Measuring lung function in airways diseases: current and emerging techniques

Assessing Lung Ventilation and Bronchodilator Response in Asthma and Chronic Obstructive Pulmonary Disease with 19F MRI

Background Pulmonary function tests are central to diagnosis and monitoring of respiratory diseases but do not provide information on regional lung function heterogeneity. Fluorine 19 (19F) MRI of inhaled perfluoropropane permits quantitative and spatially localized assessment of pulmonary ventilation properties without tracer gas hyperpolarization. Purpose To assess regional lung ventilation properties using 19F MRI of inhaled perfluoropropane in participants with asthma, participants with chronic obstructive pulmonary disease (COPD), and healthy participants, including quantitative evaluation of bronchodilator response in participants with respiratory disease. Materials and Methods This prospective, dual-center study included participants with asthma or COPD from July 2019 to September 2022 and healthy participants from May 2018 to June 2019. Participants underwent conventional spirometry, proton MRI, and 19F MRI following inhalation of a 79% perfluoropropane and 21% oxygen gas mixture. Three-dimensional 19F MRI scans were acquired during a single breath hold. For participants with asthma or COPD, spirometric and MRI measurements were repeated following administration of nebulized salbutamol. Ventilation defect percentage (VDP) was calculated from perfluoropropane distribution. Linear mixed-effects models were used to assess differences in VDP between participant groups and before and after bronchodilator administration. Results Thirty-five participants with asthma (mean age, 50 years ± 18 [SD]; 21 male participants), 21 participants with COPD (mean age, 69 years ± 6; 14 male participants), and 38 healthy participants (mean age, 41 years ± 11; 20 male participants) were evaluated. 19F MRI-derived VDP was elevated in participants with COPD (geometric mean, 27.2%) and participants with asthma (geometric mean, 8.3%) compared with healthy participants (geometric mean, 1.8%; geometric mean ratio, 15.2 [95% CI: 11.1, 20.6] for COPD and 4.6 [95% CI: 3.2, 6.6] for asthma; P < .001 for both). After bronchodilator administration, VDP was reduced by 33% in participants with asthma (from 8.3% to 5.6%) and 14% in participants with COPD (from 27.2% to 23.3%; P < .001 for both). Conclusion 19F MRI of inhaled perfluoropropane was sensitive to changes in regional ventilation properties associated with lung disease and enabled quantification of changes following bronchodilator therapy. Published under a CC BY-NC-ND 4.0 license. Supplemental material is available for this article. See also the editorial by Unger in this issue.

It is high time to discard a cut-off of 0.70 in the diagnosis of COPD

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) has traditionally been diagnosed based on the criterion of an FEV1/FVC <0.70. However, this definition has limitations as it may only detect patients with later-stage disease, when pathologic changes have become irreversible. Consequently, it potentially omits individuals with early-stage disease, in whom the pathologic changes could be delayed or reversed.

AREAS COVERED

This narrative review summarizes recent evidence regarding early-stage COPD, which may not fulfill the spirometric criteria but nonetheless exhibits features of COPD or is at risk of future COPD progression.

EXPERT OPINION

A comprehensive approach, including symptoms assessment, various physiologic tests, and radiologic features, is required to diagnose COPD. This approach is necessary to identify currently underdiagnosed patients and to halt disease progression in at- risk patients.

Lung Hyperinflation as Treatable Trait in Chronic Obstructive Pulmonary Disease: A Narrative Review

Lung hyperinflation (LH) is a common clinical feature in patients with chronic obstructive pulmonary disease (COPD). It results from a combination of reduced elastic lung recoil as a consequence of irreversible destruction of lung parenchyma and expiratory airflow limitation. LH is an important determinant of morbidity and mortality in COPD, partially independent of the degree of airflow limitation. Therefore, reducing LH has become a major target in the treatment of COPD over the last decades. Advances were made in the diagnostics of LH and several effective interventions became available. Moreover, there is increasing evidence suggesting that LH is not only an isolated feature in COPD but rather part of a distinct clinical phenotype that may require a more integrated management. This narrative review focuses on the pathophysiology and adverse consequences of LH, the assessment of LH with lung function measurements and imaging techniques and highlights LH as a treatable trait in COPD. Finally, several suggestions regarding future studies in this field are made.

