Techniques of assessing small airways dysfunction

William McNulty and Omar S. Usmani

 

Abstract

The small airways are defined as those less than 2 mm in diameter. They are a major site of pathology in many lung diseases, not least chronic obstructive pulmonary disease (COPD) and asthma. The small airways are frequently involved early in the course of these diseases, with significant pathology demonstrable often before the onset of symptoms or changes in spirometry and imaging. Despite their importance, they have proven relatively difficult to study. This is in part due to their relative inaccessibility to biopsy and their small size which makes their imaging difficult. Traditional lung function tests may only become abnormal once there is a significant burden of disease within them. This has led to the term ‘the quiet zone’ of the lung. In recent years, more specialised tests have been developed which may detect these changes earlier, perhaps offering the possibility of earlier diagnosis and intervention. These tests are now moving from the realms of clinical research laboratories into routine clinical practice and are increasingly useful in the diagnosis and monitoring of respiratory diseases. This article gives an overview of small airways physiology and some of the routine and more advanced tests of airway function.

Complete article with all references at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4629724/ 

Articles from European Clinical Respiratory Journal are provided here courtesy of Taylor & Francis

 


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Small Airways Dysfunction in Asthma: Evaluation and Management

Usmani, Os

 

Abstract

The small airways have been neglected for many years, but interest in the topic has been rekindled with recent advances in measurement techniques to assess this region and also the ability to deliver therapeutics to the distal airways. Current levels of disease control in asthmatic patients remain poor and there are several contributory factors including; poor treatment compliance, heterogeneity of asthma phenotypes and associated comorbidities. However, the proposition that we may not be targeting all the inflammation that is present throughout the whole respiratory tree may also be an important factor. Indeed decades ago, pathologists and physiologists clearly identified the importance of small airways dysfunction in asthmatic patients. With improved inhaler technology to deliver drug to target the whole respiratory tree and more sensitive measures to assess the distal airways, we should certainly give greater consideration to treating the small airway region when seeing our asthmatic patients in clinic. The aim of this review is to address the relevance of small airways dysfunction in the daily clinical management of patients with asthma. In particular the role of small particle aerosols in the management of patients with asthma will be explored.
Full article with all references at: https://doi.org/10.4168/aair.2014.6.5.376

 

Copyright © 2014 The Korean Academy of Asthma, Allergy and Clinical Immunology • The Korean Academy of Pediatric Allergy and Respiratory Disease

 


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Reference equations for respiratory system resistance and reactance in adults

Nathan J.BrownWeiXuanCheryl M.SalomeNorbertBerendMichael L.Hunter, A.W. (Bill)MuskAlan L.JamesGregory G.King

Abstract

 

Aim

To determine reference equations for respiratory system resistance and reactance in a large randomly selected sample from a general, predominantly Caucasian population.

Methods

A prospective respiratory health survey of the general population in Busselton, Western Australia, was conducted between 2005 and 2007. Subjects had measures of spirometry, and resistance and reactance at 6, 11, 19 Hz. Eligible subjects were never smokers, with no history of respiratory disease, no symptoms of cough, shortness of breath or chest tightness in the previous 12 months, and no respiratory tract infections in the previous 4 weeks.

Results

904 Eligible subjects (341 male) aged 18–92 years had technically satisfactory measurements. Reference equations were established for males and females separately. Both resistance and reactance were predicted by height and weight. Age was a predictor of reactance only.

Conclusions

These data provide reference equations for forced oscillatory parameters, in well-characterized Caucasian subjects, with no respiratory symptoms, from a large general population.

 

Full article with all references at: https://www.sciencedirect.com/science/article/pii/S1569904810001886?via%3Dihub

 Copyright © 2010 Elsevier B.V. Published by Elsevier B.V. All rights reserved.


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Respiratory impedance and bronchodilator responsiveness in healthy children aged 2-13 years

Claudia Calogero MD, Shannon J. Simpson PhD, Enrico Lombardi MD, Niccolò Parri MD, Barbara Cuomo MD, Massimo Palumbo MD, Maurizio de Martino MD, Claire Shackleton BSc (Hons), Maureen Verheggen MMedSc, Tania Gavidia MIH, Peter J. Franklin PhD, Merci M.H. Kusel MBBS, PhD, Judy Park MBiostat, Peter D. Sly DSc, Prof. Graham L Hall PhD

 

Abstract

Background

The forced oscillation technique (FOT) can be used in children as young as 2 years of age and in those unable to perform routine spirometry. There is limited information on changes in FOT outcomes in healthy children beyond the preschool years and the level of bronchodilator responsiveness (BDR) in healthy children. We aimed to create reference ranges for respiratory impedance outcomes collated from multiple centers. Outcomes included respiratory system resistance (Rrs) and reactance (Xrs), resonant frequency (Fres), frequency dependence of Rrs (Fdep), and the area under the reactance curve (AX). We also aimed to define the physiological effects of bronchodilators in a large population of healthy children using the FOT.

