Identification of Phenotypes of COPD Using Respiratory Impedance (original) (raw)
Related papers
BMC Pulmonary Medicine, 2012
Background: Current COPD guidelines advocate a fixed < 0.70 FEV1/FVC cutpoint to define airflow obstruction. We compared rate of lung function decline in respiratory symptomatic 40+ subjects who were 'obstructive' or 'non-obstructive' according to the fixed and/or age and gender specific lower limit of normal (LLN) FEV1/FVC cutpoints. Methods: We studied 3,324 respiratory symptomatic subjects referred to primary care diagnostic centres for spirometry. The cohort was subdivided into four categories based on presence or absence of obstruction according to the fixed and LLN FEV1/FVC cutpoints. Postbronchodilator FEV1 decline served as primary outcome to compare subjects between the respective categories. Results: 918 subjects were obstructive according to the fixed FEV1/FVC cutpoint; 389 (42%) of them were nonobstructive according to the LLN cutpoint. In smokers, postbronchodilator FEV1 decline was 21 (SE 3) ml/year in those non-obstructive according to both cutpoints, 21 (7) ml/year in those obstructive according to the fixed but not according to the LLN cutpoint, and 50 (5) ml/year in those obstructive according to both cutpoints (p = 0.004). Conclusion: This study showed that respiratory symptomatic 40+ smokers and non-smokers who show FEV1/FVC values below the fixed 0.70 cutpoint but above their age/gender specific LLN value did not show accelerated FEV1 decline, in contrast with those showing FEV1/FVC values below their LLN cutpoint.
Annals of Thoracic Medicine, 2018
OBJECTIVE: To ascertain: (i) if elderly patients with fixed airflow obstruction (FAO) due to asthma and chronic obstructive pulmonary disease (COPD) have distinct airway morphologic and physiologic changes; (ii) the correlation between the morphology of proximal/peripheral airways and respiratory impedance. METHODS: Twenty-five asthma cases with FAO and 22 COPD patients were enrolled. High-resolution computed tomography was used to measure the wall area (WA) and lumen area (LA) of the proximal airway at the apical segmental bronchus of the right upper lobe (RB1) adjusted by body surface area (BSA) and bronchial wall thickening (BWT r) of the peripheral airways and extent of expiratory air trapping (AT exp). Respiratory impedance included resistance at 5 Hz (R 5) and 20 Hz (R 20) and resonant frequency (Fres). Total lung capacity (TLC) and residual volume (RV) were measured. RESULTS: Asthma patients had smaller RB1-LA/BSA than COPD patients (10.5 ± 3.4 vs. 13.3 ± 5.0 mm 2 /m 2 , P = 0.037). R 5 (5.5 ± 2.0 vs. 3.4 ± 1.0 cmH 2 O/L/s, P = 0.02) and R 20 (4.2 ± 1.7 vs. 2.6 ± 0.7 cmH 2 O/L/s, P = 0.001) were higher in asthma cases. AT exp and BWT r were similar in both groups. Regression analysis in asthma showed that forced expiratory volume in one second (FEV 1) and Fres were associated with RB1-WA/BSA (R 2 = 0.34, P = 0.005) and BWT r (0.5, 0.012), whereas RV/TLC was associated with AT exp (0.38, 0.001). CONCLUSIONS: Asthma patients with FAO had a smaller LA and higher resistance of the proximal airways than COPD patients. FEV 1 and respiratory impedance correlated with airway morphology.
