Mapping the Patient and Family Liaison Role in UK Helicopter Emergency Medical Services: A Service Evaluation.

OBJECTIVE: Patient and family liaison practitioners are a relatively recent addition to UK helicopter emergency medical services to support patients with their recovery. A service evaluation was completed that mapped the current provision of patient and family liaison practitioner roles in helicopter emergency medical services in the United Kingdom. METHODS: An online survey was distributed to key stakeholders involved with UK helicopter emergency medical service patient and family liaison practitioner roles. Quantitative survey results were described, and open-ended questions were analyzed using content analysis. RESULTS: Twenty UK helicopter emergency medical services responded to the survey. Nine of these services employ patient and family liaison practitioners with 4 additional helicopter emergency medical services planning to initiate the role. There is variation in the employment models used between the services. The patient and family liaison practitioner role provides important benefits to patients and their families, clinicians, and the helicopter emergency medical service. CONCLUSION: Nine UK helicopter emergency medical services employ patient and family liaison practitioners. This role benefits patients, their families, helicopter emergency medical service clinicians, and helicopter emergency medical service charities. Further research is required to understand how the role works in practice and to understand how to maximize the benefits to stakeholders.

The addition of a flange does not improve the pressure generated during cemented acetabular cup implantation.

Flanged acetabular cups were developed with the rationale that, at insertion, they would increase the pressure of the cement and improve penetration of cement into the acetabular bone. Various studies have been inconclusive regarding their effectiveness. In this work, we aimed to eliminate all confounding factors and measure the pressures generated during acetabular pressurization and cup implantation using a simplified steel acetabulum, high precision pressure transducers, proper surgical techniques and two acetabular cups, identical apart from the addition of a flange to one. It was found that the flanged acetabular component did not significantly increase the pressure in the acetabulum and in some cases reduced the pressures generated when compared to an unflanged cup. The addition of a flange did not reduce the pressure differential between the pole and the rim of the acetabulum, nor did it have a significant effect on pressure lost over the cup implantation period. It was concluded that flanged acetabular cups provide no significant improvement in the pressures generated in the acetabulum during acetabular cup implantation. It is hypothesized that the flange may be seen as a design feature intended to slow the insertion of the cup into the cement, thus requiring the surgeon to apply a larger load in order to correctly position the acetabular cup; in this way larger pressure will be generated.

Development of a smart-fit system for CPAP interface selection.

Continuous Positive Airway Pressure (CPAP) therapy is commonly prescribed for longstanding, acute cases of Obstructive Sleep Apnea (OSA) during which patients must wear a tight-fitting breathing mask overnight for the duration of the treatment. Because this condition frequently leads to the permanent use of CPAP masks, interface selection is a crucial factor influencing the treatment quality and effectiveness. Masks/interface selection is normally performed on a trial an error basis with clinicians informing their selection based on OSA-related factors with basic fitting feedback from patients. However, it is not uncommon for patients to abandon the treatment or request additional consultations due to ill-fitting CPAP mask with the main sources of discomfort being perceived air leakage and mask/strap overtightening leading to skin damage. This work introduces a novel system (Smart-Fit), for CPAP interface selection using advanced digital technologies, such as Reverse Engineering and Computational Modeling (Finite Element Analysis) which are paired to evaluate and determine the best fitting interface for each clinical case. The model simplifies the number of 3D facial landmarks to 12 and established that a 2 mm scan resolution is enough for accurate scans. The Von Mises stress map in ANSYS serves as an indicator of potential high-pressure areas, triggering the need for a chance of mask size. Current results indicate the Smart Fit System can enable a "best fit CPAP interface" to be selected considering individual's physical characteristics and existing CPAP interface configurations. The development of the Smart Fit System is an evolution compared to traditional CPAP interface selection approach, which optimizes the CPAP interface selection process.

Does vacuum mixing affect diameter shrinkage of a PMMA cement mantle during in vitro cemented acetabulum implantation?

