Dimensionless Groups by Entropic Similarity: I - Diffusion, Chemical Reaction and Dispersion Processes.

Since the time of Buckingham in 1914, dimensional analysis and similarity arguments based on dimensionless groups have served as powerful tools for the analysis of systems in all branches of science and engineering. Dimensionless groups are generally classified into those arising from geometric similarity, based on ratios of length scales; kinematic similarity, based on ratios of velocities or accelerations; and dynamic similarity, based on ratios of forces. We propose an additional category of dimensionless groups based on entropic similarity, defined by ratios of (i) entropy production terms; (ii) entropy flow rates or fluxes; or (iii) information flow rates or fluxes. Since all processes involving work against friction, dissipation, diffusion, dispersion, mixing, separation, chemical reaction, gain of information or other irreversible changes are driven by (or must overcome) the second law of thermodynamics, it is appropriate to analyze them directly in terms of competing entropy-producing and transporting phenomena and the dominant entropic regime, rather than indirectly in terms of forces. In this study, entropic groups are derived for a wide variety of diffusion, chemical reaction and dispersion processes relevant to fluid mechanics, chemical engineering and environmental engineering. It is shown that many dimensionless groups traditionally derived by kinematic or dynamic similarity (including the Reynolds number) can also be recovered by entropic similarity-with a different entropic interpretation-while many new dimensionless groups can also be identified. The analyses significantly expand the scope of dimensional analysis and similarity arguments for the resolution of new and existing problems in science and engineering.

Dimensionless Groups by Entropic Similarity: II-Wave Phenomena and Information-Theoretic Flow Regimes.

The aim of this study is to explore the insights of the information-theoretic definition of similarity for a multitude of flow systems with wave propagation. This provides dimensionless groups of the form Πinfo=U/c, where U is a characteristic flow velocity and c is a signal velocity or wave celerity, to distinguish different information-theoretic flow regimes. Traditionally, dimensionless groups in science and engineering are defined by geometric similarity, based on ratios of length scales; kinematic similarity, based on ratios of velocities or accelerations; and dynamic similarity, based on ratios of forces. In Part I, an additional category of entropic similarity was proposed based on ratios of (i) entropy production terms; (ii) entropy flow rates or fluxes; or (iii) information flow rates or fluxes. In this Part II, the information-theoretic definition is applied to a number of flow systems with wave phenomena, including acoustic waves, blast waves, pressure waves, surface or internal gravity waves, capillary waves, inertial waves and electromagnetic waves. These are used to define the appropriate Mach, Euler, Froude, Rossby or other dimensionless number(s)-including new groups for internal gravity, inertial and electromagnetic waves-to classify their flow regimes. For flows with wave dispersion, the coexistence of different celerities for individual waves and wave groups-each with a distinct information-theoretic group-is shown to imply the existence of more than two information-theoretic flow regimes, including for some acoustic wave systems (subsonic/mesosonic/supersonic flow) and most systems with gravity, capillary or inertial waves (subcritical/mesocritical/supercritical flow). For electromagnetic wave systems, the additional vacuum celerity implies the existence of four regimes (subluminal/mesoluminal/transluminal/superluminal flow). In addition, entropic analyses are shown to provide a more complete understanding of frictional behavior and sharp transitions in compressible and open channel flows, as well as the transport of entropy by electromagnetic radiation. The analyses significantly extend the applications of entropic similarity for the analysis of flow systems with wave propagation.

Factors affecting adherence with treatment advice in a clinical trial of patients with severe asthma.

BACKGROUND: Understanding why patients with severe asthma do not follow healthcare provider (HCP) advice to adjust treatment is critical to achieving personalised disease management. METHODS: We reviewed patient choice to follow HCP advice to adjust asthma treatment in a UK-based randomised, controlled, single-blind (study participant), multicentre, parallel group 48-week clinical study comparing biomarker-directed treatment adjustment with standard care in severe asthma. RESULTS: Of 1572 treatment advisories (291 participants), instructions were followed in 1377 cases (87.6%). Patients were more likely to follow advice to remain on treatment (96.7%) than to either reduce (70.3%) or increase (67.1%) their treatment, with 64% of patients following all treatment advice. Multivariate analysis associated belonging to an ethnic minority group (OR 3.10, 95% CI 1.68-5.73) and prior study medication changes (two or more changes: OR 2.77, 95% CI 1.51-5.10) with failure to follow treatment advice. In contrast, emergency room attendance in the prior year (OR 0.54, 95% CI 0.32-0.92) was associated with following treatment advice. The largest effect was seen with transition onto or off oral corticosteroids (OR 29.28, 95% CI 16.07-53.36) when compared with those requested to maintain treatment. Centre was also an important determinant regarding the likelihood of patients to follow treatment advice. CONCLUSIONS: Belonging to an ethnic minority group and multiple prior treatment adjustments were associated with not following HCP treatment advice. Patients also responded differently to HCP advice across UK specialist centres. These findings have implications for the generalisability of models of care in severe asthma and require further focused studies.

