Factors influencing medium- and long-term occupational impact following COVID-19.

BACKGROUND: Significant numbers of individuals struggle to return to work following acute coronavirus disease 2019 (COVID-19). The UK Military developed an integrated medical and occupational pathway (Defence COVID-19 Recovery Service, DCRS) to ensure safe return to work for those with initially severe disease or persistent COVID-19 sequalae. Medical deployment status (MDS) is used to determine ability to perform job role without restriction ('fully deployable', FD) or with limitations ('medically downgraded', MDG). AIMS: To identify which variables differ between those who are FD and MDG 6 months after acute COVID-19. Within the downgraded cohort, a secondary aim is to understand which early factors are associated with persistent downgrading at 12 and 18 months. METHODS: Individuals undergoing DCRS had comprehensive clinical assessment. Following this, their electronic medical records were reviewed and MDS extracted at 6, 12 and 18 months. Fifty-seven predictors taken from DCRS were analysed. Associations were sought between initial and prolonged MDG. RESULTS: Three hundred and twenty-five participants were screened, with 222 included in the initial analysis. Those who were initially downgraded were more likely to have post-acute shortness of breath (SoB), fatigue and exercise intolerance (objective and subjective), cognitive impairment and report mental health symptoms. The presence of fatigue and SoB, cognitive impairment and mental health symptoms was associated with MDG at 12 months, and the latter two, at 18 months. There were also modest associations between cardiopulmonary function and sustained downgrading. CONCLUSIONS: Understanding the factors that are associated with initial and sustained inability to return to work allows individualized, targeted interventions to be utilized.

High tibial osteotomy to neutral alignment improves medial knee articular cartilage composition.

PURPOSE: The purpose of this study was to: (1) test the hypothesis that HTO improves articular cartilage composition in the medial compartment without adversely affecting the lateral compartment and patella, and; (2) explore associations between knee alignment and cartilage composition after surgery. METHODS: 3T MRI and standing radiographs were obtained from 34 patients before and 1-year after HTO. Articular cartilage was segmented from T2 maps. Mechanical axis angle (MAA), posterior tibial slope, and patellar height were measured from radiographs. Changes in T2 and radiographic measures were assessed using paired t tests, and associations were assessed using Pearson correlation coefficients. RESULTS: The mean (SD) MAA before and after HTO was - 6.5° (2.4) and 0.6° (3.0), respectively. There was statistically significant shortening [mean (95%CI)] of T2 in the medial femur [- 2.8 ms (- 4.2; - 1.3), p < 0.001] and medial tibia [- 2.2 ms (- 3.3; - 1.0), p < 0.001], without changes in the lateral femur [- 0.5 ms (- 1.6; 0.6), p = 0.3], lateral tibia [0.2 ms (- 0.8; 1.1), p = NS], or patella [0.5 ms (- 1.0; 2.1), p = NS). Associations between radiographic measures and T2 were low. 23% of the increase in lateral femur T2 was explained by postoperative posterior tibial slope (r = 0.48). CONCLUSION: Performing medial opening wedge HTO without overcorrection improves articular cartilage composition in the medial compartment of the knee without compromising the lateral compartment or the patella. Although further research is required, these results suggest HTO is a disease structure-modifying treatment for knee OA.

Extending the dynamic range of biomedical micro-computed tomography for application to geomaterials.

BACKGROUND: X-ray computed tomography (CT) can non-destructively examine objects by producing three-dimensional images of their internal structure. Although the availability of biomedical micro-CT offers the increased access to scanners, CT images of dense objects are susceptible to artifacts particularly due to beam hardening. OBJECTIVE: This study proposes and evaluates a simple semi-empirical correction method for beam hardening and scatter that can be applied to biomedical scanners. METHODS: Novel calibration phantoms of varying diameters were designed and built from aluminum and poly[methyl-methacrylate]. They were imaged using two biomedical micro-CT scanners. Absorbance measurements made through different phantom sections were fit to polynomial and inversely exponential functions and used to determine linearization parameters. Corrections based on the linearization equations were applied to the projection data before reconstruction. RESULTS: Correction for beam hardening was achieved when applying both scanners with the correction methods to all test objects. Among them, applying polynomial correction method based on the aluminum phantom provided the best improvement. Correction of sample data demonstrated a high agreement of percent-volume composition of dense metallic inclusions between using the Bassikounou meteorite from the micro-CT images (13.7%) and previously published results using the petrographic thin sections (14.6% 8% metal and 6.6% troilite). CONCLUSIONS: Semi-empirical linearization of X-ray projection data with custom calibration phantoms allows accurate measurements to be obtained on the radiodense samples after applying the proposed correction method on biomedical micro-CT images.

