BACKGROUND:Idiopathic subglottic stenosis (iSGS) is a rare fibrotic disease of the proximal airway affecting adult White women nearly exclusively. Life-threatening ventilatory obstruction occurs secondary to pernicious subglottic mucosal scar. Disease rarity and wide geographic patient distribution have previously limited substantive mechanistic investigation into iSGS pathogenesis. STUDY DESIGN:Harnessing pathogenic mucosa from an international iSGS patient cohort and single-cell RNA sequencing, we provide an unbiased characterization of the cell subsets present in the proximal airway scar and detail their molecular phenotypes. RESULTS:Airway epithelium in patients with iSGS is depleted of basal progenitor cells and the residual epithelial cells acquire a mesenchymal phenotype. Observed displacement of bacteria beneath the lamina propria provides functional support for the molecular evidence of epithelial dysfunction. Matched superficial and deep tissue microbiomes support displacement of the native microbiome into the lamina propria of patients iSGS rather than disrupted bacterial community structure. However, animal models confirm that bacteria are necessary for pathologic proximal airway fibrosis and suggest an equally essential role for host adaptive immunity. Human samples from iSGS airway scar demonstrate adaptive immune activation in response to the proximal airway microbiome of both matched patients with iSGS and healthy controls. Clinical outcome data from patients with iSGS suggests that surgical extirpation of airway scar and reconstitution with unaffected tracheal mucosa halts the progressive fibrosis. CONCLUSIONS:Our novel data support an iSGS disease model in which epithelial alterations facilitate microbiome displacement, dysregulated immune activation, and localized fibrosis. Overall, these results refine our understanding of iSGS and implicate shared pathogenic mechanisms with distal airway fibrotic diseases.

Background:Invasive candidiasis is a fungal infection of the blood or organs that is associated with high morbidity and mortality in critically ill patients. Current diagnosis is based on blood culture, which typically takes 2 days to confirm the presence of Candida, and longer for differentiating the species and sensitivities to antifungal drugs. Administration of antifungal treatment is time-critical, hence critically ill patients considered 'at-risk' of Candida infection are often started on antifungal treatment pending test results. However, many of these patients may not have empirical treatment stopped when test results become available because of concerns about the sensitivity of blood culture. The Antifungal STewardship Opportunities study is a multisite national diagnostic test accuracy study investigating the use of rapid tests in the intensive care unit that have the potential to influence decision-making. Objective(s), study design, settings and participants:Our aim is to understand patient and physician risk preferences for using the Antifungal STewardship Opportunities testing strategy to discontinue empirical antifungal therapy using semi-structured interviews. An a priori sample size of 30 National Health Service staff and 10 patient interviews was selected to elicit information relating to the aims. Interview schedules were developed, and all interviews were conducted via video or teleconferencing between December 2021 and December 2022 and lasted between 10 and 60 minutes. Interviews were recorded, transcribed and subjected to thematic analysis. Findings:Semi-structured interviews were conducted with 21 National Health Service clinicians and seven patients and legal representatives. National Health Service staff were risk-averse to stopping empirical antifungal therapy, especially if the patient was improving, while patients were risk-neutral. Although there is a clear unmet need for new rapid testing strategy, clinical confidence in its accuracy, clinical utility, cost-effectiveness and usability were strong factors for its consideration for use in decision-making and adoption. Patients did not exhibit strong feelings towards stopping empirical antifungal treatment as they expressed reliance on clinical judgement. Limitations:There was a potential for selection bias as interview participants being from participating sites. The target recruitment numbers of patients and their legal representatives was not achieved due to low retention rates. Conclusions:If found to have high accuracy and cost-effectiveness, the potential of the Antifungal STewardship Opportunities diagnostic strategy to aid decision-making on antifungal prescribing could change intensive care unit clinicians practice, as they are risk-averse to stopping empirical antifungal treatment. However, consideration of the resources needed including staff, and lab facilities, adequate training as well as established guidelines to facilitate its adoption is required. Future work:Our next aim is to use Antifungal STewardship Opportunities results to inform the update of National Institute for Health and Care Excellence guidelines and explore schemes such as the Accelerated Access Collaborative and MedTech funding mandate to propel the adoption of this testing strategy. Funding:This article presents independent research funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme as award number 15/116/03.