Phenotypic and functional translation of IL33 genetics in asthma.

BACKGROUND: Asthma is a complex disease with multiple phenotypes that may differ in disease pathobiology and treatment response. IL33 single nucleotide polymorphisms (SNPs) have been reproducibly associated with asthma. IL33 levels are elevated in sputum and bronchial biopsies of patients with asthma. The functional consequences of IL33 asthma SNPs remain unknown. OBJECTIVE: This study sought to determine whether IL33 SNPs associate with asthma-related phenotypes and with IL33 expression in lung or bronchial epithelium. This study investigated the effect of increased IL33 expression on human bronchial epithelial cell (HBEC) function. METHODS: Association between IL33 SNPs (Chr9: 5,815,786-6,657,983) and asthma phenotypes (Lifelines/DAG [Dutch Asthma GWAS]/GASP [Genetics of Asthma Severity & Phenotypes] cohorts) and between SNPs and expression (lung tissue, bronchial brushes, HBECs) was done using regression modeling. Lentiviral overexpression was used to study IL33 effects on HBECs. RESULTS: We found that 161 SNPs spanning the IL33 region associated with 1 or more asthma phenotypes after correction for multiple testing. We report a main independent signal tagged by rs992969 associating with blood eosinophil levels, asthma, and eosinophilic asthma. A second, independent signal tagged by rs4008366 presented modest association with eosinophilic asthma. Neither signal associated with FEV1, FEV1/forced vital capacity, atopy, and age of asthma onset. The 2 IL33 signals are expression quantitative loci in bronchial brushes and cultured HBECs, but not in lung tissue. IL33 overexpression in vitro resulted in reduced viability and reactive oxygen species-capturing of HBECs, without influencing epithelial cell count, metabolic activity, or barrier function. CONCLUSIONS: We identify IL33 as an epithelial susceptibility gene for eosinophilia and asthma, provide mechanistic insight, and implicate targeting of the IL33 pathway specifically in eosinophilic asthma.

A Hierarchy of Probability, Fluid and Generalized Densities for the Eulerian Velocivolumetric Description of Fluid Flow, for New Families of Conservation Laws.

The Reynolds transport theorem occupies a central place in continuum mechanics, providing a generalized integral conservation equation for the transport of any conserved quantity within a fluid or material volume, which can be connected to its corresponding differential equation. Recently, a more generalized framework was presented for this theorem, enabling parametric transformations between positions on a manifold or in any generalized coordinate space, exploiting the underlying continuous multivariate (Lie) symmetries of a vector or tensor field associated with a conserved quantity. We explore the implications of this framework for fluid flow systems, based on an Eulerian velocivolumetric (position-velocity) description of fluid flow. The analysis invokes a hierarchy of five probability density functions, which by convolution are used to define five fluid densities and generalized densities relevant to this description. We derive 11 formulations of the generalized Reynolds transport theorem for different choices of the coordinate space, parameter space and density, only the first of which is commonly known. These are used to generate a table of integral and differential conservation laws applicable to each formulation, for eight important conserved quantities (fluid mass, species mass, linear momentum, angular momentum, energy, charge, entropy and probability). The findings substantially expand the set of conservation laws for the analysis of fluid flow and dynamical systems.

Characterisation of patients with severe asthma in the UK Severe Asthma Registry in the biologic era.