A community laboratory drop-off option for bowel screening test kits increases participation rates: results from an interrupted time series analysis.

Background: Countries with population-based colorectal cancer screening using faecal occult blood test kits performed in the home and posted to the laboratory struggle to achieve higher than 60% uptake. We measured the impact on participation of offering a community laboratory drop-off (CLD) alternative to postal return in New Zealand's Bowel Screening Pilot. Methods: From May to September, 2015, a flyer added to the bowel screening test kit offered CLD as an alternative to returning the kit by post. Participation rates for equal-length periods before and after were measured. Interrupted time series and logistic regression models measured CLD-attributable the changes in screening participation. Results: Overall, 26% of invitees used the CLD option. The effect of the CLD option on participation varied significantly by age, gender and ethnicity. There was a significant increase in participation among males (+1.75%; P = 0.002); patients under 60 (+1.65%; P = 0.006); Maori and Pacific (+2.88%; P = 0.029); and in the European/other ethnic group (+1.04%; P = 0.045) but not in Asians. Conclusions: Both analyses showed that at little or no additional cost, the CLD option produced small but significant increases in participation for non-Asian men and younger invitees. A CLD kit return option may have benefits for other bowel screening programmes.

Whole-body vibration of mice induces articular cartilage degeneration with minimal changes in subchondral bone.

OBJECTIVE: Low-amplitude, high-frequency whole-body vibration (WBV) has been adopted for the treatment of musculoskeletal diseases including osteoarthritis (OA); however, there is limited knowledge of the direct effects of vibration on joint tissues. Our recent studies revealed striking damage to the knee joint following exposure of mice to WBV. The current study examined the effects of WBV on specific compartments of the murine tibiofemoral joint over 8 weeks, including microarchitecture of the tibia, to understand the mechanisms associated with WBV-induced joint damage. DESIGN: Ten-week-old male CD-1 mice were exposed to WBV (45 Hz, 0.3 g peak acceleration; 30 min/day, 5 days/week) for 4 weeks, 8 weeks, or 4 weeks WBV followed by 4 weeks recovery. The knee joint was evaluated histologically for tissue damage. Architecture of the subchondral bone plate, subchondral trabecular bone, primary and secondary spongiosa of the tibia was assessed using micro-CT. RESULTS: Meniscal tears and focal articular cartilage damage were induced by WBV; the extent of damage increased between 4 and 8-week exposures to WBV. WBV did not alter the subchondral bone plate, or trabecular bone of the tibial spongiosa; however, a transient increase was detected in the subchondral trabecular bone volume and density. CONCLUSIONS: The lack of WBV-induced changes in the underlying subchondral bone suggests that damage to the articular cartilage may be secondary to the meniscal injury we detected. Our findings underscore the need for further studies to assess the safety of WBV in the human population to avoid long-term joint damage.

C57BL/6 mice are resistant to joint degeneration induced by whole-body vibration.

OBJECTIVE: Whole-body vibration (WBV) platforms are commercially available devices that are used clinically to treat numerous musculoskeletal conditions based on their reported ability to increase bone mineral density and muscle strength. Despite widespread use, there is an alarming lack of understanding of the direct effects of WBV on joint health. Previous work by our lab demonstrated that repeated exposure to WBV using protocols that model those used clinically, induces intervertebral disc (IVD) degeneration and osteoarthritis-like damage in the knee of skeletally mature, male mice of a single outbred strain (CD-1). The present study examined whether exposure to WBV induces similar deleterious effects in a genetically different strain of mouse (C57BL/6). DESIGN: Male 10-week-old C57BL/6 mice were exposed to vertical sinusoidal WBV for 30 min/day, 5 days/week, for 4 or 8 weeks using previously reported protocols (45 Hz, 0.3 g peak acceleration). Following WBV, joint tissues were examined using histological analysis and gene expression was quantified using real-time PCR (qPCR). RESULTS: Our analyses show a lack of WBV-induced degeneration in either the knee or IVDs of C57BL/6 mice exposed to WBV for 4 or 8 weeks, in direct contrast to the WBV-induced damage previously reported by our lab in CD-1 mice. CONCLUSIONS: Together with previous studies from our group, the present study demonstrates that the effects of WBV on joint tissues vary in a strain-specific manner. These findings highlight the need to examine genetic or physiological differences that may underlie susceptibility to the deleterious effects of WBV on joint tissues.

