Extract
In asthma, abnormal mechanical properties of the airways and lung tissue leads to airway narrowing and changes in ventilation distribution [1]. Ventilation distribution is determined by the variation of time constants [2], the product of resistance and static compliance of individual lung units. Ventilation distribution is heterogeneous in healthy lungs, but even more so in airway diseases, including asthma [3]. This is because time constants are often even more heterogeneous in disease due to changes in resistances and compliances [3, 4]. Lung compliance measured under dynamic conditions, e.g. during breathing (dynamic compliance, or Cdyn), is sensitive to these heterogeneities in time constants. Cdyn decreases relative to static compliance (Cstat) with increasing ventilation heterogeneity [2, 3, 5], due to diversion of ventilation from lung units with longer to those with shorter time constants [6]. Hence Cdyn is a measure of lung function in relation to ventilation heterogeneity under tidal breathing conditions, that complements spirometry. However, Cdyn is not used clinically because it requires invasive oesophageal pressure measurements.
Abstract
In older non-smokers with asthma and fixed airflow obstruction, X5 measured by oscillometry reflects dynamic rather than static compliance. Distinguishing between dynamic and static compliance is important as they are due to different factors. https://bit.ly/3th0uEr
Footnotes
This study is registered at www.anzctr.org.au with identifier number ACTRN12615000985583. The data sets generated and/or analysed during the study are available from the corresponding author on reasonable request.
Conflict of interest: T. Durack has nothing to disclose.
Conflict of interest: D.G. Chapman has nothing to disclose.
Conflict of interest: S. Rutting has nothing to disclose.
Conflict of interest: C. Thamrin has a patent WO 2006130922 A1 issued which is broadly relevant to the work; and has intellectual property arrangements with Thorasys Medical Systems and Restech srl relating to research collaborations, but does not have any financial relationships with either company.
Conflict of interest: G.G. King reports grants from University of Sydney Bridging Grant, during the conduct of the study; grants, personal fees for consultancy, lectures and advisory board work, and support for meeting attendance from AstraZeneca, Boehringer Ingelheim, CycloPharm, GlaxoSmithKline, Novartis, Menarini and MundiPharma, grants from National Health and Medical Research Council, Asthma Foundation, Philanthropic donations via Sydney University, other (task force chair) from ATS and ERS, non-financial support (equipment provision) and other (intellectual property arrangements and research collaboration) from Restech, outside the submitted work.
Conflict of interest: K.O. Tonga reports personal fees for consultancy and lectures from GlaxoSmithKline and Roche, outside the submitted work.
Support statement: This study was supported by a bridging grant from the University of Sydney and by a Philanthropic grant from Anthony Berg via the Northern Clinical School, Faculty of Medicine and Health, the University of Sydney. Funding information for this article has been deposited with the Crossref Funder Registry.
- Received December 3, 2020.
- Accepted April 5, 2021.
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