BACKGROUND: The UK Severe Asthma Registry (UKSAR) is the world's largest national severe asthma registry collecting standardised data on referrals to UK specialist services. Novel biologic therapies have transformed the management of type 2(T2)-high severe asthma but have highlighted unmet need in patients with persisting symptoms despite suppression of T2-cytokine pathways with corticosteroids. METHODS: Demographic, clinical and treatments characteristics for patients meeting European Respiratory Society / American Thoracic Society severe asthma criteria were examined for 2225 patients attending 15 specialist severe asthma centres. We assessed differences in biomarker low patients (fractional exhaled nitric oxide (FeNO) <25 ppb, blood eosinophils <150/µL) compared with a biomarker high population (FeNO ≥25 ppb, blood eosinophils ≥150/µL). RESULTS: Age (mean 49.6 (14.3) y), age of asthma onset (24.2 (19.1) y) and female predominance (62.4%) were consistent with prior severe asthma cohorts. Poor symptom control (Asthma Control Questionnaire-6: 2.9 (1.4)) with high exacerbation rate (4 (IQR: 2, 7)) were common despite high-dose treatment (51.7% on maintenance oral corticosteroids (mOCS)). 68.9% were prescribed biologic therapies including mepolizumab (50.3%), benralizumab (26.1%) and omalizumab (22.6%). T2-low patients had higher body mass index (32.1 vs 30.2, p<0.001), depression/anxiety prevalence (12.3% vs 7.6%, p=0.04) and mOCS use (57.9% vs 42.1%, p<0.001). Many T2-low asthmatics had evidence of a historically elevated blood eosinophil count (0.35 (0.13, 0.60)). CONCLUSIONS: The UKSAR describes the characteristics of a large cohort of asthmatics referred to UK specialist severe asthma services. It offers the prospect of providing novel insights across a range of research areas and highlights substantial unmet need with poor asthma control, impaired lung function and high exacerbation rates. T2-high phenotypes predominate with significant differences apparent from T2-low patients. However, T2-low patients frequently have prior blood eosinophilia consistent with possible excessive corticosteroid exposure.

Attack, flare-up, or exacerbation? The terminology preferences of patients with severe asthma.

Background: People with severe asthma experience frequent life-threatening acute asthma events. A Lancet commission recently highlighted that terms "exacerbations" and "flare-ups" are seen to trivialize these episodes and recommended use of the term "attacks." Clinicians however, preferentially use the term "exacerbation" and some guidelines recommend the use of "exacerbation" with patients.Objective: This descriptive qualitative study aimed to understand the patient's experience and perspectives of these events and language used to describe them.Methods: Semi-structured one-on-one interviews were conducted in Australia and the UK in 18 people with severe asthma and 10 with mild-moderate asthma regarding their usage and preferences for such terminologies. Additionally, nine people with severe asthma participated in two focus groups in which use of preferred terminology was explored.Results: Mean age of participants was 57 ± 14.03 yr and 65% were female. A total 67 quotes were recorded in which 16 participants with severe asthma spontaneously used either the term "attack," "flare-up" and/or "exacerbation." Of these quotes, all 16 participants used "attack," one used all three terms and two used both "exacerbation" and "attack." The term "attack" was used to describe frightening events having major impacts on participant's lives, whereas "exacerbation" and "flare-up" were used to refer to both severe and mild, transient asthma-related events.Conclusion: Usage of the term "attack" was preferred by patients with severe asthma. Adoption of this language may assist in patient-clinician communication and disease management and outcomes. Wider stakeholder engagement is needed to confirm this suggestion. AbbreviationsFEV1forced expiratory volume in 1 secondATSAmerican Thoracic SocietyERSEuropean Respiratory SocietyACQAsthma Control QuestionnaireICSinhaled corticosteroidsOCSoral corticosteroidsBTSBritish Thoracic SocietySIGNScottish Intercollegiate Guidelines NetworkWAPwritten action plan.

Severe asthma assessment, management and the organisation of care in Australia and New Zealand: expert forum roundtable meetings.

Severe asthma imposes a significant burden on individuals, families and the healthcare system. Treatment is complex, due to disease heterogeneity, comorbidities and complexity in care pathways. New approaches and treatments improve health outcomes for people with severe asthma. However, emerging multidimensional and targeted treatment strategies require a reorganisation of asthma care. Consensus is required on how reorganisation should occur and what areas require further research. The Centre of Excellence in Severe Asthma convened three forums between 2015 and 2018, hosting experts from Australia, New Zealand and the UK. The forums were complemented by a survey of clinicians involved in the management of people with severe asthma. We sought to: (i) identify areas of consensus among experts; (ii) define activities and resources required for the implementation of findings into practice; and (iii) identify specific priority areas for future research. Discussions identified areas of unmet need including assessment and diagnosis of severe asthma, models of care and treatment pathways, add-on treatment approaches and patient perspectives. We recommend development of education and training activities, clinical resources and standards of care documents, increased stakeholder engagement and public awareness campaigns and improved access to infrastructure and funding. Further, we propose specific future research to inform clinical decision-making and develop novel therapies. A concerted effort is required from all stakeholders (including patients, healthcare professionals and organisations and government) to integrate new evidence-based practices into clinical care and to advance research to resolve questions relevant to improving outcomes for people with severe asthma.