Methods

Respiratory impedance was measured in 760 healthy children, aged 2–13 years, from Australia and Italy. Stepwise linear regression identified anthropometric predictors of transformed Rrs and Xrs at 6, 8, and 10 Hz, Fres, Fdep, and AX. Bronchodilator response (BDR) was assessed in 508 children after 200 µg of inhaled salbutamol.

Results

Regression analysis showed that Rrs, Xrs, and AX outcomes were dependent on height and sex. The BDR cut‐offs by absolute change in Rrs8, Xrs8, and AX were −2.74 hPa s L−1, 1.93 hPa s L−1, and −33 hPa s L−1, respectively. These corresponded to relative and Z‐score changes of −32%; −1.85 for Rrs8, 65%; 1.95 for Xrs8, and −82%; −2.04 for AX.

Conclusions

We have established generalizable reference ranges for respiratory impedance and defined cut‐offs for a positive bronchodilator response using the FOT in healthy children. Pediatr Pulmonol. 2013; 48:707–715. © 2012 Wiley Periodicals, Inc.

 

Full article with references: https://onlinelibrary.wiley.com/doi/abs/10.1002/ppul.22699
Copyright © 2012 Wiley Periodicals, Inc.

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Transient reference values for impulse oscillometry for children aged 3–18 years

Bożena Nowowiejska MD, Waldemar Tomalak PhD, Jakub Radliński PhD, Grzegorz Siergiejko MD, Wojciech Latawiec PhD, Maciej Kaczmarski MD, PhD

 

Abstract

Impulse oscillometry (IOS) is a technique of assessing mechanical properties of respiratory system by means of measuring resistances and reactances in a number of frequencies during tidal breathing. It is especially useful in preschool children, however has also been validated in older children and adults. The aim of the present study was to construct equations describing normal values of oscillatory parameters in pediatric population of healthy polish children. Six hundred twenty-six healthy children aged 3.1-18.9 years (278 boys and 348 girls) completed the study. Analysis revealed that body height was the best predictor and resistances are best described with exponential model while reactances with linear one, with correlation coefficient r reaching the value of 0.9. Oscillometric resistances decrease with height, while reactances increase. Reference values for children and adolescents will allow not only the interpretation of the measurement, but also will make possible to study changes of oscillometric indices during growth.

Full article with all references at: https://onlinelibrary.wiley.com/doi/abs/10.1002/ppul.20926

Copyright © 2008 Wiley‐Liss, Inc.


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Respiratory impedance in healthy subjects: baseline values and bronchodilator response

Ellie Oostveen1, Krisztina Boda2, Chris P.M. van der Grinten3, Alan L. James4, Sally Young4, Hans Nieland5 and Zoltán Hantos2

 

Affiliations: ¹Dept of Respiratory Medicine, Antwerp University Hospital and University of Antwerp, Antwerp, Belgium. ²Dept of Medical Physics and Informatics, University of Szeged, Szeged, Hungary. ³Dept of Respiratory Medicine, Maastricht University Medical Centre, Maastricht, and 5Dept of Lung Function, Medisch Spectrum Twente, Enschede, The Netherlands. 4Dept of Pulmonary Physiology, Sir Charles Gairdner Hospital, Nedlands, Australia.

Correspondence: E. Oostveen, Antwerp University Hospital, Wilrijkstraat 10, Edegem-Antwerp, B-2650, Belgium. E-mail: email hidden; JavaScript is requiredemail hidden; JavaScript is required

 

ABSTRACT Because of the minimal demand for cooperation by the subject, the forced oscillation technique is increasingly employed in routine lung function testing. However, comprehensive and device- independent values of respiratory impedance at baseline and after bronchodilation have not been established for healthy adults.

The aim of this multicentre study was to collect impedance data from 4 to 26 Hz in healthy Caucasian subjects between 18 and 80 years of age. Five different devices were employed to assess baseline values and the bronchodilator response.

Altogether, 368 subjects were examined. Despite adjustment for anthropometry, the impedance spectra differed in frequency dependence between the centres, and hence could not be pooled. However, resistance at all frequencies except 20 and 25 Hz, and the low-frequency (f14 Hz) values of reactance did not exhibit a centre dependence. The regression equations for resistance reflected a greater height dependence in males and a greater weight dependence in both males and females than those published previously. Bronchodilation resulted in a statistically significant decrease (11%) in resistance and a 95th percentile equal to a 32% decrease in resistance at low frequency.

We conclude that rigorous calibration procedures should be developed to ensure data compatibility. Furthermore, new reference equations based on different setups are recommended to replace those established with a single device.

 

Complete article with all references: https://www.ncbi.nlm.nih.gov/pubmed/23598954

 


This article has supplementary material available from www.erj.ersjournals.com

Received: Aug 10 2012 | Accepted after revision: Feb 06 2013 | First published online: April 18 2013 Conflict of interest: None declared.

Copyright ©ERS 2013


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