Hypersensitivity pneumonitis (HP) is characterised by an excessive pulmonary T cell response in susceptible individuals after exposure to inhaled antigens. The most effective treatment for the condition is antigen avoidance, but in most cases an antigen cannot be identified. Profiling antigen-specific T cell responses may form the basis of a strategy to identify causative antigens of the disease. We used public RNA sequencing data and reconstructed T cell receptor (TCR) repertoires from blood and bronchoalveolar lavage samples from patients with HP, idiopathic pulmonary fibrosis and healthy controls. After excluding TCR sequences likely to be related to common microbial exposures in patients with HP, we identified TCRs shared between patients with shared human leukocyte antigen alleles, indicating patients likely to have a common causative antigen. We also identified clusters of TCRs containing identical and similar TCR clones in individual patients that are plausibly related to the causative antigens in those patients. These results establish the feasibility of profiling TCR repertoires to identify antigens in HP. ### Competing Interest Statement The authors have declared no competing interest.

Background:Nintedanib slows progression of lung function decline in patients with progressive fibrosing (PF) interstitial lung disease (ILD) and was recommended for this indication within the United Kingdom (UK) National Health Service in Scotland in June 2021 and in England, Wales and Northern Ireland in November 2021. To date, there has been no national evaluation of the use of nintedanib for PF-ILD in a real-world setting. Methods:26 UK centres were invited to take part in a national service evaluation between 17 November 2021 and 30 September 2022. Summary data regarding underlying diagnosis, pulmonary function tests, diagnostic criteria, radiological appearance, concurrent immunosuppressive therapy and drug tolerability were collected via electronic survey. Results:24 UK prescribing centres responded to the service evaluation invitation. Between 17 November 2021 and 30 September 2022, 1120 patients received a multidisciplinary team recommendation to commence nintedanib for PF-ILD. The most common underlying diagnoses were hypersensitivity pneumonitis (298 out of 1120, 26.6%), connective tissue disease associated ILD (197 out of 1120, 17.6%), rheumatoid arthritis associated ILD (180 out of 1120, 16.0%), idiopathic nonspecific interstitial pneumonia (125 out of 1120, 11.1%) and unclassifiable ILD (100 out of 1120, 8.9%). Of these, 54.4% (609 out of 1120) were receiving concomitant corticosteroids, 355 (31.7%) out of 1120 were receiving concomitant mycophenolate mofetil and 340 (30.3%) out of 1120 were receiving another immunosuppressive/modulatory therapy. Radiological progression of ILD combined with worsening respiratory symptoms was the most common reason for the diagnosis of PF-ILD. Conclusion:We have demonstrated the use of nintedanib for the treatment of PF-ILD across a broad range of underlying conditions. Nintedanib is frequently co-prescribed alongside immunosuppressive and immunomodulatory therapy. The use of nintedanib for the treatment of PF-ILD has demonstrated acceptable tolerability in a real-world setting.

BackgroundTracheostomies in children are associated with significant morbidity, poor quality of life, excess healthcare costs and excess mortality. The underlying mechanisms facilitating adverse respiratory outcomes in tracheostomised children are poorly understood. We aimed to characterise airway host defence in tracheostomised children using serial molecular analyses. MethodsTracheal aspirates, tracheal cytology brushings and nasal swabs were prospectively collected from children with a tracheostomy and controls. Transcriptomic, proteomic and metabolomic methods were applied to characterise the impact of tracheostomy on host immune response and the airway microbiome. ResultsChildren followed up serially from the time of tracheostomy up to 3 months postprocedure (n=9) were studied. A further cohort of children with a long-term tracheostomy were also enrolled (n=24). Controls (n=13) comprised children without a tracheostomy undergoing bronchoscopy. Long-term tracheostomy was associated with airway neutrophilic inflammation, superoxide production and evidence of proteolysis when compared with controls. Reduced airway microbial diversity was established pre-tracheostomy and sustained thereafter. ConclusionsLong-term childhood tracheostomy is associated with a inflammatory tracheal phenotype characterised by neutrophilic inflammation and the ongoing presence of potential respiratory pathogens. These findings suggest neutrophil recruitment and activation as potential exploratory targets in seeking to prevent recurrent airway complications in this vulnerable group of patients.

