Effect of cell density on thrombin binding to a specific site on bovine vascular endothelial cells.

We studied thrombin binding to proliferating and confluent endothelial cells derived from bovine vascular endothelium. [125]thrombin was incubated with nonconfluent or confluent endothelial cells and both the total amount bound and the amount linked in a 77,000-dalton thrombin-cell complex were determined. Approximately 230,000 molecules of thrombin bound per cell in nonconfluent cultures compared to 12,800 molecules per cell in confluent cultures. Approximately 67,7000 thrombin molecules were bound in an apparently covalent complex, Mr = 77,000, with each cell in sparse cultures, whereas only 4,600 thrombin molecules per cell were bound in this complex with confluent cultures. Similar studies with [125I]thrombin and endothelial cells derived from bovine cornea revealed no difference either in the total amount of thrombin bound or in the amount bound in the 77,000-dalton complex using sparse or confluent cultures. When confluent vascular endothelial cultures were wounded, additional cellular binding sites for the 77,000-dalton complex with thrombin appeared within 24 h. A 237% increase in the amount of thrombin bound to these sites was induced by a wound which resulted in a 20% decrease in cell number in the monolayer. There was no significant increase in thrombin binding to other cellular sites at 24 h. These experiments provide evidence that the first change in thrombin binding after injury is an increase in the cellular sites involved in the 77,000-dalton complex, and suggest that thrombin binding to endothelial cells may be important in the vascular response to injury

Conjugacy classes of p-cycles of type D in alternating groups

We classify the conjugacy classes of p-cycles of type D in alternating groups. This finishes the open cases in arXiv:0812.4628. We also determine all the subracks of those conjugacy classes which are not of type D.Comment: Second paragraph of subsection 2.2 rewritten. 4-th sentence of subsection 2.4 rewritten. More explanations added in Remark 2.4. Lemma 2.5 and Corollary 2.7 added. Appendix removed and put it as Remark 3.1. Remark 3.2 (former 3.1) reorganized. References: [Da], [EGSS], [H], [IS] added, [GPPS] removed. Communications in Algebra (2014

The experience of adolescents participating in a randomised clinical trial in the field of mental health: a qualitative study

Background This descriptive study aimed to investigate adolescents’ motivations for participating in a randomised controlled trial (RCT), to explore the understanding that the young people had regarding a number of aspects of the trial design, to examine whether or not they found participation in the trial to be acceptable and what affected this, and to identify whether and how the young people felt that their participation in the RCT impacted on their experience of therapy and on therapeutic change. Methods Seventy-six adolescents who were taking part in a large-scale RCT to evaluate the clinical and cost effectiveness of psychological therapies for depression were interviewed at two time-points after completing therapy. The semi-structured interviews, which included a focus on the young people’s experience of the research study, were analysed using framework analysis. Results The vast majority of adolescents found it acceptable to participate in the clinical trial, and many agreed to participate for reasons of ‘conditional altruism’. However consent was often given without great understanding of the key elements of the trial, including the difference between treatment arms and the randomisation process. Although the adolescents were largely positive about their experiences from taking part, the study raises questions about whether clinical outcomes may be influenced by participation in the research elements of the trial. Conclusions Although adolescents are under-represented in clinical trials, those who do participate are generally positive about the experience; however, careful thought needs to be given to key elements of the trial design and the potential impact of the research participation on clinical outcomes

Haptic feedback from human tissues of various stiffness and homogeneity

This work presents methods for haptic modelling of soft and hard tissue with varying stiffness. The model provides visualization of deformation and calculates force feedback during simulated epidural needle insertion. A spring-mass-damper (SMD) network is configured from magnetic resonance image (MRI) slices of patient’s lumbar region to represent varying stiffness throughout tissue structure. Reaction force is calculated from the SMD network and a haptic device is configured to produce a needle insertion simulation. The user can feel the changing forces as the needle is inserted through tissue layers and ligaments. Methods for calculating the force feedback at various depths of needle insertion are presented. Voxelization is used to fill ligament surface meshes with spring mass damper assemblies for simulated needle insertion into soft and hard tissues. Modelled vertebrae cannot be pierced by the needle. Graphs were produced during simulated needle insertions to compare the applied force to haptic reaction force. Preliminary saline pressure measurements during Tuohy epidural needle insertion are also used as a basis for forces generated in the simulation

Devices for accurate placement of epidural Tuohy needle for Anaesthesia administration

The aim of this project is to design two sterile devices for epidural needle insertion which can measure in real time (i) the depth of needle tip during insertion and (ii) interspinous pressure changes through a pressure measurement device as the epidural needle is advanced through the tissue layers. The length measurement device uses a small wireless camera with video processing computer algorithms which can detect and measure the moving needle. The pressure measurement device uses entirely sterile components including a pressure transducer to accurately measure syringe saline in mmHg. The data from these two devices accurately describe a needle insertion allowing comparison or review of insertions. The data was then cross-referenced to pre-measured data from MRI or ultrasound scan to identify how ligament thickness correlates to our measured depth and pressure data. The developed devices have been tested on a porcine specimen during insertions performed by experienced anaesthetists. We have obtained epidural pressures for each ligament and demonstrated functionality of our devices to measure pressure and depth of epidural needle during insertion. This has not previously been possible to monitor in real-time. The benefits of these devices are (i) to provide an alternative method to identify correct needle placement during the procedure on real patients. (ii) The data describing the speed, depth and pressure during insertion can be used to configure an epidural simulator, simulating the needle insertion procedure. (iii) Our pressure and depth data can be compared to pre-measured MRI and ultrasound to identify previously unknown links between epidural pressure and depth with BMI, obesity and body shapes

