function of common lubricant so as to reduce dependence on conventional oil lubricants. The results obtained are comparable and the pressure spikes are smooth as compared to the earlier findings which are shown in terms of graphs and tables.

Predicting Flameholding for Hydrogen and Natural Gas Flames at Gas Turbine Premixer Conditions

Lean-premixed gas turbines are now common devices for low emissions stationary power generation. By creating a homogeneous mixture of fuel and air upstream of the combustion chamber, temperature variations are reduced within the combustor, which reduces emissions of nitrogen oxides. However, by premixing fuel and air, a potentially flammable mixture is established in a part of the engine not designed to contain a flame. If the flame propagates upstream from the combustor (flashback), significant engine damage can result. While significant effort has been put into developing flashback resistant combustors, these combustors are only capable of preventing flashback during steady operation of the engine. Transient events (e.g., auto-ignition within the premixer and pressure spikes during ignition) can trigger flashback that cannot be prevented with even the best combustor design. In these cases, preventing engine damage requires designing premixers that will not allow a flame to be sustained. Experimental studies were conducted to determine under what conditions premixed flames of hydrogen and natural gas can be anchored in a simulated gas turbine premixer. Tests have been conducted at pressures up to 9 atm, temperatures up to 750 K, and freestream velocities between 20 and 100 m/s. Flames were anchored in the wakes of features typical of premixer passageways, including cylinders, steps, and airfoils. The results of this study have been used to develop an engineering tool that predicts under what conditions a flame will anchor, and can be used for development of flame anchoring resistant gas turbine premixers.

Intraocular Pressure Spikes after Aflibercept Intravitreal Injections

The objective of this study was to assess the intraocular pressure (IOP) as well as the anatomical modifications of the anterior segment following an aflibercept injection. Patients underwent an aflibercept intravitreal injection (IVI) (0.05 ml) with a 30.5-gauge needle and an antireflux system. IOP was assessed before injection (T0), immediately after (T1), and 5 min (T5), 15 min (T15), and 45 min (T45) after the IVI. Before the IVI and immediately after the T1 measurement, a PENTACAM® acquisition was used to evaluate the anterior chamber parameters (anterior chamber volume, depth and measure of the iridocorneal angle). At T0, IOP was 12.9 ± 1.3 mm Hg. IOP significantly increased after IVI (42.7 ± 3 mm Hg, p < 0.001). IOP returned to baseline at T45 (13.0 ± 1.2 mm Hg, p = 0.877). Anterior chamber volume decreased after IVI (160.6 vs. 168.3 mm³, p = 0.002). No significant changes were found for iridocorneal angle and anterior chamber depth. Aflibercept IVI causes an acute increase in IOP over a short period without iridocorneal angle closure.

The rationale for a mid-scala electrode array

Today increasing numbers of cochlear implant candidates have residual hearing that can be aided and hence is worth trying to preserve. This means that surgical technique and electrode array design must be adapted to minimize trauma. Wide opening of the round window is often preferred to reduce drill related trauma and to avoid pressure spikes during electrode array insertion. A recent meta-analysis suggested that there is no significant correlation between hearing preservation and either insertion depth or scala position. However, a slow insertion speed of at least 30seconds was associated with better hearing preservation. An electrode design is proposed that targets the middle of the scala tympani. This minimizes frictional forces from either lateral or medial wall during insertion and imposes less static pressure on cochlear structures following insertion. The flexibility to insert via the round window requires a 0.7-mm maximum dimension at the proximal end of the array. Micro-anatomical analysis by micro-CT indicated that a 420-degree insertion depth was optimal between cochlear coverage and available space within the scala tympani. Physical measurements showed that mean insertion forces remained below 10mN during insertion. A series of 20 human temporal bone insertions found a mean insertion depth of 400 degrees with no scala dislocations. Six clinical series, in total 94 cases, found postoperative hearing in 81% of cases with a mean loss of 12dB compared to preoperative levels. Speech understanding out to one year post-fitting trended better for a mid-scala design group than for a straight electrode array group; although the differences were not statistically significant. A mid-scala array design appears able to be inserted with minimal trauma, to return a predictable insertion depth across various sizes of cochleae and to support reasonable levels of speech understanding without relying on residual hearing.