Invariance Properties of the Entropy Production, and the Entropic Pairing of Inertial Frames of Reference by Shear-Flow Systems.

This study examines the invariance properties of the thermodynamic entropy production in its global (integral), local (differential), bilinear, and macroscopic formulations, including dimensional scaling, invariance to fixed displacements, rotations or reflections of the coordinates, time antisymmetry, Galilean invariance, and Lie point symmetry. The Lie invariance is shown to be the most general, encompassing the other invariances. In a shear-flow system involving fluid flow relative to a solid boundary at steady state, the Galilean invariance property is then shown to preference a unique pair of inertial frames of reference-here termed an entropic pair-respectively moving with the solid or the mean fluid flow. This challenges the Newtonian viewpoint that all inertial frames of reference are equivalent. Furthermore, the existence of a shear flow subsystem with an entropic pair different to that of the surrounding system, or a subsystem with one or more changing entropic pair(s), requires a source of negentropy-a power source scaled by an absolute temperature-to drive the subsystem. Through the analysis of different shear flow subsystems, we present a series of governing principles to describe their entropic pairing properties and sources of negentropy. These are unaffected by Galilean transformations, and so can be understood to "lie above" the Galilean inertial framework of Newtonian mechanics. The analyses provide a new perspective into the field of entropic mechanics, the study of the relative motions of objects with friction.

Remotely Monitored Therapy and Nitric Oxide Suppression Identifies Nonadherence in Severe Asthma.

RATIONALE: Poor adherence is common in difficult-to-control asthma. Distinguishing patients with difficult-to-control asthma who respond to inhaled corticosteroids (ICS) from refractory asthma is an important clinical challenge. OBJECTIVES: Suppression of fractional exhaled nitric oxide (FeNO) with directly observed ICS therapy over 7 days can identify nonadherence to ICS treatment in difficult-to-control asthma. We examined the feasibility and utility of FeNO suppression testing in routine clinical care within UK severe asthma centers using remote monitoring technologies. METHODS: A web-based interface with integrated remote monitoring technology was developed to deliver FeNO suppression testing. We examined the utility of FeNO suppression testing to demonstrate ICS responsiveness and clinical benefit on electronically monitored treatment with standard high-dose ICS and long-acting ß2-agonist treatment. MEASUREMENTS AND MAIN RESULTS: Clinical response was assessed using the Asthma Control Questionnaire-5, spirometry, and biomarker measurements (FeNO and peripheral blood eosinophil count). Of 250 subjects, 201 completed the test with 130 positive suppression tests. Compared with a negative suppression test, a positive test identified a FeNO-low population when adherent with ICS/long-acting ß2-agonist (median, 26 ppb [interquartile range, 16-36 ppb] vs. 43 ppb [interquartile range, 38-73 ppb]) with significantly greater FEV1% (mean, 88.2 ± 16.4 vs. 74.1 ± 20.9; P < 0.01). Asthma Control Questionnaire-5 improved significantly in both groups (positive test: mean difference, -1.2; 95% confidence interval, -0.9 to -1.5; negative test: mean difference, -0.9; 95% confidence interval, -0.4 to -1.3). CONCLUSIONS: Remote FeNO suppression testing is an effective means of identifying nonadherence to ICS in subjects with difficult-to-control asthma and the substantial population of subjects who derive important clinical benefits from optimized ICS/long-acting ß2-agonist treatment.

Serum prednisolone levels as a marker of oral corticosteroid adherence in severe asthma.