Background: Nintedanib was approved in the UK for use in progressive fibrosing interstitial lung disease (PF-ILD) in November 2021.1 The prescribing criteria defines PF-ILD using the diagnostic criteria established by the INBUILD study.2 There has been no national evaluation of the use of nintedanib for PF-ILD in a real-world setting. Methods: A service evaluation was distributed to specialist interstitial lung disease (ILD) centres in the UK in September 2022. Local clinical audit department approval was obtained. Results: 24 centres responded to the service evaluation invitation. Between 17/11/2021 and 30/09/2022, 1120 patients were commenced on nintedanib for PF-ILD. The most common diagnoses were hypersensitivity pneumonitis (298/1120,26.6%), connective tissue disease ILD (197/1120,17.6%), rheumatoid arthritis associated ILD disease (180/1120,16.0%), idiopathic non-specific interstitial pneumonia (125/1120,11.1%) and unclassifiable idiopathic interstitial pneumonic (100/1120,8.9%). Figure 1 demonstrates dual use of immunosupression and anti-fibrotic therapy. Discussion: This real-world service evaluation demonstrates widespread use in the UK of nintedanib for a broad range of PF-ILD subtypes. Contrary to the INBUILD study, clinicians are commonly using combined immunomodulatory and anti-fibrotic therapy.2 1. NICE, England, 2021. 2. Flaherty K.R. et al. N Engl J Med.2019;381(18):1718-1727.

BACKGROUND:Lymphopenia is defined as a decrease below normal value (often 1.0 x 109 cells/L) of blood circulating lymphocyte count. In the general population, lymphopenia is associated with an increased risk of hospitalisation secondary to infection, independent of traditional clinical risk factors. In hospital, lymphopenia is associated with increased risk of healthcare-associated infection and mortality. By summarising lymphopenia's prevalence and impact on clinical outcomes, we can identify an at-risk population and inform future studies of immune dysfunction following severe illness.METHODS:Peer-reviewed search strategy was performed on three databases. Primary objective was to summarise the pooled prevalence of lymphopenia. Primary outcome was infection including pre-existing lymphopenia as a risk factor for admission with infection and as an in-hospital risk factor for healthcare-associated infection. Secondary outcomes were length of stay and mortality. Mortality data extracted included in-hospital, 28/30-day ('early'), and 90-day/1-year ('late') mortality. Meta-analysis was carried out using random-effects models for each outcome measure. Heterogeneity was assessed using I2 statistic. Joanna Briggs Institute checklist for cohort studies was used to assess risk of bias. The protocol was published on PROSPERO.RESULTS:Fifteen observational studies were included. The pooled prevalence of lymphopenia in all-cause hospitalisations was 38% (CI 0.34-0.42, I2= 97%, p< 0.01). Lymphopenia was not associated with an infection diagnosis at hospital admission and healthcare associated infection (RR 1.03; 95% CI 0.26-3.99, p=0.97, I2 = 55% and RR 1.31; 95% CI 0.78-2.20, p=0.31, I2=97%, respectively), but was associated with septic shock (RR 2.72; 95% CI 1.02-7.21, p=0.04, I2 =98%). Lymphopenia was associated with higher in-hospital mortality and higher 'early' mortality rates (RR 2.44; 95% CI 1.71-3.47, p < 0.00001, I2 = 89% and RR 2.05; 95% CI 1.64-2.56, p < 0.00001, I2 = 29%, respectively). Lymphopenia was associated with higher 'late' mortality (RR 1.59; 1.33-1.90, p < 0.00001, I2 = 0%).CONCLUSIONS:This meta-analysis demonstrates the high prevalence of lymphopenia across all-cause hospitalisations and associated increased risk of septic shock, early and late mortality. Lymphopenia is a readily available marker that may identify immune dysfunctional patients. Greater understanding of immune trajectories following survival may provide insights into longer-term poor clinical outcomes.