Area-Detector Computed Tomography for Pulmonary Functional Imaging

An area-detector CT (ADCT) has a 320-detector row and can obtain isotropic volume data without helical scanning within an area of nearly 160 mm. The actual-perfusion CT data within this area can, thus, be obtained by means of continuous dynamic scanning for the qualitative or quantitative evaluation of regional perfusion within nodules, lymph nodes, or tumors. Moreover, this system can obtain CT data with not only helical but also step-and-shoot or wide-volume scanning for body CT imaging. ADCT also has the potential to use dual-energy CT and subtraction CT to enable contrast-enhanced visualization by means of not only iodine but also xenon or krypton for functional evaluations. Therefore, systems using ADCT may be able to function as a pulmonary functional imaging tool. This review is intended to help the reader understand, with study results published during the last a few decades, the basic or clinical evidence about (1) newly applied reconstruction methods for radiation dose reduction for functional ADCT, (2) morphology-based pulmonary functional imaging, (3) pulmonary perfusion evaluation, (4) ventilation assessment, and (5) biomechanical evaluation.

Toward a Predict and Prevent Approach in Obstructive Airway Diseases

Asthma and chronic obstructive pulmonary disease are currently diagnosed and treated after the demonstration of variable airflow limitation and symptoms. Under this framework, undiagnosed and unchecked airway inflammation is associated with recurrent acute attacks, airway remodeling, airflow limitation, adverse effects of corticosteroids, and impaired quality of life, ultimately leading to the collection of side effects termed "people remodeling." This one-size-fits-all damage control approach aims to control symptoms and treat exacerbations rather than modify the underlying disease process. The advent of highly effective therapies targeting proximal drivers of airway inflammation calls for a paradigm shift; upstream-acting therapies offer potential to alter the disease course and achieve clinical remission. We propose moving away from downstream firefighting and toward a "predict and prevent" model, measuring inflammation and providing anti-inflammatory therapy early, without waiting for further clinical deterioration. Much in the same way that high blood pressure and cholesterol are used to predict and prevent heart attacks, in asthma, elevated blood eosinophils and/or exhaled nitric oxide can be used to predict and prevent asthma attacks. We also advocate moving research further upstream by identifying patients with subclinical airway inflammation or disease who may be at risk of progressing to airflow limitation and associated morbidities and intervening early to prevent them. In summary, we call for a predict and prevent approach in obstructive airway disease.

Impact of Forced Exhalation Maneuvers During Spirometry on Airway Resistance Measured by Oscillometry in Healthy Children

OBJECTIVE

To analyze the impact of repeated forced spirometry maneuvers on oscillometry parameters of healthy children.

METHODS

This is a cross-sectional study with healthy children (6-12 y old) from schools in Florianopolis-SC/Brazil. Good health condition was confirmed through questionnaires, health history, and normal spirometry. Spirometry maneuvers and impulse oscillometry were conducted according to the American Thoracic Society guidelines. The school children were grouped according to the number of spirometry maneuvers performed: 1) 3 maneuvers; 2) 4 maneuvers and 3) 5 to 8 maneuvers. The following oscillometry values were considered: at rest (T₀); after the first spirometry maneuver (T₁); and after the last maneuver (T₂), according to the groups' allocation. The mixed model ANOVA was applied to verify the interaction of oscillometry parameters in all 3 moments and groups. The Friedman test was used for analysis of Fres (p < 0.05).

RESULTS

In 149 school children (mean age: 9.13 y old ± 1.98), there was a significant increase in Z5, R5, R20, and X5 values at rest and after the first spirometry maneuver, and values at rest and after the last maneuver in all groups. The effects on analyzed variables were significant in Z5 (F: 12.35; gl: 2; p < 0.001), R5 (F: 11.14; df: 2, p < 0.001), R20 (F: 7.53; df: 2, p < 0.001), and X5 (F: 4.30; df: 2, p = 0.014).