Acute intoxication of four individuals following use of the synthetic cannabinoid MAB-CHMINACA

Context: The largest group of new psychoactive substances (NPS) are synthetic cannabinoids (SC). Those that become controlled are immediately replaced by new uncontrolled substances. The recent resurgence of the NPS market in Poland resulted in a further amendment to the Drug Addiction Counteraction Act. This resulted in significant changes in the composition of “legal high” preparations, and consequently a large outbreak of intoxications with SC was reported in Poland at the beginning of July 2015.Case details: This paper describes the circumstances of intoxication and toxicological findings in an acute intoxication of four individuals with MAB-CHMINACA. They each smoked tobacco mixed with powder from the package with the description “AM-2201”. The adverse effects observed in the individuals included vomiting, seizures, limb twisting, muscle tremors, aggression, agitation, slurred speech, blood pressure spikes, wheezing, respiratory failure and losses of consciousness. Blood samples were analysed using liquid chromatography with mass spectrometry. Results from analysis performed on the blood samples showed the presence of MAB-CHMINACA, while AM-2201 was not found (LOD 0.09 ng/mL). The determined concentrations were 5.2, 1.3, 1.7 and 14.6 ng/mL, respectively. The analyses of the blood did not reveal any other substances (excluding medicines given in hospital).Conclusion: The presented cases show the health risks associated with MAB-CHMINACA use and confirm that “legal high” preparations do not always contain a substance represented on the package.

Electromagnetic Wave Excitation, Propagation, and Absorption in High Current Storage Rings

We analyze a variety of electromagnetic effects in storage rings with extremely high currents. Specifically, we discuss our experience in the operation of the PEP-II (SLAC B-factory). We present some outstanding and sometimes unpredictable effects of the behavior of electromagnetic waves excited by intense beams inside a vacuum chamber in storage rings. Although the impedance of the rings is usually designed to be small, intense high-current beams can still generate significant microwave power. This power can be enough to damage vacuum beam chamber elements, which may absorb electromagnetic waves. The most sensitive elements are RF seals, vacuum valves, shielded bellows, beam position monitor buttons, and ceramic tiles. Additionally, microwave heating leads to vacuum pressure spikes or even vacuum pressure instabilities that brings high detector background. Resonance excitation of the electromagnetic field may lead to a very high electric component amplitude that can cause breakdowns leading to sparks and discharges. Finally, high-power electromagnetic waves can be responsible for beam instabilities in the ring. Proper absorption of these generated waves may eliminate these effects. We feel our experience will be helpful in the design of new high current synchrotron light sources and storage rings.

Earth Pressure Measurements Using Tactile Pressure Sensors in a Saturated Sand During Static and Dynamic Centrifuge Testing

The performance of tactile pressure sensors used in centrifuge testing involving pressure measurements of laterally-spreading soils against a large, rigid, foundation element is evaluated. The tactile pressure sensor measurements were consistent with hydrostatic pressures measured by pressure transducers under most testing conditions, and agreed with at-rest geostatic pressures provided that the measurements were made against a rigid surface (i.e., no relative soil-structure movement). However, measured pressures decreased substantially under some conditions when shearing forces were transmitted to the pressure sensors. Dynamic pressures (minima and maxima pressure spikes) measured by the tactile pressure sensors differed from pressures measured by pore pressure transducers and, when uncorrected, they were considered unreliable. A dynamic pressure correction was developed to address this issue. Lastly, a comprehensive verification testing program was recommended for each unique centrifuge test configuration to improve interpretation of pressure sensor output.

Study of Variation in Intraocular Pressure Spike (IOP) Following Nd- YAG Laser Capsulotomy

Posterior Capsular Opacifications (PCO) is a frequent complication of cataract surgery following posterior chamber intraocular lens implantation. Nd -Yag laser capsulotomy is the treatment of choice for PCO and is known to be associated with complications like Raised Intraocular Pressure (IOP), Intraocular lens pitting, intraocular lens cracks, cystoid macular oedema, retinal detachment, corneal burns. Raised IOP is the most common complication and prescribing anti-glaucoma drugs post capsulotomy is a common practise. Our study helps us to anticipate the post procedural IOP rise in specific patients and treat only selected group of patients with anti- glaucoma medications. To study and correlate the effect of energy used and number of shots with post procedural IOP spike following Nd-YAG laser capsulotomy cases. All patients with PCO presenting to Ophthalmology Out Patient Department at Sri Siddhartha Medical College between November 2014 to November 2015 were included. All the patients with glaucoma, uveitis and high myopia were excluded from the study. Data relevant to history, ocular examination and IOP were recorded. Significant correlation of IOP spike with the number of Nd- YAG Laser shots delivered was found by One-way ANOVA Post-Hoc Tukeys Test. The p-value was significant for shots more than 40, provided the energy was restricted to 20 mJ and below. Correlation of energy with IOP spike was not significant as found by One-way ANOVA, Post-Hoc Tukey test. Predictability of 2 hours post-procedure IOP regarding persistent IOP rise was significant. It was observed that all pseudophakic patients may not require anti-glaucoma medication pre, or post Nd YAG laser capsulotomy. Only patients who required more than 40 shots during the procedure would need a close observation and if persistent rise is documented, ocular hypotensives may be advised.