Current clinical guideline definitions of airflow obstruction and COPD overdiagnosis in primary care
European Respiratory Journal, 2008
The aim of the present study was to establish the agreement between two recommended definitions of airflow obstruction in symptomatic adults referred for spirometry by their general practitioner, and investigate how rates of airflow obstruction change when prebronchodilator instead of post-bronchodilator spirometry is performed. The diagnostic spirometric results of 14,056 adults with respiratory obstruction were analysed. Differences in interpretation between a fixed 0.70 forced expiratory volume in one second (FEV1)/ forced vital capacity (FVC) cutoff point and a sex-and age-specific lower limit of normal cutoff point for this ratio were investigated. Of the subjects, 53% were female and 69% were current or ex-smokers. The mean postbronchodilator FEV1/FVC was 0.73 in males and 0.78 in females. The sensitivity of the fixed relative to the lower limit of normal cutoff point definition was 97.9%, with a specificity of 91.2%, positive predictive value of 72.0% and negative predictive value of 99.5%. For the subgroup of current or ex-smokers aged o50 yrs, these values were 100, 82.0, 69.2 and 100%, respectively. The proportion of false positive diagnoses using the fixed cutoff point increased with age. The positive predictive value of pre-bronchodilator airflow obstruction was 74.7% among current or ex-smokers aged o50 yrs. The current clinical guideline-recommended fixed 0.70 forced expiratory volume in one second/ forced vital capacity cutoff point leads to substantial overdiagnosis of obstruction in middle-aged and elderly patients in primary care. Using pre-bronchodilator spirometry leads to a high rate of false positive interpretations of obstruction in primary care.
COPD prognosis in relation to diagnostic criteria for airflow obstruction in smokers
European Respiratory Journal, 2013
The aim of this study was to establish which cutoff point for the forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) ratio (i.e. fixed 0.70 or lower limit of normal (LLN) cutoff point) best predicts accelerated lung function decline and exacerbations in middle-aged smokers. We performed secondary analyses on the Lung Health Study dataset. 4045 smokers aged 35-60 years with mild-to-moderate obstructive pulmonary disease were subdivided into categories based on presence or absence of obstruction according to both FEV1/FVC cutoff points. Post-bronchodilator FEV1 decline served as the primary outcome to compare subjects between the categories. 583 (14.4%) subjects were nonobstructed and 3230 (79.8%) subjects were obstructed according to both FEV1/FVC cutoff points. 173 (4.3%) subjects were obstructed according to the fixed cutoff point, but not according to the LLN cutoff point (''discordant'' subjects). Mean¡SE post-bronchodilator FEV1 decline was 41.8¡2.0 mL?year-1 in nonobstructed subjects, 43.8¡3.8 mL?year-1 in discordant subjects and 53.5¡0.9 mL?year-1 in obstructed subjects (p,0.001). Our study showed that FEV1 decline in subjects deemed obstructed according to a fixed criterion (FEV1/ FVC ,0.70), but non-obstructed by a sex-and age-specific criterion (LLN) closely resembles FEV1 decline in subjects designated as non-obstructed by both criteria. Sex and age should be taken into account when assessing airflow obstruction in middle-aged smokers. @ERSpublications Lower limit of normal cutoff best predicts accelerated lung function decline and exacerbation in middle-aged smokers http://ow.ly/qaZnz This article has supplementary material available from www.erj.ersjournals.com
Fixed airflow obstruction due to asthma or chronic obstructive pulmonary disease: 5-year follow-up
Journal of Allergy and Clinical Immunology, 2010
Background: Both smokers and patients with asthma can experience fixed airflow obstruction, which is associated with distinctive patterns of airway pathology. The influence of fixed airflow obstruction on the prognosis of these patients is unknown. Objective: We sought to investigate lung function decline and exacerbations in a 5-year prospective study of subjects with fixed airflow obstruction due to asthma or chronic obstructive pulmonary disease (COPD). We also sought to explore correlations between functional, pathological, and clinical features. Methods: Patients with fixed airflow obstruction due to asthma (n 5 16) or COPD (n 5 21) and a control group of asthmatic patients with fully reversible airflow obstruction (n 5 15) were followed for 5 years. Results: The rates of decline in FEV 1 were similar in patients with fixed airflow obstruction caused by asthma (249.7 6 10.6 mL/y) or COPD (251.4 6 9.8 mL/y) and were higher than in asthmatic patients with reversible airflow obstruction (218.1 6 10.1 mL/y, P < .01). Exacerbation rates were also higher in patients with fixed airflow obstruction caused by asthma (1.41 6 0.26 per patient-year) or COPD (1.98 6 0.3 per patient-year) compared with those seen in asthmatic patients with reversible airflow obstruction (0.53 6 0.11 per patient-year, P < .01). Baseline exhaled nitric oxide levels and sputum eosinophil counts correlated with the FEV 1 decline in asthmatic patients with fixed airflow obstruction. By contrast, baseline sputum neutrophil counts, emphysema scores, comorbidities, and exacerbation frequency correlated directly and pulmonary diffusion capacity correlated inversely with the FEV 1 decline in patients with COPD. Conclusion: In both patients with asthma and those with COPD, fixed airflow obstruction is associated with increased lung function decline and frequency of exacerbations. Nevertheless, the decline in lung function entails the specific pathological and clinical features of the underlying diseases. (J Allergy Clin Immunol 2010;125:830-7.)