The British Services Dhaulagiri Medical Research Expedition 2016: a unique military and civilian research collaboration.

INTRODUCTION: High-altitude environments lead to a significant physiological challenge and disease processes which can be life threatening; operational effectiveness at high altitude can be severely compromised. The UK military research is investigating ways of mitigating the physiological effects of high altitude. METHODS: The British Service Dhaulagiri Research Expedition took place from March to May 2016, and the military personnel were invited to consent to a variety of study protocols investigating adaptation to high altitudes and diagnosis of high-altitude illness. The studies took place in remote and austere environments at altitudes of up to 7500 m. RESULTS: This paper gives an overview of the individual research protocols investigated, the execution of the expedition and the challenges involved. 129 servicemen and women were involved at altitudes of up to 7500 m; 8 research protocols were investigated. CONCLUSIONS: The outputs from these studies will help to individualise the acclimatisation process and inform strategies for pre-acclimatisation should troops ever need to deploy at high altitude at short notice.

Iodine potassium iodide improves the contrast-to-noise ratio of micro-computed tomography images of the human middle ear.

High-resolution imaging of middle-ear geometry is necessary for finite-element modeling. Although micro-computed tomography (microCT) is widely used because of its ability to image bony structures of the middle ear, it is difficult to visualize soft tissues - including the tympanic membrane and the suspensory ligaments/tendons - because of lack of contrast. The objective of this research is to quantitatively evaluate the efficacy of iodine potassium iodide (IKI) solution as a contrast agent. Six human temporal bones were used in this experiment, which were obtained in right-left pairs, from three cadaveric heads. All bones were fixed using formaldehyde. Three bones (one from each pair) were stained in IKI solution for 2 days, whereas the other three were not stained. Samples were scanned using a microCT system at a resolution of 20 µm. Eight soft tissues in the middle ear were segmented: anterior mallear ligament, incudomallear joint, lateral mallear ligament, posterior incudal ligament, stapedial annular ligament, stapedius muscle, tympanic membrane and tensor tympani muscle. Contrast-to-noise ratios (CNRs) of each soft tissue were calculated for each temporal bone. Combined CNRs of the soft tissues in unstained samples were 6.1 ± 3.0, whereas they were 8.1 ± 2.7 in stained samples. Results from Welch's t-test indicate significant difference between the two groups at a 95% confidence interval. Results for paired t-tests for each of the individual soft tissues also indicated significant improvement of contrast in all tissues after staining. Relatively large soft tissues in the middle ear such as the tympanic membrane and the tensor tympani muscle were impacted by staining more than smaller tissues such as the stapedial annular ligament. The increase in contrast with IKI solution confirms its potential application in automatic segmentation of the middle-ear soft tissues.

Managing palpitations in the military patient.

'Palpitations' include a broad range of symptoms relating to the perception of abnormal activity of the heart. They may reflect an underlying arrhythmia or a hyperawareness of normal cardiac activity caused by stress or anxiety. The challenge to a clinician assessing patients with palpitations is to assess the likely cause of symptoms, to stratify the individual patient risk and to choose the correct management strategy delivered with appropriate urgency. The young military population, subject to increased exposure to environmental stress, is at an increased risk of palpitations. Due to the distracting nature of this symptom and the frequently sudden and unheralded onset, a common consequence is medical downgrading. This article will provide a guide to assessing the heterogeneous group presenting with palpitations and how to both establish the cause and identify the correct treatment for each patient in a timely manner.

Valvular heart disease and the military patient.

Valvular heart disease refers to all inherited and acquired abnormalities impairing the function of one or more of the four cardiac valves. Pathology may be of the valve leaflets themselves, of the subvalvular apparatus or of the annulus or other surrounding structures that influences valve function. This paper examines the most common valve lesions, with specific reference to a military population; it focuses on detection and initial management of valve disease in a young adult population and specifically describes how the diagnosis and treatment of valve disease impacts military medical grading.

