Supine and prone differences in regional lung density and pleural pressure gradients in the human lung with constant shape

Tawhai, Merryn H.; Nash, Martyn P.; Lin, Ching‐Long; Hoffman, Eric A.

doi:10.1152/japplphysiol.00324.2009

Cited by 137 publications

(184 citation statements)

References 32 publications

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“…-A simplified intra-acinar flow model [13] consisting of nine symmetric branches of intra-acinar arteries and veins coupled in a serial and parallel arrangement through a 'sheet' flow representation of the pulmonary capillaries [66]. -A model of parenchymal tissue deformation [67], to which the vascular networks are tethered. Tissue deformation influences perfusion via shift in the vessel locations (the 'Slinky' effect [68]), elastic recoil pressures acting to distend the extra-capillary vessels, and the effect of alveolar inflation levels on capillary sheet distensibility [15,41].…”

Section: (B) Distribution Of Embolimentioning

confidence: 99%

Pulmonary embolism: predicting disease severity

Burrowes

Clark

Marcinkowski

et al. 2011

Phil. Trans. R. Soc. A.

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Pulmonary embolism (PE) is the most common cause of acute pulmonary hypertension, yet it is commonly undiagnosed, with risk of death if not recognized promptly and managed accordingly. Patients typically present with hypoxemia and hypocapnia, although the presentation varies greatly, being confounded by co-mordidities such as preexisting cardio-respiratory disease. Previous studies have demonstrated variable patient outcomes in spite of similar extent and distribution of pulmonary vascular occlusion, but the pathophysiological determinants of outcome remain unclear. Computational models enable exact control over many of the compounding factors leading to functional outcomes and therefore provide a useful tool to understand and assess these mechanisms. We review the current state of pulmonary blood flow models. We present a pilot study within 10 patients presenting with acute PE, where patient-derived vascular occlusions are imposed onto an existing model of the pulmonary circulation enabling predictions of resultant haemodynamics after embolus occlusion. Results show that mechanical obstruction alone is not sufficient to cause pulmonary arterial hypertension, even when up to 65 per cent of lung tissue is occluded. Blood flow is found to preferentially redistribute to the gravitationally non-dependent regions. The presence of an additional downstream occlusion is found to significantly increase pressures.

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Section: (B) Distribution Of Embolimentioning

confidence: 99%

Pulmonary embolism: predicting disease severity

Burrowes

Clark

Marcinkowski

et al. 2011

Phil. Trans. R. Soc. A.

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“…The lung tissue was modeled as a compressible and nonlinearly elastic continuum with homogeneous and isotropic material properties (Fung, 1993;Kowalczyk and Kleiber, 1994;Tawhai et al, 2009). The von Mises stress was obtained from the three principal x-y-z stresses PS 1 , PS 2 and PS 3 and the nonlinear strain energy density function where J 1 and J 2 are the first and second invariants of the Green-Lagrangian finite strain tensor.…”

Section: Methodsmentioning

confidence: 99%

Influence Of Parenchymal Heterogeneity On Airway-Parenchymal Interdependence

Ma¹,

Bates²

2012

B29. The Lung on the Border Between Order and Chaos

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To estimate the influence of parenchymal heterogeneities on airway-parenchymal interdependence, we considered a circular airway embedded within elastic parenchyma modeled as 1) a hexagonal spring network, 2) a triangular spring network, or 3) a continuum. The deformation in the parenchyma due to active airway contraction was simulated using the finite element method. Random perturbations of elastic moduli in the parenchyma did not significantly affect the overall pattern of force transmission. By contrast, when elastic moduli were increased along a path projecting radially outward from the airway, the hexagonal spring network model predicted significantly increased force along this line as the airway contracted, but this was not observed in other two models. These results indicate that tissue heterogeneities generally have minimal effect on the global nature of airway-parenchymal interdependence. However, in the exceptional circumstance of scar tissue aligned radially from the airway wall, parenchymal distortion forces may propagate much farther from the airway wall than was previously thought.

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“…(2009) was used to solve for deformation of lung tissue under normal gravitational loading. The lung tissue was treated as a compressible, homogeneous, and isotropic material.…”

Section: Table A1mentioning

confidence: 99%

In silico modeling of oxygen-enhanced MRI of specific ventilation

et al. 2018

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Specific ventilation imaging (SVI) proposes that using oxygen‐enhanced 1H MRI to capture signal change as subjects alternatively breathe room air and 100% O2 provides an estimate of specific ventilation distribution in the lung. How well this technique measures SV and the effect of currently adopted approaches of the technique on resulting SV measurement is open for further exploration. We investigated (1) How well does imaging a single sagittal lung slice represent whole lung SV? (2) What is the influence of pulmonary venous blood on the measured MRI signal and resultant SVI measure? and (3) How does inclusion of misaligned images affect SVI measurement? In this study, we utilized two patient‐based in silico models of ventilation, perfusion, and gas exchange to address these questions for normal healthy lungs. Simulation results from the two healthy young subjects show that imaging a single slice is generally representative of whole lung SV distribution, with a calculated SV gradient within 90% of that calculated for whole lung distributions. Contribution of O2 from the venous circulation results in overestimation of SV at a regional level where major pulmonary veins cross the imaging plane, resulting in a 10% increase in SV gradient for the imaging slice. A worst‐case scenario simulation of image misalignment increased the SV gradient by 11.4% for the imaged slice.

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Supine and prone differences in regional lung density and pleural pressure gradients in the human lung with constant shape

Cited by 137 publications

References 32 publications

Pulmonary embolism: predicting disease severity

Pulmonary embolism: predicting disease severity

Influence Of Parenchymal Heterogeneity On Airway-Parenchymal Interdependence

In silico modeling of oxygen-enhanced MRI of specific ventilation

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