Using nominal group technique to identify the planning considerations for UK Armed Forces medical personnel delivering defence engagement first aid training activities

INTRODUCTION

Defence Medical Services personnel regularly deploy overseas to deliver training activities as part of defence engagement (DE) to positively influence partners and others. There remains scope for medical planners to enhance our understanding of how to optimally use medical staff and assets for DE. We aimed to develop a tool to improve planning for DE activities delivering first aid training.

METHODS

We used nominal group technique to conduct a focus group with UK experts in planning first aid training DE activities to identify and prioritise important planning considerations within a conceptual framework based on the Defence Lines of Development. We validated and refined this framework with international experts from partner nation militaries to help strengthen the final planning tool.

RESULTS

We developed a detailed tool covering training curriculum and logistical and infrastructure requirements to deliver safe and effective DE training activities. First aid training engagement priorities include being tailored to the training audience and in harmony with the national or military healthcare services of that country. Messaging around the women, peace and security agenda should be integrated into training packages at conception to be effective.

CONCLUSIONS

We propose a planning tool to aid in designing first aid training that considers the necessary components to support meaningful education and effective engagement in support of UK's strategic goals. We welcome the use of and feedback on this tool and its impact to those planning first aid training activities as part of DE operations.

Dynamic voltage attenuation identifies atrial fibrosis in a rabbit model: simultaneous assessment with optical mapping and contact electrogram mapping

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation. Academy of Medical Sciences.

Background

Bipolar voltage amplitude is a widely-used clinical parameter in atrial electrophysiology procedures. However, voltage amplitude is variable, and it has been shown that increasing activation rate decreases bipolar voltage amplitude in patients with atrial fibrillation. It is not known whether such voltage attenuation is a marker of the presence of atrial fibrosis which could therefore be used to improve intra-procedural assessment of atrial cardiomyopathy.

Purpose

We sought to investigate the effect of increasing activation rate on bipolar voltage amplitude in both healthy and fibrotic left atrial tissue.

Methods

10 New Zealand Rabbits were fed a high cholesterol diet (0.75%) for a period of 12 weeks to create an atrial fibrosis model. 10 Animals were fed normal chow. After terminal anaesthesia the heart was excised, and optical and voltage mapping of the excised left atrial tissue was performed. Blebbistatin was used to maintain cardiac stasis and the voltage sensitive dye RH237 was used for optical mapping. Voltage and optical recordings were made during pacing was from 3 different directions at rates from 2-6Hz and at 3 sites across the atrial tissue. Voltage amplitude was recorded as the mean amplitude over 10 beats during steady-state pacing. Optical recordings were used to measure conduction velocity and action potential characteristics. Only pacing runs showing 1:1 conduction were included in analysis. Atrial fibrosis was assessed using Masson’s Trichrome staining.

Results

The degree of atrial fibrosis was significantly greater in the atrial fibrosis model compared to healthy controls (15±3.24% vs. 9.74±4.98%, p=0.0069). Median voltage at base rate pacing of 2Hz was not significantly different between control and fibrotic atria (11.63mV, IQR 6.35mV vs. 10.3mV, IQR 6.81mV, p=0.71, respectively). Median voltage was significantly lower at 6Hz than at 2Hz in the control group (9.84mV, IQR 6.87mV, p=0.046). The degree of voltage attenuation between study groups was not significantly different between when pacing at 3hz or 4hz, whereas pacing at 5Hz and 6Hz showed significantly greater attenuation in fibrotic atria. At 5Hz the median reduction in amplitude from baseline in control vs fibrotic atria was 0.88mV, IQR 2.36mV vs 1.92mV, IQR 1.63mV (p=0.031). At 6 Hz the median reduction was 0.94mV, IQR 1.69mV vs 2.68mV, IQR 1.11mV, p=0.013 in control and fibrotic groups respectively.

Discussion

High cholesterol diet increased atrial fibrosis in a rabbit model. Bipolar voltage amplitude attenuation occurred in both control and fibrotic atria however the degree of voltage attenuation was significantly greater in fibrotic atria. These findings support the further evaluation of dynamic voltage attenuation for intraprocedural identification of atrial fibrosis.

