Effect of surface forces on oscillatory behavior of lungs

1995 ◽  
Vol 79 (5) ◽  
pp. 1578-1585 ◽  
Author(s):  
D. Stamenovic ◽  
G. M. Barnas
Keyword(s):  
Surface Tension ◽  
Airway Resistance ◽  
Surface Film ◽  
Oscillatory Behavior ◽  
Tissue Impedance ◽  
Dimethyl Siloxane ◽  
Tissue Resistance ◽  
Before And After ◽  
Alveolar Duct ◽  
The Difference

The effect of alveolar surface tension on lung dynamic behavior was investigated by measuring total lung and tissue impedances in excised rabbit lungs at breathing frequencies of 0.2–0.8 Hz and tidal volumes of 10, 20, and 30 ml before and after lavage with 3-dimethyl siloxane, which provided a constant surface tension of 16 dyn/cm. The lungs were oscillated around the mean deflation pressures of 5 (control) and 8 cmH2O (lavaged), i.e., lung volume of 60% of total lung capacity. The total lung impedance was calculated from measurements of pressure and airflow at the trachea, and tissue impedance was measured by the alveolar capsule technique. The airway contribution was obtained as the difference between total lung and tissue impedances. In the lavaged lungs, dynamic elastance (Edyn) decreased and tissue resistance (Rti) increased relative to the control values over the entire frequency range. Airway resistance increased at the higher flow rates only. The decrease in Edyn could be attributed to the absence of surface film elastance in the lavaged lungs. The increase in airway resistance could be attributed to accentuated flow dependence due to changes in airway geometry and residual lavage liquid. However, the most intriguing result was the increase in Rti in the lavaged lungs. It could be attributed to altered mechanics at the alveolar duct level after lavage. It is concluded that dissipative properties of lung tissue are major determinants of Rti, whereas elastic properties of both tissue and surface film are important determinants of Edyn.

The bronchodilator test in patients with airway obstruction: the responsiveness of lung function parameters

2021 ◽  
pp. 57-61
Author(s):  
M. I. Chushkin ◽  
L. A. Popova ◽  
E. A. Shergina ◽  
N. L. Karpina
Keyword(s):  
Pulmonary Function ◽  
Airway Obstruction ◽  
Airway Resistance ◽  
Lung Volumes ◽  
Before And After ◽  
Calculated Effect ◽  
Volume Measurements ◽  
The Difference ◽  
Bronchodilator Responsiveness ◽  
Chronic Airway

Interpretation of bronchodilator (BD) test based on reaction of forced expiratory in one second (FEV 1). For assessing bronchodilator responsiveness of lung volumes, airway resistance remains largely unexplored. Therefore, we assessed the response of pulmonary function parameters to BD to reveal the most responsive parameter. 90 patients with chronic airway obstruction (61 male and 29 female; aged 55±11; post-  BD FEV 1 was 63.1+18.3 % predicted) performed spirometry and static lung volume measurements before and after inhalation of BD. We calculated effect size (ES) for each parameter from the difference between two means divided by the standard deviation of baseline score. There was a significant increase both FVC and FEV 1by 8.2 and 12.3 % from baseline (p<0.001). ES were 0.34 for FEV1 and 0.26 for FVC. The ES for lung volumes were from -0.07 (total lung capacity) to -0.31 (residual volume). The ES for sRtot (specific airway resistance) was -0.5 and ES for sGeff (specific effective airway conductance) was 0.95. The parameters of airway resistance and conductance were more responsive for the assessment of pulmonary function changes than spirometry and lung volumes parameters in patients with chronic airway obstruction.