Hypertension in the military patient.

Hypertension and hypertension-related diseases are a leading cause of morbidity and mortality worldwide. A diagnosis of hypertension can have serious occupational implications for military personnel. This article examines the diagnosis and management of hypertension in military personnel, in the context of current international standards. We consider the consequences of hypertension in the military environment and potential military-specific issues relating to hypertension.

Cardiomyopathies and the Armed Forces.

Cardiomyopathies are a group of heterogeneous myocardial diseases that are frequently inherited and are a recognised cause of premature sudden cardiac death in young individuals. Incomplete expressions of disease and the overlap with the physiological cardiac manifestations of regular intensive exercise create diagnostic challenges in young athletes and military recruits. Early identification is important because sudden death in the absence of prodromal symptoms is a common presentation, and there are several therapeutic strategies to minimise this risk. This paper examines the classification and clinical features of cardiomyopathies with specific reference to a military population and provides a detailed account of the optimum strategy for diagnosis, indications for specialist referral and specific guidance on the occupational significance of cardiomyopathy. A 27-year-old Lance Corporal Signaller presents to his Regimental medical officer (RMO) after feeling 'light-headed' following an 8 mile unloaded run. While waiting to see the RMO, the medical sergeant records a 12-lead ECG. The ECG is reviewed by the RMO immediately prior to the consultation and shows voltage criteria for left ventricular (LV) hypertrophy and inverted T-waves in II, III, aVF and V1-V3 (Figure 1). This Lance Corporal is a unit physical training instructor and engages in >10 h of aerobic exercise per week. He is a non-smoker and does not have any significant medical history.

How long is Long-COVID? Symptomatic improvement between 12 and 18 months in a prospective cohort study.

INTRODUCTION: COVID-19 infection can precede, in a proportion of patients, a prolonged syndrome including fatigue, exercise intolerance, mood and cognitive problems. This study aimed to describe the profile of fatigue-related, exercise-related, mood-related and cognitive-related outcomes in a COVID-19-exposed group compared with controls. METHODS: 113 serving UK Armed Forces participants were followed up at 5, 12 (n=88) and 18 months (n=70) following COVID-19. At 18 months, 56 were in the COVID-19-exposed group with 14 matched controls. Exposed participants included hospitalised (n=25) and community (n=31) managed participants. 43 described at least one of the six most frequent symptoms at 5 months: fatigue, shortness of breath, chest pain, joint pain, exercise intolerance and anosmia. Participants completed a symptom checklist, patient-reported outcome measures (PROMs), the National Institute for Health cognitive battery and a 6-minute walk test (6MWT). PROMs included the Fatigue Assessment Scale (FAS), Generalised Anxiety Disorder-7 (GAD-7), Patient Health Questionnaire-9 (PHQ-9) and Patient Checklist-5 (PCL-5) for post-traumatic stress. RESULTS: At 5 and 12 months, exposed participants presented with higher PHQ-9, PCL-5 and FAS scores than controls (ES (effect size) ≥0.25, p≤0.04). By 12 months, GAD-7 was not significantly different to controls (ES <0.13, p=0.292). Remaining PROMs lost significant difference by 18 months (ES ≤0.11, p≥0.28). No significant differences in the cognitive scales were observed at any time point (F=1.96, p=0.167). At 5 and 12 months, exposed participants recorded significantly lower distances on the 6MWT (ηp 2≥0.126, p<0.01). 6MWT distance lost significant difference by 18 months (ηp 2<0.039, p>0.15). CONCLUSIONS: This prospective cohort-controlled study observed adverse outcomes in depression, post-traumatic stress, fatigue and submaximal exercise performance up to 12 months but improved by 18-month follow-up, in participants exposed to COVID-19 compared with a matched control group.

Defence Medical Rehabilitation Centre (DMRC) COVID-19 Recovery Service.