An automated algorithm minimising ATP failure: re-initiation to enhance anti-tachycardia pacing efficacy

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Medical Research Council, UK

Background

Re-initiation is an important mechanism of anti-tachycardia pacing (ATP) failure, whereby VT is first terminated by the initial ATP application, before being re-initiated by successive pulses. Current ICD designs are able to measure and store electrograms (EGMs) for detecting and classifying arrhythmias, which contain information that may also be used during ATP application. Developing an algorithm that automatically processes EGMs during ATP, with the goal of detecting the initial VT termination and truncating subsequent ATP pulses (which has the potential to re-initiate), may thus increase ATP efficacy.

Purpose

To develop a proof-of-concept ATP detection algorithm: Early Termination Detection Algorithm (ETDA), to automatically sense the signs of early VT termination and cease further ATP pulses based on real-time sensed EGMs from implanted devices.

Methods

A cohort of 7 porcine infarcted ventricular computational models were subject to virtual induction protocols to induce sustained VTs. Functional model properties were adjusted to provide 73 unique VT episodes (260≤VT cycle length (CL)≤480ms). For each episode, burst ATP was delivered from typical pacing sites near the right ventricle (RV) septum to evaluate its efficacy. The ATP failures and their failure mechanisms were identified, accordingly. During ATP application, five common sensing EGM vectors from implanted devices were recovered from simulations including can-to-Superior vena cava (SVC) coil, can-to-RV ring, SVC coil-to-RV coil ring, RV coil tip-to-RV coil ring and LV coil at the lateral base-to-RV tip. Our proposed ETDA utilises those EGMs for VT termination detection. Specifically, correlation coefficients (CCs) of the EGMs between two successive ATP pulses were calculated and averaged to identify sudden changes in EGM morphology that indicate VT termination (Fig A). A discriminating threshold on the CCs was chosen by comparing all re-initiation cases with detailed analysis of the actual VT termination time observed from simulation results. ETDA was then applied to all cases to identify initial termination and improvement in efficacy.

Results

Before ETDA application, ATP terminated 42 cases (58%, Fig C), with re-initiation attributing to 11 (35%) of ATP failures. Application of ETDA accurately detected VT termination in 91% of re-initiated cases, 90% of terminated cases and 81% of not-terminated cases (Fig B), which enhanced the overall ATP efficacy to 71% (P=0.08) (Fig C).

Conclusions

The real-time EGMs measured from standard ICD/CRT-D devices may be used to improve ATP efficacy through an approach such as ETDA. ETDA detects signs of early termination automatically in real time which enables identification of successful VT termination, truncating subsequent pulses that may re-initiate the VT, which enhances overall ATP efficacy.

In silico study of anti-tachycardia pacing efficacy optimisation through scar-targeted stimulation

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Medical Research Council, UK

Background

Anti-tachycardia pacing (ATP) is a reliable electrotherapy to painlessly terminate ventricular tachycardia (VT). However, ATP is often ineffective, particularly for fast VTs, which is often due to the inability of paced wavefronts to reach the re-entrant circuit, because of functional or anatomical barriers. It is thought that efficacy may be enhanced by optimised delivery closer to the re-entrant circuit driving the VT.

Purpose

To quantitatively assess the dependence of ATP efficacy upon different delivery locations with respect to the re-entrant circuit.

Methods

A cohort of 7 porcine ventricular infarct computational models were generated based on in vivo magnetic resonance imaging. Rapid-pacing protocols were applied to the cohort to induce VTs. Functional model parameters were adjusted to produce 73 episodes of sustained monomorphic VT, including 32 fast VTs (cycle length (CL)≤320ms) and 41 slow VTs (320ms-<VTCL≤<VTCL≤>480ms). Burst ATP (2 sequences of 8 pulses at 88% of VTCL) was separately delivered from 3 locations proximal to the re-entrant circuit (along the RV septum), specifically within the critical isthmus (CI), and at the Exit and Entrance sites, along with 3 locations distal to the circuit (lateral/posterior LV), based on multipolar implanted devices with LV epicardial leads, constituting 438 virtual scenarios and efficacy compared (Fig A).

Results

ATP efficacy was significantly higher for slow VTs than for fast VTs (65% vs 46%, P=0.00004) (Fig B). Separate analysis of slow VT cases revealed that delivering from distal locations to the re-entrant circuit was significantly more effective than delivering from proximal locations (72% vs 59%, P=0.04). However, for fast VT cases, the trend was reversed with proximal application (41%) being more effective than distal application (51%, P=0.15) (Fig B). Moreover, individual analysis on specific proximal locations revealed that in slow VT cases, delivering at the Exit site of VT was significantly less efficient than delivering at the Entrance site (46% vs 73%, P=0.01), with a similar (although non-significant) trend also being seen for fast VTs (44% vs 53%, P=0.5) (Fig C). Moreover, for fast VT cases, ATP delivery within the CI was overall the most effective (56%) than all other locations while this trend was not seen in slow VT cases.

