Assessing the Effects of Changing Patterns of Inhaled Corticosteroid Dosing and Adherence with Fluticasone Furoate and Budesonide on Asthma Management.

INTRODUCTION: Pharmacological asthma management focuses on the use of inhaled corticosteroid (ICS)-containing therapies, which reduce airway inflammation and provide bronchoprotection, improving symptom control and reducing exacerbation risk. ICS underuse due to poor adherence is common, leading to poor clinical outcomes including increased risk of mortality. This article reviews efficacy versus systemic activity profiles for various adherence patterns and dosing regimens of fluticasone furoate (FF)-containing and budesonide (BUD)-containing asthma therapies in clinical trials and real-world studies. METHODS: We performed a structured literature review (1 January 2000-3 March 2022) and mathematical modelling analysis of FF-containing and BUD-containing regular daily dosing in patients with mild-to-severe asthma, as-needed BUD/formoterol (FOR) in mild asthma, and BUD/FOR maintenance and reliever therapy (MART) dosing in moderate-to-severe asthma, to assess efficacy (bronchoprotection) and systemic activity (cortisol suppression) profiles of dosing patterns of ICS use in multiple adherence scenarios. RESULTS: A total of 22 manuscripts were included in full-text review and 18 in the model simulations. Focusing on FF-containing or BUD-containing treatments at comparable adherence rates, regular daily FF or FF/vilanterol (VI) dosing provided more prolonged bronchoprotection and fewer systemic effects than daily BUD, daily BUD/FOR, or BUD/FOR MART dosing, especially in low adherence scenarios. In model simulations and the real-world setting, FF/VI generally provided longer bronchoprotection, lower systemic activity, and greater clinical benefits over BUD/FOR as well as consistently higher adherence. CONCLUSION: In this literature review and modelling analysis, FF/VI was found to show clinical advantages on asthma control over BUD/FOR. These findings have implications for helping clinicians select the most suitable inhaled therapy for their patients with asthma.

Consensus on mild asthma management: results of a modified Delphi study.

OBJECTIVE: In order to understand the role of regular controller inhaled corticosteroids (ICS) versus as-needed ICS-formoterol in managing mild asthma, we performed a modified Delphi procedure. METHODS: Opinions from 16 respiratory experts to three surveys and during a virtual scientific workshop helped to develop final consensus statements (pre-defined as 70% agreement). RESULTS: Thirteen participants completed all rounds (response rate 81%). At the end of the procedure, there was final consensus on: regular daily ICS being the recommended treatment approach in mild persistent asthma, with better symptom control and robust long-term clinical data compared with as-needed ICS-formoterol (85%); to avoid noncompliance, frequently seen in mild asthma patients, regular ICS dosing should be accompanied by ongoing education on treatment adherence (100%); treatment aims should be targeting asthma control (92%) and reduction of exacerbation risk (85%). No consensus was reached on whether GINA or national guidelines most influence prescribing decisions. CONCLUSIONS: It is important to encourage patients to be adherent and to target both asthma control and exacerbation risk reduction. There is robust clinical evidence to support proactive regular dosing with ICS controller therapy plus as-needed short-acting beta-agonists for the management of patients with mild asthma.

New Versus Old: The Impact of Changing Patterns of Inhaled Corticosteroid Prescribing and Dosing Regimens in Asthma Management.

Inhaled corticosteroid (ICS)-containing therapies are the mainstay of pharmacological management of asthma. They can be administered alone or in combination with a long-acting bronchodilator, depending on asthma severity, and may also be supplemented with short-acting bronchodilators for as-needed rescue medication. Adherence to asthma therapies is generally poor and characterized by underuse of ICS therapies and over-reliance on short-acting bronchodilators, which leads to poor clinical outcomes. This article reviews efficacy versus systemic activity profiles for various dosing regimens of budesonide (BUD) and fluticasone propionate (FP). We performed a structured literature review of BUD and FP regular daily dosing, and BUD/formoterol (FOR) as-needed dosing, to explore the relationship between various dosing patterns of ICS regimens and the risk-benefit profile in terms of the extent of bronchoprotection and cortisol suppression. In addition, we explored how adherence could potentially affect the risk-benefit profile, in patients with mild, moderate, and moderate-to-severe asthma. With a specific focus on BUD or FP-containing treatments, we found that regular daily ICS and ICS/long-acting ß2-agonist (LABA) dosing had a greater degree of bronchoprotection than as-needed BUD/FOR dosing or BUD/FOR maintenance and reliever therapy (MART) dosing, and still maintained low systemic activity. We also found that the benefits of regular daily ICS dosing regimens were diminished when adherence was low (50%); the shorter duration of bronchoprotection observed was similar to that seen with typical as-needed BUD/FOR usage. These findings have implications for aiding clinicians with selecting the most suitable treatment option for asthma management, and subsequent implications for the advice clinicians give their patients.