Оптимизация параметров энергосберегающего гидропривода механизма поворота манипулятора лесной машины

Presented multifactor optimization for studying the simultaneous effect of several factors to find the optimal combination of factors that enable to accumulate as much energy per operating cycle of the mechanism of rotation of the manipulator column while reducing pressure spikes and fluctuations of the load when changing modes. On the basis of preliminary estimates of computer experiments were chosen two parameters of fluid accumulator that affect the efficiency of energy-saving hydraulic drive: a working volume of fluid and battery charge pressure of the gas.

A CFD and experimental study on cavitation in positive displacement pumps: Benefits and drawbacks of the ‘full’ cavitation model

ABSTRACTTo fill the gap in the literature in terms of numerical studies of positive displacement (PD) pumps in a cavitating condition, a comprehensive and transient computational fluid dynamics (CFD) model of a PD pump, simulating the cavitation arising during the suction stroke, was created. The ‘full’ cavitation model was utilized to study its capability on PD pump cavitation. A set of three plunger speeds were simulated. Using the highest plunger speed, an assessment was made of the effect of 1.5, 3, 4.5 and 15 parts per million (ppm) of air mass fraction on pump performance and cavitation. An experimental test rig, replicating the CFD model, was designed and built in order to validate the numerical model and find its weaknesses. CFD modeled, in a consistent way, the fluid dynamics phenomena related to cavitation (the chamber pressure approaching the vapor pressure, the vaporization/condensation and the pressure spike occurrence at the end of the suction stroke marking the end of cavitation). On the other hand the CFD pressure trends calculated appeared stretched along the time axis with respect to the experimental data, and this highlighted issues in the multiphase and cavitation models: the vaporization/condensation rate calculated by CFD did not follow the real dynamics correctly because the non-condensable gas expansion was overestimated. This was seen when comparing the CFD/experimental results where the simulated pressure drop gradient at the beginning of the suction stroke and the pressure peaks as the valve closed exhibited a delay in their occurrence. The simulation results were sensitive to the dissolved air mass fraction as the delay depended on the amount of air dissolved in the water. Although the influence of the air mass fraction was considered consistent, the 3 ppm CFD case was the closest to the experimental results, whereas the analyst expected the 15 ppm case to be more accurate.

Focused Ultrasound and Lithotripsy.

Shock wave lithotripsy has generally been a first choice for kidney stone removal. The shock wave lithotripter uses an order of microsecond pulse durations and up to a 100 MPa pressure spike triggered at approximately 0.5-2 Hz to fragment kidney stones through mechanical mechanisms. One important mechanism is cavitation. We proposed an alternative type of lithotripsy method that maximizes cavitation activity to disintegrate kidney stones using high-intensity focused ultrasound (HIFU). Here we outline the method according to the previously published literature (Matsumoto et al., Dynamics of bubble cloud in focused ultrasound. Proceedings of the second international symposium on therapeutic ultrasound, pp 290-299, 2002; Ikeda et al., Ultrasound Med Biol 32:1383-1397, 2006; Yoshizawa et al., Med Biol Eng Comput 47:851-860, 2009; Koizumi et al., A control framework for the non-invasive ultrasound the ragnostic system. Proceedings of 2009 IEEE/RSJ International Conference on Intelligent Robotics and Systems (IROS), pp 4511-4516, 2009; Koizumi et al., IEEE Trans Robot 25:522-538, 2009). Cavitation activity is highly unpredictable; thus, a precise control system is needed. The proposed method comprises three steps of control in kidney stone treatment. The first step is control of localized high pressure fluctuation on the stone. The second step is monitoring of cavitation activity and giving feedback on the optimized ultrasound conditions. The third step is stone tracking and precise ultrasound focusing on the stone. For the high pressure control we designed a two-frequency wave (cavitation control (C-C) waveform); a high frequency ultrasound pulse (1-4 MHz) to create a cavitation cloud, and a low frequency trailing pulse (0.5 MHz) following the high frequency pulse to force the cloud into collapse. High speed photography showed cavitation collapse on a kidney stone and shock wave emission from the cloud. We also conducted in-vitro erosion tests of model and natural kidney stones. For the model stones, the erosion rate of the C-C waveform showed a distinct advantage with the combined high and low frequency waves over either wave alone. For optimization of the high frequency ultrasound intensity, we investigated the relationship between subharmonic emission from cavitation bubbles and stone erosion volume. For stone tracking we have also developed a non-invasive ultrasound theragnostic system (NIUTS) that compensates for kidney motion. Natural stones were eroded and most of the resulting fragments were less than 1 mm in diameter. The small fragments were small enough to pass through the urethra. The results demonstrate that, with the precise control of cavitation activity, focused ultrasound has the potential to be used to develop a less invasive and more controllable lithotripsy system.