Conclusions

ATP delivery proximal to the re-entrant circuit improves efficacy in fast VTs, but less so in slow VTs, where delivering from distal sites is superior. Specifically, for fast VTs, ATP delivery within the CI is the most effective. This work suggests that real-time alteration in applied ATP delivery site choice in a multipolar device (guided by the sensed VT rate by the device prior to therapy delivery) may be beneficial. Combined with the state-of-art leadless pacing technology, this also provides a clinical opportunity for patient-specific ATP delivery configuration and programming.

Multimodality planning of stereotactic radio-ablation for ventricular tachycardia. Results from the international MUSIC consortium

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Research Council

Background

Optimal SBRT planning methods for VT ablation are yet to be defined.

Purpose

To evaluate a multimodal approach for SBRT planning.

Methods

30 pts (age 70±10, 90% men, LVEF 26±9%, 67% ICM, 47% NICM or mixed, 1.7±1.2 prior catheter ablations) with drug-refractory VT underwent imaging prior to SBRT. The inHEART technology was used to create image-based 3D models of substrate, cardiac anatomy, and organs at risk (coronaries, phrenic nerve, GI tract, AV node). In MUSIC software (IHU Liryc-Inria), 3D models were fused with prior EP maps, and SBRT targets were interactively drawn in 3D by the referring EP cardiologist. Transmural target volumes and organs at risk were fused with a 4D planning CT and used to plan SBRT in Eclipse (Varian).

Results

SBRT was delivered on median PTVs of 96[63-149] mL (total dose 25 Gy) with either Truebeam or Edge systems (Varian). Over a median FU of 4[2-8] months, death occurred in 11(37%) pts, due to arrhythmia recurrence in 4(13%). FU at 6 months was available in 14 pts. In these, the median numbers of VT episodes and ICD shocks over the 6 months preceding SBRT were 20[9-27] and 8[5-15], respectively. In the 6 months following SBRT, these decreased to 0[0-30] and 0[0-0], respectively (P<0.001 for both). 8/14(57%) pts were free from any VT recurrence, and 11/14(79%) were free from any ICD shock. In the total cohort, complications attributed to SBRT were observed in 2/30 (7%), none of which were fatal (heart failure and pneumonitis, both managed with steroids).

Conclusion

In patients with severe drug- and catheter ablation-refractory VT, SBRT planning based on 3D image-based models fused with prior EP maps is feasible, and associated with favorable efficacy and safety profiles.

In-silico optimisation of ICD defibrillation efficacy by modifying lead/can configurations using a cohort of high-resolution whole-torso heart models

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Medical Research Council, UK

Background

ICD is an effective direct therapy against VT/VF by applying a strong electrical shock across the heart between the shocking coil and can. Conventionally, patients will have a shocking coil inside the right ventricle (RV) and a can at the upper left chest. However, due to infections or other conditions, the can may need to place towards the right chest. The placement of the RV coil may also vary in different cases, for example avoiding scar. However, it is unclear how defibrillation efficacy may be altered by these unavoidable modifications to conventional lead/can configurations and whether optimisation may be possible.

Purpose

To compare defibrillation efficacy of modifications of ICD configurations in a cohort of whole-torso models.

Methods

A cohort of 15 whole torso models was generated from high resolution CT data and contrast CT cardiac scans, including 5 dilated cardiomyopathy (DCM), 5 hypertrophic cardiomyopathy (HCM) and 5 structurally normal patients (Fig A). Transvenous ICDs were represented by a shocking coil inside the RV (near apex) and a (ground) can at the upper left chest as default settings. Configurations were then varied by moving the can to the right chest, moving the RV coil up the mid-septum or adding extra grounds (Superior Vena Cava (SVC) coil, coronary sinus (CS) coil (Fig A)). Defibrillation-strength shocks were applied to all models (Fig B). DFTs and mean electrical field were evaluated across the whole heart as well as specific LV, RV, RV insertion regions, along with overall impedance.