On the imperfect elasticity of lung tissue

1989 ◽  
Vol 67 (6) ◽  
pp. 2408-2419 ◽  
Author(s):  
J. J. Fredberg ◽  
D. Stamenovic
Keyword(s):  
Lung Tissue ◽  
Surface Film ◽  
Underlying Mechanism ◽  
Necessary Condition ◽  
Connective Tissues ◽  
Bearing Element ◽  
Tissue Resistance ◽  
Frequency Independent ◽  
Alveolar Duct ◽  
Elastic Processes

This paper deals with a unifying hypothesis addressed at lung tissue resistance and its responses to neurohumoral and biophysical stimuli. The hypothesis holds that dissipative and elastic processes within lung tissue are coupled at the level of the stress-bearing element. Such a description leads naturally to consideration of a readily measured attribute of organ-level dissipative behavior called lung tissue hysteresivity, eta. On preliminary analysis this attribute is found to be nearly frequency independent and numerically conserved across species. To the degree that the numerical value of eta might be conserved during an intervention in which tissue dynamic elastance changes, such behavior would be consistent with the notion that elastic energy storage and dissipative energy loss reside within the very same stress-bearing element and, moreover, that those processes within the stress-bearing element bear an approximately fixed relationship. Tissue hysteresivity is closely related to the parameter K used by Bachofen and Hildebrandt (J. Appl. Physiol. 30: 493-497, 1971) to describe energy dissipation per cycle, and both lend themselves directly to interpretation based on processes ongoing at the levels of microstructure and molecule. Intraparenchymal connective tissues, surface film, and contractile elements appear to submit individually to this description and, in doing so, yield respective hysteresivities that are relatively well matched; this suggests that such hysteretic matching may be a necessary condition for synchronous expansion of the alveolar duct. The overriding simplicity with which this description organizes diverse observations implies that it may capture some unifying attribute of underlying mechanism.

Variation in the Composition and Properties of Fresh Latex. And Subsequent Changes on Ammoniation

1939 ◽  
Vol 12 (4) ◽  
pp. 646-654
Author(s):  
Edgar Rhodes
Keyword(s):  
Surface Tension ◽  
Acid Value ◽  
Acid Number ◽  
Acetone Extract ◽  
Latex Film ◽  
Rubber Content ◽  
Total Solids ◽  
Before And After ◽  
The Difference ◽  
Approximate Rate

Abstract Systematic examination has been made of 163 samples of latex drawn at the approximate rate of three per week over a period of fourteen months from a single tapper's task on old seedling trees, newly opened after several years' rest on the continuous alternate daily system. The latex samples were all examined, both in the fresh condition and after 10 days and 15 days preservation with 0.7% ammonia; during the last eight months certain tests were also made on the latex immediately after ammoniation on the day of collection. The tests included dry rubber content, total solids, acetone extract and acid number of whole-latex rubber films, surface tension, viscosity, stirring stability and ease of creaming. It has been observed that: (1) The difference between percentage total solids and percentage dry rubber content is greater after 10 days' preservation than in the fresh condition. (2) The acetone extract and its acid number from whole-latex film are less in freshly-ammoniated latex than in fresh latex, and very much greater in ammoniated latex stored for 10 days. The acid number after 10 days preservation is usually about twice that of the fresh latex. These findings and their implications are discussed in the text, in which experimental figures are given. High dry rubber content usually connotes low acetone extract and acid value in the fresh latex. (3) Values for surface tension before and after ammoniation are given. The fall in surface tension as a result of ammoniation has not been proven to be governed by the changes in acetone-soluble material, or the acid number thereof. (4) The viscosity of ammoniated latex is shown to be very significantly correlated with its dry rubber content. In the case of fresh latex the degree of correlation is much less; a possible reason for this is advanced. Experimental results are given. (5) The initial stirring stability is shown to be influenced by the initial dry rubber content of the latex. The data do not provide an adequate explanation of the changes in stability which take place on storage. (6) The creaming ease of new latex appears also to be influenced by its initial dry rubber content, but the present data are not adequate fully to explain the variations which are noted.

Relationship between frequency and amplitude dependence in the lung: a nonlinear block-structured modeling approach

1995 ◽  
Vol 79 (2) ◽  
pp. 660-671 ◽  
Author(s):  
B. Suki ◽  
Q. Zhang ◽  
K. R. Lutchen
Keyword(s):  
Sine Wave ◽  
Lung Model ◽  
Amplitude Dependence ◽  
Tissue Impedance ◽  
Basic Model ◽  
Time Domain Data ◽  
Tissue Resistance ◽  
Before And After ◽  
Airway Opening ◽  
Block Structured