Introduction: People with long-term health conditions often attend clinics for kidney function tests. The Self-Testing Own Kidneys (STOK) study assessed feasibility of kidney transplant recipients using hand-held devices to self-test kidney function at home and investigated agreement between home self-test and standard clinic test results.Methods: A prospective, observational, single-center, clinical feasibility study (TRN: ISRCTN68116915), with N = 15 stable kidney transplant recipients, investigated blood potassium and creatinine results agreement between index self-tests at home (patient self-testing of capillary blood, using Abbott i-STAT Alinity analyzers [i-STAT]) and reference tests in clinic (staff sampled venous blood, analyzed with labo-ratory Siemens Advia Chemistry XPT analyzer) using Bland-Altman and error grid analysis.Results: The mean within-patient difference between index and reference test in creatinine was 2.25 mmol/l (95% confidence interval [CI]: -12.13, 16.81 mmol/l) and in potassium was 0.66 mmol/l (95% CI: -1.47, 2.79 mmol/l). All creatinine pairs and 27 of 40 (67.5%) potassium pairs were judged clinically equivalent. Planned follow-up analysis suggests that biochemical variables associated with potassium measurement in capillary blood were predominant sources of paired test result differences. Paired patient and nurse i-STAT capillary blood test potassium results were not statistically significantly different.Conclusions: This small feasibility study observed that training selected patients to competently use hand-held devices to self-test kidney function at home is possible. Self-test creatinine results showed good analytical and clinical agreement with standard clinic test results. Self-test potassium results showed poorer agreement with standard clinic test results; however, patient self-use of i-STATs at home was not a statistically significant source of difference between paired potassium test results.

Introduction: Tissue factor expression on monocytes is implicated in the pathophysiology of sepsis-induced coagulopathy. How tissue factor is expressed by monocyte subsets (classical, intermediate and non-classical) is unknown. Methods: Monocytic tissue factor surface expression was investigated during three conditions. Primary human monocytes and microvascular endothelial cell co-cultures were used for in vitro studies. Volunteers received a bolus of lipopolysaccharide (2 ng/kg) to induce endotoxemia. Patients with sepsis, or controls with critical illness unrelated to sepsis, were recruited from four intensive care units. Results: Contact with endothelium and stimulation with lipopolysaccharide reduced the proportion of intermediate monocytes. Lipopolysaccharide increased tissue factor surface expression on classical and non-classical monocytes. Endotoxemia induced profound, transient monocytopenia, along with activation of coagulation pathways. In the remaining circulating monocytes, tissue factor was up-regulated in intermediate monocytes, though approximately 60 % of individuals (responders) up-regulated tissue factor across all monocyte subsets. In critically ill patients, tissue factor expression on intermediate and non-classical monocytes was significantly higher in patients with established sepsis than among non-septic patients. Upon recovery of sepsis, expression of tissue factor increased significantly in classical monocytes. Conclusion: Tissue factor expression in monocyte subsets varies significantly during health, endotoxemia and sepsis.

IntroductIon This BTS Clinical Statement addresses the risk assessment, prevention and management of communityacquired pneumonia (CAP) in people with a learning disability of all ages. Each section is summarised with key clinical practice points. The recommendations made are based on a comprehensive review of the published evidence, where available and pertinent, but are predominantly based on expert opinion aimed at providing useful pragmatic guidance. Learning disability is the preferred term used in the UK to refer to individuals who have ‘significantly reduced ability to understand new or complex information, to learn new skills’ and a ‘reduced ability to cope independently which starts before adulthood with lasting effects on development’. Individuals with learning disability represent a widely heterogeneous group of people and can be associated with a broad range of primary diagnoses and comorbidities. There is no definitive record of the number of people with learning disability in England. However, Public Health England (PHE) estimates that in 2015 the population was 1 087 100, including 930 400 adults (approximating 2% of the adult population). The estimated prevalence of learning disability in children and young people (CYP) is 2.5%. Far fewer individuals with learning disability were recorded in health and welfare systems. For example, only 324 291 children and adults were identified as having learning disability on general practitioner (GP) practicebased registers in 2021. It is likely that those registered have a more severe learning disability or more commonly associated conditions, for example, Down syndrome. This is important, as it means that many individuals with learning disability do not have their diagnosis recognised within health and welfare systems potentially increasing their vulnerability through lack of access to regular health reviews and other relevant public health programmes, for example, vaccination programmes. A series of measures have been introduced by the National Health Service (NHS) to help improve the identification of people with learning disability. The life expectancy of people with learning disability is reduced compared with the general population; only 37% of adults with learning disability live beyond 65 years of age compared with 85% of the general population. Pneumonia is the most common cause of death among adults with learning disability and is also a common cause of death in CYP with learning disability, with bacterial pneumonia accounting for a significant proportion of these (adults 24%, children 21%). A further 16% of adult and 3% of paediatric deaths in the learning disability population are caused by aspiration pneumonia (AP). CAP is a major contributor to the increased hospitalisation risk that has been described for people with learning disability and results in longer hospital stays than the general population. People with learning disability also experience increased rates of repeated admission secondary to CAP. As CAP is a major cause of death in people with learning disability, prevention, early detection and proactive management are key to reducing mortality from avoidable causes. It is important that public sector organisations make reasonable adjustments in their approach or provision to ensure that people with learning disability have equitable access to good quality healthcare. 10