Inhaled corticosteroid (ICS)-containing therapies can be administered in a variety of ways depending on a patient's asthma severity. Patients with mild asthma tend to experience symptom relief with as-needed or regular daily use of an ICS alone, whereas patients with more severe asthma may require regular daily use of an ICS plus a long-acting ß₂-agonist (LABA) to experience sufficient asthma control. However, failure to correctly adhere to ICS-containing therapies or an over-reliance on short-acting bronchodilators for symptom relief hinders optimal asthma management, thus negatively affecting overall patient health and wellbeing. Understanding how different dosing regimens affect the degree of bronchoprotection (efficacy) and cortisol suppression (systemic activity) of ICS treatments would benefit physicians by helping them to prescribe the most appropriate treatment for their patient's asthma. We performed a structured literature review of two ICS molecules­budesonide (BUD) (alone and combined with formoterol [FOR]) and fluticasone propionate (FP)­to explore the relationship between various ICS dosing regimens, and then used these findings to construct models for ICS risk­benefit profiles. Our models factored in different ICS dosing regimens­as-needed, regular daily dosing, and maintenance and reliever therapy (MART)­and various degrees of treatment adherence. We found that regular daily ICS and ICS/LABA dosing provided better bronchoprotection than as-needed BUD/FOR dosing or BUD/FOR MART dosing, but this benefit was diminished with low adherence. Regular daily dosing maintained low cortisol suppression, which indicated a fairly low risk of negative side effects. Our findings have subsequent implications for optimizing treatment in patients with asthma.

Assessment and diagnosis of chronic dyspnoea: a literature review.

Dyspnoea or breathlessness is a common presenting symptom among patients attending primary care services. This review aimed to determine whether there are clinical tools that can be incorporated into a clinical decision support system for primary care for efficient and accurate diagnosis of causes of chronic dyspnoea. We searched MEDLINE, EMBASE and Google Scholar for all literature published between 1946 and 2020. Studies that evaluated a clinical algorithm for assessment of chronic dyspnoea in patients of any age group presenting to physicians with chronic dyspnoea were included. We identified 326 abstracts, 55 papers were reviewed, and eight included. A total 2026 patients aged between 20-80 years were included, 60% were women. The duration of dyspnoea was three weeks to 25 years. All studies undertook a stepwise or algorithmic approach to the assessment of dyspnoea. The results indicate that following history taking and physical examination, the first stage should include simply performed tests such as pulse oximetry, spirometry, and electrocardiography. If the patient remains undiagnosed, the second stage includes investigations such as chest x-ray, thyroid function tests, full blood count and NT-proBNP. In the third stage patients are referred for more advanced tests such as echocardiogram and thoracic CT. If dyspnoea remains unexplained, the fourth stage of assessment will require secondary care referral for more advanced diagnostic testing such as exercise tests. Utilising this proposed stepwise approach is expected to ascertain a cause for dyspnoea for 35% of the patients in stage 1, 83% by stage 3 and >90% of patients by stage 4.

Blood Eosinophils in Chinese COPD Participants and Response to Treatment with Combination Low-Dose Theophylline and Prednisone: A Post-Hoc Analysis of the TASCS Trial.

