Evaluation of Respiratory Impedance in Asthma and COPD by an Impulse Oscillation System

Kanda, Shintarou; Fujimoto, Keisaku; Komatsu, Yoshimichi; Matsumura, Yasuo; Hanaoka, Masayuki; Kubo, Keishi

doi:10.2169/internalmedicine.49.2191

Cited by 82 publications

(91 citation statements)

References 29 publications

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“…Impedance and impedance entropy parameters in healthy subjects and patients with asthma In line with previous studies [27,28], we found significant increases in R5-R20 and AX, and to a lesser extent R20, in patients with severe asthma compared with healthy controls, suggesting that the baseline level of airway narrowing, and the accompanying heterogeneity of narrowing and closure, are increased in patients with severe asthma. We were unable to demonstrate a difference in these parameters between patients with severe asthma established on maintenance oral corticosteroids (GINA treatment step 5) and patients on high-dose inhaled corticosteroids (GINA treatment step 4), suggesting that these processes may be resistant to corticosteroid therapy.…”

Section: Discussionsupporting

confidence: 91%

Airway impedance entropy and exacerbations in severe asthma

et al. 2012

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Variability of peak flow measurements has been related to clinical outcomes in asthma. We hypothesised that the entropy, or information content, of airway impedance over short time scales may predict asthma exacerbation frequency.66 patients with severe asthma and 30 healthy control subjects underwent impulse oscillometry at baseline and following bronchodilator administration. On each occasion, airway impedance parameters were measured at 0.2-s intervals for 150 s, yielding a time series that was then subjected to sample entropy (SampEn) analysis.Airway impedance and SampEn of impedance were increased in asthmatic patients compared with healthy controls. In a logistic regression model, SampEn of the resistance at 5 Hz minus the resistance at 20 Hz, a marker of the fluctuation of the heterogeneity of airway constriction over time, was the variable most strongly associated with the frequent exacerbation phenotype (OR 3.23 for every 0.1 increase in SampEn).Increased airway impedance and SampEn of impedance are associated with the frequent exacerbation phenotype. Prospective studies are required to assess their predictive value.KEYWORDS: Airflow obstruction, asthma, entropy, oscillometry A cute exacerbations of asthma account for much of the morbidity and mortality associated with this condition [1]. However, there is no currently available biomarker that can accurately predict the risk of future exacerbations. Previous studies have suggested that a geometrically self-similar airway tree may confer increased risk of asthma exacerbations and that fatal asthma is associated with a reduction in the structural complexity of the airway tree [2]. Similarly, the ventilation heterogeneity observed in asthma follows power law behaviour, which predicts catastrophic closure of small airways [3]. Therefore, characterising structural complexity may have utility in predicting asthma exacerbations.It has been speculated that the temporal variability in lung function may also exhibit self-similarity at multiple time scales [4]. This would suggest that monitoring lung function over short time scales may provide insights into lung function variability over longer time scales of weeks to months, thus providing a more practical predictive tool for exacerbations. A number of tools have been utilised to characterise time series properties of physiological signals, including those that predict scaling and power law behaviour of information over multiple time scales and those that predict the probability of information repeating itself within a time series [5,6]. Fluctuations and power law behaviour observed in a time series of lung function measurements such as peak expiratory flow (PEF) may predict poor asthma control or exacerbations [7,8]. THAMRIN et al [9] found that the degree of long-range correlation (self-similarity at different temporal length scales) in PEF measurements appeared to provide additional predictive information with respect to exacerbations in mildto-moderate asthma, but less so in severe asthma.The force...

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Section: Discussionsupporting

confidence: 91%

Airway impedance entropy and exacerbations in severe asthma

et al. 2012

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“…Therefore, the criterion of MEF50/MEF25, as a marker of small airway disease, can only be used in younger populations, whereas for older populations, the single criterion of MEF50/MEF25 does not appear to be sufficient for diagnosing the presence of small airway disease. Further measurements such as the closing volume test and respiratory resistance test using the impulse oscillation system, are also required to evaluate the function of the small airways (25,26). Moreover, in the present study, since there was no difference in the MEF50/MEF25 between smokers and never-smokers, MEF50/MEF25 was not confirmed to be a useful marker for cigarette smoke-induced airway damage.…”

Section: Discussionmentioning

confidence: 66%

Impact of Cigarette Smoking on Maximal Expiratory Flows in a General Population: the Takahata Study

et al. 2011

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Background Maximal expiratory flows (MEFs) depend on the elastic recoil pressure in the alveoli, airway resistance and bronchial collapsibility. MEFs at lower levels of vital capacity [MEFs at x% FVC (MEFx)] would indicate the patency of peripheral airways. In Japan, a ratio of MEF50 to MEF25 (MEF50/MEF25) greater than 4.0 is used as an index of injury to the small airways in subjects without airflow limitation. However, to date there have been no epidemiological investigations relating to this index. The aim of this study was to evaluate the impact of cigarette smoking on MEFs in a general population, and to assess the validity of using this index to evaluate injury to the small airways. Methods Subjects aged 40 years or older (n=2,917), who had participated in a community-based annual health-check in Takahata, Japan, were enrolled in the study. MEF75, MEF50 and MEF25 were measured in these subjects. Results In smokers, as compared with never-smokers, the percentage predicted MEFs (%MEFs) decreased according to the aging of the population, except in the case of %MEF25 in females. In males, but not in females, %MEFs decreased significantly with an increase in cigarette consumption. In both genders, MEF50/ MEF25 was slightly, but significantly, elevated with aging of the population. In addition, 36.5% of subjects who participated in this health-check had MEF50/MEF25 values greater than 4.0. No difference in MEF50/ MEF25 was observed between smokers and never-smokers. Conclusion Cigarette smoking enhanced the age-related decline in MEFs. Since many healthy subjects aged 40 years or older have MEF50/MEF25 values greater than 4.0, the use of this criterion may over-estimate the presence of small airway disease.

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“…Indeed, in general, R5 only moderately correlates with FEV1 in asthma and COPD (12,13). R5 is higher in patients with COPD than in healthy controls, but not in those with asthma (12,14).…”

Section: Rrsmentioning

confidence: 85%

Clinical Application of the Forced Oscillation Technique

Shirai

Kurosawa

2016

Intern. Med.

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The forced oscillation technique (FOT) is a noninvasive method with which to measure respiratory system resistance and reactance during tidal breathing. Recently, its clinical application has spread worldwide with the expansion of commercially available broadband frequency FOT devices, including MostGraph and Impulse Oscillometry. An increasing number of reports have supported the usefulness of the FOT in the management of asthma and chronic obstructive pulmonary disease (COPD). However, the FOT is not a surrogate test for spirometry, but should be used complementarily. Furthermore, reference values are not necessarily available and the interpretation of some measured data is controversial. There is a need to update the international statement for not only technical aspects but also the clinical use of the FOT. In this review, we summarize the previously published studies and discuss how to use the FOT in a clinical setting.

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Evaluation of Respiratory Impedance in Asthma and COPD by an Impulse Oscillation System

Abstract: Objective The purpose of this study was to clarify the differences in physiological properties of the airways between asthma and COPD using an impulse oscillation system (IOS). Patients and Methods

Cited by 82 publications

References 29 publications

Airway impedance entropy and exacerbations in severe asthma

Airway impedance entropy and exacerbations in severe asthma

Impact of Cigarette Smoking on Maximal Expiratory Flows in a General Population: the Takahata Study

Clinical Application of the Forced Oscillation Technique

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