| Estimated vs actual values for dead space/tidal volume ratios during incremental exercise in patients evaluated for dyspnea. | |
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MedLine Citation:
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PMID: 8020259 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The physiologic dead space/tidal volume ratio (VD/VT) at rest and during exercise is a sensitive measurement of gas exchange that reflects matching of ventilation to perfusion, but requires an invasive measurement for its calculation. Determining VD/VT noninvasively uses estimations of arterial PCO2 based on the end-tidal PCO2. To further standardize incremental cardiopulmonary exercise testing, we compared actual VD/VT with estimated VD/VT values in 35 patients referred for evaluation of dyspnea. Estimates of VD/VT used the Jones' equation (VD/VT[J]) derived from healthy subjects during steady-state exercise or PETCO2 alone (VD/VT[ET]) to approximate PaCO2. At rest, mean values for VD/VT(J) and actual VD/VT were not different: 0.372 +/- 0.08 vs 0.376 +/- 0.09, p = not significant (NS). Each method identified 61 percent of values > or = to 0.36. In 26 subjects who achieved higher work rates, the mean difference between actual VD/VT and VD/VT(J) increased from 0.009 +/- 0.04 (NS) at low work rate (VO2 = 28.3 percent pred max) to 0.040 +/- 0.06 at high work rate (VO2 = 54.7 percent pred max), p = 0.006. Actual VD/VT identified 18 (69 percent) patients as abnormal vs 13 (50 percent) so identified by VD/VT(J). With exercise, VD/VT(J) was no better than VD/VT(ET). We conclude that during incremental exercise in a patient population, methods for estimating VD/VT progressively underestimate this measurement; and therefore, "normal" estimated VD/VT values may fail to identify underlying pulmonary and/or pulmonary vascular impairment. |
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Authors:
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M I Zimmerman; A Miller; L K Brown; A Bhuptani; M F Sloane; A S Teirstein |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Chest Volume: 106 ISSN: 0012-3692 ISO Abbreviation: Chest Publication Date: 1994 Jul |
Date Detail:
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Created Date: 1994-08-02 Completed Date: 1994-08-02 Revised Date: 2004-11-17 |
Medline Journal Info:
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Nlm Unique ID: 0231335 Medline TA: Chest Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: 131-6 Citation Subset: AIM; IM |
Affiliation:
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Pulmonary Physiology Laboratory, Mount Sinai School of Medicine, New York. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Adult Aged Dyspnea / diagnosis, etiology, physiopathology* Exercise Test* Female Humans Male Middle Aged Pulmonary Diffusing Capacity Respiratory Dead Space* Tidal Volume* |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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