Impact of exacerbations on respiratory system impedance measured by a forced oscillation technique in COPD: a prospective observational study

Abstract

BackgroundForced oscillation technique (FOT) has been reported to be useful in the evaluation and management of obstructive lung disease, including COPD. To date, no data are available concerning long-term changes in respiratory system impedance measured by FOT. Additionally, although exacerbations have been reported to be associated with excessive lung function decline in COPD, the impact of exacerbations on the results of FOT has not been demonstrated. The aim of this study was to investigate the longitudinal changes in respiratory system impedance and the influence of exacerbations thereon.MethodsBetween March 2011 and March 2012, outpatients who attended Kobe City Medical Center West Hospital with a diagnosis of COPD were assessed for eligibility. Baseline patient characteristics (age, sex, body mass index, smoking history, current smoking status, COPD stage), lung function (post-bronchodilator forced expiratory volume in 1 second [FEV1]), blood tests (neutrophils and eosinophils), FOT, and COPD assessment test results were collected at enrollment. Lung function and FOT were examined every 6 months until March 2016. Annual changes in FEV1 and FOT parameters were obtained from the slope of the linear regression curve. The patients were divided into 2 groups based on exacerbation history.ResultsFifty-one of 58 patients with COPD were enrolled in this study. The median follow-up period was 57 (52–59) months. Twenty-five (49%) patients experienced exacerbations. A significant annual decline in FEV1 and respiratory system impedance were shown. Additionally, annual changes in FEV1, respiratory system resistance at 5 Hz, respiratory system reactance at 5 Hz, and resonant frequency were greater in patients with exacerbations than in those without exacerbations.ConclusionExacerbations of COPD lead not only to a decline in lung function but also to an increase in respiratory system impedance.

Impulse oscillometry and spirometry measurements relative to personal best values at the time of acute exacerbations of cystic fibrosis in adults

“…We observed significant differences of X5 (kPa.s.L −1 ), R5−R20 (kPa.s.L −1 ) and AX (kPa/L) at AE in comparison with Stable state, consistent with variation of X5, X10 and AX at AE in children with CF (Ren et al., 2006; Sakarya et al., 2016) and in CF adults in comparison with healthy patients (Lima et al., 2015). This result is also consistent with variation of oscillometry indices including R5−R20 and X5 (Kamada et al., 2017; Yamagami et al., 2018) in other airway diseases. In COPD, significant differences between variations of R5−R20 and of AX were reported in exacerbator versus non‐exacerbator patients, whereas FEV1 variations were not different (Yamagami et al., 2018).…”

Comparison of respiratory system impedance in asthma and COPD: A prospective observational study

“…All patients with COPD fulfilled the following inclusion criteria which had been used in our previous study 15 : (i) a smoking history of more than 20 packyears; (ii) maximal forced expiratory volume in 1 s (FEV 1 )/forced vital capacity (FVC) ratio (FEV 1 %) of <0.7; (iii) regular management and treatment at our outpatient clinic over 6 months; (iv) no exacerbations requiring systemic corticosteroid and/or antibiotics in the previous 3 months; (v) no other lung diseases or uncontrolled co-morbidities such as severe cardiovascular diseases and malignant disorders; and (vi) sufficient cognitive function to complete the questionnaire. The staging of COPD was assessed in accordance with the Global Initiative Chronic Obstructive Lung Disease (GOLD) 2014 guidelines.…”

Effects of combination therapy indacaterol/glycopyrronium versus tiotropium on moderate to severe COPD: evaluation of impulse oscillometry and exacerbation rate

“…A COPD exacerbation is defined as an acute worsening of respiratory symptoms which needs additional therapy, regardless the factors that cause it [ 17 ].…”