Fuld Matthew K, Easley R Blaine, Saba Osama I, Chon Deokiee, Reinhardt Joseph M, Hoffman Eric A, Simon Brett A
Department of Anesthesiology, Johns Hopkins Hospital, Baltimore, MD 21287, USA.
J Appl Physiol (1985). 2008 Apr;104(4):1177-84. doi: 10.1152/japplphysiol.00212.2007. Epub 2008 Feb 7.
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.
计算机断层扫描（CT）成像技术可实现对局部肺功能的无创测量。根据潮气呼吸过程中肺密度的变化确定的局部比容变化（sVol），应与用其他技术测量的局部通气和局部肺扩张相关。在四只麻醉、插管、机械通气的绵羊中，将sVol与氙气（Xe）-CT特异性通气（sV）进行了验证。Xe-CT在55% Xe的冲洗和洗脱过程中使用呼气门控轴向扫描。使用sVol = [1,000(Hi - He)]/[He(1,000 + Hi)]的关系，从肺区域组织密度（H，亨氏单位）的潮气变化中测量sVol，其中He和Hi分别是呼气和吸气时的局部密度。使用不同的解剖标记来定义吸气、呼气和Xe-CT图像之间相应的感兴趣肺区域，感兴趣区域的平均大小为1.6 +/- 0.7 ml。此外，在另一只动物中，将sVol与直接从植入的金属标记物位置测量的局部体积变化进行了比较。在正常仰卧位肺中发现的广泛局部sV范围内，sVol与sV之间呈现线性关系，总体相关系数（R(2)）为0.66。标记物测量的体积变化与sVol之间存在紧密相关性（R(2) = 0.97）。与Xe-CT方法相比，局部sVol涉及的辐射和Xe气暴露显著减少，是实验研究和患者中测量局部通气的一种安全有效的替代方法。