Radiolucent lines on immediate postoperative cemented acetabular component radiographs between the PMMA bone cement mantle and bone are an indicator of an increased risk of early loosening. The cause of these lines has yet to be identified. Thermal and chemical necrosis, fluid interposition and cement shrinkage have all been suggested in the literature. The aim of the study reported here was to take an engineering approach - eliminating confounding variables present during surgery - to quantify the size of the interstice created by cement shrinkage when a 50 mm diameter flanged acetabular cup is implanted in a model acetabulum with a 52 mm hemispherical bore under controlled conditions using vacuum and non-vacuum mixed cement. Irrespective of the mixing method used, a significant interstice was created between the bone cement and the mock acetabulum. When the cement was mixed under vacuum the interstice created between the mock acetabulum and the cement mantle was 0.60 mm ± 0.09 mm; when the cement was mixed under non-vacuum conditions the interstice created was 0.39 mm ± 0.15 mm. Possible explanations for radiolucent lines are discussed.

Wear properties of poly-ether-ether-ketone bearing combinations under zero and cross shear kinematics in total knee arthroplasty.

Poly-ether-ether-ketone (PEEK), having shown favorable biocompatibility in spinal applications is being considered as an alternative biomaterial in orthopaedics, either as part of an all-polymer bearing couple, or a replacement for the metallic component in hard-on-soft bearings. Throughout the literature ultra-high molecular weight polyethylene exhibits a range of wear behavior dependent upon the amount of cross shear (CS) present in the bearing motion; in comparison, the behavior of PEEK bearing combinations subject to cross shear conditions is less understood. The aim of this study was to investigate the effect of cross shear on PEEK-on-PEEK and PEEK-on-Metal bearing couples. Wear tests were conducted using a four station pin-on-plate rig capable of uni-directional motion (zero cross shear) and multidirectional motion (cross shear); reciprocation (1 Hz), rotation (0 or 1 Hz), with gravimetric wear analysis used to determine the wear factors. The combined wear factors from the PEEK pins articulating on either PEEK or metal plates in this study suggest that it is preferable to use PEEK-on-Metal bearing couples under zero cross shear kinematic conditions and PEEK-on-PEEK for high cross shear applications. PEEK appears to demonstrate a CS dependency when articulating on hard surfaces. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 445-453, 2019.

Mask interface for continuous positive airway pressure therapy: selection and design considerations.

INTRODUCTION: Continuous positive airway pressure (CPAP) therapy is a clinical treatment for moderate or severe obstructive sleep apnea (OSA). Commercial CPAP mask designs normally come in standard sizes and the configuration is not commonly tailored to the patients' characteristics such as face topology, skin sensitivity, and severity of OSA syndrome; however, an optimal mask/interface selection is a key factor influencing the compliance and effectiveness of CPAP treatment. AREAS COVERED: This review investigates the conventional CPAP mask design, its effect on OSA treatment, and the related risk factors that can lead to skin damage after long-term repeated use. Through a literature search on common databases, Scopus, PubMed, and Google Scholar, we identified reported facts on the influence of the mask interface and current trends toward customized devices. EXPERT COMMENTARY: There is potential for optimizing the CPAP mask fit by adapting the interface to the patients' individual characteristics. This holds particularly true for users with abnormal features or simply outside conventional industry sizing standards. Enabling technologies for undertaking this adaptation include reverse engineering, computational modeling, and additive manufacturing. There is to date no integrated system that integrates those elements into a standard solution, but several studies have shown its effectiveness for specific cohorts.

Wear characteristics of an unconstrained lumbar total disc replacement under a range of in vitro test conditions.

The effect of kinematics, loading and centre of rotation on the wear of an unconstrained total disc replacement have been investigated using the ISO 18192-1 standard test as a baseline. Mean volumetric wear rate and surface morphological effects were reported. Changing the phasing of the flexions to create a low (but finite) amount of crossing path motion at the bearing surfaces resulted in a significant fall in wear volume. However, the rate of wear was still much larger than previously reported values under zero cross shear conditions. Reducing the load did not result in a significant change in wear rate. Moving the centre of rotation of the disc inferiorly did significantly increase wear rate. A phenomenon of debris re-attachment on the UHMWPE surface was observed and hypothesised to be due to a relatively harsh tribological operating regime in which lubricant replenishment and particle migration out of the bearing contact zone were limited. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 46-52, 2017.

Availability and utilisation of physician-based pre-hospital critical care support to the NHS ambulance service in England, Wales and Northern Ireland.

