A continuum mechanics analysis of pulmonary vascular interdependence in isolated dog lobes

1979 ◽  
Vol 46 (3) ◽  
pp. 419-429 ◽  
Author(s):  
S. J. Lai-Fook
Keyword(s):  
Nonlinear Analysis ◽  
Continuum Mechanics ◽  
Vessel Diameter ◽  
Lung Inflation ◽  
Mean Values ◽  
Pulmonary Vessels ◽  
Mechanics Analysis ◽  
Residual Capacity ◽  
The Difference ◽  
Physiological Values

The pressure-diameter (PD) behavior of intact pulmonary vessels was measured roentgenographically at several fixed deflation transpulmonary pressures (Ptp). At any constant vascular pressure (Pv), the intact-vessel diameter was larger for higher Ptp. The behavior of the parenchyma was described by a nonlinear analysis. An excised-vessel PD behavior was computed which was consistent with both nonlinear parenchymal behavior and measured intact-vessel PD behavior. Estimates of Px', the difference between the perivascular pressure and the pleural pressure, as a function of Ptp and Pv were obtained. For physiological values of Pv, mean values of Px' for arteries were -1 cmH2O at Ptp of 4 cmH20 and decreased almost linearly to -15 cmH20 at Ptp of 25 cmH2O. Veins showed a similar behavior, but Px' was more positive. Increasing Pv raised Px' and decreasing Pv lowered Px' at all values of Ptp. These results indicate that the interdependence effect is small at functional residual capacity, increases with lung inflation, and is greater for arteries than veins.

Regional differences in alveolar density in the human lung are related to lung height

2015 ◽  
Vol 118 (11) ◽  
pp. 1429-1434 ◽  
Author(s):  
John E. McDonough ◽  
Lars Knudsen ◽  
Alexander C. Wright ◽  
W. Mark Elliott ◽  
Matthias Ochs ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Regional Differences ◽  
Volume Fraction ◽  
Transpulmonary Pressure ◽  
Pleural Pressure ◽  
Lung Inflation ◽  
Residual Capacity ◽  
Alveolar Duct ◽  
The Difference

The gravity-dependent pleural pressure gradient within the thorax produces regional differences in lung inflation that have a profound effect on the distribution of ventilation within the lung. This study examines the hypothesis that gravitationally induced differences in stress within the thorax also influence alveolar density in terms of the number of alveoli contained per unit volume of lung. To test this hypothesis, we measured the number of alveoli within known volumes of lung located at regular intervals between the apex and base of four normal adult human lungs that were rapidly frozen at a constant transpulmonary pressure, and used microcomputed tomographic imaging to measure alveolar density (number alveoli/mm3) at regular intervals between the lung apex and base. These results show that at total lung capacity, alveolar density in the lung apex is 31.6 ± 3.4 alveoli/mm3, with 15 ± 6% of parenchymal tissue consisting of alveolar duct. The base of the lung had an alveolar density of 21.2 ± 1.6 alveoli/mm3 and alveolar duct volume fraction of 29 ± 6%. The difference in alveolar density can be negated by factoring in the effects of alveolar compression due to the pleural pressure gradient at the base of the lung in vivo and at functional residual capacity.

Dispersion of aerosol boluses in the human lung: dependence on lung volume, bolus volume, and gender

1995 ◽  
Vol 79 (5) ◽  
pp. 1787-1795 ◽  
Author(s):  
J. S. Brown ◽  
T. R. Gerrity ◽  
W. D. Bennett ◽  
C. S. Kim ◽  
D. E. House
Keyword(s):  
Gender Effects ◽  
Bolus Volume ◽  
Mixing Processes ◽  
Lung Inflation ◽  
Convective Mixing ◽  
Human Lungs ◽  
Residual Capacity ◽  
Health And Disease ◽  
The Difference ◽  
And Gender

