Document Detail

Use of the alveolar dead space fraction (Vd/Vt) and plasma D-dimers to exclude acute pulmonary embolism in ambulatory patients.
MedLine Citation:
PMID:  9305426     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: To evaluate the utility of a modified calculation of the alveolar dead space fraction (Vd/Vt), combined with plasma D-dimers, to aid in the exclusion of acute pulmonary embolism (PE). METHODS: A prospective comparison of screening modalities was performed in a metropolitan teaching ED. Ambulatory patients evaluated for PE underwent simultaneous end-tidal CO2 and arterial blood gas determinations, as well as venous latex-agglutination D-dimer quantification. The modified Bohr equation was used to calculate Vd/Vt as an index of alveolar dead space. Acute PE was diagnosed or excluded using appropriate combinations of clinical suspicion, ventilation-perfusion lung scanning, lower-extremity venous Doppler ultrasonography, pulmonary angiography, and comprehensive follow-up. RESULTS: Of 170 subjects studied, PE was confirmed (PE+) in 26 (15%) and excluded (PE-) in 144 (85%). In the PE+ group, Vd/Vt was 0.31 +/- 0.13 (mean +/- SD), and in the PE- group, Vd/Vt was 0.06 +/- 0.10 (p < 0.05, t-test). Regarding false-negative rates, Vd/Vt was normal (i.e., < 0.2) in 3/26 PE+ patients and D-dimer concentrations were normal (< 0.5 microgram/L) in 4/26 patients in the PE+ group. The combination of a normal Vd/Vt and D-dimer concentration was 100% sensitive (95% CI = 88-100%) in excluding PE. False-positive testing (either test positive) occurred in 49/144 subjects (specificity 65%, 95% CI = 52-73%). The age-adjusted alveolar-arterial O2 gradient was 33 +/- 38 torr in the PE+ group vs 13 +/- 37 torr in the PE- group (p = 0.11). CONCLUSIONS: In ambulatory patients, the finding of Vd/Vt < 0.2 and D-dimers < 0.5 microgram/L lowers the probability of acute PE.
J A Kline; S Meek; D Boudrow; D Warner; S Colucciello
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Publication Detail:
Type:  Clinical Trial; Comparative Study; Journal Article    
Journal Detail:
Title:  Academic emergency medicine : official journal of the Society for Academic Emergency Medicine     Volume:  4     ISSN:  1069-6563     ISO Abbreviation:  Acad Emerg Med     Publication Date:  1997 Sep 
Date Detail:
Created Date:  1997-11-06     Completed Date:  1997-11-06     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9418450     Medline TA:  Acad Emerg Med     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  856-63     Citation Subset:  IM    
Department of Emergency Medicine, Carolinas Medical Center, Charlotte, NC 28232-2861, USA.
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MeSH Terms
Acute Disease
Ambulatory Care
Blood Gas Analysis
Cross-Sectional Studies
Diagnosis, Differential
Fibrin Fibrinogen Degradation Products / analysis*
Lung / radionuclide imaging
Middle Aged
Prospective Studies
Pulmonary Embolism / diagnosis*
ROC Curve
Respiratory Dead Space*
Respiratory Function Tests
Sensitivity and Specificity
Technetium Tc 99m Aggregated Albumin / diagnostic use
Technetium Tc 99m Pentetate / diagnostic use
Ventilation-Perfusion Ratio
Reg. No./Substance:
0/Fibrin Fibrinogen Degradation Products; 0/Technetium Tc 99m Aggregated Albumin; 0/fibrin fragment D; 65454-61-7/Technetium Tc 99m Pentetate

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

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