Anterior Segment Nd:YAG Laser Procedures: to Study Intraocular Pressure Spikes and Their Prevention

Purpose: To find out quantum of increase in intraocular pressure (IOP) following anterior segment Nd:YAG laser procedures and extent to which this increase is preventable by different groups of anti- glaucoma drugs. Methods: Study design: Cross sectional, randomized, double blind analytical study. One hundred and seventy four eyes of 174 patients who underwent anterior segment Nd:YAG laser procedures {peripheral iridotomy (LPI)/ capsulotomy (YLC)}, using energy limited to 50 mJ, were randomized into five groups. Patients in group 1, 2, 3, 4 and 5 received topical Brimonidine tartarate 0.2%, oral Acetazolamide 250mg, topical Dorzolamide hydrochloride 2%, lubricating eye drops plus oral calcium tablets and topical Timolol maleate 0.5% respectively.Patients getting active topical drug were additionally given oral calcium and those getting oral active drug were given topical lubricating drops in a double blind manner. Intraocular pressure was measured at 1, 3, 5 and 24 hours post laser. Results: Rise of IOP from baseline to 1, 3, 5 or 24 hours was not found to be significant in any of the groups receiving ocular hypotensive drug (p>0.05). In the placebo group, the rise of IOP was significant only in one patient at 1, 3 and 5 hours post laser which came down to insignificant levels at 24 hours. Conclusion: Limiting the use of energy (< 50 mJ/ sitting) during Nd:YAG laser procedures may prevent post laser IOP spikes and obviate the use of ocular hypotensive drugs. In high risk cases, amongst the anti glaucoma drugs, a agonists can be prescribed.

Comparative Effectiveness of Three Prophylactic Strategies to Prevent Clinical Macular Edema after Phacoemulsification Surgery

To study the relationship of chemoprophylaxis and other factors with the occurrence of acute, clinical, postoperative macular edema. Retrospective cohort study. The drug regimens consisted of postoperative topical prednisolone acetate (PA) alone or with a nonsteroidal anti-inflammatory drug (NSAID) or intraoperative subconjunctival injection of 2 mg triamcinolone acetonide (TA) alone. Patients undergoing phacoemulsification at Kaiser Permanente, Diablo Service Area, Northern California, from 2007 through 2013. We identified incident macular edema diagnoses that had been recorded 5 to 120 days after phacoemulsification with visual acuity 20/40 or worse and evidence of macular thickening by optical coherence tomography. Odds ratios (ORs) and 95% confidence intervals (CIs) were obtained from logistic regression analysis, conditioned on the surgeon and adjusted for year, patient age and race, diabetic retinopathy status, other ocular comorbidities, systemic comorbidities, and posterior capsular rupture status. Incident rates of acute, clinical, postoperative macular edema. We confirmed 118 cases among 16 070 cataract surgeries (incidence, 0.73%). Compared with PA alone, the OR for the relationship of macular edema with PA+NSAID was 0.45 (95% CI, 0.21-0.95) and that for TA injection was 1.21 (95% CI, 0.48-3.06). The frequency of intraocular pressure spikes of 30 mmHg or more between postoperative days 16 and 45 was 0.6% in the topical PA group, 0.3% in the topical PA+NSAID group (P = 0.13), and 0.8% for the TA group (P = 0.52). Black race was associated with a risk of macular edema (OR, 2.86; 95% CI, 1.41-5.79). Adding a prophylactic NSAID to PA treatment was associated with a reduced risk of macular edema with visual acuity of 20/40 or worse. The risk and safety of TA injection were similar to those of PA alone. Further research is needed on the prognostic significance of postoperative macular edema, the role of prophylaxis, the risk among black people, and the effectiveness of depot medications.