The dispersion of aerosol boluses in the human lungs has been studied in health and disease, usually as a means of investigating convective mixing. However, there are limited data on the roles of critical factors, such as the volume of inhaled boluses, lung inflation, and gender on dispersion. To examine these factors, we measured the difference in volume variance between exhaled and inhaled boluses (sigma 2V) of a 0.5-micron aerosol in 11 healthy male and 12 healthy female subjects as a function of tidal volume (VT = 1,000 and 1,500 ml in females and 1,000 and 2,000 ml in males), bolus penetration volume (Vi at 250-ml increments over each VT), and bolus volume (target VBol = 75, 150, and 300 ml). Analysis of variance showed marginally significant gender effects (P = 0.073) on sigma 2V, with sigma 2V greater in males than in females. There was also a significant effect of VBol on sigma 2V (P < 0.001). A Vi-dependent mean volume shift between inhaled and exhaled boluses (delta V) was observed at all Vi except 500 ml. The observation of gender and VBol effects and the existence of a nonzero delta V suggest that convective mixing mechanisms other than longitudinal dispersion alone occur in the healthy lung. The lack of VT dependence suggests a minimal role of lung inflation above functional residual capacity on dispersion. The dependence of sigma 2V on Vi2 up to 1,750 ml and minimal VBol effects demonstrates that convective mixing processes continue far into the gas exchange regions of the lung and support a significant role for axial streaming.

Elasticity of Small Pulmonary Arteries in the Cat

1980 ◽  
Vol 102 (2) ◽  
pp. 170-177 ◽  
Author(s):  
R. T. Yen ◽  
Y. C. Fung ◽  
Nancy Bingham
Keyword(s):  
Perfusion Pressure ◽  
Pulmonary Arteries ◽  
Vessel Diameter ◽  
Transmural Pressure ◽  
Pleural Pressure ◽  
Mean Values ◽  
Intermediate Range ◽  
Mammalian Lung ◽  
The Mean ◽  
The Difference

When synthesizing the available data of vessel elasticity of mammalian lung from the literature, the lack of data in the intermediate range of vessel sizes becomes evident. In an effort to fill this gap, the distensibility of pulmonary arteries of cats, in the range of 100–1600 μm diameter was studied as a function of the perfusion pressure. The resulting percentage changes in vessel diameter (D) were expressed as polynomials of “transmural” pressure, which is taken to be the difference between the perfusion pressure and the pleural pressure, pa − pPL, in the form D/Do=1+α(pa−pPL)−β(pa−pPL)2. where Do is the value of D when pa = pPL, and α and β are constants. Our results show that for vessels whose diameters Do are in the range of 100–200 μ;m, the mean values of D/Do are represented by α = 2.02 percent per cm H2O or 0.202 (KPa)−1, β = 0.046 percent per (cm H2O)2 or 0.046 (KPa)−2. For vessels with diameter Do greater than 200 μm, the pressure-diameter relationship is linear in the ranges tested, so that β = 0. The values of the compliance constant α (slopes of the curves) for vessels in the diameter (Do) ranges 200–300 μm, 300–400 μm, 400–600 μm, 600–1000 μm, and 1000–1600 μm are, respectively, 0.93, 0.78, 0.70, 1.10, and 2.61 percent per cm H2O, (i.e., these numbers × 10−1 (KPa)−1). Thus the compliance of the pulmonary arteries appears to be the smallest in the diameter range 400–600 μm; and that the compliance of vessels in the 1000–1600 μm range is more than twice that of the smaller vessels.

