RT Journal Article
SR Electronic
T1 Computer model simulation of alveolar phase III slopes: Implications for tidal single-breath washout
JF European Respiratory Journal
JO Eur Respir J
FD European Respiratory Society
SP P4521
VO 44
IS Suppl 58
A1 Sylvia Nyilas
A1 David Borer
A1 David Hasler
A1 Florian Singer
A1 Sophie Yammine
A1 Philipp Latzin
A1 Dominik Obrist
YR 2014
UL http://erj.ersjournals.com/content/44/Suppl_58/P4521.abstract
AB BackgroundThe double-tracer gas single-breath washout (DTG-SBW) is a promising lung function test to assess small airways disease. The SBW derived alveolar phase III slope (SIII) accumulates the washout behavior of the two tracer gases helium and sulfur hexafluoride. We developed a numeric model to assess the influence of lung volumes on SIII and compared these to in-vivo measurements.MethodsThe computer model is based on a one-dimensional advection-diffusion equation solved for asymmetric dichotomous tree morphology. Ten healthy adults performed the tidal DTG-SBW measurement with different breathing pattern (double and half tidal volume). Similar parameters were used in the model and compared with the in-vivo measurements.ResultsApplying different tidal volumes leads to significant changes in SIII, both in humans and the model. Half tidal volume lead to a mean change in SIII of -3.0 g/mol/L (p=0.01) in the model and -0.64 g/mol/L (p=0.002) in humans. A comparable significant change of SIII in the other direction was observed upon doubling tidal volume. Using the model to simulate effects of other factors than tidal volume showed that also FRC, breathing period and introducing asymmetries resulted in changes of SIII.ConclusionThe lung model predicts reasonably well the influence of tidal volume on SIII. Differences between model and human data are most likely due to the complex interaction between fractal geometry and dynamic changes in volumes of the human lung. Further advancement of the model including asymmetries and fractality may improve modeling of DTG-SBW. In general, these data suggest that changes in breathing pattern influence SIII results.