TY - JOUR T1 - Dynamic compliance and reactance in older non-smokers with asthma and fixed airflow obstruction JF - European Respiratory Journal JO - Eur Respir J DO - 10.1183/13993003.04400-2020 VL - 58 IS - 2 SP - 2004400 AU - Timothy Durack AU - David G. Chapman AU - Sandra Rutting AU - Cindy Thamrin AU - Gregory G. King AU - Katrina O. Tonga Y1 - 2021/08/01 UR - http://erj.ersjournals.com/content/58/2/2004400.abstract N2 - 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.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 ER -