Postural and Perfusion Related Effects on Lobar Deformation Heterogeneity Following Pneumonectomy Assessed by High Resolution Computed Tomography (HRCT)

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Selective redistribution of lobar perfusion by surgical pulmonary artery banding (PAB) of one lobe impairs post-pneumonectomy (PNX) volume expansion and alveolar tissue growth while enhancing angiogenesis in all remaining lobes of adult canines (J Appl Physiol 121:312–23, 2016). Here we examined whether the selective perfusion and growth perturbations are associated with alterations in regional parenchymal mechanics assessed by HRCT. Adult male dogs (20.3±2.5 kg body weight) underwent PAB of the left caudal lobe, restricting its circumference to the relaxed state (1.8 cm). Control animals underwent sham PAB (n=4 each). After recovery (4wk), right PNX was performed. Before and 3mo post-PNX, HRCT was performed at two lung volumes (transpulmonary pressures of 10 and 30 cm H2O) in supine and prone positions. Using non-rigid registration (Advanced Normalization Tools), linear strain magnitude along 3D axes, principal strains and shear distortion in xy, xz, and yz planes were estimated in each remaining lobe. Mean±SD. P≤0.05: * vs. Sham, § vs. supine, † vs. L cranial, ‡ vs. L middle lobe by 2-tailed paired t-test. In both PAB and Sham groups pre- and post-PNX, parenchymal strains were significantly higher in the caudal lobe than other lobes in supine but not prone position. Pre-PNX, the highest shear is supine in the right infracardiac lobe in the yz plane, and shear is lower in the prone posture in all lobes. Post-PNX specific compliance is reduced and shear is increased in all lobes in the xz plane. PAB further increased shear distortion in the xy and yz planes. Compared to Sham banding, post-PNX shear in PAB group was higher in all lobes in xy plane and in the caudal lobe in yz plane; shear in the yz plane also failed to decline from supine to prone. Results demonstrate significant mechanical heterogeneity in normal and post-PNX lungs especially in the caudal lobe in supine posture while PAB accentuates shear distortion in both banded and unbanded lobes. Thus, pulmonary perfusion perturbations due to PAB are associated with mechanical derangement of the parenchyma, which may contribute to the observed changes in the magnitude and course of compensatory lung growth and remodeling. Support or Funding Information Supported by NHLBI RO1 HL40070 and UO1 HL111146.

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