CONCLUSION

There were changes in respiratory mechanics after spirometry, like the increase in baseline Z5, R5, R20, and X5 after the first forced spirometry maneuver, and in comparison to the last maneuver obtained.

Cystic fibrosis exacerbations treated with medical therapy with and without concurrent sinus surgery

OBJECTIVE

This analysis investigates any potential differences in pulmonary function test (PFT) outcomes among pediatric patients with cystic fibrosis (CF) receiving both medical management (MM) and functional endoscopic sinus surgery (FESS) versus MM alone for CF exacerbation.

STUDY DESIGN

Prospective cohort.

SETTING

Pediatric tertiary care facility.

METHODS

The data was prospectively collected from July 2011 to March 2020. Diagnosis of CF and age ≤ to 18 were required. All patients were hospitalized and treated for CF exacerbations with both FESS with MM and MM alone at variable time intervals, although the order of initial treatment received differed. Two-way ANOVA with repeated measures were used to determine the effect of receiving FESS with MM versus MM alone on PFT outcomes over time (during admission, at discharge, at 3 months, at 6 months, and at 12 months).

RESULTS

13 pediatric patients, 7 of which had FESS with MM initially and 6 who had MM alone initially, and 20 events of both FESS and MM were included for analysis. For PFT outcomes, there was no statistically significant two-way interaction between treatment type and time following treatment, p = 0.492. The main effect of treatment did not show a statistically significant difference in FEV1 between treatment types, p = 0.737. There was no statistically significant association between treatment type and time between hospital readmission in months, p = 0.111.

CONCLUSION

There was no significant difference between PFT outcomes in pediatric patients hospitalized for CF exacerbation treated with MM with or without FESS at any time interval.

Respiratory morbidities and lung function abnormalities in survivors of Bhopal Gas Disaster: A cross-sectional study

BACKGROUND

Respiratory morbidities remained significant for the last four decades among the survivors of the Bhopal gas disaster. We hypothesized that lung function abnormalities, especially small airway dysfunctions, were responsible for the ongoing respiratory morbidities.

METHODS

We conducted a cross-sectional study between 2018 and 2020 in the severely exposed cohort of the Bhopal gas disaster. A standardized questionnaire was used to record their respiratory symptoms. The forced oscillometry (FOT) and spirometry were utilized for assessing lung functions. Univariate and multivariate logistic regression analyses were used to examine the association.

RESULTS

Of 916 enrolled individuals (men: 442, mean age: 55.2 ± 12.3 years), 558 participated in lung function assessments. Breathlessness was the most common complaint (71.7%), followed by cough (15.1%). The R5 > upper limit of normal (ULN), R_5-19 > ULN, and X5 < lower limit of normal (LLN) were observed in 29.3%, 23.3%, and 21.2% participants, respectively. Normal, obstructive, and restrictive spirometry was observed in 46.2%, 26.1%, and 27.7%, participants, respectively. FOT parameters were abnormal in 25.3% individuals with normal spirometry. Individuals with obstructive spirometry had the highest risk of having abnormal FOT parameters (adjusted odds ratio [adj OR]:3.93, 95% confidence interval [CI]: 2.24-6.89). Breathlessness showed a significant association with abnormal R5 (adj OR: 1.81; 95% CI: 1.13-2.91) and obstructive spirometry (adj OR: 2.26; 95% CI: 1.29-3.95).

CONCLUSIONS

Assessment of small airway functions along with spirometry are useful to identify complex lung function abnormalities in cases of toxic inhalation.