Intra‐ocular pressure spike after Aflibercept and Ranibizumab intravitreal injections

PurposeSince anti‐VEGFsapproval, intra vitreous injections (IVI) represent a booming therapeutic delivery mode. Immediate ocular hypertension (OHT) induced is known after these IVIs. The purpose of this study is to compare the OHT after Aflibercept and Ranibizumab IVI.MethodsIn this prospective study, we compared 30 patients who received an Aflibercept IVI (0.05 mL) to 30 patients who received Ranibizumab for wet AMD. IVI were performed with a 30G needle pushed to the hilt with an anti‐reflux system. We measured intraocular pressure (IOP) using a portable aplanation tonometer PERKINS MK2 (Haag‐Streit, Koeniz, Switzerland) before injection (T0), immediately after IVI (T1), 5 minutes (T5), 15 minutes (T15) and 45 minutes (T45) after the IVI. IOP were compared by a t‐test.ResultsIn Aflibercept group, at T0, IOP was 13.4 mmHg+1.5. All patients had a significant increase in IOP at T1 (42.7 mmHg+3, p &lt; 0.001). At T5, IOP decreased but was still statistically higher than baseline IOP (23.6 mmHg+3.1, p &lt; 0.001). At T15, IOP returned to normal values but was higher than T0 (16.2mmHG + 2.1, p = 0.009). At T45, IOP was 13 mmHg + 1.2, with no significant difference from baseline (p = 0.65). In Ranibizumab group, baseline IOP was 13.8 mmHg + 1.1. IOP increased at T1 (45.6 mmHg + 2.2, p &lt; 0.001). At T5 and T15, IOP were still higher than baseline (24.6 mmHg + 2.2, p &lt; 0.001 and 17.9 + 1.5, p &lt; 0.001). At T45, IOP was 12.7 mmHg + 1.5, with no significant difference from baseline (p = 0.12). At each time measure, there is no statistically difference between two groups.ConclusionsAflibercept and Ranibizumab IVI induce an IOP spike for a short time. It seems to be equal between the two drugs and essentially related to the injected volume.

MON-PP018: Clinical Benefits of Pump Infusion Pressure Monitoring in Patients on Home Parenteral Nutrition

Rationale: Previous industry liaison resulted in a system to monitor infusion pressures [1]. This follow-on study aimed to identify the normal pressures in patients on home parenteral nutrition (HPN) and if these could aid in the diagnosis and treatment of catheter problems. Methods: 27 patients consented to be monitored. Pressures were recorded on the Micrel PN+ pump and exported to a secure server. Any HPN patient with a partial or total catheter occlusion had infusion pressures measured pre and post patency intervention. Results: 5910 infusions were recorded from 27 patients. Average infusion pressure was 0.29±0.1 bar (0.01 0.85) and did not increase with infusion rate (r = 0.3). 21 (78%) patients had open ended devices, 4 (15%) valved and 2 (7%) implanted ports. There was no difference between devices p = 0.91. There were 62 (1%) readings above the Upper Confidence Interval of 0.58 bar from 7 patients. 50 (81%) were from 1 patient with a valved port who reported multiple downstream occlusions. The alarms stopped after changing to a longer HuberTM needle, but high readings were still recorded. Comparison with readings from a non valved port revealed those from the valved port were significantly higher p < 0.0001. 1 patient with clinically confirmed thrombosis had a pressure spike of 0.67 bar 5 days before presenting with symptoms. Pressures in the preceding 6 months were within normal limits ( 0.58 bar). 6 patients (not on the Micrel PN+) had a partial or total occlusion. Mean preintervention pressure was 0.31±0.048 bar, post-intervention it was 0.2±0.055 bar, p = 0.007. Conclusion: This study describes the normal range of infusion pressures in patients on HPN and how these might be used in the diagnosis and treatment of catheter problems such as occlusion or thrombosis. Sudden spikes in infusion pressure may be indicative of an upcoming complication, however further study is needed.

Comparative study on the behavior of soil fills on rigid acrylic and flexible geotextile containers

Comparative study has been performed to investigate the behavior of dredged fills on rigid (Model 1) and flexible (Model 2) containers. The study was focused on the sedimentation of soil fills and the development of total stresses. Model 1 is made of an acrylic cylinder and Model two is a scale-size geotextile tube. Results indicate that for rigid containers, significant decrease of the sediment height is apparent during the dewatering process. On the other hand, because the geotextile is permeable, the water is gradually dissipated during the filling process on flexible containers. Hence, significant loss in the tube height is not apparent during the duration of the test. Pressure spikes are apparent on rigid containers during the filling process which can be attributed to the confining effect due to hydrostatic pressure. For the flexible containers, the pressure readings gradually increases with time during the filling process and normalize at the end on the filling stage. No pressure spikes were apparent due to the gradual dissipation of pore water pressure.