Personalized Pressure-Volume Curve of the Lung Through CT-Based Network Modeling

The elastic constants of dog lungs were determined at various degrees of inflation. In one set of experiments, the lobes were subjected to deformations that approximated the conditions of uniaxial loading. These data, together with the bulk modulus data obtained from the local slope of the pressure-volume curve, were used to determine the two elastic moduli that are needed to describe small nonuniform deformations about an initial state of uniform inflation. The bulk modulus was approximately 4 times the inflation pressure, and Young's modulus was approximately 1.5 times the inflation pressure. In a second set of experiments, lobes were subjected to indentation tests using cylindric punches 1–3 cm in diameter. The value for Young's modulus obtained from these data was slightly higher, approximately twice the inflation pressure. These experiments indicate that the lung is much more easily deformable in shear than in dilatation and that the Poisson ratio for the lung is high, approximately 0.43.

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Lung volumes and alveolar expansion pattern in immature rabbits treated with serum-diluted surfactant

Journal of Applied Physiology ◽

10.1152/japplphysiol.01043.2003 ◽

2004 ◽

Vol 97 (4) ◽

pp. 1408-1413 ◽

Cited By ~ 4

Author(s):

Yongmei Xu ◽

Tsutomu Kobayashi ◽

Xiaoguang Cui ◽

Keisuke Ohta ◽

Chiharu Kabata ◽

...

Keyword(s):

Mechanical Ventilation ◽

Acute Respiratory Distress Syndrome ◽

Respiratory Distress Syndrome ◽

Respiratory Distress ◽

Distress Syndrome ◽

Ringer Solution ◽

Natural Surfactant ◽

Volume Curve ◽

Pressure Volume Curve ◽

Expansion Pattern

In acute respiratory distress syndrome, mechanical ventilation often induces alveolar overdistension aggravating the primary insult. To examine the mechanism of overdistension, surfactant-deficient immature rabbits were anesthetized with pentobarbital sodium, and their lungs were treated with serum-diluted modified natural surfactant (porcine lung extract; 2 mg/ml, 10 ml/kg). By mechanical ventilation with a peak inspiration pressure of 22.5 cmH2O, the animals had a tidal volume of 14.7 ml/kg (mean), when 2.5 cmH2O positive end-expiratory pressure was added. This volume was similar to that in animals treated with nondiluted modified natural surfactant (24 mg/ml in Ringer solution, 10 ml/kg). However, the lungs fixed at 10 cmH2O on the deflation limbs of the pressure-volume curve had the largest alveolar/alveolar duct profiles (≥48,000 μm2), accounting for 38% of the terminal air spaces, and the smallest (<6,000 μm2), accounting for 31%. These values were higher than those in animals treated with nondiluted modified natural surfactant ( P < 0.05). We conclude that administration of serum-diluted surfactant to immature neonatal lungs leads to patchy overdistension of terminal air spaces, similar to the expansion pattern that may be seen after dilution of endogenous surfactant with proteinaceous edema fluid in acute respiratory distress syndrome.

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Improved measurements of shear modulus and pleural membrane tension of the lung

Journal of Applied Physiology ◽

10.1152/jappl.1979.47.1.175 ◽

1979 ◽

Vol 47 (1) ◽

pp. 175-181 ◽

Cited By ~ 65

Author(s):

M. A. Hajji ◽

T. A. Wilson ◽

S. J. Lai-Fook

Keyword(s):

Shear Modulus ◽

Transpulmonary Pressure ◽

Elastic Half Space ◽

Concentrated Force ◽

Membrane Area ◽

Volume Curve ◽

Pressure Volume Curve ◽

Pressure Independent ◽

Work Done ◽

The Continuum

The continuum solution for the deformation of an elastic half space covered by a membrane is used to interpret measurements of the indentation of lung lobes under a column of fluid. The shear modulus mu of the underlying parenchyma is found to be approximately 0.7 times transpulmonary pressure, independent of species size. The tension in the pleural membrane T increases rapidly with increasing membrane area. For dog lungs, the value of T is 10(3) to 10(4) dyn/cm. For the larger species tested, pigs and horses, T is larger. The continuum solution shows that a concentrated force applied to the pleural surface is distributed over a distance T/mu as it is transmitted across the pleural membrane. The membrane is important in determining the displacement produced by forces that act within a region that is small compared to this distance, approximately 2 cm for dog lungs. By comparing the tension-area curve of the pleural membrane with the pressure-volume curve of the lobe, it is found that the pleural membrane contributes about 20% of the work done by the lung during deflation.

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