Results

Shifting the can from left to right significantly increased DFT for the whole heart (23 J vs 15 J, P=0.03) and LV (25 J vs 17 J, P=0.03) (Fig C) and reduced the mean electrical field. Moving the RV coil further up the septum did not significantly alter DFT (Fig D), but did reduce mean electrical field for all regions and reduce impedance significantly. Additional separate coils significantly reduced DFT for all regions (Fig D) by increasing mean electrical field, whilst adding both coils significantly reduced DFT the most (whole heart: 15 J vs 6 J, P=0.03) (Fig E). Impedance was increased significantly by adding SVC coil, but reduced significantly by adding CS coil. Adding both coils increased impedance slightly.

Conclusions

Although a right-sided can increases DFT by over 50%, additional leads (grounds) may mitigate this increase by increasing mean electrical field. Moving the RV coil closer to the mid-septum reduces DFT slightly, but also reduces mean electrical field and impedance significantly.

Subthreshold delayed afterdepolarizations mediated by reduced tissue conductivity form a substrate for unidirectional block and reentry within the infarcted heart

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): British Heart Foundation, Wellcome Trust

Background

Delayed afterdepolarizations (DADs) due to spontaneous calcium release (SCR) events at the subcellular scale have been associated with arrhythmia formation in the border zone (BZ) of infarcted hearts. DADs may not only summate to form ectopic focal sources but may also inactivate sodium channels forming a substrate for unidirectional conduction block and reentry. The role played by infarct anatomy and altered intracellular coupling in facilitating this phenomenon is not fully understood.

Purpose

To use computational modelling to investigate the role of anatomical properties of the infarct BZ in creating a substrate for DAD-mediated conduction block and reentry.

Methods

MRI data from a porcine post-infarction heart was used to build the computational model. A phenomenological model was used to simulate SCRs in the BZ. Arrhythmia susceptibility was quantified by pacing the model followed by a pause, to see whether DADs would occur, and an extra S2 beat with different coupling intervals (CIs). Tissue conductivity in the BZ was decreased to investigate the effect of uncoupling on DAD-mediated conduction block.

Results

Subthreshold DADs occurring within the infarct BZ inactivated the fast sodium channels which resulted in block of S2 beats. This occurred most readily in narrow isthmuses where electrotonic load was attenuated by the non-conducting scar. DADs rendered the entire isthmus area refractory establishing a substrate for unidirectional block and reentry (see Fig. A). Reduced tissue conductivity in the BZ reduced electrotonic load on cells undergoing DADs. This led to more local tissue depolarization (Vm) as uncoupling prevented current from flowing to neighboring cells at rest (Fig. B-C). Reduced tissue conductivity also enhanced DAD-mediated block by increasing the vulnerable window for reentry initiation (700ms < S2 CI < 900ms as shown in Fig. D).

Conclusion

Subthreshold DADs provide a substrate for arrhythmogenesis in the infarct BZ. Tissue uncoupling enhanced the arrhythmogenic risk by increasing the time window of unidirectional block.

Interpolation of electrophysiology parameters using OpenEP: technology development and clinical application

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation

Background

Interpolation of data is common during clinical electrophysiology procedures. Applications include local activation mapping, voltage mapping and novel techniques including Sparkle and Coherence mapping. Nevertheless, underlying interpolation algorithms are proprietary and therefore challenging to reproduce. Importantly, direct comparison of electroanatomic datasets between system vendors is therefore not possible.

Purpose

We sought to (1) develop an open-source architecture for interpolation within the Open Electrophysiology Framework for Research (OpenEP; https://openep.io); (2) to provide three interpolation methods within this architecture and (3) to evaluate their performance against clinical data.

Method

The software architecture is shown in Figure 1A. The currently available methods are Radial Basis [1], Scattered Interpolant [2] and Local Smoothing [3]. Default parameters for each method are shown in Figure 1B.

The performance of each method was assessed using clinical left atrial mapping data, using the default options for each scheme. Following interpolation, a sample of 1000 activation/voltage points per mesh was used for analysis. For each interpolation method, correlation with clinical data was assessed using the intra-class correlation coefficient, whilst agreement was assessed using Bland Altman limits of agreement.