BACKGROUND AND OBJECTIVES: The burden of chronic obstructive pulmonary disease (COPD) disproportionately affects patients in low to middle-income countries. Although the Theophylline and Steroids in COPD Study (TASCS) showed no clinical benefit from administering low-dose theophylline and prednisone in COPD patients compared to placebo, it was hypothesized that those with elevated blood eosinophil counts would receive clinical benefit from the intervention. METHODS: This was a post-hoc analysis of the TASCS dataset - a double-blinded, placebo-controlled trial conducted in patients with moderate-severe COPD in China. Participants were allocated 1:1:1 to low-dose oral theophylline (100mg bd) and prednisone (5mg qd; PrT), theophylline (100mg bd) and prednisone-matched placebo (TP), or double-matched placebo (DP) groups and followed-up for 48 weeks. A baseline count of ≥300 eosinophils/µL blood was categorized as elevated/eosinophilic, and the primary outcome was the annualized moderate-severe exacerbation rate. RESULTS: Of 1487 participants eligible for analysis, 325 (22%) were eosinophilic. These participants were predominantly male (82%), had a mean (SD) age of 64 (±8) years and a predicted forced expiratory volume in 1s (FEV1) of 43% (±16). The annualized moderate-severe exacerbation rate was significantly higher in the PrT group compared to the pooled results of the TP and DP groups (incidence rate ratio = 1.6; ([95% CI 1.06-1.76]) p = 0.016). Changes in spirometry values and reported disease impact scores (St. George's Respiratory Questionnaire and COPD Assessment Test) at week 48 were not significantly different between groups. CONCLUSION: Combination low-dose theophylline and prednisone was associated with a significant increase in the annual moderate-severe exacerbation rate in participants with a blood eosinophil count ≥300 cells/µL compared to placebo.

Normal limits for oscillometric bronchodilator responses and relationships with clinical factors.

INTRODUCTION: We aimed to determine normal thresholds for positive bronchodilator responses for oscillometry in an Australian general population sample aged ≥40 years, to guide clinical interpretation. We also examined relationships between bronchodilator responses and respiratory symptoms, asthma diagnosis, smoking and baseline lung function. METHODS: Subjects recruited from Sydney, Melbourne and Busselton, Australia, underwent measurements of spirometry, resistance (R rs6 ) and reactance (X rs6 ) at 6 Hz, before and after inhalation of salbutamol 200 µg. Respiratory symptoms and/or medication use, asthma diagnosis, and smoking were recorded. Threshold bronchodilator responses were defined as the fifth percentile of decrease in R rs6 and 95th percentile increase in X rs6 in a healthy subgroup. RESULTS: Of 1318 participants, 1145 (570 female) were analysed. The lower threshold for ΔR rs6 was -1.38 cmH2O·s·L-1 (-30.0% or -1.42 Z-scores) and upper threshold for ΔX rs6 was 0.57 cmH2O·s·L-1 (1.36 Z-scores). Respiratory symptoms and/or medication use, asthma diagnosis, and smoking all predicted bronchodilator response, as did baseline oscillometry and spirometry. When categorised into clinically relevant groups according to those predictors, ΔX rs6 was more sensitive than spirometry in smokers without current asthma or chronic obstructive pulmonary disease (COPD), ∼20% having a positive response. Using absolute or Z-score change provided similar prevalences of responsiveness, except in COPD, in which responsiveness measured by absolute change was twice that for Z-score. DISCUSSION: This study describes normative thresholds for bronchodilator responses in oscillometry parameters, including intra-breath parameters, as determined by absolute, relative and Z-score changes. Positive bronchodilator response by oscillometry correlated with clinical factors and baseline function, which may inform the clinical interpretation of oscillometry.

The effect of low-dose corticosteroids and theophylline on the risk of acute exacerbations of COPD: the TASCS randomised controlled trial.

BACKGROUND: The highest burden of chronic obstructive pulmonary disease (COPD) occurs in low- and middle-income countries. Low-cost oral medications, if effective, could enable affordable, accessible COPD treatment. METHODS: In this randomised, three-arm, double-blind, double-dummy, placebo-controlled study conducted in 37 centres in China, symptomatic patients with moderate to very severe COPD were randomised 1:1:1 to placebo twice daily plus placebo once daily, low-dose theophylline 100 mg twice daily plus placebo once daily or low-dose theophylline 100 mg twice daily plus low-dose oral prednisone 5 mg once daily for 48 weeks. The primary end-point was annualised exacerbation rate. RESULTS: 1670 subjects were randomised and 1242 completed the study (1142 with acceptable data at week 48). Subjects (75.7% male) had a mean age of 64.4 years, with mean±sd baseline post-bronchodilator forced expiratory volume in 1 s (FEV1) 1.1±0.4 L (42.2% predicted) and St George's Respiratory Questionnaire (SGRQ) score 45.8±20.1. There were negligible differences between annualised exacerbation rates across the three treatments: 0.89 (95% CI 0.78-1.02) on theophylline plus prednisone, 0.86 (95% CI 0.75-0.99) on theophylline plus placebo and 1.00 (95% CI 0.87-1.14) on placebo. The rate ratio for theophylline plus prednisone versus pooled theophylline plus placebo and placebo was 0.96 (95% CI 0.83-1.12), for theophylline plus placebo versus placebo was 0.87 (95% CI 0.73-1.03; p=0.101) and for theophylline plus prednisone versus placebo was 0.90 (95% CI 0.76-1.06; p=0.201). Secondary outcomes of hospitalisations, FEV1, SGRQ and COPD Assessment Test score showed no statistically significant difference between treatment arms. Serious adverse events other than exacerbations were <2% and did not differ between treatment arms. CONCLUSIONS: Low-dose theophylline alone or in combination with prednisone did not reduce exacerbation rates or clinically important secondary end-points compared with placebo.