During lung constriction, there is an increase in both the frequency and tidal volume (VT) dependences of lung tissue resistance (Rti) and elastance (Eti). This suggests that 1) significant alterations take place in the mechanisms contributing to both the linear and nonlinear characteristics of lung tissues; and 2) the frequency and VT dependences of Rti and Eti are coupled. We examined these issues for the case of sine wave and special pseudorandom inputs by utilizing the theory of nonlinear block-structured systems. Two basic model structures were considered: the Hammerstein and the Wiener structures. The Hammerstein structure is a cascade connection of a nonlinear zero-memory (N) system and a linear dynamic process (L). This structure predicts that frequency and VT dependences of Rti and Eti are decoupled. The Wiener structure is an inverse cascade of these two blocks (i.e., L-N) in which the frequency and VT dependences of Rti and Eti are coupled. These two structures were combined with a nonlinear airway compartment and fitted to measured airway opening and alveolar capsule pressure-flow time domain data in dogs before and after histamine-induced constriction. The best lung model was a linear airway compartment combined with a Wiener structure consisting of a constant-phase linear tissue impedance in cascade with a polynomial nonlinearity, suggesting that frequency and VT dependences of Rti and Eti are indeed coupled during control and constricted conditions. Moreover, histamine caused much larger changes in the linear tissue parameters than in the nonlinear coefficients.

Endogenous nitric oxide modulates responses of tissue and airway resistance to vagal stimulation in piglets

2002 ◽  
Vol 93 (2) ◽  
pp. 450-456 ◽  
Author(s):  
Mohammad Y. Khassawneh ◽  
Ismail A. Dreshaj ◽  
Shijian Liu ◽  
Chung-Ho Chang ◽  
Musa A. Haxhiu ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Airway Resistance ◽  
Vagal Stimulation ◽  
No Synthase ◽  
Excitatory Response ◽  
Tissue Resistance ◽  
Before And After ◽  
Endogenous Nitric Oxide ◽  
Cholinergic Effects

The role of endogenous nitric oxide (NO) in modulating the excitatory response of distal airways to vagal stimulation is unknown. In decerebrate, ventilated, open-chest piglets aged 3–10 days, lung resistance (Rl) was partitioned into tissue resistance (Rti) and airway resistance (Raw) by using alveolar capsules. Changes in Rl, Rti, and Raw were evaluated during vagal stimulation at increasing frequency before and after NO synthase blockade with N ω-nitro-l-arginine methyl ester (l-NAME). Vagal stimulation increased Rl by elevating both Rti and Raw. NO synthase blockade significantly increased baseline Rti, but not Raw, and significantly augmented the effects of vagal stimulation on both Rti and Raw. Vagal stimulation also resulted in a significant increase in cGMP levels in lung tissue before, but not after, l-NAME infusion. In seven additional piglets after Rl was elevated by histamine infusion in the presence of cholinergic blockade with atropine, vagal stimulation failed to elicit any change in Rl, Rti, or Raw. Therefore, endogenous NO not only plays a role in modulating baseline Rti, but it opposes the excitatory cholinergic effects on both the tissue and airway components of Rl. We speculate that activation of the NO/cGMP pathway during cholinergic stimulation plays an important role in modulating peripheral as well as central contractile elements in the developing lung.

Surface forces in lungs. I. Alveolar surface tension-lung volume relationships

1986 ◽  
Vol 60 (4) ◽  
pp. 1341-1350 ◽  
Author(s):  
J. C. Smith ◽  
D. Stamenovic
Keyword(s):  
Surface Tension ◽  
Lung Volume ◽  
Surface Film ◽  
Dipalmitoyl Phosphatidylcholine ◽  
Interfacial Tensions ◽  
Equilibrium Surface Tension ◽  
Before And After ◽  
Surface Active ◽  
Lung Deflation ◽  
Alveolar Surface

