Lung Parenchymal Mechanics in Health and Disease

Abstract

The mechanical properties of lung tissue are important determinants of lung physiological functions. The connective tissue is composed mainly of cells and extracellular matrix, where collagen and elastic fibers are the main determinants of lung tissue mechanical properties. These fibers have essentially different elastic properties, form a continuous network along the lungs, and are responsible for passive expiration. In the last decade, many studies analyzed the relationship between tissue composition, microstructure, and macrophysiology, showing that the lung physiological behavior reflects both the mechanical properties of tissue individual components and its complex structural organization. Different lung pathologies such as acute respiratory distress syndrome, fibrosis, inflammation, and emphysema can affect the extracellular matrix. This review focuses on the mechanical properties of lung tissue and how the stress-bearing elements of lung parenchyma can influence its behavior.

The effect of angiotensin-converting enzyme inhibition by captopril on respiratory mechanics in healthy rats

“…Nevertheless, R visc,rs is included in R max,rs , which has been here shown to decrease significantly after ACE inhibition, strongly suggesting that angiotensin effects in basal conditions are to increase not only the ohmic airway resistance but also the viscoelastic one, which is measurable as stress relaxation [13][14][15][16] . In basal conditions, the viscous component of the inspiratory pressure dissipation represented by stress relaxation substantially contributes to the total resistive work of breathing [13][14][15][16]32 , but its molecular mechanism(s) remain largely unclear and poorly understood.…”

“…In fact, it has previously been shown that smooth muscle cells contraction influencing agents such as nitric oxide may change the activity of the contractile peripheral lung cellular elements 17,18 . Influences of these cellular elements activity on the viscoelastic characteristics of the respiratory system can not be excluded 32 . Angiotensin is known to exert its stimulating activity in a wide population of contractile cells, and captopril has been shown to induce nitric oxide release 36 , so that an effect on stress relaxation may be hypothesized, although more work is needed to verify this working hypothesis.…”

Comparison of Poroviscoelastic Models for Sound and Vibration in the Lungs

“…Like no other anatomical region in the body, the lungs are a unique, multiphase porous structure that has defied conventional noninvasive medical imaging methods and our ability to contrast and quantify changes in its macroscopic properties that can be indicative of disease and that may be fundamentally linked to behavioral and structural changes at the microscopic scale. Patients can suffer from a wide range of pulmonary ailments that result in significant changes, locally or diffusely, to the stiffness or density in the lungs [1]. For example, lung parenchymal stiffness increases with the degree of fibrosis in fibrotic lung [2,3].…”

“…MRE seeks to provide a map of the viscoelastic properties within the region of interest that will affect the shear wave motion that MRE measures. Previously, MRE has been successfully applied to the study of the mechanical properties of a variety of other organs and soft tissue 1 regions in vivo, including the breast, brain, kidney, prostate, liver, and muscle [20][21][22][23][24]. Application to the lungs has proven more challenging, given the poor signal-to-noise available in imaging due to a lower presence of hydrogen in air than in soft tissue (water) and the complex nature of vibratory wave propagation found in the lungs.…”

Automated quantification of lung structures from optical coherence tomography images

“…However, the invasiveness of obtaining histological sections precludes longitudinal assessment and limits its use in live models. Furthermore, histological analysis cannot be used to assess the dynamic and viscoelastic properties of the lung, which are altered in lung disease [8].…”