Results

For activation mapping, radial basis interpolation resulted in a smoother field than local smoothing, whilst scattered interpolation required more filtering of extreme values. Correlations between interpolated and original activation times were excellent for all interpolation schemes (radial basis R=0.91, p<0.0001; local smoothing R=0.95, p<0.0001; scattered interpolant R=0.92, p<0.0001). Local smoothing resulted in the narrowest 95 percent limits of agreement (-19 to +20ms), compared to radial basis (-24 to +28ms) and scattered interpolation (-22 to +25ms).

For voltage mapping, the interpolation schemes resulted in similar appearances of low voltage areas, however correlations with clinical data were weaker than for activation mapping (radial basis R=0.84, p<0.0001; local smoothing R=0.82, p<0.0001; scattered interpolant R=0.79, p<0.0001). The 95 percent limits of agreement were wide as a proportion of the mean data values, ranging from 83% (-0.8 to +0.66mV) for local smoothing to 97% (-0.78 to +0.63mV) for radial basis interpolation.

Conclusion

An extensible architecture is provided for data interpolation in OpenEP together with three interpolation methods. The methods performed wellfor local activation time interpolation but variation compared to clinical data was greater for voltage mapping. This new architecture will permit the optimisation of interpolation methods against "gold standard" simulation or histological data and facilitate comparison of datasets between system vendors.

Framework for the evaluation of military health systems

The organisation of a military health system (MHS) differs from the civilian system due to the role of the armed forces, the unique nature of the supported population and their occupational health requirements. A previously published review of the Military Medical Corps Worldwide Almanac demonstrated the value of a standardised framework for evaluation and comparison of MHSs. This paper proposes such a framework which highlights the unique features of MHSs not covered by health services research of national health systems. These include: national context and summary; organisational structure; firm base facilities, healthcare beneficiaries and medical research; operational capabilities, overseas deployments, collaborations and alliances; personnel including recruitment, training and education; and history and culture. This common framework can help facilitate international collaboration between military medical services including capability development, training exercises and mutual support during military operations. It can also inform national contributions to future editions of the Almanac.

P920Understanding arrhythmia mechanisms in patients with atrial septal defects

Background

Atrial arrhythmias represent a major cause of morbidity and hospitalization in patients with atrial septal defects (ASD). Optimum treatment strategies are unknown since the mechanisms of arrhythmia are undefined in this cohort.

Purpose

We investigated whether percutaneous ASD closure reduces atrial arrhythmias and subsequently examined the electrical and structural changes underpinning arrhythmogenesis in ASD patients.

Methods

Meta-analysis was used to study the effect of closure on arrhythmias. Bi-atrial electrical dysfunction was assessed through invasive measurement of atrial voltage, refractory periods (ERP) over three drive trains (600, 450 and 300ms) and local conduction velocity (CV) with subsequent assessment of ERP and CV restitution. Structural remodelling was assessed through non-invasive quantification of fibrosis using cardiac MRI (CMR). Origin of ectopy was evaluated invasively using isoprenaline infusion and non-invasively using 24-hour Holter monitoring. Comparison was made to normal heart controls.

Results

Meta-analysis

Meta-analysis of 25 studies found that percutaneous closure was associated with a weak reduction in atrial arrhythmias only in patients >40 years old (OR 0.777, 95% CI 0.616-0.979, P = 0.032).

Electrical Remodelling

On invasive assessment (21 ASDs; 21 controls), proportion of right atrial low voltage (<0.5mV) and scar (<0.05mV) was greater in ASD vs control patients (P = 0.02 and P = 0.039). In ASD patients, these parameters were greater in the right atrium vs the left atrium (P = 0.002 and P = 0.01). Right atrial ERP restitution slopes were steeper in ASD vs control patients (P = 0.016). Maximum right atrial CV and CV restitution slopes were greater in ASD vs control patients (P= 0.005 and P < 0.001 respectively) and CV decrement occurred at longer coupling intervals in the right atrium in ASD patients (P = 0.015).

Structural Remodelling

On CMR assessment (36 ASDs; 36 controls), bi-atrial fibrosis was greater in ASD vs control patients (P < 0.001). In ASD patients right atrial fibrosis was burden greater in patients with vs without atrial arrhythmias (P = 0.034).

Arrhythmia Triggers

On 24-hour Holter monitoring and during invasive isoprenaline infusion right and left atrial ectopy was equally prevalent in ASD vs control patients.