Abstract Summary Lung inflammation is a major cause of respiratory failure. Although infection is a common precipitant of inflammation, it is far from the only cause. Distinguishing sterile from infective inflammation is a challenge. This chapter discusses the approaches to sampling the lungs directly for microbiological and host response assessment. It also examines the role of clinical examination and testing of the systemic and pulmonary compartments in monitoring lung inflammation.

Background:Idiopathic subglottic stenosis (iSGS) is a rare fibrotic disease of the proximal airway affecting adult Caucasian women nearly exclusively. Life-threatening ventilatory obstruction occurs secondary to pernicious subglottic mucosal scar. Disease rarity and wide geographic patient distribution has previously limited substantive mechanistic investigation into iSGS pathogenesis. Result:By harnessing pathogenic mucosa from an international iSGS patient cohort and single-cell RNA sequencing, we unbiasedly characterize the cell subsets in the proximal airway scar and detail their molecular phenotypes. Results show that the airway epithelium in iSGS patients is depleted of basal progenitor cells, and the residual epithelial cells acquire a mesenchymal phenotype. Observed displacement of bacteria beneath the lamina propria provides functional support for the molecular evidence of epithelial dysfunction. Matched tissue microbiomes support displacement of the native microbiome into the lamina propria of iSGS patients rather than disrupted bacterial community structure. However, animal models confirm that bacteria are necessary for pathologic proximal airway fibrosis and suggest an equally essential role for host adaptive immunity. Human samples from iSGS airway scar demonstrate adaptive immune activation in response to the proximal airway microbiome of both matched iSGS patients and healthy controls. Clinical outcome data from iSGS patients suggests surgical extirpation of airway scar and reconstitution with unaffected tracheal mucosa halts the progressive fibrosis. Conclusion:Our data support an iSGS disease model where epithelial alterations facilitate microbiome displacement, dysregulated immune activation, and localized fibrosis. These results refine our understanding of iSGS and implicate shared pathogenic mechanisms with distal airway fibrotic diseases.

