Regional lung growth following pneumonectomy assessed by computed tomography

Abstract

After pneumonectomy (PNX), mechanical strain on the remaining lung is greatly increased. To assess whether remaining lobes expand uniformly after left or right PNX (removing 42 and 58% of lung mass, respectively), we performed high-resolution computed tomography (CT) scans at 45 ml/kg above end-expiratory lung volume on adult male foxhounds after left or right PNX, which were compared with adult Sham controls. Air and tissue volumes were separately measured in each lobe. After left PNX, air and tissue volumes in the right upper and cardiac lobes increased approximately 2.2-fold above and below the heart, whereas volumes in right middle and lower lobes did not change significantly. After right PNX, air and tissue volumes in the left upper and middle lobes increased 2.3- to 2.7-fold across the midline anterior to the heart, whereas the left lower lobe expanded approximately 1.9-fold posterior to the heart. Regional changes in volume density of tissue post-PNX estimated by CT scan parallel postmortem estimates by morphometric analyses. Data indicate heterogeneous regional distribution of mechanical lung strain, which could influence the differential cellular compensatory response following right and left PNX.

Quantitative morphology of compensatory lung growth

“…The present author's group has also observed by HRCT that volume density of lung tissue declines in young dogs from 6.5-12.5 months of age [34]. In vivo, HRCTderived tissue volume correlates significantly with physiological estimates of gas exchange septal volume by a rebreathing method at comparable lung volumes [69] and with post mortem morphometric estimates of septal volume [70]; these correlations demonstrate internal consistency of independent methods. However, HRCT estimates are systematically larger than the corresponding rebreathing and morphometric estimates, probably because the so-called HRCT-derived ''tissue volume'' includes not only the volume of alveolar septa but also extra-septal tissue of conducting airways and vessels up to 1 mm in diameter and the blood within these small vessels.…”

An Official Research Policy Statement of the American Thoracic Society/European Respiratory Society: Standards for Quantitative Assessment of Lung Structure

“…Lung or lobar volume can be measured in the intact state by saline immersion (105) or radiologic imaging (CT or MRI) (106)(107)(108)(109), and after serial sectioning by point counting of the cut surfaces (Cavalieri method) (110).…”

“…These CT-derived parameters have been used to follow developmental and compensatory lung growth (180)(181)(182), and to assess structural derangement in idiopathic pulmonary fibrosis (183) and emphysema (107). In vivo CT estimates of air and tissue volumes significantly correlate with independent estimates obtained by histomorphometry (106,108), although in direct comparisons CT-derived (tissue1blood) volume is systematically larger than alveolar septal volume estimated after fixation by morphometry (108) and antemortem by physiological methods (181); CT-derived lung gas volume is modestly lower than that measured antemortem by helium dilution (181,184). Additional measures (e.g., parenchymal texture analysis) take into account the pattern as well as the magnitude of attenuation values, permitting further quantitative detection of regional pathology (185,186).…”

Computational and bioengineered lungs as alternatives to whole animal, isolated organ, and cell-based lung models

“…The flexible and dynamic structure of the lung, in which mechanical forces play an essential role, would require the design of often-complex bioreactors (53). Physical stimuli involved in the action of breathing were shown to be involved in the initiation and maintenance of lung regeneration of mature lungs (133). Therefore, the understanding of this dynamic balance and its application to tissue-engineered models will depend on the ability to integrate the biology, the chemistry, the physics, and the surrounding physiological environment to efficiently produce lung substitutes in vitro (28,70,134).…”