Journal
JOURNAL OF APPLIED PHYSIOLOGY
Volume 104, Issue 4, Pages 1177-1184Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/japplphysiol.00212.2007
Keywords
multidetector-row computer tomography scanning; xenon computer tomography; implanted markers; lung mechanics
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Funding
- NHLBI NIH HHS [HL-64368] Funding Source: Medline
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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 (sV.) 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 sV. was demonstrated over a wide range of regional sV. found in the normal supine lung, with an overall correlation coefficient (R-2) of 0.66. There was a tight correlation (R-2 = 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.
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