Coronavirus disease 2019 (COVID-19) causes significant mortality and morbidity, with an unknown impact in the medium to long term. Evidence from previous coronavirus epidemics indicates that there is likely to be a substantial burden of disease, potentially even in those with a mild acute illness. The clinical and occupational effects of COVID-19 are likely to impact on the operational effectiveness of the Armed Forces. Collaboration between Defence Primary Healthcare, Defence Secondary Healthcare, Defence Rehabilitation and Defence Occupational Medicine resulted in the Defence Medical Rehabilitation Centre COVID-19 Recovery Service (DCRS). This integrated clinical and occupational pathway uses cardiopulmonary assessment as a cornerstone to identify, diagnose and manage post-COVID-19 pathology.

CBRN response and the future.

The Haywood Medical Society met in June 2011 to discuss issues surrounding the preparedness of both civilian and military emergency services to deal with a CBRN threat.

Development, design and experience of the UK Military's return to diving pathway following SARS-CoV-2 infection.

After the emergence of the SARS-CoV-2 virus in early 2020, it quickly became clear that symptomatic or asymptomatic infection had the potential to negatively impact on an individual's fitness to dive through effects on the respiratory, cardiovascular or neurological systems. The significance of these effects in the military diving environment was initially unclear due to an absence of data concerning incidence, chronology or severity. In order to safely return divers to the water and maintain operational capability, the UK Military developed a pathway for SARS-CoV-2 positive divers that stratified risk of sequelae and extent of required clinical investigation, while minimising reliance on viral testing and hospital-based investigations. We present this process, provide rationale and support for its design and detail the number of SARS-CoV-2 positive divers who have been returned to full diving fitness following infection of varying degrees of severity.

Cardiopulmonary exercise testing excludes significant disease in patients recovering from COVID-19.

OBJECTIVE: Post-COVID-19 syndrome presents a health and economic challenge affecting ~10% of patients recovering from COVID-19. Accurate assessment of patients with post-COVID-19 syndrome is complicated by health anxiety and coincident symptomatic autonomic dysfunction. We sought to determine whether either symptoms or objective cardiopulmonary exercise testing could predict clinically significant findings. METHODS: 113 consecutive military patients were assessed in a comprehensive clinical pathway. This included symptom reporting, history, examination, spirometry, echocardiography and cardiopulmonary exercise testing (CPET) in all, with chest CT, dual-energy CT pulmonary angiography and cardiac MRI where indicated. Symptoms, CPET findings and presence/absence of significant pathology were reviewed. Data were analysed to identify diagnostic strategies that may be used to exclude significant disease. RESULTS: 7/113 (6%) patients had clinically significant disease adjudicated by cardiothoracic multidisciplinary team (MDT). These patients had reduced fitness (V̇O2 26.7 (±5.1) vs 34.6 (±7.0) mL/kg/min; p=0.002) and functional capacity (peak power 200 (±36) vs 247 (±55) W; p=0.026) compared with those without significant disease. Simple CPET criteria (oxygen uptake (V̇O2) >100% predicted and minute ventilation (VE)/carbon dioxide elimination (V̇CO2) slope <30.0 or VE/V̇CO2 slope <35.0 in isolation) excluded significant disease with sensitivity and specificity of 86% and 83%, respectively (area under the receiver operating characteristic curve (AUC) 0.89). The addition of capillary blood gases to estimate alveolar-arterial gradient improved diagnostic performance to 100% sensitivity and 78% specificity (AUC 0.92). Symptoms and spirometry did not discriminate significant disease. CONCLUSIONS: In a population recovering from SARS-CoV-2, there is reassuringly little organ pathology. CPET and functional capacity testing, but not reported symptoms, permit the exclusion of clinically significant disease.

Quantifying lung morphology with respiratory-gated micro-CT in a murine model of emphysema.

Non-invasive micro-CT imaging techniques have been developed to investigate lung structure in free-breathing rodents. In this study, we investigate the utility of retrospectively respiratory-gated micro-CT imaging in an emphysema model to determine if anatomical changes could be observed in the image-derived quantitative analysis at two respiratory phases. The emphysema model chosen was a well-characterized, genetically altered model (TIMP-3 knockout mice) that exhibits a homogeneous phenotype. Micro-CT scans of the free-breathing, anaesthetized mice were obtained in 50 s and retrospectively respiratory sorted and reconstructed, providing 3D images representing peak inspiration and end expiration with 0.15 mm isotropic voxel spacing. Anatomical measurements included the volume and CT density of the lungs and the volume of the major airways, along with the diameters of the trachea, left bronchus and right bronchus. From these measurements, functional parameters such as functional residual capacity and tidal volume were calculated. Significant differences between the wild-type and TIMP-3 knockout groups were observed for measurements of CT density over the entire lung, indicating increased air content in the lungs of TIMP-3 knockout mice. These results demonstrate retrospective respiratory-gated micro-CT, providing images at multiple respiratory phases that can be analyzed quantitatively to investigate anatomical changes in murine models of emphysema.

