Behavior of artificially produced holes in lung parenchyma

1977 ◽  
Vol 43 (4) ◽  
pp. 648-655 ◽  
Author(s):  
S. J. Lai-Fook ◽  
R. E. Hyatt ◽  
J. R. Rodarte ◽  
T. A. Wilson
Keyword(s):  
Shear Modulus ◽  
Continuum Mechanics ◽  
Transpulmonary Pressure ◽  
Lung Parenchyma ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Mechanics Analysis ◽  
Cylindrical Holes ◽  
Hole Boundary ◽  
Lung Lobes

Spherical and cylindrical holes were cut in the parenchyma of isolated dog lung lobes. The holes were insufflated with tantalum dust and the hole diameters were measured along the deflation limb of the lobe pressure-volume curve from transpulmonary pressures of 20 to 0 cmH2O. Hole volume as a fraction of lobe volume was found to be independent of transpulmonary pressure. The hole volume relative to the amount of tissue removed was used to determine the displacement at the hole boundary. A comparison of this displacement with the displacement predicted by a continuum mechanics analysis provides evidence for the applicability of the methods of continuum mechanics and further evidence that the shear modulus of the parenchyma is relatively small.

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

1979 ◽  
Vol 47 (1) ◽  
pp. 175-181 ◽  
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.

Distortion of submerged dog lung lobes

1985 ◽  
Vol 59 (2) ◽  
pp. 521-527 ◽  
Author(s):  
L. E. Olson ◽  
T. A. Wilson ◽  
J. R. Rodarte
Keyword(s):  
Buoyancy Force ◽  
Transpulmonary Pressure ◽  
Vertical Position ◽  
Pressure Curve ◽  
Engineering Analysis ◽  
Vertical Strain ◽  
Analytical Results ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Lung Lobes

The conically shaped caudal lobes of dog lungs were submerged, tip downward in saline, and the lateral surfaces of the lobes were thereby exposed to a hydrostatic gradient in transpulmonary pressure. The force that was required to balance the buoyancy was applied through a clip attached to the tip of the lobe. The locations of metal markers implanted in the parenchyma and attached to the surface were tracked, and regional volume and the horizontal and vertical components of strain were obtained as functions of vertical position. An engineering analysis of the deformation is qualitatively consistent with the data, but the predicted strains are larger than the observed strains. From the experimental and analytical results, we conclude that, for this deformation, the regional volume-local transpulmonary pressure curve closely follows the pressure-volume curve because negative horizontal strains nearly balance the positive vertical strain caused by the buoyancy force.

Evidence for increased intrathoracic fluid volume in man at high altitude

1979 ◽  
Vol 47 (4) ◽  
pp. 670-676 ◽  
Author(s):  
J. J. Jaeger ◽  
J. T. Sylvester ◽  
A. Cymerman ◽  
J. J. Berberich ◽  
J. C. Denniston ◽  
...  
Keyword(s):  
Pulmonary Edema ◽  
High Altitude ◽  
Transpulmonary Pressure ◽  
Fluid Volume ◽  
Pulmonary Mechanics ◽  
Volume Curve ◽  
Extravascular Fluid ◽  
Pressure Volume Curve ◽  
Transthoracic Electrical Impedance ◽  
Extravascular Fluid Volume

To determine if subclinical pulmonary edema occurs commonly at high altitude, 25 soldiers participated in two consecutive 72-h field exercises, the first at low altitude (200–875 m) and the second at high altitude (3,000–4,300 m). Various aspects of ventilatory function and pulmonary mechanics were measured at 0, 36, and 72 h of each exercise. Based on physical examination and chest radiographs there was no evidence of pulmonary edema at high altitude. There was, however, an immediate and sustained decrease in vital capacity and transthoracic electrical impedance as well as a clockwise rotation of the transpulmonary pressure-volume curve. In contrast, closing capacity and residual volume did not change immediately upon arrival at high altitude but did increase later during the exposure. These observations are consistent with an abrupt increase in thoracic intravascular fluid volume upon arrival at high altitude followed by a more gradual increase in extravascular fluid volume in the peribronchial spaces of dependent lung regions.