Background, definitions, aims and scope of the clinical statement This BTS Clinical Statement seeks to provide practical clinical guidance on aspiration pneumonia (AP), through sections covering the relevant epidemiology, pathogenesis, prevention, diagnosis and management (including palliative care considerations where appropriate). Key clinical practice points appear at the end of each of these sections and are brought together in the highlighted summary below. Areas requiring important research to fill key knowledge gaps are highlighted in a separate section. The Statement arose because AP is disproportionately represented in people with a learning disability, in whom it is a major cause of death. The management of patients with communityacquired pneumonia (CAP) and learning disability is, therefore, the focus of a comprehensive parallel BTS Clinical Statement, in which learning disability is carefully defined. Despite this, however, most AP still occurs in people who do not have a learning disability. The existing literature on AP is of insufficient depth and quality to construct formal, comprehensive guidelines. For these reasons, the BTS proposed a Clinical Statement devoted to AP as a standalone document, but which specifically crossreferences the sister Clinical Statement. All of the general preventive, diagnostic and management principles described in this document can be applied to people with a learning disability, and the reader is directed to the relevant page of the statement on communityacquired pneumonia in people with learning disability. Importantly, this Clinical Statement seeks to complement the BTS Guidelines on CAP in adults and in children by giving an APspecific context. However, readers should appreciate that the evidence base in the Guidelines has far stronger foundations than the evidence base for AP. As AP predominantly occurs in older adults, this Clinical Statement principally refers to practice in adults. However, we were eager to provide context specific to children, and subsections considering special considerations in children are added throughout the document. AP refers to the microaspiration of bacteriarich oropharyngeal or gastrointestinal (GI) secretions into the lungs in sufficient amounts to cause alveolar and systemic inflammation. Microaspiration sufficient to cause pneumonia is usually associated with abnormal swallowing. To avoid any potential confusion, the terms swallowing impairment, abnormal swallowing or swallowing difficulties are used instead of the term dysphagia, throughout. AP is a common condition predominantly affecting older patients, and as the world’s population continues to expand and age, AP will become an increasing concern for healthcare systems globally. Impaired swallowing can lead to malnutrition, dehydration, choking, reduced quality of life and death. Because so many people are at risk of developing AP, a significant emphasis of this Statement is on prevention. AP has been the subject of excellent reviews and commentaries. However, two broad factors make it harder to generalise findings across studies on AP. First, it is often hard to diagnose AP with certainty, as microaspiration may be clinically ‘silent’ and unwitnessed. Second, microaspiration due to abnormal swallowing results from a wide range of pathologies, and so heterogeneous patient groups are included in published studies on AP. The Statement focuses on the common clinical setting in which bacteriarich oropharyngeal secretions are microaspirated into the lung. The following are not considered here: aspiration pneumonitis/“gross aspiration” (in which a large volume of vomitus of low pH suddenly enters the lungs, initially causing a chemical insult rather than infection); lipoid pneumonia; inhalation of foreign bodies; and meconium aspiration in the newborn. Similarly, microaspiration of infected secretions can cause disease of the airways (eg, bronchospasm, bronchiectasis and forms of bronchiolitis). We have focused on AP, but the interested reader is referred to articles describing aspirationrelated airway disease. 10 14

Objectives To explore the experience of caring for children with tracheostomies from the perspectives of parents and health professional caregivers. Design Qualitative semistructured interview study. Setting One region in England covered by a tertiary care centre that includes urban and remote rural areas and has a high level of deprivation. Participants A purposive sample of health professionals and parents who care for children who have, or have had, tracheostomies and who received care at the tertiary care centre. Intervention Interviews undertaken by telephone or video link. Primary and secondary outcome measures Qualitative reflexive thematic analysis with QSR Nvivo 12. Results This paper outlines key determinants and mediators of the experiences of caregiving and the impact on psychological and physical health and quality of life of parents and their families, confidence of healthcare providers and perceived quality of care. For parents, access to care packages and respite care at home as well as communication and relationships with healthcare providers are key mediators of their experience of caregiving, whereas for health professionals, an essential influence is multidisciplinary team working and support. We also highlight a range of challenges focused on the shared care space, including: a lack of standardisation in access to different support teams, care packages and respite care, irregular training and updates, and differences in health provider expertise and experiences across departments and shift patterns, exacerbated in some settings by limited contact with children with tracheostomies. Conclusions Understanding the experiences of caregiving can help inform measures to support caregivers and improve quality standards. Our findings suggest there is a need to facilitate further standardisation of care and support available for parent caregivers and that this may be transferable to other regions. Potential solutions to be explored could include the development of a paediatric tracheostomy service specification, increasing use of paediatric tracheostomy specialist nurse roles, and addressing the emotional and psychological support needs of caregivers.

Chemokine CXCL8 is a key facilitator of the human host immune response, mediating neutrophil migration, and activation at the site of infection and injury. The oxidative burst is an important effector mechanism which leads to the generation of reactive nitrogen species (RNS), including peroxynitrite. The current study was performed to determine the potential for nitration to alter the biological properties of CXCL8 and its detection in human disease. Here, we show peroxynitrite nitrates CXCL8 and thereby regulates neutrophil migration and activation. The nitrated chemokine was unable to induce transendothelial neutrophil migration in vitro and failed to promote leukocyte recruitment in vivo. This reduced activity is due to impairment in both G protein-coupled receptor signaling and glycosaminoglycan binding. Using a novel antibody, nitrated CXCL8 was detected in bronchoalveolar lavage samples from patients with pneumonia. These findings were validated by mass spectrometry. Our results provide the first direct evidence of chemokine nitration in human pathophysiology and suggest a natural mechanism that limits acute inflammation.