BACKGROUND: Severe asthma is a complex heterogeneous disease typically requiring advanced therapies. Underlying the treatment of all asthma, however, is the consistent recommendation across international guidelines to ensure that adherence to therapy is adequate. Currently, there is no consensus on an objective marker of adherence. METHODS: We performed a prospective observational study of 17 participants taking oral prednisolone using serum prednisolone levels as a marker of adherence, and sputum eosinophilia as a marker of control of type 2 airway inflammation. Based on these biomarkers, we classified participants into a non-adherent and an adherent cohort, and further stratified by the presence of ongoing sputum eosinophilia. RESULTS: We identified 3 non-adherent participants and 14 who were adherent, based on their serum prednisolone levels. Stratification using sputum eosinophil counts identified one participant as having ongoing sputum eosinophilia in the setting of non-adherence, while six were identified as steroid resistant with ongoing sputum eosinophilia despite adherence to oral prednisolone therapy. CONCLUSION: Serum prednisolone can be used an objective marker of adherence in those patients with severe asthma taking daily oral prednisolone. In combination with sputum eosinophil counts, a steroid resistant cohort can be distinguished from one with ongoing inflammation in the setting of non-adherence. This information can then be used by clinicians to differentiate the optimal next steps for treatment in these specific populations. TRIAL REGISTRATION: Participants were recruited as part of the Markers of Inflammation in the Management of Severe Asthma (MIMOSA) study, trial registration ACTRN12616001015437 , 02 August 2016.

Change in type-2 biomarkers and related cytokines with prednisolone in uncontrolled severe oral corticosteroid dependent asthmatics: an interventional open-label study.

Type-2 biomarkers and related cytokines (IL-5, IL-13), lung function and asthma symptoms were measured in 44 poorly-controlled severe oral corticosteroid (OCS)-dependent asthmatics for up to 88 days after a 7-day prednisolone boost (0.5 mg/kg). High-dose OCS reduced median blood eosinophils (-60 cells/µl; 95% CI -140 to 10), periostin (-8.4 ng/mL; -11.6 to -2.8), FeNO (-19.0 ppb; -28.5 to -4.0), IL-5 (-0.17 pg/mL; -0.28 to -0.08) and IL-13 (-0.15 pg/mL; -0.27 to -0.03). There were small improvements in mean FEV1 (0.16 L; 0.05 to 0.27) and (Asthma Control Questionnaire) ACQ-7 score (0.3; 0.0 to 0.7). Study measures returned to baseline 1-month postintervention. Following rescue OCS, 1 month is sufficient before using type-2 biomarkers to guide long-term treatment. TRIAL REGISTRATION NUMBER: NCT01948401.

Maximum Entropy Analysis of Flow Networks: Theoretical Foundation and Applications.

The concept of a "flow network"-a set of nodes and links which carries one or more flows-unites many different disciplines, including pipe flow, fluid flow, electrical, chemical reaction, ecological, epidemiological, neurological, communications, transportation, financial, economic and human social networks. This Feature Paper presents a generalized maximum entropy framework to infer the state of a flow network, including its flow rates and other properties, in probabilistic form. In this method, the network uncertainty is represented by a joint probability function over its unknowns, subject to all that is known. This gives a relative entropy function which is maximized, subject to the constraints, to determine the most probable or most representative state of the network. The constraints can include "observable" constraints on various parameters, "physical" constraints such as conservation laws and frictional properties, and "graphical" constraints arising from uncertainty in the network structure itself. Since the method is probabilistic, it enables the prediction of network properties when there is insufficient information to obtain a deterministic solution. The derived framework can incorporate nonlinear constraints or nonlinear interdependencies between variables, at the cost of requiring numerical solution. The theoretical foundations of the method are first presented, followed by its application to a variety of flow networks.

Indirect comparison of bronchial thermoplasty versus omalizumab for uncontrolled severe asthma.

OBJECTIVE: Bronchial thermoplasty (BT) as an add-on therapy for uncontrolled severe asthma is an alternative to biologic therapies like omalizumab (OM). We conducted an indirect treatment comparison (ITC) to appraise comparative effectiveness of BT and OM. METHODS: A systematic literature review identified relevant randomized controlled trials. The ITC followed accepted methodology. RESULTS: The ITC comprised a sham-controlled trial of BT (AIR2) and two placebo-controlled trials of OM (INNOVATE; EXTRA). Comparing the BT post-treatment period to ongoing treatment with OM, showed no significant differences in the rate ratios (RRs) for severe exacerbations (RR of BT versus OM = 0.91 [95% CI: 0.64, 1.30]; p = 0.62) or hospitalizations (RR = 0.57 [95% CI: 0.17, 1.86]; p = 0.53); emergency department visits were significantly reduced by 75% with BT (RR = 0.25 [95% CI: 0.07, 0.91]; p = 0.04); the proportions of patients with clinically meaningful response on the asthma quality-of-life questionnaire were comparable (RR = 1.06 [95% CI: 0.86, 1.34]; p = 0.59). The RR for exacerbations statistically favours OM over the total study period in AIR2 (RR = 1.50 [95% CI: 1.11, 2.02]; p = 0.009) likely reflecting a transient increase in events during the BT peri-treatment period. CONCLUSIONS: The ITC should be interpreted cautiously considering the differences between patient populations in the included trials. However, based on the analysis, BT compares well with a potentially more costly pharmacotherapy for asthma. Clinicians evaluating the relative merits of using these treatments should consider the totality of evidence and patient preferences to make an informed decision.