Alveolar surface tension (gamma)-lung volume relationships were obtained for quasi-static and dynamic lung pressure-volume (PV) histories from measurements of PV curves of liquid- and air-filled excised rabbit lungs. PV relationships were measured at room temperature in lungs filled with test liquids with constant liquid-liquid interfacial tensions with alveolar surface-active materials; and air-filled lungs before and after the normal alveolar surface film was covered with test liquids with constant values of liquid- and air-liquid interfacial tensions. Interfacial tensions of test liquids were measured in a surface balance on monolayers of dipalmitoyl phosphatidylcholine. Values of gamma for the normal air-filled lung were obtained either from points of intersection between PV curves with the normal and test liquid interface or from a general relationship between gamma and the component of recoil pressure due to surface tension derived from the data. In contrast to previous analyses that have used PV measurements, this approach does not depend on assumptions about lung microstructural geometry. Surface tension-volume relationships for the normal air-filled lung show a prominent hysteresis with surface tension ranging from near 0 at low volumes during lung deflation to transiently high values near 40 dyn/cm during inflation; value of equilibrium surface tension (gamma EQ) near 28 dyn/cm; and characteristic transitions in surface film compressibility and associated transitions in film kinetic behavior in nonequilibrium film states where gamma deviates from gamma EQ. These features are consistent with the behavior predicted from current models of alveolar surface film behavior.

Effects of lung volume on airway resistance during induced constriction in papain-treated rabbits

1996 ◽  
Vol 80 (6) ◽  
pp. 1872-1879 ◽  
Author(s):  
T. Nagase ◽  
H. Matsui ◽  
E. Sudo ◽  
T. Matsuse ◽  
M. S. Ludwig ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Lung Volume ◽  
Airway Resistance ◽  
Transpulmonary Pressure ◽  
Airway Narrowing ◽  
Tissue Resistance ◽  
Before And After ◽  
Baseline Conditions ◽  
Different Levels

It has been reported that both the elasticity of the cartilage and airway-parenchymal interdependence can modify shortening of the airway smooth muscle and airway narrowing during induced constriction. We hypothesized that induced softening of the cartilage could alter airway compliance and/or the forces of mechanical interdependence, resulting in an increased degree of airway narrowing in response to a contractile stimulus. To test this hypothesis, we compared the effects of changing lung volume on airway resistance (Raw) under baseline conditions and during methacholine (MCh)-induced constriction in papain-treated (n = 6) and control rabbits (n = 6). With use of the alveolar capsule technique, Raw was directly measured under baseline conditions at different levels of end-expiratory transpulmonary pressure (Ptp = 4-12 cmH2O). Then aerosolized MCh was delivered (0.2-25 mg/ml) and measurements were performed at different levels of Ptp (4 and 12 cmH2O). From measured tracheal flow and tracheal and alveolar pressure in open-chest animals during mechanical ventilation (tidal volume = 6 ml/kg, breathing frequency = 1 Hz), we calculated Raw by subtracting tissue resistance from lung resistance. Papain treatment significantly increased Raw both under baseline conditions and after induced constriction. We found that increasing Ptp decreased Raw before and after MCh in both groups; however, the effects of changing Ptp on Raw were less in papain-treated animals. These observations suggest that both cartilage elasticity and mechanical interdependence are important determinants of airway smooth muscle shortening. The observation that volume dependence of Raw was less in papain-treated animals is consistent with the hypothesis that papain effects significant changes in the parenchymal attachments.

Viscoelastic Behavior of a Lung Alveolar Duct Model

1999 ◽  
Vol 122 (2) ◽  
pp. 143-151 ◽  
Author(s):  
E. Denny ◽  
R. C. Schroter
Keyword(s):  
Surface Tension ◽  
Tidal Volume ◽  
Viscoelastic Behavior ◽  
Surface Tension Force ◽  
Element Model ◽  
Lung Parenchyma ◽  
Oscillatory Behavior ◽  
Published Data ◽  
Elastic Model ◽  
Alveolar Duct

