Document Detail

Computational model for forced expiration from asymmetric normal lungs.
MedLine Citation:
PMID:  12918904     Owner:  NLM     Status:  MEDLINE    
We present a computational model to predict maximal expiration through a morphometry-based asymmetrical bronchial tree. A computational model with the Horsfield-like geometry of the airway structure, including wave-speed flow limitation and taking into consideration separate airflows from several independent alveolar compartments has been derived. The airflow values are calculated for quasistatic conditions by solving a system of nonlinear differential equations describing static pressure losses along the airway branches. Calculations done for succeeding lung volumes result in the semidynamic maximal expiratory flow-volume (MEFV) curve. Simulations performed show that the model captures the main phenomena observed in vivo during forced expiration: effort independence of the flow-volume curve for the most of vital capacity, independence of limited flow on the properties of airways downstream to the choke points, characteristic differences of lung regional pressures and volumes, and a shape of their variability during exhalation. Some new insights into the flow limitation mechanism were achieved. First, flow limitation begins at slightly different time instants in individual branches of the bronchial tree, however after a short period of time, all regional flows are limited in a parallel fashion. Hence, total flow at the mouth is limited for most of the expired lung volume. Second, each of the airway branches contribute their own flow-volume shape and just these individual flows constitute the measured MEFV curve. Third, central airway heterogeneity can play a crucial role in modification of the entire flow. Fourth, the bronchial tree asymmetry is responsible for a nongravitational component of regional volume variability. Finally, increased inhomogeneity yields results that cannot be explained nor re-created with the use of a symmetrical structure of the bronchial tree.
Adam G Polak; Kenneth R Lutchen
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Publication Detail:
Type:  Comparative Study; Evaluation Studies; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.; Validation Studies    
Journal Detail:
Title:  Annals of biomedical engineering     Volume:  31     ISSN:  0090-6964     ISO Abbreviation:  Ann Biomed Eng     Publication Date:  2003 Sep 
Date Detail:
Created Date:  2003-08-15     Completed Date:  2004-04-28     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0361512     Medline TA:  Ann Biomed Eng     Country:  United States    
Other Details:
Languages:  eng     Pagination:  891-907     Citation Subset:  IM    
Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA.
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MeSH Terms
Air Pressure
Bronchi / physiology
Computer Simulation
Exhalation / physiology*
Forced Expiratory Flow Rates / physiology*
Forced Expiratory Volume / physiology*
Lung / physiology*
Models, Biological*
Reproducibility of Results
Sensitivity and Specificity
Grant Support

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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