Bronchial Thermoplasty in Severe Asthma: Best Practice Recommendations from an Expert Panel.

Bronchial thermoplasty (BT) is a bronchoscopic treatment for patients with severe asthma who remain symptomatic despite optimal medical therapy. In this "expert best practice" paper, the background and practical aspects of BT are highlighted. Randomized, controlled clinical trials have shown BT to be safe and effective in reducing severe exacerbations, improving quality of life, and decreasing emergency department visits. Five-year follow-up studies have provided evidence of the functional stability of BT-treated patients with persistence of a clinical benefit. The Global Initiative for Asthma (GINA) guidelines state that BT can be considered as a treatment option for adult asthma patients at step 5. Patient selection for BT requires close collaboration between interventional pulmonologists and severe asthma specialists. Key patient selection criteria for BT will be reviewed. BT therapy is delivered in 3 separate bronchoscopy sessions at least 3 weeks apart, covering different regions of the lung separately. Patients are treated with 50 mg/day of prednisolone or equivalent for 5 days, starting treatment 3 days prior to the procedure. The procedure is performed under moderate-to-deep sedation or general anesthesia. At bronchos-copy a single-use catheter with a basket design is inserted through the instrument channel and the energy is delivered by a radiofrequency (RF) generator (AlairTM Bronchial Thermoplasty System). BT uses temperature-controlled RF energy to impact airway remodeling, including a reduction of excessive airway smooth muscle within the airway wall, which has been recognized as a predominant feature of asthma. The treatment should be performed in a systemic manner, starting at the most distal part of the (sub)segmental airway, then moving proximally to the main bronchi, ensuring that the majority of the airways are treated. In general, 40-70 RF activations are provided in the lower lobes, and between 50 and 100 activations in the upper lobes combined. The main periprocedural adverse events are exacerbation of asthma symptoms and increased cough and sputum production. Occasionally, atelectasis has been observed following the procedure. The long-term safety of BT is excellent. An optimized BT responder profile - i.e., which specific asthma phenotype benefits most - is a topic of current research.

Procedural and short-term safety of bronchial thermoplasty in clinical practice: evidence from a national registry and Hospital Episode Statistics.

OBJECTIVE: Bronchial thermoplasty (BT) is a novel treatment for severe asthma. Its mode of action and ideal target patient group remain poorly defined, though clinical trials provided some evidence on efficacy and safety. This study presents procedural and short-term safety evidence from routine UK clinical practice. METHODS: Patient characteristics and safety outcomes (procedural complications, 30-day readmission and accident and emergency (A&E) attendance, length of stay) were assessed using two independent data sources, the British Thoracic Society UK Difficult Asthma Registry (DAR) and Hospital Episodes Statistics (HES) database. A matched cohort (with records in both) was used to estimate safety outcome event rates and compare them with clinical trials. RESULTS: Between June 2011 and January 2015, 215 procedure records (83 patients; 68 treated in England) were available from DAR and 203 (85 patients) from HES. 152 procedures matched (59 patients; 6 centres), and of these, 11.2% reported a procedural complication, 11.8% resulted in emergency respiratory readmission, 0.7% in respiratory A&E attendance within 30 days (20.4% had at least one event) and 46.1% involved a post-procedure stay. Compared with published clinical trials which found lower hospitalisation rates, BT patients in routine clinical practice were, on average, older, had worse baseline lung function and asthma quality of life. CONCLUSIONS: A higher proportion of patients experienced adverse events compared with clinical trials. The greater severity of disease amongst patients treated in clinical practice may explain the observed rate of post-procedural stay and readmission. Study of long-term safety and efficacy requires continuing data collection.

Research in progress: Medical Research Council United Kingdom Refractory Asthma Stratification Programme (RASP-UK).

