Document Detail

The effect of incomplete acetylene washout on cardiac output measurement using open circuit acetylene uptake.
MedLine Citation:
PMID:  16714151     Owner:  NLM     Status:  MEDLINE    
The open circuit acetylene uptake method is a useful non-invasive means of measuring cardiac output. However, because of accumulation of inhaled acetylene in tissues, the cardiac output uptake is underestimated, if residual acetylene is not allowed to wash out completely in between measurements. We determined the effect of applying a correction factor that estimates mixed venous acetylene concentration from endtidal values to the calculation of cardiac output. This accounts for mixed venous acetylene present during measurements made before complete washout. Six healthy subjects performed steady-state exercise at approximately 30% and 60% of V(O2 max). Cardiac output measurements were made at each exercise intensity using the open circuit acetylene uptake method (inspired [acetylene] approximately 1%), with the first and last measurements having no detectible levels of acetylene in expired gas (reference measurement). Data were also obtained with immediate pre-measurement endtidal concentrations ranging from 3% to 15% of the inspired [acetylene], in random order in between. Oxygen consumption, carbon dioxide production and heart rate did not change significantly during testing at each exercise intensity. Reference cardiac output also did not change significantly and averaged 11.1+/-0.8 L/min at 30% of V(O2 max) and 16.5+/-2.0 L/min at 60% of V(O2 max). Uncorrected cardiac output measurements progressively underestimated cardiac output by 15% at the 3% of inspired endtidal [acetylene] and by over 50% at 15% [acetylene] (p<0.0001). However, when corrected for residual endtidal [acetylene], cardiac outputs were not significantly different from the reference measurements. The results of this study suggest that by accounting for residual endtidal acetylene in mixed venous blood, cardiac output can be accurately measured even when washout of acetylene is incomplete, allowing measurements as often as every 10-15 s.
Jamal Balouch; I Mark Olfert; Peter D Wagner; Susan R Hopkins
Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, N.I.H., Extramural     Date:  2006-05-22
Journal Detail:
Title:  Respiratory physiology & neurobiology     Volume:  155     ISSN:  1569-9048     ISO Abbreviation:  Respir Physiol Neurobiol     Publication Date:  2007 Feb 
Date Detail:
Created Date:  2007-01-29     Completed Date:  2007-04-24     Revised Date:  2007-12-03    
Medline Journal Info:
Nlm Unique ID:  101140022     Medline TA:  Respir Physiol Neurobiol     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  177-83     Citation Subset:  IM    
Department of Medicine, Division of Physiology, University of California, San Diego, La Jolla, California 92093-0623, USA.
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MeSH Terms
Acetylene / pharmacology*
Analysis of Variance
Cardiac Output / drug effects*,  physiology
Exercise / physiology*
Helium / pharmacokinetics
Pulmonary Gas Exchange
Sensitivity and Specificity
Grant Support
Reg. No./Substance:
74-86-2/Acetylene; 7440-59-7/Helium

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

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