Modeling the influence of gravity and the mechanical properties of elastin and collagen fibers on alveolar and lung pressure–volume curves

Abstract

The relationship between pressure (P) and volume (V) in the human lung has been extensively studied. However, the combined effects of gravity and the mechanical properties of elastin and collagen on alveolar and lung P–V curves during breathing are not well understood. Here, we extended a previously established thick-walled spherical model of a single alveolus with wavy collagen fibers during positive pressure inflation. First, we updated the model for negative pressure-driven inflation that allowed incorporation of a gravity-induced pleural pressure gradient to predict how the static alveolar P–V relations vary spatially throughout an upright human lung. Second, by introducing dynamic surface tension and collagen viscoelasticity, we computed the hysteresis loop of the lung P–V curve. The model was tested by comparing its predicted regional ventilation to literature data, which offered insight into the effects of microgravity on ventilation. The model has also produced novel testable predictions for future experiments about the variation of mechanical stresses in the septal walls and the contribution of collagen and elastin fibers to the P–V curve and throughout the lung. The model may help us better understand how mechanical stresses arising from breathing and pleural pressure variations affect regional cellular mechanotransduction in the lung.

Stress-strain curve and elastic behavior of the fibrotic lung with usual interstitial pneumonia pattern during protective mechanical ventilation

“…The shell is initially stress-free, and it is subject to the internal pressure . As shown in previous studies [19][20][21][22][23][24][25][26][27][28]29 elastin and collagen dominate the elastic behavior of the alveolar tissue, the contribution of interstitial cells being negligible 30,31 . It is well known that collagen and elastin bers form an interlinked random mesh in lung parenchyma.…”

“…We propose a computational model for the lung based on the mechanical behavior of a single alveolus. Alveolar models and their generalizations have been successfully proposed to explain the pressurevolume response of the normal lung [21,28,29]. In particular, they allow to relate the macroscopic response of the lung (the pressure-volume curve) and the mechanical behavior of the alveolus.…”

A 3D Printed Ventilated Perfused Lung Model Platform to Dissect the Lung’s Response to Viral Infection in the Presence of Respiration

“…However, the strain plot indicated that the bottom of the lung experienced more strain than the rest of the structure. This discrepancy suggested that while the sides may have shifted more, the overall displacement of the bottom was constrained, possibly due to rigid body motion or structural stability mechanisms ( 46 , 47 ). As a result of these simulation findings, a practical adjustment was made in the experimental setup.…”

Ventilation Mechanics

“…However, this hypothesis is questioned in some important ventilatory conditions in healthy subjects and particularly in patients. [48][49][50][51][52][53][54][55][56][57][58][59][60] A clear example in healthy subjects is exercise given the considerable flow values associated with high-amplitude and high-rate breathing.…”

“…13 shows that in the normal standing position, and simply caused by the lung weight, there is a vertical distribution of pleural pressure. [52][53][54] The lower parts of the lungs are supporting the weight of their upper parts. As illustrated by ►Fig.…”