Series distribution of airway collapsibility in dogs

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.

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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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Evidence for increased intrathoracic fluid volume in man at high altitude

Journal of Applied Physiology ◽

10.1152/jappl.1979.47.4.670 ◽

1979 ◽

Vol 47 (4) ◽

pp. 670-676 ◽

Cited By ~ 36

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.

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Gravitational independence of single-breath washout tests in recumbent dogs

Journal of Applied Physiology ◽

10.1152/jappl.1988.64.2.642 ◽

1988 ◽

Vol 64 (2) ◽

pp. 642-648 ◽

Cited By ~ 4

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.

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Airway pressure-volume curve estimated by flow interruption during forced expiration

Journal of Applied Physiology ◽

10.1152/jappl.1989.67.6.2631 ◽

1989 ◽

Vol 67 (6) ◽

pp. 2631-2638 ◽

Cited By ~ 6

Author(s):

N. Ohya ◽

J. Huang ◽

T. Fukunaga ◽

H. Toga

Keyword(s):

Maximum Flow ◽

Normal Subjects ◽

Chronic Obstructive ◽

Forced Expiration ◽

Obstructive Pulmonary Disease ◽

Volume Curve ◽

Pressure Volume Curve ◽

Mouth Pressure ◽

Short Period ◽

Volume Characteristics

We attempted to estimate the pressure-volume characteristics of airways downstream from the choke point when the airflow was abruptly interrupted during forced expiration. The change of gas volume of the downstream segment after interruption could be estimated by multiplying the maximum flow (Vmax) immediately before interruption by the interruption time because the Vmax is maintained for a short period after airflow interruption at the mouth, as described in our previous report (J. Appl. Physiol. 66: 509-517, 1989). For the pressure of the downstream segment, we used the mouth pressure itself. Airway compliance, a slope of the pressure-volume curve, was measured in an airway model in eight normal subjects, in six patients with chronic obstructive pulmonary disease (COPD), and in one patient with tracheobronchopathia osteochondroplastica. Airway compliance was 0.96 ml/cmH2O in normal subjects and 2.49 ml/cmH2O in COPD patients. This difference of airway compliance was believed to be caused by the longitudinal expansion of the downstream segment and changes in the properties of the airway wall.

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Positive airway pressure and vertical transpulmonary pressure gradient in man

Journal of Applied Physiology ◽

10.1152/jappl.1975.38.5.896 ◽

1975 ◽

Vol 38 (5) ◽

pp. 896-899 ◽

Cited By ~ 6

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.

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Distortion of submerged dog lung lobes

Journal of Applied Physiology ◽

10.1152/jappl.1985.59.2.521 ◽

1985 ◽

Vol 59 (2) ◽

pp. 521-527 ◽

Cited By ~ 3

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.

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An analysis of pressure-volume characteristics of the lungs

Journal of Applied Physiology ◽

10.1152/jappl.1964.19.1.97 ◽

1964 ◽

Vol 19 (1) ◽

pp. 97-104 ◽

Cited By ~ 222

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

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Static pressure-volume characteristics of lungs in normal males

Journal of Applied Physiology ◽

10.1152/jappl.1960.15.5.819 ◽

1960 ◽

Vol 15 (5) ◽

pp. 819-825 ◽

Cited By ~ 20

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

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Exponential fitting of pressure-volume curves: confidence limits and sensitivity to noise

Journal of Applied Physiology ◽

10.1152/jappl.1990.69.4.1538 ◽

1990 ◽

Vol 69 (4) ◽

pp. 1538-1541 ◽

Cited By ~ 7

Author(s):

D. H. Eidelman ◽

H. Ghezzo ◽

J. H. Bates

Keyword(s):

Confidence Intervals ◽

Static Pressure ◽

Transpulmonary Pressure ◽

Exponential Fitting ◽

Confidence Limits ◽

Data Set ◽

Volume Curve ◽

Pressure Volume Curve ◽

Parameter Values ◽

Biased Estimates

It has recently become common to model the static pressure-volume curve of the lung as a monoexponential function of the form V = A - Be-KP, where V is volume and P is transpulmonary pressure. The parameters A, B, and particularly K have been employed as descriptors of the intrinsic mechanical properties of the lung. The purpose of the present study was to investigate the sensitivities of A, B, and K to noise in measurements of P and V and to incompleteness of data. Using Monte-Carlo simulation, we found that the presence of typical levels of noise in P led to biased estimates of K and that the 95% confidence intervals about A and K were large compared with the parameter values themselves. These effects were increased as points were systematically removed from either end of the data set. These findings show that values of K estimated from PV data are difficult to interpret without accompanying confidence intervals.

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