Development of a customized density-modulus relationship for use in subject-specific finite element models of the ulna.

Assigning an appropriate density-modulus relationship is an important factor when applying inhomogeneous material properties to finite element models of bone. The purpose of this study was to develop a customized density-modulus equation for the distal ulna, using beam theory combined with experimental results. Five custom equations of the form E= ap(b) were used to apply material properties to models of eight ulnae. All equations passed through a point (1.85, Ec), where p = 1.85 g/cm3 represents the average density of cortical bone. For custom equations (1) to (3), Ec was predicted using beam theory, and the value of b was varied within the range reported in the literature. Custom equations (4) and (5) used other values of Ec from the literature, while keeping b constant. Results obtained from the custom equations were compared with those from other equations in the literature, and with experimental results. The beam theory analysis predicted Ec = 21 +/- 1.6 GPa, and the three custom equations using this value tended to have the lowest errors. The power of the equations did not affect the results as much as the value used for Ec. Overall, a customized density-modulus relationship for the ulna was generated, which provided improved results over using previously reported density-modulus equations.

Implementation of dual- and triple-energy cone-beam micro-CT for postreconstruction material decomposition.

Micro-CT has become a powerful tool for small animal research, having the ability to obtain high-resolution in vivo and ex vivo images for analyzing bone mineral content, organ vasculature, and bone microarchitecture extraction. The use of exogenous contrast agents further extends the use of micro-CT techniques, but despite advancements in contrast agents, single-energy micro-CT is still limited in cases where two different materials share similar grey-scale intensity values. This study specifically addresses the development of multiple-energy cone-beam micro-CT, for applications where bone must be separated from blood vessels filled with a Pb-based contrast material (Microfil) in ex vivo studies of rodents and tissue specimens. The authors report the implementation of dual- and triple-energy CT algorithms for material-specific imaging using postreconstruction decomposition of micro-CT data; the algorithms were implemented on a volumetric cone-beam micro-CT scanner (GE Locus Ultra). For the dual-energy approach, extrinsic filtration was applied to the x-ray beam to produce spectra with different proportions of x rays above the K edge of Pb. The optimum x-ray tube energies (140 kVp filtered with 1.45 mm Cu and 96 kVp filtered with 0.3 mm Pb) that maximize the contrast between bone and Microfil were determined through numerical simulation. For the triple-energy decomposition, an additional low-energy spectrum (70 kVp, no added filtration) was used. The accuracy of decomposition was evaluated through simulations and experimental verification of a phantom containing a cortical bone simulating material (SB3), Microfil, and acrylic. Using simulations and phantom experiments, an accuracy greater than 95% was achieved in decompositions of bone and Microfil (for noise levels lower than 11 HU), while soft tissue was separated with accuracy better than 99%. The triple-energy technique demonstrated a slightly higher, but not significantly different, decomposition accuracy than the dual-energy technique for the same achieved noise level in the micro-CT images acquired at the multiple energies. The dual-energy technique was applied to the decomposition of an ex vivo rat specimen perfused with Microfil; successful decomposition of the bone and Microfil was achieved, enabling the visualization and characterization of the vasculature both in areas where the vessels traverse soft tissue and when they are surrounded by bone. In comparison, in single energy micro-CT, vessels surrounded by bone could not be distinguished from the cortical bone, based on grey-scale intensity alone. This work represents the first postreconstruction application of material-specific decomposition that directly takes advantage of the K edge characteristics of a contrast material injected into an animal specimen; the application of the technique resulted in automatic, accurate segmentation of 3D micro-CT images into bone, vessel, and tissue components. The algorithm uses only reconstructed images, rather than projection data, and is calibrated by an operator with signal values in regions identified as being comprised entirely of either cortical bone, contrast-enhanced vessel, or soft tissue; these required calibration values are observed directly within reconstructed CT images acquired at the multiple energies. These features facilitate future implementation on existing research micro-CT systems.