Conclusion

This study highlights the importance of right atrial electrical dysfunction to the occurrence of arrhythmias in ASD patients with extensive right atrial remodelling (fibrosis, low voltage, steeper ERP and CV restitution) seen in ASD patients compared to normal heart controls.

From the results of the meta-analysis it appears that percutaneous closure alone is insufficient to treat arrhythmias in ASD patients. Given the predominance of right atrial remodelling, right-sided ablation as an adjunct to conventional left-sided ablation should be investigated as a strategy to treat atrial arrhythmias in these patients.

Abstract Figure.

221Evaluating the ability of different substrate mapping techniques to identify scar-related ventricular tachycardia circuits using computational modelling

Funding Acknowledgements

National Institute for Health Research; British Heart Foundation; and The Wellcome Trust and Engineering and Physical Sciences Research Council.

Background

Accurate identification of targets for catheter ablation therapy of ventricular tachycardias (VTs) in the postinfarction heart remains a significant challenge. Identification of such targets often requires VT-induction to delineate the entry/exit points of the reentrant circuit sustaining the VT. However, inducibility may not be possible due to hemodynamic instability. In this scenario, substrate ablation strategies can still be performed to uncover the arrhythmogenic substrate during sinus or paced rhythm. However, substrate mapping may fail to accurately delineate the reentrant circuit resulting in VT recurrence after the procedure.

Purpose

To use computer simulations to compare the ability of different electroanatomical maps constructed following typical substrate ablation strategies to identify the VT exit site.

Methods

An image-based computational model of the porcine post-infarction left ventricle was constructed to simulate VT and paced rhythm. Electroanatomical maps were constructed based on the following features extracted from electrograms computed on the endocardial surface: activation time (AT), bipolar electrogram amplitude, signal fractionation and the reentry vulnerability index (RVI - a metric combining activation and repolarization timings to identify tissue susceptibility to reentry). Potential ablation targets during substrate mapping were compared for: highest 5% AT gradient; lowest 5% bipolar signal amplitudes; areas with fragmented signals (more than one peak); and lowest 5% RVI. The minimum distance, d, between the manually identified VT exit site and the targets was measured.

Results

The RVI performed better than the other metrics at detecting the VT exit site (see Figure). The minimum distance between sites of lowest RVI and the exit site was 3.2mm compared to 13.1mm and 15.9mm in traditional AT and voltage maps, respectively. As the scar was not transmural, parameters derived from all electrograms (including those located on dense scar regions) were used to construct the electroanatomical maps. This improved the performance of the RVI significantly, making it more specific than the other metrics as can be seen in the Figure.

Conclusions

Among all metrics investigated here, the RVI identified the vulnerable region closest to VT exit site. This finding suggests that activation-repolarization metrics may improve the detection of pro-arrhythmic regions without having to induce VT. Moreover, the RVI may be particularly well suited for detecting vulnerable regions within non-transmural scars.

Abstract Figure. VT and Substrate Mapping

Ambient and laboratory evaluation of a low-cost particulate matter sensor

Low-cost, light-scattering-based particulate matter (PM) sensors are becoming more widely available and are being increasingly deployed in ambient and indoor environments because of their low cost and ability to provide high spatial and temporal resolution PM information. Researchers have begun to evaluate some of these sensors under laboratory and environmental conditions. In this study, a low-cost, particulate matter sensor (Plantower PMS 1003/3003) used by a community air-quality network is evaluated in a controlled wind-tunnel environment and in the ambient environment during several winter-time, cold-pool events that are associated with high ambient levels of PM. In the wind-tunnel, the PMS sensor performance is compared to two research-grade, light-scattering instruments, and in the ambient tests, the sensor performance is compared to two federal equivalent (one tapered element oscillating microbalance and one beta attenuation monitor) and gravimetric federal reference methods (FEMs/FRMs) as well as one research-grade instrument (GRIMM). The PMS sensor response correlates well with research-grade instruments in the wind-tunnel tests, and its response is linear over the concentration range tested (200-850 μg/m3). In the ambient tests, this PM sensor correlates better with gravimetric methods than previous studies with correlation coefficients of 0.88. However additional measurements under a variety of ambient conditions are needed. Although the PMS sensor correlated as well as the research-grade instrument to the FRM/FEMs in ambient conditions, its response varies with particle properties to a much greater degree than the research-grade instrument. In addition, the PMS sensors overestimate ambient PM concentrations and begin to exhibit a non-linear response when PM2.5 concentrations exceed 40 μg/m3. These results have important implications for communicating results from low-cost sensor networks, and they highlight the importance of using an appropriate correction factor for the target environmental conditions if the user wants to compare the results to FEM/FRMs.