Series distribution of airway collapsibility in dogs

1981 ◽  
Vol 50 (2) ◽  
pp. 325-333 ◽  
Author(s):  
M. Nakamura ◽  
H. Sasaki ◽  
K. Sekizawa ◽  
M. Ishii ◽  
T. Takishima ◽  
...  
Keyword(s):  
Transpulmonary Pressure ◽  
Forced Expiration ◽  
Peripheral Airways ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Airway Collapsibility

We studied the series distribution of collapsibility in four different-sized airways in dogs. The trachea and the extrapulmonary main bronchi in situ were isolated from the rest of the lungs by glued beads of 6-12 mm OD. In excised dog lungs, the intrapulmonary large and small bronchi were isolated from the rest of the lung by glued beads of 1-9 mm OD. Pressure-volume relationships were measured directly in the trachea and in the extrapulmonary bronchi; those of the intrapulmonary bronchi were derived from orthogonal bronchograms. Airway collapsibility, defined as the slope of the pressure-volume curve, was found to increase in all airways as transpulmonary pressure (PL) decreased. At PL 30 cmH2O there was little difference of airway collapsibility among the different sized airways; but, as PL decreased, the peripheral airways became more collapsible than the central airways. It is concluded that the tissues surrounding the trachea provided as much or more stiffness than did the lung tissues that surrounded the intrapulmonary airways. The larger collapsibility in the peripheral airways. The larger collapsibility in the peripheral airways relative to that of the central airways at lower PL may account for the peripheral migration of the flow-limiting segment during forced expiration.

Gravitational independence of single-breath washout tests in recumbent dogs

1988 ◽  
Vol 64 (2) ◽  
pp. 642-648 ◽  
Author(s):  
S. Tomioka ◽  
S. Kubo ◽  
H. J. Guy ◽  
G. K. Prisk
Keyword(s):  
Prone Position ◽  
Regional Distribution ◽  
Transpulmonary Pressure ◽  
Phase Iii ◽  
Closing Volume ◽  
Body Rotation ◽  
Single Breath ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Phase Iv

To examine the mechanisms of lung filling and emptying, Ar-bolus and N2 single-breath washout tests were conducted in 10 anesthetized dogs (prone and supine) and in three of those dogs with body rotation. Transpulmonary pressure was measured simultaneously, allowing identification of the lung volume above residual volume at which there was an inflection point in the pressure-volume curve (VIP). Although phase IV for Ar was upward, phase IV for N2 was small and variable, especially in the prone position. No significant prone to supine differences in closing capacity for Ar were seen, indicating that airway closure was generated at the same lung volumes. The maximum deflections of phase IV for Ar and N2 from extrapolated phase III slopes were smaller in the prone position, suggesting more uniform tracer gas concentrations across the lungs. VIP was smaller than the closing volume for Ar, which is consistent with the effects of well-developed collateral ventilation in dogs. Body rotation tests in three dogs did not generally cause an inversion of phase III or IV. We conclude that in recumbent dogs regional distribution of ventilation is not primarily determined by the effect of gravity, but by lung, thorax, and mediastinum interactions and/or differences in regional mechanical properties of the lungs.

Comparison of the shear modulus of mature and immature rabbit lungs

1999 ◽  
Vol 87 (2) ◽  
pp. 711-714 ◽  
Author(s):  
Robert S. Tepper ◽  
Barry Wiggs ◽  
Susan J. Gunst ◽  
Peter D. Paré
Keyword(s):  
Shear Modulus ◽  
Bulk Modulus ◽  
Transpulmonary Pressure ◽  
Lung Parenchyma ◽  
Local Deformation ◽  
Mean Value ◽  
Airway Narrowing ◽  
Significant Difference ◽  
Muscle Shortening ◽  
Immature Lung

Maximal airway narrowing during bronchoconstriction is greater in immature than in mature rabbits. At a given transpulmonary pressure (Pl), the lung parenchyma surrounding the airway resists local deformation and provides a load that opposes airway smooth muscle shortening. We hypothesized that the force required to produce lung parenchymal deformation, quantified by the shear modulus, is lower in immature rabbit lungs. The shear modulus and the bulk modulus were measured in isolated mature ( n = 8; 6 mo) and immature ( n = 9; 3 wk) rabbit lungs at Pl of 2, 4, 6, 8, and 10 cmH2O. The bulk modulus increased with increasing Pl for mature and immature lungs; however, there was no significant difference between the groups. The shear modulus was lower for the immature than the mature lungs ( P < 0.025), progressively increasing with increasing Pl( P < 0.001) for both groups, and there was no difference between the slopes for shear modulus vs. Pl for the mature and the immature lungs. The mean value of the shear modulus for mature and immature rabbit lungs at Pl = 6 cmH2O was 4.5 vs. 3.8 cmH2O. We conclude that the shear modulus is less in immature than mature rabbit lungs. This small maturational difference in the shear modulus probably does not account for the greater airway narrowing in the immature lung, unless its effect is coupled with a relatively thicker and more compliant airway wall in the immature animal.