Seasonal trends in the stable isotopic composition of snow and meltwater runoff in a subarctic catchment at Okstindan, Norway

2004 ◽  
Vol 35 (2) ◽  
pp. 119-137 ◽  
Author(s):  
S.D. Gurney ◽  
D.S.L. Lawrence
Keyword(s):  
Isotopic Composition ◽  
Mean Value ◽  
Mean Values ◽  
Stable Isotopic Composition ◽  
Meltwater Runoff ◽  
Stable Isotopic ◽  
The Mean ◽  
The Difference ◽  
Δ18o And Δd

Seasonal variations in the stable isotopic composition of snow and meltwater were investigated in a sub-arctic, mountainous, but non-glacial, catchment at Okstindan in northern Norway based on analyses of δ18O and δD. Samples were collected during four field periods (August 1998; April 1999; June 1999 and August 1999) at three sites lying on an altitudinal transect (740–970 m a.s.l.). Snowpack data display an increase in the mean values of δ18O (increasing from a mean value of −13.51 to −11.49‰ between April and August), as well as a decrease in variability through the melt period. Comparison with a regional meteoric water line indicates that the slope of the δ18O–δD line for the snowpacks decreases over the same period, dropping from 7.49 to approximately 6.2.This change points to the role of evaporation in snowpack ablation and is confirmed by the vertical profile of deuterium excess. Snowpack seepage data, although limited, also suggest reduced values of δD, as might be associated with local evaporation during meltwater generation. In general, meltwaters were depleted in δ18O relative to the source snowpack at the peak of the melt (June), but later in the year (August) the difference between the two was not statistically significant. The diurnal pattern of isotopic composition indicates that the most depleted meltwaters coincide with the peak in temperature and, hence, meltwater production.

Relationship of end-expiratory pressure, lung volume, and 99mTc-DTPA clearance

1987 ◽  
Vol 63 (4) ◽  
pp. 1586-1590 ◽  
Author(s):  
J. A. Cooper ◽  
H. van der Zee ◽  
B. R. Line ◽  
A. B. Malik
Keyword(s):  
Lung Volume ◽  
Clearance Rate ◽  
Base Line ◽  
Lung Inflation ◽  
Alveolar Epithelial ◽  
Pulmonary Clearance ◽  
Residual Capacity ◽  
Dose Response Effect ◽  
Relationship Of ◽  
Line P

We investigated the dose-response effect of positive end-expiratory pressure (PEEP) and increased lung volume on the pulmonary clearance rate of aerosolized technetium-99m-labeled diethylenetriaminepentaacetic acid (99mTc-DTPA). Clearance of lung radioactivity was expressed as percent decrease per minute. Base-line clearance was measured while anesthetized sheep (n = 20) were ventilated with 0 cmH2O end-expiratory pressure. Clearance was remeasured during ventilation at 2.5, 5, 10, 15, or 20 cmH2O PEEP. Further studies showed stepwise increases in functional residual capacity (FRC) (P less than 0.05) measured at 0, 2.5, 5, 10, 15, and 20 cmH2O PEEP. At 2.5 cmH2O PEEP, the clearance rate was not different from that at base line (P less than 0.05), although FRC was increased from base line. Clearance rate increased progressively with increasing PEEP at 5, 10, and 15 cmH2O (P less than 0.05). Between 15 and 20 cmH2O PEEP, clearance rate was again unchanged, despite an increase in FRC. The pulmonary clearance of aerosolized 99mTc-DTPA shows a sigmoidal response to increasing FRC and PEEP, having both threshold and maximal effects. This relationship is most consistent with the hypothesis that alveolar epithelial permeability is increased by lung inflation.

DIE AUSSCHEIDUNG VON TESTOSTERON UND EPITESTOSTERON BEI FRAUEN AM ENDE DER SCHWANGERSCHAFT

1969 ◽  
Vol 60 (4) ◽  
pp. 579-585
Author(s):  
K. Schollberg ◽  
E. Seiler ◽  
J. Holtorff
Keyword(s):  
Urinary Excretion ◽  
Late Pregnancy ◽  
Mean Values ◽  
Pregnant Females ◽  
Female Foetus ◽  
The Mean ◽  
The Difference ◽  
Normal Women ◽  
In Pregnancy

ABSTRACT The urinary excretion of testosterone and epitestosterone by women in late pregnancy has been studied. The mean values of 22 normal women in pregnancy mens X are 12.9 ± 9.2 μg/24 h in the case of testosterone and 16.1 ± 16.2 μg/24 h in the case of epitestosterone. Both values do not differ significantly from those of non-pregnant females. The excretion values of mothers bearing a male foetus (17.3 ± 8.9 μg/24 h) are higher than those of mothers with a female foetus (6.4 ± 4.8 μg/24 h). The difference is statistically significant with P = 0.01.

