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This paper provides an overview of the usability engineering process and relevant standards informing the development of medical devices, together with adaptations to accommodate situations such as global pandemics where use of traditional face-to-face methods is restricted. To highlight some of those adaptations, a case study of a project developing a novel electronic rehabilitation device is referenced, which commenced in November 2020 amidst the COVID-19 pandemic. The Sheffield Adaptive Patterned Electrical Stimulation (SHAPES) project, led by Sheffield Teaching Hospitals NHS Foundation Trust (STH), aimed to design, manufacture and trial an intervention for use to treat upper arm spasticity after stroke. Presented is an outline and discussion of the challenges experienced in developing the SHAPES health technology intended for at-home use by stroke survivors and in implementing usability engineering approaches. Also highlighted, are the benefits that arose, which can offer easier involvement of vulnerable users and add flexibility in the ways that user feedback is sought. Challenges included: restricted travel; access to usual prototyping facilities; social distancing; infection prevention and control; availability of components; and changing work pressures and demands. Whereas benefits include: less travel; less time commitment; and greater scope for participants with restricted mobility to participate in the process. The paper advocates a more flexible approach to usability engineering and outlines the onward path for development and trialling of the SHAPES technology.

A mismatch in electrode impedance is a common and significant source of artefact in electrical impedance spectroscopy systems. We have analysed these artefacts, identifying key parameters in the optimisation of both current and voltage excited electrical impedance spectroscopy systems. We have used this information to develop a new clinical system for investigating muscle impedance anisotropy in human limbs, with the aim of developing biomarkers for various muscle pathologies. This new instrumentation integrates buffering at the front-end, which isolates the electrodes from both multiplexing and wiring parasitics. Modelling of the front-end instrumentation demonstrates an input impedance of over 1 $\text{G}\Omega $ in parallel with 0.4 pF. The clinical system currently has 16 electrodes, with the capability for more, and operates over a physiologically relevant frequency range of 76 Hz to 625 kHz. Results presented in this paper show that the new system operates with reduced levels of artefact, even in the presence of a significant mismatch in electrode impedances.

We developed a 64 channel sensory electrical stimulator which delivers a dynamic and variable ‘Sensory Barrage’ Stimulation (SBS). Our aim was to assess the feasibility of caregivers delivering the stimulation in the community for a clinical trial comparing single channel Transcutaneous Electrical Nerve Stimulation (TENS) with SBS for post stroke upper limb spasticity. We trained caregivers of 16 participants with post stroke upper limb spasticity to sequentially administer SBS and TENS for 60 min daily for four weeks each, with a washout period of two weeks in between. Outcome measures tested were recruitment and retention rates, compliance with interventions and daily recording of Participant -reported Numerical Rating Scale (NRS). We also collected results of Action Research Arm Test (ARAT), Leeds Arm Spasticity Impact Scale (LASIS) and Modified Ashworth Scale (MAS) for spasticity. Out of 21 potential participants, 16 consented and 15 completed the protocol. Ten participants received TENS for 80% (23/28) of the intended hours. Eleven participants completed NRS for at 80% (45/56) of the study days. All participants attended all visits. The MAS reduced by at least one in five participants after SBS and in three after TENS. Minimal Clinically Important Difference (MCID) of four points increase in ARAT was seen in five participants following TENS, and in four following SBS. A MCID of 18% decrease in NRS was reported by eight participants after TENS and three after SBS. This study demonstrated the feasibility of undertaking a trial of sensory electrical stimulation for post-stroke spasticity with caregivers delivering intervention in community. The study was not powered to detect efficacy of the interventions.Trial registration number:NCT02907775.Date 20-9-2016.

In amyotrophic lateral sclerosis (ALS) bulbar disease biomarkers are lacking. We evaluated a novel tongue electrical impedance myography (EIM) system, utilising both 2D and 3D electrode configurations for detection of tongue pathology.Longitudinal multi-frequency phase angle spectra were recorded from 41 patients with ALS (baseline, 3 and 6 months) and 30 healthy volunteers (baseline and 6 months). ALS functional rating scale-revised (ALSFRS-R) data and quantitative tongue strength measurements were collected. EIM data were analysed for reliability (intra-class correlation coefficient; ICC) and differences between patients and volunteers ascertained using both univariate (Mann-Whitney U test) and multivariate techniques (feature selection and L2 norm).The device produced highly reliable data (pooled ICC: 0.836). Significant EIM differences were apparent between ALS patients and healthy volunteers (P 0.001). EIM data demonstrated a significant relationship to tongue strength and bulbar ALSFRS-R scores (P 0.015). The EIM recordings revealed a group level longitudinal change over 6 months and consistently identified patients in whom symptoms or tongue strength changed.The novel EIM tongue system produces reliable data and can differentiate between healthy muscle and ALS-related disease.Tongue EIM utilising multiple frequencies and electrode configurations has potential as a bulbar disease biomarker in ALS.

