Millar A B, Denison D M
Lung Function and Computed Tomography Units, Brompton Hospital, London.
Thorax. 1989 Jun;44(6):485-90. doi: 10.1136/thx.44.6.485.
Computed tomography was used to determine the vertical gradient of physical density in peripheral lung tissue of 12 healthy supine subjects, at total lung capacity and residual volume. At total lung capacity the mean (SD) density of peripheral lung tissue at the level of the mid right atrium was 0.0715 (0.017) g/cm3 and the vertical gradient of density was slight. At residual volume the density of peripheral tissue at the same level was 0.272 (0.067) g/cm3 and the vertical density gradient was curvilinear and more pronounced. Predictions of the gradient at residual volume were made on the basis of the known compliance of the lung and measured effects were attributed to the action of gravity on blood vessel distensibility at total lung capacity. These predictions agreed closely with the actual density gradient measured at residual volume and provide a basis for forecasting the vertical density gradient that would exist in healthy lungs at any degree of inflation. Departure from these gradients would imply local abnormalities of lung compliance, distribution of mechanical stress, or distensibility of vessels.
利用计算机断层扫描技术测定了12名健康仰卧受试者在肺总量和残气量时外周肺组织的物理密度垂直梯度。在肺总量时，右心房中部水平外周肺组织的平均（标准差）密度为0.0715（0.017）g/cm³，密度垂直梯度较小。在残气量时，同一水平外周组织的密度为0.272（0.067）g/cm³，密度垂直梯度呈曲线状且更为明显。基于已知的肺顺应性对残气量时的梯度进行了预测，测量结果归因于重力对肺总量时血管扩张性的作用。这些预测与在残气量时测量的实际密度梯度密切相符，并为预测健康肺在任何充气程度下存在的垂直密度梯度提供了基础。偏离这些梯度将意味着肺顺应性、机械应力分布或血管扩张性的局部异常。