Respiratory mechanics in supine subjects during progressive partial curarization

1982 ◽  
Vol 52 (1) ◽  
pp. 57-63 ◽  
Author(s):  
T. J. Gal ◽  
N. S. Arora
Keyword(s):  
Muscle Strength ◽  
Muscle Weakness ◽  
Respiratory Mechanics ◽  
Handgrip Strength ◽  
Elastic Recoil ◽  
Lung Inflation ◽  
Progressive Muscle Weakness ◽  
Inspiratory Resistance ◽  
Residual Capacity ◽  
Partial Curarization

Respiratory mechanics were studied in six supine conscious volunteers during progressive muscle weakness produced by infusion of d-tubocurarine. Partial curarization was carried out to the point of abolishing head lift ability and handgrip strength. At all levels of partial paralysis, expiratory muscle strength was significantly more impaired than inspiratory strength. Despite this, subjects maintained relatively normal maximal expiratory flow rates, whereas inspiratory flows decreased significantly. The diminished inspiratory flows are not fully explained by decreased driving pressures during force inspiration, since inspiratory resistance increased significantly with the decreased flow. Inspiratory flow patterns suggest a variable extrathoracic obstruction most likely due to the absence of normal airway abductor activity during inspiration. Maximal respiratory muscle weakness decreased forced vital capacity by 29% and total lung capacity by 15%. The decreased level of lung inflation did not alter lung elastic recoil. Functional residual capacity was unchanged, but inspiratory capacity decreased by 25% and residual volume increased by 38%. These changes are in accord with predictions based on the decreased muscle strength and normal respiratory system recoil.

Effects of expiratory loading on respiration in humans

1980 ◽  
Vol 49 (4) ◽  
pp. 601-608 ◽  
Author(s):  
B. Gothe ◽  
N. S. Cherniack
Keyword(s):  
Muscle Activity ◽  
Healthy Subjects ◽  
Respiratory Muscle ◽  
Resistive Load ◽  
Similar Magnitude ◽  
Occlusion Pressure ◽  
Ventilatory Responses ◽  
Residual Capacity ◽  
Resistive Loads ◽  
The Difference

We examined the effects of expiratory resistive loads of 10 and 18 cmH2O.l-1.s in healthy subjects on ventilation and occlusion pressure responses to CO2, respiratory muscle electromyogram, pattern of breathing, and thoracoabdominal movements. In addition, we compared ventilation and occlusion pressure responses to CO2 breathing elicited by breathing through an inspiratory resistive load of 10 cmH2O.l-1.s to those produced by an expiratory load of similar magnitude. Both inspiratory and expiratory loads decreased ventilatory responses to CO2 and increased the tidal volume achieved at any given level of ventilation. Depression of ventilatory responses to Co2 was greater with the larger than with the smaller expiratory load, but the decrease was in proportion to the difference in the severity of the loads. Occlusion pressure responses were increased significantly by the inspiratory resistive load but not by the smaller expiratory load. However, occlusion pressure responses to CO2 were significantly larger with the greater expiratory load than control. Increase in occlusion pressure observed could not be explained by changes in functional residual capacity or chemical drive. The larger expiratory load also produced significant increases in electrical activity measured during both inspiration and expiration. These results suggest that sufficiently severe impediments to breathing, even when they are exclusively expiratory, can enhance inspiratory muscle activity in conscious humans.

