Document Detail

Characteristics of a simple measure of respiratory impedance.
MedLine Citation:
PMID:  3602616     Owner:  NLM     Status:  MEDLINE    
The ratio of mouth pressure developed 0.1 sec after occlusion at end-expiration (P0.1) to average inspiratory flow rate (VT/TI) has been proposed as 'effective inspiratory impedance', Imeff. We have studied a simple mathematical model of lung mechanics, consisting of an effective resistance, an effective compliance and a single pressure generator, to learn how Imeff is altered by changes in resistance (R), compliance (C), inspiratory duration (TI), and the degree of curvature of the inspiratory pressure wave form. The degree of curvature was varied between concave with respect to the time axis to convex and included a linear inspiratory muscle pressure function. Assuming a linear pressure function, we obtained an explicit equation for Imeff as a function of R, C, and TI. Using the same model we also studied the classical impedance as a function of R, C and frequency (of a sinusoidal excitation pressure). We found that Imeff was increased by increases in R, increasing degrees of concavity, decreases in C, and by decreases in TI. For this model the classical impedance was about 5 times larger than Imeff. Classical impedance was increased by increases in R, decreases in C, and decreases in excitation frequency. In conclusion, measurements of effective inspiratory impedance need to be interpreted in terms of R, C, TI, and the shape of the inspiratory muscle pressure function.
W E Fordyce; R M Whetstone
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Respiration physiology     Volume:  68     ISSN:  0034-5687     ISO Abbreviation:  Respir Physiol     Publication Date:  1987 May 
Date Detail:
Created Date:  1987-08-04     Completed Date:  1987-08-04     Revised Date:  2009-11-11    
Medline Journal Info:
Nlm Unique ID:  0047142     Medline TA:  Respir Physiol     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  145-59     Citation Subset:  IM    
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MeSH Terms
Child, Preschool
Lung / physiology*
Models, Biological
Models, Theoretical
Physical Exertion
Respiratory Function Tests
Respiratory Muscles / physiology
Grant Support
5 R23 H130653-02//PHS HHS

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