Objective: Electrical impedance myography (EIM) performed on the centre of the tongue shows promise in detecting amyotrophic lateral sclerosis (ALS). Lateral recordings may improve diagnostic performance and provide pathophysiological insights through the assessment of asymmetry. However, it is not known if electrode proximity to the muscle edge, or electrode rotation, distort spectra. We evaluated this using finite element-based modelling. Approach: Nine thousand EIM from patients and healthy volunteers were used to develop a finite element model for phase and magnitude. Simulations varied electrode proximity to the muscle edge and electrode rotation. LT-Spice simulations assessed disease effects. Patient data were assessed for reliability, agreement and classification performance. Main results: No effect on phase spectra was seen if all electrodes remained in contact with the tissue. Small effects on magnitude were observed. Cole-Cole circuit simulations indicated capacitance reduced with disease severity. Lateral tongue muscle recordings in both patients and healthy volunteers were reproducible and symmetrical. Combined lateral/central tongue EIM improved disease classification compared to either placement alone. Significance: Lateral EIM tongue measurements using phase angle are feasible. Such measurements are reliable, find no evidence of tongue muscle asymmetry in ALS and improve disease classification. Lateral measurements enhance tongue EIM in ALS.

Functional electrical stimulation has been shown to be a safe and effective means of correcting drop foot of central neurological origin. However, despite recent technological advances, the set-up of surface stimulators remains a challenge for many users with drop foot. The automation of the setup process through the use of electrode arrays has been proposed as a way to address this problem. This paper describes a series of research and clinical studies which have led to the first demonstration of unsupervised automated setup of an electrode-array based drop foot stimulator. Finally, future research plans are discussed.

Functional electrical stimulation is commonly used to correct drop foot following stroke or multiple sclerosis. This technique is successful for many patients, but previous studies have shown that a significant minority have difficulty identifying correct sites to place the electrodes in order to produce acceptable foot movement. Recently there has been some interest in the use of 'virtual electrodes', the process of stimulating a subset of electrodes chosen from an array, thus allowing the site of stimulation to be moved electronically rather than physically. We have developed an algorithm for automatically determining the best site of stimulation and tested it on a computer linked to a small, battery-powered prototype stimulator with 64 individual output channels. Stimulation was delivered via an 8×8 array adhered to the leg by high-resistivity self-adhesive hydrogel. Ten participants with stroke (ages 53-71 years) and 11 with MS (ages 40-80 years) were recruited onto the study and performed two walks of 10 m for each of the following conditions: own setup (PS), clinician setup (CS), automated setup (AS) and no stimulation (NS). The PS and CS conditions used the participant's own stimulator with two conventional electrodes; the AS condition used the new stimulator and algorithm. Outcome measures were walking speed, foot angle at initial contact and the Borg Rating of Perceived Exertion. Mean walking speed with no stimulation was 0.61 m/s; all FES setups significantly increased speed relative to this (AS p0.05, PS p0.01, CS p0.01). Speed for PS (0.72 m/s) was faster than both AS (0.65 m/s, p0.01) and CS (0.68 m/s, p0.05). Frontal plane foot orientation at heel-strike was more neutral for AS (0.3° everted) than in the NS (11.2° inverted, p0.01), PS (4.5° inverted, p0.05) and CS (3.1° inverted, p0.05) conditions. Dorsiflexion angles for AS (4.2°) were larger than NS (-3.0°, p0.01), not different to PS (4.3°, p0.05) and less dorsiflexed than CS (6.0°, p0.05). This proof of principle study has demonstrated that automated setup of an array stimulator produces results broadly comparable to clinician setup. Slower walking speed for automated and clinician setups compared to the participants' own setup may be due to the participants' lack of familiarity with responses different to their usual setups. Automated setup using the method described here seems sufficiently reliable for future longer-term investigation outside the laboratory and may lead to FES becoming more viable for patients who, at present, have difficulty setting up conventional stimulators.

