Document Detail

How does HeO2 increase maximum expiratory flow in human lungs?
MedLine Citation:
PMID:  7419718     Owner:  NLM     Status:  MEDLINE    
We used the retrograde catheter technique to investigate the effect of HeO2 on resistance to maximum expiratory flow (Vmax) in airways subsegments between alveoli and the equal pressure point (EPP), and between EPP and the flow-limiting segment (FLS). FLS were found at the same airway site in sublobar bronchi (i.d., 0.54 +/- 0.13 cm) on both air and HeO2 in the six human excised lungs studied. Static elastic recoil pressure (5 +/- 1 cm H2O) and the lateral pressure at FLS (critical transmural airway pressure -6 +/- 3 cm H2O) were not different on the two gases. delta Vmax averaged 37 +/- 8.9% and was similar to the value found in healthy subjects of similar age (66 +/- 10 yr). EPP were located on HeO2 in peripheral airways (i.d., 0.33 +/- 0.03 cm), and EPP on air were located more downstream. Resistance between EPP and FLS was highly density dependent. Resistance between alveoli and EPP behaved as if it were density independent, due in part to Poiseuille flow in the peripheral airways and in part to the consequent narrowing of peripheral airways on HeO2. This density-independent behavior in peripheral airways reduced delta Vmax on HeO2 from its predicted maximal amount of 62%. Assuming that FLS is the "choke point" these findings are consistent with wave-speed theory of flow limitation modified to include functionally density-independent pressure losses in peripheral airways. These results and conclusions are similar to those found in living dogs. They question previous interpretation of delta Vmax as an index of peripheral airway obstruction, and demonstrate the utility of the wave-speed theory in explaining complicated mechanisms of expiratory flow limitation.
S N Mink; L D Wood
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Publication Detail:
Type:  In Vitro; Journal Article    
Journal Detail:
Title:  The Journal of clinical investigation     Volume:  66     ISSN:  0021-9738     ISO Abbreviation:  J. Clin. Invest.     Publication Date:  1980 Oct 
Date Detail:
Created Date:  1980-12-16     Completed Date:  1980-12-16     Revised Date:  2010-09-10    
Medline Journal Info:
Nlm Unique ID:  7802877     Medline TA:  J Clin Invest     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  720-9     Citation Subset:  AIM; IM    
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MeSH Terms
Airway Resistance / drug effects
Forced Expiratory Flow Rates*
Helium / pharmacology*
Maximal Expiratory Flow Rate*
Middle Aged
Oxygen / pharmacology*
Pulmonary Ventilation / drug effects
Reg. No./Substance:
7440-59-7/Helium; 7782-44-7/Oxygen

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

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