Positive airway pressure and vertical transpulmonary pressure gradient in man

1975 ◽  
Vol 38 (5) ◽  
pp. 896-899 ◽  
Author(s):  
K. Rehder ◽  
N. Abboud ◽  
J. R. Rodarte ◽  
R. E. Hyatt
Keyword(s):  
Continuous Positive Airway Pressure ◽  
Pressure Gradient ◽  
Airway Pressure ◽  
Positive Airway Pressure ◽  
Transpulmonary Pressure ◽  
Vertical Gradient ◽  
Normal Subjects ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Consistent Change

Static transpulmonary pressure (Pao-Pes) and the vertical gradient of transpulmonary pressure were determined in five sitting conscious normal subjects at mean airway pressures of 0 (ambient), 11, and 21 cmH2O. All subjects exhibited a nonuniform transpulmonary pressure gradient down the esophagus. The vertical pressure gradient was consistently larger in the lower (8–20cm below esophageal artifact) than in the middle region (0–8cm) of the esophagus. The gradient was not significantly altered by continuous positive airway pressure (11 and 21 cmH2O) or by changes in lung volume (60, 70, and 80% of total lung capacity (TLC)). Continuous positive airway pressure also did not result in a consistent change of the overall static pressure-volume curve of the lung. There was a small but statistically significant increase in TLC with each increase in airway pressure.

An analysis of pressure-volume characteristics of the lungs

1964 ◽  
Vol 19 (1) ◽  
pp. 97-104 ◽  
Author(s):  
Eduardo Salazar ◽  
John H. Knowles
Keyword(s):  
Transpulmonary Pressure ◽  
Normal Subjects ◽  
Mean Value ◽  
Inflation Pressure ◽  
Inspiratory Capacity ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
The Mean ◽  
Volume Characteristics ◽  
Pulmonary Volume

By analysis of the retractive forces of the lungs it was found that the pressure-volume characteristics of the lungs may be expressed by an exponential function. The curve described by such expression could be fitted to the experimental data obtained in 20 normal subjects. A half-inflation pressure (h) was defined which makes possible the evaluation of the retractive forces of the lungs by a measurement independent of lung size and accounting for known curvilinearity. H is a useful index of the stiffness of the organ and it is defined as the increase in transpulmonary pressure necessary to inflate the lungs halfway to the maximal pulmonary volume from any resting level. The mean value of h for the group was 7.58 ± 2.53 cm H2O. The half-inflation pressure is independent of the level of measurement within the inspiratory capacity and it does not vary with or depend on the size of the lungs. It may therefore be a more useful expression of the retractive forces of the lungs than compliance. pulmonary retractive forces; lung stiffness; compliance half-inflation pressure and lung size; VC and half-inflation pressure; FRC and half-inflation pressure; new expression for compliance; pressure-volume curve Submitted on March 4, 1963

Static pressure-volume characteristics of lungs in normal males

1960 ◽  
Vol 15 (5) ◽  
pp. 819-825 ◽  
Author(s):  
Solbert Permutt ◽  
H. B. Martin
Keyword(s):  
Vital Capacity ◽  
Static Pressure ◽  
Muscle Power ◽  
Transpulmonary Pressure ◽  
Residual Volume ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Older Subjects ◽  
Normal Males ◽  
Volume Characteristics

The static pressure-volume characteristics of the lungs were determined in 28 normal males between the ages of 21 and 76 years. Transpulmonary pressures were measured in relation to absolute lung volumes throughout the entire range of the vital capacity, both on inspiration and expiration. There was an increase in residual volume and a decrease in vital capacity, but no change in the slope or position of the pressure-volume curve with advancing age. It appeared that the older subjects were unable to change transpulmonary pressure between residual volume and total lung capacity to the same extent as the younger subjects. The results suggest that with advancing age there is little change in the intrinsic static pressure-volume characteristics of the lungs themselves, and that all of the significant changes with age are more likely due to changes in either the compliance or muscle power of the thorax. Submitted on December 24, 1959

Pressure-volume studies on lung lobes in man

1964 ◽  
Vol 19 (4) ◽  
pp. 823-826 ◽  
Author(s):  
Koh Ishikawa ◽  
C. J. Martin ◽  
A. C. Young
Keyword(s):  
Mechanical Properties ◽  
Vital Capacity ◽  
Esophageal Pressure ◽  
Chest Cavity ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Mean Pressure ◽  
Lower Magnitude ◽  
Balloon System ◽  
Lung Lobes

This study has sought to measure pressure differences occurring within the chest cavity and some of the mechanical properties of lung lobes. One lobe in the hemithorax has been used as an intrapleural pressure capsule by blocking it with a catheter and balloon system. After insertion of an esophageal, a bronchospirometric, and a lobar pressure-measuring catheter, the interrupted vital capacity maneuver has been used to compare pressures within the lungs and esophagus. Pressure differences, which increased as lung volumes increased, were found between lobes, and between lobes and esophagus. Esophageal pressure swings were of lower magnitude than lobar pressure swings. Esophageal pressure was neither linearly related to lobe pressure nor a mean pressure for the hemithorax. Thus, lung volume is not a function of a single pressure within the chest, and the concept of the commonly used pressure-volume curve is oversimplified. mechanical properties; pressure capsules Submitted on October 18, 1963

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