Failure to deliver the formal therapy prescribed in an NHS rehabilitation unit

The objectives of the study were to ascertain the extent to which short-term goals of therapy were achieved and to assess the discrepancy, if any, between the therapy prescribed and the therapy delivered.

The weekly therapy prescribed and delivered over a two-month period was recorded. The outcome of goal setting was assessed in relation to the predicted time set for achieving the goal.

All patients admitted to a rehabilitation ward in an NHS teaching hospital during the two months were studied.

No patients received the full treatment prescribed. The percentage of prescribed treatment given to patients ranged from 33.3% to 66.4%. Over 95% of the goals set during the period were achieved but only 60% were achieved on time and 37% were achieved later than expected.

The therapy prescribed for patients was not being delivered due to inadequate resourcing of therapy time. A 5% increase in funding to the rehabilitation ward would generate a 50% increase in the amount of formal therapy given which would be likely to shorten patients' stay in hospital.

Clinical audit of a lymphoedema bandaging system: a foam roll and cohesive short stretch bandages

OBJECTIVE

Late-stage lymphoedema is characterised by chronic swelling, shape distortion, inflammatory processes and tissue fibrosis. Our aim was to perform a clinical audit of a lymphoedema compression bandaging system (Rosidal Soft foam roll layer and figure-of-eight application of Actico cohesive inelastic bandages) specifically designed for patients with late stage lower limb lymphoedema.

METHOD

The audit explored suitability of the bandaging system, benchmarking limb volume changes with research evidence, and reporting patient and practitioner evaluations.

RESULTS

A mean reduction (33%) in excess limb volume was reported for the 11 patients with unilateral lymphoedema who completed a course of bandaging over 12 days. Mean percentage reduction of absolute limb volume after treatment was 8%. Patient and practitioner evaluations indicated the suitability of this bandage system for patients with late stage lymphoedema in terms of comfort and effectiveness.

CONCLUSION

The bandaging system is suitable for patients with late stage chronic swelling. Two parameters for calculating change in limb volume are not interchangeable. Future evaluation of the bandaging system, using validated outcome measures within a comprehensive research study is required.

DECLARATION OF INTEREST

Activa Healthcare provided financial support to the project and supplied the materials.

Cold injuries in contemporary conflict

OBJECTIVES

To describe the cases of cold injury sustained during the most recent winter operational tour of Afghanistan, Op HERRICK 15.

METHODS

Retrospective review of all notified British military cases of cold injury sustained between 1 Oct 11 and 30 Mar 12 recorded by UK Medical Group Environmental Health Team.

RESULTS

14 patients with 13 Non-freezing Cold Injuries (NFCI) and two hypothermic injuries were identified. Five patients were of African ethnic decent. Eight out of 13 NFCI patients had probably suffered a previous injury, injuries were sustained from December until February and 9/13 NFCI patients had periods of static duties implicated in the injury mechanism. Eight patients were able to remain in operational theatre on restricted duties whilst 6/14 were evacuated home after sustaining their injuries.

CONCLUSIONS

Although awareness and equipment have improved, cold injuries remain an important cause of Disease and Non Battle Injury on current operations within the British Military. Cases of cold injury are probably under reported and often stem from situations where risk would seem predicable. It is hoped this article will assist in enabling greater understanding of contemporary operational cold injuries and continuing the development of preventative strategies.

The comparative toxicity to soil invertebrates of natural chemicals and their synthetic analogues