Dynamic mechanisms determine functional residual capacity in mice, Mus musculus

1979 ◽  
Vol 46 (5) ◽  
pp. 867-871 ◽  
Author(s):  
A. Vinegar ◽  
E. E. Sinnett ◽  
D. E. Leith
Keyword(s):  
Tidal Volume ◽  
Functional Residual Capacity ◽  
Flow Volume ◽  
Linear Portion ◽  
Volume Curve ◽  
Flow Volume Curve ◽  
Residual Capacity ◽  
Expiratory Flow ◽  
The Difference ◽  
Pentobarbital Sodium Anesthesia

Awake mice (22.6--32.6 g) were anesthetized intravenously during head-out body plethysmography. One minute after pentobarbital sodium anesthesia, tidal volume had fallen from 0.28 +/- 0.04 to 0.14 +/- 0.02 ml and frequency from 181 +/- 20 to 142 +/- 8. Functional residual capacity (FRC) decreased by 0.10 +/- 0.02 ml. Expiratory flow-volume curves were linear, highly repeatable, and submaximal over substantial portions of expiration in awake and anesthetized mice; and expiration was interrupted at substantial flows that abruptly fell to and crossed zero as inspiration interrupted relaxed expiration. FRC is maintained at a higher level in awake mice due to a higher tidal volume and frequency coupled with expiratory braking (persistent inspiratory muscle activity or increased glottal resistance). In anesthetized mice, the absence of braking, coupled with reductions in tidal volume and frequency and a prolonged expiratory period, leads to FRCs that approach relaxation volume (Vr). An equation in derived to express the difference between FRC and Vr in terms of the portion of tidal volume expired without braking, the slope of the linear portion of the expiratory flow-volume curve expressed as V/V, the time fraction of one respiratory cycle spent in unbraked expiration, and respiratory frequency.

scholarly journals Influence of Apical Patency and Cleaning of the Apical Foramen on Periapical Extrusion in Retreatment

2013 ◽  
Vol 24 (5) ◽  
pp. 482-486 ◽  
Author(s):  
Marili Doro Andrade Deonizio ◽  
Gilson Blitzkow Sydney ◽  
Antonio Batista ◽  
Roberto Pontarolo ◽  
Paulo Ricardo Bittencourt Guimarães ◽  
...  
Keyword(s):  
Material Removal ◽  
Filling Material ◽  
Mean Values ◽  
Filtration System ◽  
Root Canal Retreatment ◽  
Significant Difference ◽  
Before And After ◽  
The Mean ◽  
The Difference ◽  
Removal Technique

This study evaluated the influence of apical patency, root filling removal technique and cleaning of the apical foramen, concerning the amount of debris extruded during root canal retreatment. Forty mandibular incisors were randomly assigned to 4 groups - GIM (n=10), GIIM (n=10), GIPT (n=10) and GIIPT (n=10), which were named according to leaving (I) or not (II) apical patency during canal preparation and filling removal technique (manual - M or ProTaper system - PT). After filling material removal, each specimen of each group had the apical foramen cleaned by sizes 15, 20 and 25 instruments, generating 12 subgroups: GIM15, GIM20, GIM25, GIIM15, GIIM20, GIIM25, GIPT15, GIPT20, GIPT25, GIIPT15, GIIPT20 and GIIPT25. Extruded filling debris was collected by a Milipore filtration system, an HV-durapore, 0.45 µm pore filter with a 25 mm diameter. The filters were weighed before and after the collection on an analytical scale (10–5 g), and the difference was calculated. The mean weight of extruded filling debris was analyzed statistically by Kruskal-Wallis and Friedman ANOVA tests (α=0.05). The mean values found in the groups (in mg) were: GIM (0.95±0.94), GIIM (0.47±0.62), GIPT (0.30±0.31) and GIIPT (0.32±0.44). There was no statistically significant difference among any of the groups or subgroups (p>0.05). ProTaper provided the smallest amount of extruded filling material, regardless of presence or absence of apical patency, followed by manual technique, without and with apical patency. Additional amounts of debris were collected during cleaning of the apical foramen, regardless of the instrument, presence/absence of patency or root filling removal technique.

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