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This Article Full Text Full Text (PDF) All Versions of this Article: 104/4/1177    most recent 00212.2007v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Fuld, M. K. Articles by Simon, B. A. Search for Related Content PubMed PubMed Citation Articles by Fuld, M. K. Articles by Simon, B. A.

CT-measured regional specific volume change reflects regional ventilation in supine sheep

Departments of ¹Anesthesiology and Critical Care Medicine, and ²Medicine, The Johns Hopkins University, Baltimore, Maryland; and Departments of ³Radiology, and ⁴Biomedical Engineering, University of Iowa College of Medicine, Iowa City, Iowa

Submitted 20 February 2007 ; accepted in final form 4 February 2008

Computer tomography (CT) imaging techniques permit the noninvasive measurement of regional lung function. Regional specific volume change (sVol), determined from the change in lung density over a tidal breath, should correlate with regional ventilation and regional lung expansion measured with other techniques. sVol was validated against xenon (Xe)-CT-specific ventilation (s) in four anesthetized, intubated, mechanically ventilated sheep. Xe-CT used expiratory gated axial scanning during the washin and washout of 55% Xe. sVol was measured from the tidal changes in tissue density (H, houndsfield units) of lung regions using the relationship sVol = [1,000(Hi – He)]/[He(1,000 + Hi)], where He and Hi are expiratory and inspiratory regional density. Distinct anatomical markings were used to define corresponding lung regions of interest between inspiratory, expiratory, and Xe-CT images, with an average region of interest size of 1.6 ± 0.7 ml. In addition, sVol was compared with regional volume changes measured directly from the positions of implanted metal markers in an additional animal. A linear relationship between sVol and s was demonstrated over a wide range of regional s found in the normal supine lung, with an overall correlation coefficient (R²) of 0.66. There was a tight correlation (R² = 0.97) between marker-measured volume changes and sVol. Regional sVol, which involves significantly reduced exposure to radiation and Xe gas compared with the Xe-CT method, represents a safe and efficient surrogate for measuring regional ventilation in experimental studies and patients.

multidetector-row computer tomography scanning; xenon computer tomography; implanted markers; lung mechanics