BACKGROUND: Every day throughout the UK, ambulance services seek medical assistance in providing critically ill or injured patients with pre-hospital care. OBJECTIVE: To identify the current availability and utilisation of physician-based pre-hospital critical care capability across England, Wales and Northern Ireland. DESIGN: A postal and telephone survey was undertaken between April and December 2009 of all 13 regional NHS ambulance services, 17 air ambulance charities, 34 organisations affiliated to the British Association for Immediate Care and 215 type 1 emergency departments in England, Wales and Northern Ireland. The survey focused on the availability and use of physician-based pre-hospital critical care support. RESULTS: The response rate was 100%. Although nine NHS ambulance services recorded physician attendance at 6155 incidents, few could quantify doctor availability and utilisation. All but one of the British Association for Immediate Care organisations deployed 'only when available' and only 45% of active doctors could provide critical care support. Eleven air ambulance services (65%) operated with a doctor but only 5 (29%) operated 7 days a week. Fifty-nine EDs (27%) had a pre-hospital team but only 5 (2%) had 24 h deployable critical care capability and none were used regularly. CONCLUSION: There is wide geographical and diurnal variability in availability and utilisation of physician-based pre-hospital critical care support. Only London ambulance service has access to NHS-commissioned 24 h physician-based pre-hospital critical care support. Throughout the rest of the UK, extensive use is made of volunteer doctors and charity sector providers of varying availability and capability.

Cross-shear implementation in sliding-distance-coupled finite element analysis of wear in metal-on-polyethylene total joint arthroplasty: intervertebral total disc replacement as an illustrative application.

Computational simulations of wear of orthopaedic total joint replacement implants have proven to valuably complement laboratory physical simulators, for pre-clinical estimation of abrasive/adhesive wear propensity. This class of numerical formulations has primarily involved implementation of the Archard/Lancaster relationship, with local wear computed as the product of (finite element) contact stress, sliding speed, and a bearing-couple-dependent wear factor. The present study introduces an augmentation, whereby the influence of interface cross-shearing motion transverse to the prevailing molecular orientation of the polyethylene articular surface is taken into account in assigning the instantaneous local wear factor. The formulation augment is implemented within a widely utilized commercial finite element software environment (ABAQUS). Using a contemporary metal-on-polyethylene total disc replacement (ProDisc-L) as an illustrative implant, physically validated computational results are presented to document the role of cross-shearing effects in alternative laboratory consensus testing protocols. Going forward, this formulation permits systematically accounting for cross-shear effects in parametric computational wear studies of metal-on-polyethylene joint replacements, heretofore a substantial limitation of such analyses.

Pulseless electrical activity after rapid administration of fresh frozen plasma.

We present two extreme low birthweight preterm neonates who developed pulseless electrical activity during dilutional exchange transfusions with fresh frozen plasma (FFP). Both were polycythaemic recipient twins delivered prematurely because of foetal compromise as a result of twin-to-twin transfusion syndrome. The two events were associated with an acute fall in ionised calcium. We discuss the mechanism of these cardiac arrests and highlight the care required when infusing citrate containing blood products, particularly FFP, in order to avoid causing acute life-threatening hypocalcaemia.

Diffusivity and distribution of vinblastine in three-dimensional tumour tissue: experimental and mathematical modelling.

The distribution of chemotherapeutics in solid tumours is poorly understood and the contribution it makes to treatment failure is unknown. Novel approaches are required to understand how the three-dimensional organisation of cancer cells in solid tumours affects drug availability. Since convective drug transport is limited by increased interstitial pressure in poorly vascularised cancers, the aim of this study was to measure the diffusive hindrance exerted by solid tumour tissue. Multicell layer tumour models comprising DLD1 colon cancer cells were characterised and fluxes were determined for [3H]-vinblastine and [14C]-sucrose. The mathematical models provided the diffusion coefficients for both compounds and predicted higher exposure of cells in the vicinity of vessels. The diffusion of vinblastine was three times slower than that of sucrose. Although slow diffusion delays vinblastine penetration into the avascular regions of tumours, the proliferating cells are generally in the marginal area of tumours. The mathematical model that we have developed enabled accurate quantification of drug pharmacokinetic behaviour, in particular, the diffusivity of vinblastine within solid tissue. This mathematical model may be adapted readily to incorporate the influence of factors mediating pharmacokinetic drug resistance.