Respirology, 2015
Background and objective: The relative contributions of emphysema and airway remodelling to airflow limitation remain unclear in chronic obstructive pulmonary disease (COPD).We aimed to evaluate the relative contributions of emphysema and airway wall thickness measured by quantitative computed tomography (CT) to the prediction of airflow limitation in two separate COPD cohorts. Methods: Pulmonary function tests and whole-lung CT were performed in 250 male smokers with COPD, including 167 from University Medical Center at Ho Chi Minh City, Vietnam, and 83 from Shiga University of Medical Science Hospital, Japan. The same CT analysis software was used to measure the percentage of low attenuation volume (%LAV) at the threshold of −950 Hounsfield units and the square root of wall area of a hypothetical airway with an internal perimeter of 10 mm (Pi10). The standardized coefficients in multiple linear regressions were used to evaluate the relative contributions of %LAV and Pi10 to predictions of FEV1/ FVC and FEV1% predicted. Results: Both %LAV and Pi10 independently predicted either forced expiratory volume in 1 s/forced vital capacity (FEV1/FVC) or FEV1% predicted (P ≤ 0.001 for all standardized coefficients). However, the absolute values of the standardized coefficients were 2−3 times higher for %LAV than for Pi10 in all prediction models. The results were consistent in the two COPD cohorts. Conclusions: %LAV predicts both FEV1/FVC and FEV1 better than Pi10 in patients with COPD. Thus, emphysema may make a greater contribution to airflow limitation than airway remodelling in COPD.
Assessment of bronchodilator response through changes in lung volumes in chronic airflow obstruction
Medicina, 2003
Although FEV1 improvement is routinely used to define bronchodilator (BD) response, it correlates poorly with clinical effects. Changes in lung volumes (LV) have shown better correlation with exercise tolerance and might be more sensitive to detect BD effects. We assessed the additional contribution of measuring LV before and after BD to detect acute improvement in lung function not demonstrated by FEV1, and the influence of the response criteria selected on this contribution. We analyzed 98 spirometries and plethismographies performed pre and post BD in patients with airflow obstruction (FEV1/FVC < 70%). BD response was defined for FEV1 and FVC as per ATS guidelines and for other LV as delta > or = 10% of baseline (delta > or = 5 and > or = 15% were also analyzed). FEV1 identified as responders 32% of patients. Greater proportions were uncovered by slow vital capacity (51%, p < 0.001), inspiratory capacity (43%, p < 0.05) and residual volume (54%, p < 0.001). S...
Respiration, 2012
emphysema score in all patients was 25.6 8 25.4%. There was a weak but significant correlation between the percentage of pulmonary emphysema and numbers of pack/years (R = +0.31, p = 0.024). The percentage of emphysema was inversely correlated with the FEV 1 /FVC ratio before and after bronchodilator use (R = -0.44, p = 0.002, and R = -0.39, p = 0.005), DL CO % (R = -0.64, p = 0.0003) and DL CO /VA% (R = -0.68, p ! 0.0001). A weak positive correlation was also found with TLC% (R = +0.28, p = 0.048). When patients with documented emphysema were considered separately, the best significant correlation observed was between DL CO /VA% and HRCT scan score (p = 0.007). Conclusions: These data suggest that in patients with stable chronic obstructive pulmonary disease of varying severity, the presence of pulmonary emphysema is best represented by the impaired gas exchange capability of the respiratory system.