The introduction of Registration, Evaluation and Authorisation of Chemicals (REACH), requires companies to register and risk assess all substances produced or imported in volumes of >1 tonne per year. Extrapolation methods which use existing data for estimating the effects of chemicals are attractive to industry, and comparative data are therefore increasingly in demand. Data on natural toxic chemicals could be used for extrapolation methods such as read-across. To test this hypothesis, the toxicity of natural chemicals and their synthetic analogues were compared using standardised toxicity tests. Two chemical pairs: the napthoquinones, juglone (natural) and 1,4-naphthoquinone (synthetic); and anthraquinones, emodin (natural) and quinizarin (synthetic) were chosen, and their comparative effects on the survival and reproduction of collembolans, earthworms, enchytraeids and predatory mites were assessed. Differences in sensitivity between the species were observed with the predatory mite (Hypoaspis aculeifer) showing the least sensitivity. Within the chemical pairs, toxicity to lethal and sub-lethal endpoints was very similar for the four invertebrate species. The exception was earthworm reproduction, which showed differential sensitivity to the chemicals in both naphthoquinone and anthraquinone pairs. Differences in toxicity identified in the present study may be related to degree of exposure and/or subtle differences in the mode of toxic action for the chemicals and species tested. It may be possible to predict differences by identifying functional groups which infer increased or decreased toxicity in one or other chemical. The development of such techniques would enable the use of read-across from natural to synthetic chemicals for a wider group of compounds.

Myocardial infarction associated with the administration of intravenous ephedrine and metaraminol for spinal-induced hypotension

A 31-year-old female with no risk factors for cardiac disease suffered a peri-operative myocardial infarction during an elective gynaecological procedure under spinal anaesthesia. The timing and nature of cardiac symptoms suggest that the myocardial infarction was caused by coronary artery vasospasm secondary to ephedrine and/or metaraminol, which were administered to treat spinal-induced hypotension. We review the recent literature and case reports on myocardial infarction attributed to sympathomimetic drugs, and recommend the use of sublingual or intravenous nitrates when signs or symptoms of coronary arterial vasospasm become evident during their use.

The use of botulinum toxin type-B in the treatment of patients who have become unresponsive to botulinum toxin type-A -- initial experiences

The increasing use of botulinum toxin type-A, especially for focal dystonia and spasticity has highlighted the issue of secondary non-responsiveness. Within the last few years botulinum toxin type-B (Myobloc/Neurobloc) has become commercially available as an alternative to type-A. This paper discusses our initial experience of botulinum toxin type-B in a total of 63 individuals who attended our botulinum clinic. Thirty-six patients had cervical dystonia and a secondary non-response to type-A toxin. Thirteen of these patients (36%) had a reasonable clinical response to Neurobloc and continue to have injections. The other 23 patients either had no response, or a poor response, or had unacceptable side effects and ceased treatment. A small number of people with blepharospasm, hemifacial spasm and foot dystonia also had a disappointing response to injection. Twenty patients with spasticity were also type-A resistant. Seven of these show some continuing response to type-B, without unacceptable side effects. These findings demonstrate that botulinum toxin type-B has a place in the management of patients who have become non-responsive to type-A, but overall the responses to type-B toxin were disappointing.

Botulinum toxin for people with dystonia treated by an outreach nurse practitioner: a comparative study between a home and a clinic treatment service

OBJECTIVE

To study whether a trained outreach nurse practitioner could provide a service that is as good as, or better than, that provided at a hospital outpatient clinic for people who had been diagnosed with dystonia and required treatment with botulinum toxin.

DESIGN

Randomized trial.

SETTING

An outpatient department of a regional neurorehabilitation center and patients' homes in northern England.

PATIENTS

Eighty-nine patients with a clinical diagnosis of spasmodic torticollis, blepharospasm, or hemifacial spasm who had ongoing treatment of dystonia with botulinum injections.

INTERVENTIONS

Individuals were randomly allocated either to receive ongoing botulinum injections at home by the nurse practitioner or to continue attending the hospital outpatient clinic and be injected by medical staff.

MAIN OUTCOME MEASURES

The following measures were recorded at each visit: demographic descriptors, dosage of botulinum toxin, treatment interval, side-effect profile, external referrals, and a questionnaire to determine qualitative opinion.

RESULTS

Efficacy and duration of the botulinum was similar in both groups. Botulinum dosage and side-effect profiles were similar in both groups except for significantly less dysphagia (p < .018) in the home group (7 vs 24 occasions). Subjective opinion by the patients indicated statistically significant preference for home injections. Economic analysis indicated that the overall cost of the treatment was less in the home injection group (total cost per visit $36.90 [ pound 23.36] vs $79.00 [ pound 50.01]), but this difference was not statistically significant.

CONCLUSION

A trained outreach nurse practitioner provided a service that was as good as, and in certain aspects better than, that provided by a hospital outpatient clinic. The nurse practitioner provided a more flexible, much appreciated, safe, and cost-effective service for this client group. Wider use of outreach nurse practitioners for dystonia should be encouraged.