Ultrasound assessment of the rectus femoris in patients with chronic obstructive pulmonary disease predicts poor exercise tolerance: an exploratory study

Background

Reduced exercise tolerance is an important clinical feature of chronic obstructive pulmonary disease (COPD) and is associated with poor prognosis. The 6-min walk test (6MWT) is widely used to assess exercise capacity; however, it is not commonly administered in primary medical institutions because it requires a suitable site and professional training. Ultrasound has great potential for evaluating skeletal muscle dimensions in COPD. However, whether skeletal muscle ultrasound can predict impaired exercise tolerance is unclear.

Methods

The study included 154 stable patients with COPD, who were randomly divided into a development set and a validation set. The thickness (RF_thick) and cross-sectional area (RF_csa) of the rectus femoris were measured using ultrasound. Standardized RF_thick (STD- RF_thick) and Standardized RF_csa (STD-RFcsa) were obtained via standardization of RF_thick and RF_csa by patients' height.

Results

Strong correlations were observed between the 6MWD and RF_thick (r = 0.84, p < 0.001) and between the 6MWD and RF_csa (r = 0.81, p < 0.001). In the development set, the optimal cut-off values for men and women for predicting poor exercise tolerance were < 3.098 cm/m and < 3.319 cm/m for STD-RF_thick and < 4.052 cm²/m and < 4.366 cm²/m for STD-RF_csa, respectively. In the validation set, the area under the curve (AUC) values for the prediction of a 6MWD < 350 by STD-RF_thick and STD-RF_csa were 0.881 and 0.903, respectively. Finally, the predictive efficacy of STD-RF_thick (AUC: 0.922), STD-RF_csa (AUC: 0.904), and the derived nomogram model (AUC: 0.98) for exercise tolerance was superior to that of the sit-to-stand test and traditional clinical features.

Conclusions

Rectus femoris ultrasound has potential clinical application to predict impaired exercise tolerance in patients with COPD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01663-8.

Seven Pillars of Small Airways Disease in Asthma and COPD: Supporting Opportunities for Novel Therapies

Identification of pathologic changes in early and mild obstructive lung disease has shown the importance of the small airways and their contribution to symptoms. Indeed, significant small airways dysfunction has been found prior to any overt airway obstruction being detectable by conventional spirometry techniques. However, most therapies for the treatment of obstructive lung disease target the physiological changes and associated symptoms that result from chronic lung disease, rather than directly targeting the specific underlying causes of airflow disruption or the drivers of disease progression. In addition, although spirometry is the current standard for diagnosis and monitoring of response to therapy, the most widely used measure, FEV1 , does not align with the pathologic changes in early or mild disease and may not align with symptoms or exacerbation frequency in the individual patient. Newer functional and imaging techniques allow more effective assessment of small airways dysfunction; however, significant gaps in our understanding remain. Improving our knowledge of the role of small airways dysfunction in early disease in the airways, along with the identification of novel end points to measure subclinical changes in this region (ie, those not captured as symptoms or identified through standard FEV1), may lead to the development of novel therapies that directly combat early airways disease processes with a view to slowing disease progression and reversing damage. This expert opinion paper discusses small airways disease in the context of asthma and COPD and highlights gaps in current knowledge that impede earlier identification of obstructive lung disease and the development and standardization of novel small airways-specific end points for use in clinical trials.

Functional respiratory imaging assessment of glycopyrrolate and formoterol fumarate metered dose inhalers formulated using co-suspension delivery technology in patients with COPD

Background:

Functional respiratory imaging (FRI) is a quantitative postprocessing imaging technique used to assess changes in the respiratory system. Using FRI, we characterized the effects of the long-acting muscarinic antagonist (LAMA), glycopyrrolate metered dose inhaler (GP MDI), and the long-acting β₂-agonist (LABA), formoterol fumarate metered dose inhaler (FF MDI), on airway volume and resistance in patients with moderate-to-severe chronic obstructive pulmonary disease.

Methods:

Patients in this phase IIIb, randomized, double-blind crossover study received twice-daily GP MDI (18 μg) and FF MDI (9.6 μg). Primary endpoints were specific (i.e. corrected for lobar volume) image-based airway volume (siVaw) and specific image-based airway resistance (siRaw), measured using FRI. Secondary and other endpoints included additional FRI, spirometry, and body plethysmography parameters. Postdose efficacy assessments were performed within 60–150 min of dosing on day 15.