Reduced lung elastic recoil and fixed airflow obstruction in asthma.

BACKGROUND AND OBJECTIVE: Fixed airflow obstruction (FAO) in asthma occurs despite optimal inhaled treatment and no smoking history, and remains a significant problem, particularly with increasing age and duration of asthma. Increased lung compliance and loss of lung elastic recoil has been observed in older people with asthma, but their link to FAO has not been established. We determined the relationship between abnormal lung elasticity and airflow obstruction in asthma. METHODS: Non-smoking asthmatic subjects aged >40 years, treated with 2 months of high-dose inhaled corticosteroid/long-acting beta-agonist (ICS/LABA), had FAO measured by spirometry, and respiratory system resistance at 5 Hz (Rrs5 ) and respiratory system reactance at 5 Hz (Xrs5 ) measured by forced oscillation technique. Lung compliance (K) and elastic recoil (B/A) were calculated from pressure-volume curves measured by an oesophageal balloon. Linear correlations between K and B/A, and forced expiratory volume in 1 s/forced vital capacity (FEV1 /FVC), Rrs5 and Xrs5 were assessed. RESULTS: Eighteen subjects (11 males; mean ± SD age: 64 ± 8 years, asthma duration: 39 ± 22 years) had moderate FAO measured by spirometry ((mean ± SD z-score) post-bronchodilator FEV1 : -2.2 ± 0.5, FVC: -0.7 ± 1.0, FEV1 /FVC: -2.6 ± 0.7) and by increased Rrs5 (median (IQR) z-score) 2.7 (1.9 to 3.2) and decreased Xrs5 : -4.1(-2.4 to -7.3). Lung compliance (K) was increased in 9 of 18 subjects and lung elastic recoil (B/A) reduced in 5 of 18 subjects. FEV1 /FVC correlated negatively with K (rs = -0.60, P = 0.008) and Rrs5 correlated negatively with B/A (rs = -0.52, P = 0.026), independent of age. Xrs5 did not correlate with lung elasticity indices. CONCLUSION: Increased lung compliance and loss of elastic recoil relate to airflow obstruction in older non-smoking asthmatic subjects, independent of ageing. Thus, structural lung tissue changes may contribute to persistent, steroid-resistant airflow obstruction. CLINICAL TRIAL REGISTRATION: ACTRN126150000985583 at anzctr.org.au (UTN: U1111-1156-2795).

Exercise-induced bronchoconstriction: prevalence, pathophysiology, patient impact, diagnosis and management.

Exercise-induced bronchoconstriction (EIB) can occur in individuals with and without asthma, and is prevalent among athletes of all levels. In patients with asthma, symptoms of EIB significantly increase the proportion reporting feelings of fearfulness, frustration, isolation, depression and embarrassment compared with those without symptoms. EIB can also prevent patients with asthma from participating in exercise and negatively impact their quality of life. Diagnosis of EIB is based on symptoms and spirometry or bronchial provocation tests; owing to low awareness of EIB and lack of simple, standardised diagnostic methods, under-diagnosis and mis-diagnosis of EIB are common. To improve the rates of diagnosis of EIB in primary care, validated and widely accepted symptom-based questionnaires are needed that can accurately replicate the current diagnostic standards (forced expiratory volume in 1 s reductions observed following exercise or bronchoprovocation challenge) in patients with and without asthma. In patients without asthma, EIB can be managed by various non-pharmacological methods and the use of pre-exercise short-acting ß2-agonists (SABAs). In patients with asthma, EIB is often associated with poor asthma control but can also occur in individuals who have good control when not exercising. Inhaled corticosteroids are recommended when asthma control is suboptimal; however, pre-exercise SABAs are also widely used and are recommended as the first-line therapy. This review describes the burden, key features, diagnosis and current treatment approaches for EIB in patients with and without asthma and serves as a call to action for family physicians to be aware of EIB and consider it as a potential diagnosis.

