Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
J Appl Physiol (1985). 2011 Oct;111(4):1150-8. doi: 10.1152/japplphysiol.00527.2011. Epub 2011 Jul 28.
In adult canines following major lung resection, the remaining lobes expand asymmetrically, associated with alveolar tissue regrowth, remodeling, and progressive functional compensation over many months. To permit noninvasive longitudinal assessment of regional growth and function, we performed serial high-resolution computed tomography (HRCT) on six male dogs (∼9 mo old, 25.0 ± 4.5 kg, ±SD) at 15 and 30 cmH(2)O transpulmonary pressure (Ptp) before resection (PRE) and 3 and 15 mo postresection (POST3 and POST15, respectively) of 65-70% of lung units. At POST3, lobar air volume increased 83-148% and tissue (including microvascular blood) volume 120-234% above PRE values without further changes at POST15. Lobar-specific compliance (Cs) increased 52-137% from PRE to POST3 and 28-79% from POST3 to POST15. Inflation-related parenchyma strain and shear were estimated by detailed registration of corresponding anatomical features at each Ptp. Within each lobe, regional displacement was most pronounced at the caudal region, whereas strain was pronounced in the periphery. Regional three-dimensional strain magnitudes increased heterogeneously from PRE to POST3, with further medial-lateral increases from POST3 to POST15. Lobar principal strains (PSs) were unchanged or modestly elevated postresection; changes in lobar maximum PS correlated inversely with changes in lobar air and tissue volumes. Lobar shear distortion increased in coronal and transverse planes at POST3 without further changes thereafter. These results establish a novel use of functional HRCT to map heterogeneous regional deformation during compensatory lung growth and illustrate a stimulus-response feedback loop whereby postresection mechanical stress initiates differential lobar regrowth and sustained remodeling, which in turn, relieves parenchyma stress and strain, resulting in progressive increases in lobar Cs and a delayed increase in whole lung Cs.
在成人犬中，进行主要肺切除术后，剩余的肺叶会不对称地扩张，伴随着肺泡组织的再生、重塑和数月来的功能逐渐代偿。为了允许对区域性生长和功能进行非侵入性的纵向评估，我们在 6 只雄性犬（约 9 个月龄，25.0 ± 4.5 千克，±SD）中，在肺切除术前（PRE）和肺切除术后 3 个月（POST3）和 15 个月（POST15），分别在跨肺压（Ptp）为 15 和 30 cmH(2)O 时，进行了连续的高分辨率计算机断层扫描（HRCT）。在 POST3 时，肺叶空气体积增加了 83-148%，组织（包括微血管血液）体积增加了 120-234%，而在 POST15 时没有进一步变化。肺叶特异性顺应性（Cs）从 PRE 增加了 52-137%，从 POST3 增加了 28-79%。通过在每个 Ptp 处详细注册相应的解剖特征，估计了与充气相关的实质应变和剪切。在每个肺叶内，区域位移在尾部区域最为明显，而应变在周边区域最为明显。从 PRE 到 POST3，区域性三维应变幅度增加不均匀，从 POST3 到 POST15，横向和纵向应变进一步增加。肺叶主应变（PS）在肺切除术后不变或略有升高；肺叶最大 PS 的变化与肺叶空气和组织体积的变化呈反比。肺叶剪切变形在 POST3 时在冠状面和横断面上增加，此后没有进一步变化。这些结果确立了一种使用功能 HRCT 来描绘代偿性肺生长过程中区域性不均匀变形的新方法，并说明了一种刺激-反应反馈回路，其中术后机械应力引发了不同的肺叶再生和持续重塑，这反过来又缓解了实质的应力和应变，导致肺叶 Cs 的逐渐增加和整个肺 Cs 的延迟增加。