Objective To assess the influence of high-risk Human Papilloma Virus (hrHPV) genotyping on the detection of high-grade disease (CIN2+) using colposcopic impression both with and without electrical impedance spectroscopy (ZedScan I) as an adjunct. Study design A prospective cohort of women with a known hrHPV genotype referred to a single colposcopy service. Results 839 women underwent colposcopy and ZedScan I examination. 613 women were referred with abnormal cytology; 411 (67%) with low-grade dyskaryosis (67%) and 202 (33%) with high-grade dyskaryosis. 187 were referred with persistent hrHPV but negative cytology. 35 were attended for follow up and 4 for a clinical indication. 159 (19%) women were positive for HPV16 only; 54 (6%) with HPV18 only, 443 (53%) women were positive for hrHPV other types (HPV O). 183 (22%) were positive for multiple hrHPV genotypes. CIN2+ was present in 170 (84.2%) of high-grade and 69 (16.7%) of low-grade cytology referrals. Colposcopy was better at detecting HPV16 associated CIN2+ than that associated with HPV18 or HPV O (86.9% vs 79.7%, p = 0.0191). ZedScan I increased the detection of CIN2+ from 85.6% to 96% irrespective of hrHPV genotype status (p Conclusion The use of an electrical impedance spectroscopic device (ZedScan I) increases detection of CIN2+ irrespective of hrHPV genotype.

Background Radiofrequency (RF) devices are widely used in arthroscopic shoulder surgery for tissue ablation and other effects. They have heating effect during tissue application. It is known that chondrocyte death occurs with temperatures above 45 °C. The present study aimed to investigate the effect of various factors on the heating effect of RF probes in a controlled in vitro model. Methods A perspex model was used, in which volume, flow, outflow position, duration of RF probe use and inflow temperature could be closely controlled. Results Temperature rises in the bathing fluid sufficient to cause cell death were seen. The temperature rise was most noticeable when there was no fluid flow through the compartment, at smaller fluid volumes, if the fluid inflow temperature is elevated, and if the outflow is distant from the RF device. Of note, 30 seconds of use in a volume of 20 mL with no flow led to temperatures above 50 °C. Discussion Most of the factors affecting temperature rises using RF devices are directly under the surgeon's control. Further work is needed in this area to define the potential clinical effects of the use of these devices.

Craig Murdoch,1 Brian H Brown,6 Vanessa Hearnden,1 Paul M Speight,3 Katy D’Apice,1,2 Anne M Hegarty,2 John A Tidy,4 T Jamie Healey,5 Peter E Highfield,7 Martin H Thornhill1,2 1Unit of Oral and Maxillofacial Medicine and Surgery, University of Sheffield School of Clinical Dentistry, Sheffield, United Kingdom; 2Unit of Oral Medicine, Charles Clifford Dental Hospital, Sheffield Teaching Hospitals National Health Service Foundation Trust, Sheffield, United Kingdom; 3Unit of Oral and Maxillofacial Pathology, University of Sheffield School of Clinical Dentistry, Sheffield, United Kingdom; 4Department of Gynaecological Oncology, 5Department of Medical Physics, Royal Hallamshire Hospital, Sheffield, United Kingdom; 6University of Sheffield Medical School, Beech Hill Road, Sheffield, United Kingdom; 7Zilico Ltd., The MedTECH Centre, Rutherford House, Manchester Science Park, Manchester, United Kingdom Abstract: The electrical properties of tissues depend on their architecture and cellular composition. We have previously shown that changes in electrical impedance can be used to differentiate between different degrees of cervical dysplasia and cancer of the cervix. In this proof-of-concept study, we aimed to determine whether electrical impedance spectroscopy (EIS) could distinguish between normal oral mucosa; benign, potentially malignant lesions (PML); and oral cancer. EIS data were collected from oral cancer (n=10), PML (n=27), and benign (n=10) lesions. EIS from lesions was compared with the EIS reading from the normal mucosa on the contralateral side of the mouth or with reference spectra from mucosal sites of control subjects (n=51). Healthy controls displayed significant differences in the EIS obtained from different oral sites. In addition, there were significant differences in the EIS of cancer and high-risk PML versus low-risk PML and controls. There was no significant difference between benign lesions and normal controls. Study subjects also deemed the EIS procedure considerably less painful and more convenient than the scalpel biopsy procedure. EIS shows promise at distinguishing among malignant, PML, and normal oral mucosa and has the potential to be developed into a clinical diagnostic tool. Keywords: oral cancer, head and neck cancer, potentially malignant lesions, dysplasia, impedance spectroscopy