Peripheral airway dysfunction and relationship with symptoms in smokers with preserved spirometry.

BACKGROUND AND OBJECTIVE: Smokers develop respiratory symptoms and peripheral airway dysfunction even when spirometry is preserved. Multiple breath nitrogen washout (MBNW) and impulse oscillometry system (IOS) are potentially useful measures of peripheral airway function but they have not been compared in such subjects. We hypothesized that MBNW and IOS are jointly abnormal in smokers with normal spirometry and that these abnormalities relate to respiratory symptoms. METHODS: Eighty smokers with normal spirometry completed a symptom questionnaire, had ventilation heterogeneity in diffusion (Sacin) and convection-dependent (Scond) airways and trapped gas volume at functional residual capacity as a percentage of vital capacity (%VtrFRC/VC) measured by MBNW. Respiratory resistance and reactance at 5 and 20 Hz were measured using IOS. RESULTS: Respiratory symptoms were reported in 55 (68%) subjects. Forty (50%) subjects had at least one abnormal MBNW parameter, predominantly in Sacin. Forty-one (51%) subjects had at least one abnormal IOS parameter, predominantly in resistance. Sixty-one (76%) subjects had an abnormality in either MBNW or IOS. Chronic bronchitis symptoms were associated with an increased Scond, while wheeze was associated with lower spirometry and an increased resistance. Abnormalities in MBNW and IOS parameters were unrelated to each other. CONCLUSIONS: Respiratory symptoms and peripheral airway dysfunction are common in smokers with normal spirometry. Symptoms of chronic bronchitis related to conductive airway abnormalities, while wheeze was related to spirometry and IOS. The clinical significance of abnormalities in peripheral airway function in smokers remains undetermined.

Peripheral ventilation heterogeneity determines the extent of bronchoconstriction in asthma.

In asthma, bronchoconstriction causes topographically heterogeneous airway narrowing, as measured by three-dimensional ventilation imaging. Computation modeling suggests that peripheral airway dysfunction is a potential determinant of acute airway narrowing measured by imaging. We hypothesized that the development of low-ventilation regions measured topographically by three-dimensional imaging after bronchoconstriction is predicted by peripheral airway function. Fourteen asthmatic subjects underwent ventilation single-photon-emission computed tomography/computed tomography scan imaging before and after methacholine challenge. One-liter breaths of Technegas were inhaled from functional residual capacity in upright posture before supine scanning. The lung regions with the lowest ventilation (Ventlow) were calculated using a thresholding method and expressed as a percentage of total ventilation (Venttotal). Multiple-breath nitrogen washout was used to measure diffusion-dependent and convection-dependent ventilation heterogeneity (Sacin and Scond, respectively) and lung clearance index (LCI), before and after challenge. Forced expiratory volume in 1 s (FEV1) was 87.6 ± 15.8% predicted, and seven subjects had airway hyperresponsiveness. Ventlow at baseline was unrelated to spirometry or multiple-breath nitrogen washout indices. Methacholine challenge decreased FEV1 by 23 ± 5% of baseline while Ventlow increased from 21.5 ± 2.3%Venttotal to 26.3 ± 6.7%Venttotal (P = 0.03). The change in Ventlow was predicted by baseline Sacin (rs = 0.60, P = 0.03) and by LCI (rs = 0.70, P = 0.006) but not by Scond (rs = 0.30, P = 0.30). The development of low-ventilation lung units in three-dimensional ventilation imaging is predicted by ventilation heterogeneity in diffusion-dependent airways. This relationship suggests that acinar ventilation heterogeneity in asthma may be of mechanistic importance in terms of bronchoconstriction and airway narrowing.NEW & NOTEWORTHY Using ventilation SPECT/CT imaging in asthmatics, we show induced bronchoconstriction leads to the development of areas of low ventilation. Furthermore, the relative volume of the low-ventilation regions was predicted by ventilation heterogeneity in diffusion-dependent acinar airways. This suggests that the pattern of regional airway narrowing in asthma is determined by acinar airway function.

Bronchodilator responsiveness of peripheral airways in smokers with normal spirometry.