The UK Refractory Asthma Stratification Programme (RASP-UK) will explore novel biomarker stratification strategies in severe asthma to improve clinical management and accelerate development of new therapies. Prior asthma mechanistic studies have not stratified on inflammatory phenotype and the understanding of pathophysiological mechanisms in asthma without Type 2 cytokine inflammation is limited. RASP-UK will objectively assess adherence to corticosteroids (CS) and examine a novel composite biomarker strategy to optimise CS dose; this will also address what proportion of patients with severe asthma have persistent symptoms without eosinophilic airways inflammation after progressive CS withdrawal. There will be interactive partnership with the pharmaceutical industry to facilitate access to stratified populations for novel therapeutic studies.

T1-weighted Dynamic Contrast-enhanced MR Imaging of the Lung in Asthma: Semiquantitative Analysis for the Assessment of Contrast Agent Kinetic Characteristics.

PURPOSE: To evaluate the contrast agent kinetics of dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging in healthy lungs and asthmatic lungs by using non-model-based semiquantitative parameters and to explore the relationships with pulmonary function testing and eosinophil level. MATERIALS AND METHODS: The study was approved by the National Research Ethical Committee (reference no. 11/NW/0387), and written informed consent was obtained from all individuals. Ten healthy subjects and 30 patients with asthma underwent pulmonary function tests, blood and sputum eosinophil counts, and 1.5-T DCE MR imaging within 7 days. Semiquantitative parameters of contrast agent kinetics were calculated from the relative signal intensity-time course curves on a pixel-by-pixel basis and were summarized by using whole-lung median values. The distribution heterogeneity was assessed by using the regional coefficient of variation. DCE MR imaging readouts were compared between groups by using one-way analysis of variance, and the relationships with pulmonary function testing and eosinophil counts were assessed by using Pearson correlation analysis. RESULTS: Asthmatic patients showed significantly lower peak enhancement (P < .001) and initial areas under the relative signal intensity curve in the first 60 seconds (P = .002) and significantly reduced late-phase washout slope (P = .002) when compared with healthy control subjects. The distribution heterogeneity of bolus arrival time (P = .029), time to peak (P = .008), upslope of the first-pass peak (P = .011), and late-phase washout slope (P = .032), estimated by using the median coefficient of variation, were significantly higher in asthmatic patients than in healthy control subjects. These imaging readouts also showed significant linear correlations with measurements of pulmonary function testing but not with eosinophil level in patients with asthma. CONCLUSION: The contrast agent kinetic characteristics of T1-weighted DCE MR images of asthmatic lungs are different from those of healthy lungs and are related to measurements of pulmonary function testing but not to eosinophil level.

Fungal sensitisation in severe asthma is associated with the identification of Aspergillus fumigatus in sputum.

BACKGROUND: Fungal sensitisation is an important factor in severe asthma, not only for allergic bronchopulmonary aspergillosis (ABPA) but also the more recently described severe asthma with fungal sensitisation (SAFS). It is not known whether these diseases are driven by the presence of airway fungal colonisation. We aimed to determine if both SAFS and ABPA were associated with airway isolation of Aspergillus fumigatus and whether the frequency of isolation changed following anti-fungal treatment. METHODS: Sputum samples were collected from patients with SAFS, ABPA and a control group without fungal sensitisation. We recorded details of antifungal treatment, serum IgE and A. fumigatus specific IgE levels. In a subgroup (n = 9) we recorded serial sputum PCR measurements before and during itraconazole therapy. RESULTS: 244 sputum samples were provided by 135 patients, 41(17%) ABPA, 168(69%) SAFS, and 35(14%) controls. Sputum Aspergillus fumigatus PCR was positive in 61 SAFS patients (70%) and 6 ABPA patients (50%) not on anti-fungal treatment at the time of the test, compared to 3 (9%) in controls (χ(2) = 37.90, p < 0.001). Consequently, 19 patients with SAFS who were taking antifungal treatment (23%) were significantly less likely to be PCR positive than the 61 patients not on treatment (70%) (χ(2) = 36.66, p < 0.001). All 9 patients assessed serially during therapy had positive sputum PCR pre-treatment and all became negative during itraconazole treatment. CONCLUSION: We have shown that isolation of fungus from the airway of severe asthma patients with fungal sensitisation is very common, supporting the hypothesis of a mechanistic link between fungal colonisation and sensitisation.