A survey of trainees’ perspectives on epidural training in the United Kingdom

Background: Establishment of epidural analgesia is one of the most difficult technical skills in which to become proficient. We explored the current United Kingdom system of training in epidural insertion amongst trainee members of the Obstetric Anaesthetists’ Association (OAA). Methods: An electronic questionnaire was sent to 452 OAA trainee members in May 2012. Questions were based upon own personal experience, challenges currently faced and the use of epidural simulation to enhance training. Results: Although the majority felt ready and prepared when initially performing epidurals solo, 66% found the experience very stressful and 25% felt under considerable time pressure. Although senior support was readily available, 36% felt uncertain much of the time and 9% were unsure when to call for help. The European Working Time Directive was felt to have impacted upon training by 54% of respondents. 40% believe that there exists more challenging patients who require more experienced operators. Although 53% had used an epidural simulator previously, 84% would recommend its use for trainees and 49% would support simulator use as a compulsory element of training. Conclusions: In spite of changes to the medical profession, there appears to be a robust system of training for epidural analgesia. However, there still exists the need to reduce the impact of the learning curve upon workplace stress for trainees. Whether this involves increased direct supervision for more than just the bare minimum, structured feedback tools to enhance the supervisor/trainee experience or the use of high-fidelity epidural simulation remains to be seen

A pilot study to measure the insertion force of a Tuohy needle in a porcine spine. Abstract

There is a complex interplay of forces during an in-vivo epidural needle insertion and without accurate measurement of these forces it is difficult to create realistic epidural simulators. Previous models have relied upon expert user opinion rather than numerical force data, thus making validity difficult to assess. This pilot study presents the results of insertion pressures as a Tuohy needle is advanced through to the epidural space on a porcine cadaver. The primary aim was to test novel and innovative wireless pressure measuring and receiving equipment to facilitate a clinical trial in labouring parturients

MRI based patient-specific computer models of vertebrae, ligament and soft tissue with various density for epidural needle insertion simulation

Epidural simulations previously used layers of synthetic silicate materials to represent tissues. Graphical modelling has enabled visual representation of vertebrae and tissues. The accuracy with which previous simulators modelled the physical properties of tissue layer deformation, density distributions and reaction force during needle insertion has been lacking. Anatomical models are generally static, not considering individual differences between patients especially in obese. Our developed epidural simulator aimed to solve these issues. MRI scans of patients were taken after receiving epidural. The MRI and pressure measurement data was used to reconstruct a density model of the tissues, ligament and vertebrae taking into account the internal structure revealed by MRI intensities. Models were generated from MRI matching individual patients with tissue density varying throughout layers, matching the in vivo tissue. When patient MRI is not available a neural network is alternatively used to estimate the patient's ligament thicknesses with over 92% accuracy. A haptic device is incorporated with the graphics tissue model allowing anaesthetists to practice inserting a needle into the simulated epidural space. Changes in pressure, force and resistance to insertion can be felt as the needle pierces each layer of fat and ligament. The main problem with learning to perform epidural is the inability to see the needle location beneath the skin. MRI reveals the internal tissue structure so that anaesthetists can practice insertions on patient-specific models, visualising epidural space distance and needle obstructions. The developed simulator provides a realistic platform to practice and reduces risks of problems during in-vivo procedures

Quantification of the pressures generated during insertion of an epidural needle in labouring women of varying body mass indices

Objective: The primary aim of this study was to measure pressure generated on a Tuohy needle during the epidural procedure in labouring women of varying body mass indices (BMI) with a view of utilising the data for the future development of a high fi delity epidural simulator. High-fi delity epidural simulators have a role in improving training and safety but current simulators lack a realistic experience and can be improved. Methods: This study was approved by the National Research Ethics Service Committee South Central, Portsmouth (REC reference 11/SC/0196). After informed consent epidural needle insertion pressure was measured using a Portex 16-gauge Tuohy needle, loss-of-resistance syringe, a three-way tap, pressure transducer and a custom-designed wireless transmitter. This was performed in four groups of labouring women, stratifi ed according to BMI kg/m2: 18-24.9; 25-34.9; 35-44.9 and >=45. One-way ANOVA was used to compare difference in needle insertion pressure between the BMI groups. A paired t-test was performed between BMI group 18-24.9 and the three other BMI groups. Ultrasound images of the lumbar spine were undertaken prior to the epidural procedure and lumbar magnetic resonance imaging (MRI) was performed within 72h post-delivery. These images will be used in the development of a high fi delity epidural simulator. Results: The mean epidural needle insertion pressure of labouring women with BMI 18-24.9 was 461mmHg; BMI 25-34.9 was 430mmHg; BMI 35-44.9 was 415mmHg and BMI >=45 was 376mmHg, (p=0.52). Conclusion: Although statistically insignifi cant, the study did show a decreasing trend of epidural insertion pressure with increasing body mass indices