BACKGROUND AND OBJECTIVE: Cigarette smoke exposure increases airway smooth muscle (ASM) contractility. Abnormalities in peripheral airway function in smokers with normal spirometry could be due to the effects of ASM tone. We aimed to determine the contribution of ASM tone to peripheral airway function in smokers with normal spirometry from the response to bronchodilator (BD). METHODS: Ventilation heterogeneity in peripheral conductive (Scond) and acinar (Sacin) airways were measured in 50 asymptomatic smokers and 20 never-smokers using multiple breath nitrogen washout, before and 20 min after inhalation of 200 µg salbutamol and 80 µg ipratropium bromide. Z-scores were calculated to define abnormality in Sacin and Scond. RESULTS: Nineteen smokers had abnormal Sacin, and 12 had abnormal Scond; 7 had abnormalities in both. After BD, Sacin improved in smokers with normal Sacin (6.5 ± 15.9%, P = 0.02), smokers with abnormal Sacin (9.2 ± 16.9%, P = 0.03) and in control subjects (11.7 ± 18.2%, P = 0.01), with no differences in improvements between groups. Sacin remained abnormal in 15/19 smokers and their post-BD values correlated with smoking exposure (r = 0.53, P = 0.02). After BD, Scond improved in smokers with abnormal Scond (28.3 ± 15.9%, P = 0.002) and normalized in 9/12 subjects, but not in those with normal Scond (0.25 ± 32.7%, P = 0.44) or control subjects (-1.7 ± 21.2%, P = 0.64). CONCLUSION: In smokers with normal spirometry, abnormal conductive airway function could be attributed to increased bronchomotor tone. In contrast, bronchomotor tone in acinar airways is unaffected by smoking and functional abnormality. There may be different causal mechanisms underlying acinar and conductive airway abnormalities in smokers with normal spirometry.

Contribution of air pollution to COPD and small airway dysfunction.

Although in many Western countries levels of ambient air pollution have been improving with the setting of upper limits and better urban planning, air pollution in developing countries and particularly those with rapid industrialization has become a major global problem. Together with increased motor vehicle ownership and traffic congestion, there is a growing issue with airborne particles of respirable size. These particles are thought responsible for respiratory and cardiovascular effects and have also been implicated in cancer pathogenesis. The pathologic effects in the lung are mediated via inflammatory pathways and involve oxidative stress similar to cigarette smoking. These effects are seen in the peripheral airways where the smaller particle fractions are deposited and lead to airway remodelling. However, emphysema and loss of bronchioles seen with cigarette smoking have not been described with ambient air pollution, and there are few studies specifically looking at peripheral airway function. Definitive evidence of air pollution causing COPD is lacking and a different study design is required to link air pollution and COPD.

Expiratory flow limitation relates to symptoms during COPD exacerbations requiring hospital admission.

BACKGROUND: Expiratory flow limitation (EFL) is seen in some patients presenting with a COPD exacerbation; however, it is unclear how EFL relates to the clinical features of the exacerbation. We hypothesized that EFL when present contributes to symptoms and duration of recovery during a COPD exacerbation. Our aim was to compare changes in EFL with symptoms in subjects with and without flow-limited breathing admitted for a COPD exacerbation. SUBJECTS AND METHODS: A total of 29 subjects with COPD were recruited within 48 hours of admission to West China Hospital for an acute exacerbation. Daily measurements of post-bronchodilator spirometry, resistance, and reactance using the forced oscillation technique and symptom (Borg) scores until discharge were made. Flow-limited breathing was defined as the difference between inspiratory and expiratory respiratory system reactance (EFL index) greater than 2.8 cmH2O·s·L(-1). The physiological predictors of symptoms during recovery were determined by mixed-effect analysis. RESULTS: Nine subjects (31%) had flow-limited breathing on admission despite similar spirometry compared to subjects without flow-limited breathing. Spirometry and resistance measures did not change between enrolment and discharge. EFL index values improved in subjects with flow-limited breathing on admission, with resolution in four patients. In subjects with flow-limited breathing on admission, symptoms were related to inspiratory resistance and EFL index values. In subjects without flow-limited breathing, symptoms related to forced expiratory volume in 1 second/forced vital capacity. In the whole cohort, EFL index values at admission was related to duration of stay (Rs=0.4, P=0.03). CONCLUSION: The presence of flow-limited breathing as well as abnormal respiratory system mechanics contribute independently to symptoms during COPD exacerbations.