Results:

A total of 23 patients were randomized and 19 completed both treatment periods. GP MDI and FF MDI both achieved significant improvements from baseline to day 15 in siVaw [11% (p = 0.0187) and 23% (p < 0.0001) increases, respectively] and siRaw [25% (p = 0.0219) and 44% (p < 0.0001) reductions, respectively]. Although, on average, improvements were larger for FF MDI than GP MDI, some individuals displayed greater responses with each of the two treatments. These within-patient differences increased with airway generation number. Spirometry and body plethysmography endpoints showed significant improvements from baseline in inspiratory capacity for both treatments, and numeric improvements for other endpoints.

Conclusion:

Both GP MDI and FF MDI significantly improved siRaw and siVaw at day 15 versus baseline. FRI endpoints demonstrated increased sensitivity relative to spirometry and body plethysmography in detecting differences between treatments in a small number of patients. Intra-patient differences in treatment response between the LAMA and the LABA provide further support for the benefit of dual bronchodilator therapies.

ClinicalTrials.gov registration number:

NCT02937584

The reviews of this paper are available via the supplemental material section.

Within-session reproducibility of forced oscillometry

BACKGROUND

The forced oscillation technique (FOT) provides detailed information about the mechanics of the respiratory system, while requiring minimal co-operation by the patient. FOT may be abnormal in subjects with normal spirometry and appears to be more closely related to airway symptoms. It is, therefore, attractive in epidemiological studies, where a large number of different examinations are made in each subjects in a short period of time. Current technical standards recommend the mean of three consecutive measurements to be used, but there is limited information regarding within-session variability of FOT measurements.

OBJECTIVE

The purpose of this study was to examine the within-session variability in FOT measurements in a large, population-based sample.

METHODS

We performed three consecutive FOT measurements in 700 subjects using the impulse oscillometry system. The first measurement was compared to the mean of three measurements for resistance at 5 and 20 Hz (R5 and R20, respectively), R5-R20, reactance at 5 Hz (X5) and resonant frequency (f_res ).

RESULTS

The differences between the first and the mean of three measurements (median, interquartile range) were minimal, for example 0.002, -0.008 to 0.014 kPa L^-1  s for R5 and -0.001, -0.008 to 0.005 kPa L^-1  s for X5. Findings were numerically similar for men and women as well as for subjects with and without airflow obstruction at spirometry.

CONCLUSIONS

We conclude that, whereas in clinical situations, three FOT measurements are to be preferred, a single measurement may suffice in epidemiological studies.

Small Airway Dysfunction in Asthma Is Associated with Perceived Respiratory Symptoms, Non-Type 2 Airway Inflammation, and Poor Responses to Therapy

BACKGROUND

Emerging evidence has indicated that small airway dysfunction (SAD) contributes to the clinical expression of asthma.

OBJECTIVES

The aim of the study was to explore the relationships of SAD assessed by forced expiratory flow between 25 and 75% (FEF25-75%), with clinical and inflammatory profile and treatment responsiveness in asthma.

METHOD

In study I, dyspnea intensity (Borg scale), chest tightness, wheezing and cough (visual analog scales, VASs), and pre- and post-methacholine challenge testing (MCT) were analyzed in asthma patients with SAD and non-SAD. In study II, asthma subjects with SAD and non-SAD underwent sputum induction, and inflammatory mediators in sputum were detected. Asthma patients with SAD and non-SAD receiving fixed treatments were prospectively followed up for 4 weeks in study III. Spirometry, Asthma Control Questionnaire (ACQ), and Asthma Control Test (ACT) were carried out to define treatment responsiveness.

