PT - JOURNAL ARTICLE AU - Ole Pedersen AU - Riccardo Pellegrino AU - Pasquale Pompilio TI - Change of CP location during bronchodilatation DP - 2012 Sep 01 TA - European Respiratory Journal PG - P866 VI - 40 IP - Suppl 56 4099 - http://erj.ersjournals.com/content/40/Suppl_56/P866.short 4100 - http://erj.ersjournals.com/content/40/Suppl_56/P866.full SO - Eur Respir J2012 Sep 01; 40 AB - Background: The wave-speed concept of flow limitation predicts a unique relationship between the MFSR-curve and the tube laws of the airways containing the choke points (CP). If the frictional pressure loss (Pfr) cannot be neglected J = Pel – Pfr must be substituted for Pel.Aim: 1) To analyse data from Lambert et al. (JAP 52:44-46) in terms of motion of CP during expiration.2) To measure upstream viscous pressure losses (Pfr) and J = Pel – Pfr (Comprehensive Physiology Volume 1, 2011: 1861-1881). The relationship between cross-sectional area (A) and transmural pressure (Ptm) – the tube laws were calculated from the relationship between V'max and J.Results:Bronchial dilatation increases maximal flow in all cases, but Pfr increases in two cases and decreases in two. Pfr increases when density dependence DD decreases, and increases when DD decreases. The A-Ptm curves show an irregular appearance reflecting the elastic properties of the more and more peripheral airways containing the CP during the expiration. Central and peripheral airways could be detected in each case. In three of four subjects CP at 50%FVC moved to more central airways after bronchodilatation.Conclusion: The magnitude of Pfr is small, and the study is inconclusive. However, the study indicates that CP moves centrally in 3 of the 4 subjects with bronchodilatation. More experiments are needed.