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Constant phase lung model examined in terms of pressure-volume (P-V) loop analysis.

Authors
Frazer-DG; Reynolds-JS; McKinney-WG
Source
Proc Am Thorac Soc 2006 Apr; 3(Abstracts):A317
NIOSHTIC No.
20031251
Abstract
The constant phase description of lung input impedance is Zin = Raw + (G + H )/ assuming the inertance of airway gas is negligible and Raw = airway resistance, G = tissue damping, H = tissue elasticity and = hysteresivity = G/H. There is concern that non-uniform air-flow conditions in the airways at low lung volume produce changes in Zin which are incorrectly interpreted as alterations in the lungs tissue properties. The tissue properties of the constant phase model can be written in terms of quasi-static PV loop parameters described by Hildebrandt (Bul. Math. Biophy., 31, 1968, JAP,35, 1973) as: k = AH/dP dV (see fig. 1) , = 1/((/4k)2 -1)1/2 , = 2/ tan-1(1/ ), Edyn =dP/dV(1/(1+ 2)1/2), H = Edyn(-1), G = (4AH/dV2) (-1), where is the quasi-static radial frequency at which the loops were recorded. The equivalent constant phase parameters calculated from quasi-static P-V loop analysis at low frequencies are not complicated by airway airflow inequalities. An analysis of small P-V loops recorded at various points during a complete inflation-deflation cycle of excised rat lungs shows that the of lung tissue decreases then increases as a function of end expiratory pressure during lung deflation and does not have to be explained by unequal airflow patterns in the airways.
Keywords
Models; Airway-resistance; Airway-obstruction; Air-flow; Lung-tissue; Lung-disorders
CODEN
PATSBB
Publication Date
20060401
Document Type
Abstract; Conference/Symposia Proceedings
Fiscal Year
2006
NTIS Accession No.
NTIS Price
Issue of Publication
Abstracts
ISSN
1546-3222
NIOSH Division
HELD
Source Name
Proceedings of the American Thoracic Society
State
WV; CA
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