RESULTS

SAD subjects had more elevated ΔVAS for dyspnea (p = 0.027) and chest tightness (p = 0.032) after MCT. Asthma patients with SAD had significantly elevated interferon (IFN)-γ in sputum (p < 0.05), and Spearman partial correlation found FEF25-75% significantly related to IFN-γ and interleukin-8 (both having p < 0.05). Furthermore, multivariable regression analysis indicated SAD was significantly associated with worse treatment responses (decrease in ACQ ≥0.5 and increase in ACT ≥3) (p = 0.022 and p = 0.032).

CONCLUSIONS

This study indicates that SAD in asthma predisposes patients to greater dyspnea intensity and chest tightness during bronchoconstriction. SAD patients with asthma are characterized by non-type 2 inflammation that may account for poor responsiveness to therapy.

A multimodal approach to detect and monitor early lung disease in cystic fibrosis

Introduction: In the early stages, lung involvement in cystic fibrosis (CF) can be silent, with disease progression occurring in the absence of clinical symptoms. Irreversible airway damage is present in the early stages of disease; however, reliable biomarkers of early damage due to inflammation and infection that are universally applicable in day-to-day patient management have yet to be identified.Areas covered: At present, the main methods of detecting and monitoring early lung disease in CF are the lung clearance index (LCI), computed tomography (CT), and magnetic resonance imaging (MRI). LCI can be used to detect patients who may require more intense monitoring, identify exacerbations, and monitor responses to new interventions. High-resolution CT detects structural alterations in the lungs of CF patients with the best resolution of current imaging techniques. MRI is a radiation-free imaging alternative that provides both morphological and functional information. The role of MRI for short-term follow-up and pulmonary exacerbations is currently being investigated.Expert opinion: The roles of LCI and MRI are expected to expand considerably over the next few years. Meanwhile, closer collaboration between pulmonology and radiology specialties is an important goal toward improving care and optimizing outcomes in young patients with CF.

Lost in transition: biomarkers of remodeling in patients with asthma

PURPOSE OF REVIEW

'Biomarkers of remodeling' represent a loose collection of features referring to several biological adaptations of the lung to cope with stressing factors. In addition, remodel-'ing' infers a dynamic process that would require a spatiotemporal resolution. This review focuses on different aspects of remodeling in pediatric and adult care.

RECENT FINDINGS

This review will cover aspects of pediatric remodeling, adult remodeling and techniques and procedures to adequately assess remodeling across different age spectra. In pediatrics, the onset and first features of remodeling are discussed and the continuation into adolescence is addressed. For adults, this review addresses predominant features of remodeling throughout the adult life span and whether there are currently interventions available to treat or reverse remodeling.

SUMMARY

The term 'remodeling' is often referred to via biomarkers that reflect the endstage of a process, although it rather reflects a continuous process starting in childhood and progressing to all age-levels in patients with asthma. Hence, only few biomarkers or surrogates are able to 'capture' its spatiotemporal component, and hardly any are ready for routine use in clinical practice. Given the clinical impact of the remodeling processes, new biomarkers are needed to adequately treat patients with asthma and objectively monitor treatment response beyond symptom control and lung function.

The short-term effects of ORKAMBI (lumacaftor/ivacaftor) on regional and distal lung structures using functional respiratory imaging

BACKGROUND

Lumacaftor/ivacaftor (LUM/IVA) has shown modest benefits in previous research, but the exact effects in the cystic fibrosis (CF) lung remain unclear. This study aims to offer novel information on the mode of action of the cystic fibrosis transmembrane conductance regulator (CFTR)-modulating drug by assessing lung structure and function using functional respiratory imaging (FRI).

METHODS

CF patients aged ⩾12 years homozygous for F508del were recruited in an open-label study. Before and after 12 weeks of treatment with LUM/IVA, FRI was used to visualize regional information, such as air trapping, lobar volume and airway wall volume. Secondary outcomes included the CF-CT scoring system, spirometry, the Cystic Fibrosis Questionnaire-Revised (CFQ-R) questionnaire, exercise tolerance and nutritional status.