A study is conducted into the oscillatory behavior of a finite element model of an alveolar duct. Its load-bearing components consist of a network of elastin and collagen fibers and surface tension acting over the air–liquid interfaces. The tissue is simulated using a visco-elastic model involving nonlinear quasi-static stress–strain behavior combined with a reduced relaxation function. The surface tension force is simulated with a time- and area-dependent model of surfactant behavior. The model was used to simulate lung parenchyma under three surface tension cases: air-filled, liquid-filled, and lavaged with 3-dimethyl siloxane, which has a constant surface tension of 16 dyn/cm. The dynamic elastance Edyn and tissue resistance Rti were computed for sinusoidal tidal volume oscillations over a range of frequencies from 0.16–2.0 Hz. A comparison of the variation of Edyn and Rti with frequency between the model and published experimental data showed good qualitative agreement. Little difference was found in the model between Rti for the air-filled and lavaged models; in contrast, published data revealed a significantly higher value of Rti in the lavaged lung. The absence of a significant increase in Rti for the lavaged model can be attributed to only minor changes in the individual fiber bundle resistances with changes in their configuration. The surface tension was found to make an important contribution to both Edyn and Rti in the air-filled duct model. It was also found to amplify any existing tissue dissipative properties, despite exhibiting none itself over the small tidal volume cycles examined. [S0148-0731(00)00502-1]

Dynamic behavior of lung parenchyma in shear

1996 ◽  
Vol 80 (6) ◽  
pp. 1880-1890 ◽  
Author(s):  
M. F. Coughlin ◽  
B. Suki ◽  
D. Stamenovic
Keyword(s):  
Dynamic Properties ◽  
Surface Film ◽  
Transpulmonary Pressure ◽  
Lung Parenchyma ◽  
Model Parameters ◽  
Indentation Force ◽  
Dimethyl Siloxane ◽  
Before And After ◽  
Primary Determinant ◽  
Order Of Magnitude

Dynamic shear properties of excised rabbit lungs were studied by measuring creep deformation after application of a step indentation force to the pleural surfaces by a rigid cylindrical punch. The punch diameter was 9.5 mm, and punch forces were 2,4, and 6 g. Measurements were made at lung volumes of 40, 60, and 90% of the total lung capacity before and after lavage with 3-dimethyl siloxane, which provided a constant surface tension of 16 dyn/cm at the alveolar surfaces. A power-law model was fitted to creep data and then transformed into the frequency (f) domain by using Laplace transforms. The optimum model parameters were used to calculate shear elastance (E mu), shear resistance (R mu), and shear hysteresivity (2 pi fR mu/E mu) between 0.01 and 2.0 Hz. It was found that E mu slightly increased and R mu decreased nearly hyperbolically with increasing f, both decreased with increasing indentation force, and both increased with increasing mean lung volume. Shear hysteresivity decreased sharply from 0.01 to 0.25 Hz and then assumed a nearly steady value that was an order of magnitude lower than the value reported previously for uniformly oscillated lungs. Changes in E mu and R mu after lavage were correlated with changes in transpulmonary pressure and not with changes in surface film properties. These results suggest that in the breathing range of frequencies 1) the energy loss of lung parenchyma is a much smaller fraction of the stored elastic energy in shear than in uniformly oscillated lungs and 2) transpulmonary pressure, not dynamic properties of surface film, is the primary determinant of lung dynamic properties in shear.

Tem analysis of multiple-energy arsenic implanted and Rta'd silicon

1987 ◽  
Vol 45 ◽  
pp. 246-247
Author(s):  
R.A. Herring
Keyword(s):  
Device Fabrication ◽  
High Concentration ◽  
Tem Analysis ◽  
Defect Clusters ◽  
High Fluences ◽  
Small Defect ◽  
Before And After ◽  
The Matrix ◽  
The Difference ◽  
Factor Type

Rapid thermal annealing (RTA) of ion-implanted Si is important for device fabrication. The defect structures of 2.5, 4.0, and 6.0 MeV As-implanted silicon irradiated to fluences of 2E14, 4E14, and 6E14, respectively, have been analyzed by electron diffraction both before and after RTA at 1100°C for 10 seconds. At such high fluences and energies the implanted As ions change the Si from crystalline to amorphous. Three distinct amorphous regions emerge due to the three implantation energies used (Fig. 1). The amorphous regions are separated from each other by crystalline Si (marked L1, L2, and L3 in Fig. 1) which contains a high concentration of small defect clusters. The small defect clusters were similar to what had been determined earlier as being amorphous zones since their contrast was principally of the structure-factor type that arises due to the difference in extinction distance between the matrix and damage regions.

Sign in / Sign up

Export Citation Format

Share Document