RESULTS

Of the 12 patients enrolled in the study, 11 completed all study visits. Concerning the FRI parameters, hyperinflation of the lung decreased, indicated by a reduction in air trapping and lobar volume at expiration. Also, a decrease in airway wall volume and a redistribution of pulmonary blood volume were noted, which might be related to a decrease in mucus impaction. Airway resistance, airway volume, internal airflow distribution and aerosol deposition pattern did not show significant changes. No significant improvements were found in any of the CF-CT scores or in the spirometric parameters. Other secondary outcomes showed similar results compared with previous research. Correlations at baseline were found between FRI and conventional outcomes, including physical functioning, spirometry and CF-CT scores.

CONCLUSIONS

LUM/IVA decreased lung hyperinflation in combination with a potential decrease in mucus impaction, which can be related to an improved mucociliary transport. These results indicate that several FRI parameters, reflecting regional and distal lung structures, are more sensitive to changes caused by LUM/IVA than conventional respiratory outcomes.

The Impact of Lung Function on Extra-Pulmonary Diseases and All-Cause Mortality in US Adult Population with and without COPD

Objective

Spirometric lung function is usually used to evaluate respiratory health. However, the impact of lung function on extra-pulmonary diseases and all-cause mortality has not been fully elucidated, especially in people without chronic obstructive pulmonary disease (COPD).

Patients and Methods

Participants aged ≥20 and underwent spirometry test from the US National Health and Nutrition Examination Surveys (NHANES) 2007-2012 were analyzed in this study. Multivariate logistic and Cox regressions were used to evaluate the impact of forced expiratory volume in 1 second percent of predicted (FEV₁% predicted) and forced vital capacity percent of predicted (FVC% predicted) on 14 extra-pulmonary diseases and all-cause morbidity after adjusting for multiple confounders.

Results

During 2007-2012, 1800 COPD patients and 11,437 non-COPD subjects were included. The prevalence of hypertension, diabetes mellitus (DM), dyslipidemia, metabolic syndrome (MS), congestive heart failure (CHF), coronary disease, stroke, chronic kidney disease (CKD), arthritis, cancer, underweight and osteoporosis in COPD patients was higher than that in the non-COPD population. After adjusting for confounders, the decrease of FEV₁% predicted and FVC% predicted was related with higher odds of having hypertension, DM, obesity, MS, CHF, coronary disease and depression (OR > 1, P<0.05) in both the COPD and non-COPD populations. These 2 indices were also related with higher odds of dyslipidemia, CKD, arthritis and osteoporosis in the non-COPD population. The risk of stroke, anemia and cancer was not related with the decrease of lung function. In addition, the decrease of lung function was independent risk factors for the increase of all-cause mortality. These risks were gradually increased with the decrease of lung function.

Conclusion

The decrease of FEV₁% predicted and FVC% predicted was related with higher risk of multiple extra-pulmonary diseases and all-cause mortality in both the COPD and non-COPD population.

Diagnostic approach to chronic dyspnoea in adults

Chronic dyspnoea, or breathlessness for more than four weeks duration, is a common symptom in adults presenting to primary and tertiary care. It often presents a diagnostic challenge due to the wide spectrum of underlying disease, which is multifactorial in approximately one third of cases. Challenges in diagnosis include an often non-diagnostic clinical assessment, difficulty in selecting the most appropriate investigations and correct speciality referral for further diagnostic assessment. In patients presenting with chronic dyspnoea, history and physical examination are often non-specific with key findings more useful as negative predictive factors. There is a broad range of simple to specialised investigations that may be utilised in the diagnostic workup. Several diagnostic algorithms incorporating different tiers of investigations have been tested in studies of chronic dyspnoea patients but there is currently very limited data that test a diagnostic algorithm against standard clinical care. In this review we propose a diagnostic pathway with primary, secondary and tertiary level investigations for patients with chronic dyspnoea. This pathway is based on the combination of previously tested diagnostic algorithms in the literature, to assist clinicians in their diagnostic workup of chronic dyspnoea patients. Further research is needed to further evaluate diagnostic algorithms in this setting and to test this diagnostic pathway in clinical practice.