Can a/ distributions in the lung be recovered from inert gas retention data?

A computer model was developed to study the relationship between ventilation-to-perfusion (V/Q) mismatch and the development of inert gas arterial-to-alveolar partial pressure differences (a-A differences). Increasing inhomogeneity of V/Q ratio is revealed directly as an increase in the a-A difference of each gas. The quantitative relationships between the Q vs. V/Q distribution and the fractional a-A difference solubility plot (a-A difference plot) were studied and described. These studies demonstrated that for log normally distributed V/Q ratios, the area under the a-A difference plot is linearly related to the log variance of the V/Q distribution and can be estimated directly from the values obtained from six gases. The maximum a-A difference occurs for a gas whose solubility is numerically equal to the mean V/Q. The effects of departure from log normality and multimodality are discussed. We conclude from these studies that quantitative information regarding the degree of inhomogeneity of V/Q for log normal distribution is available from direct calculations of inert gas retention and excretion data. Qualitative information is also available indicating the departure from log normality and the region toward which the distribution is skewed.

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Linear programming analysis of VA/Q distributions: limits on central moments

Journal of Applied Physiology ◽

10.1152/jappl.1986.60.5.1772 ◽

1986 ◽

Vol 60 (5) ◽

pp. 1772-1781 ◽

Cited By ~ 9

Author(s):

K. S. Kapitan ◽

P. D. Wagner

Keyword(s):

Linear Programming ◽

Confidence Intervals ◽

Infinite Family ◽

Blood Gases ◽

Basic Structure ◽

Inert Gas ◽

Retention Data ◽

Arterial Blood Gases ◽

Central Moments ◽

Arterial Blood

Linear programming examines the boundaries of infinite sets. We used this method with the multiple-inert gas-elimination technique to examine the central moments and arterial blood gases of the infinite family of ventilation perfusion (VA/Q) distributions that are compatible with a measured inert gas-retention set. A linear program was applied with Monte-Carlo error simulation to theoretical retention data, and 95% confidence intervals were constructed for the first three moments (mean, dispersion, and skew) and the arterial PO2 and PCO2 of all compatible blood flow distributions. Six typical cases were studied. Results demonstrate narrow confidence intervals for both the lower moments and predicted arterial blood gases of all test cases, which widen as moment number or error increase. We conclude that the blood gas composition and basic structure of all compatible VA/Q distributions are tightly constrained and that even subtle changes in this structure, as may occur experimentally, can be identified.

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Interpretation of inert gas retention and excretion in the presence of stratified inhomogeneity

Respiration Physiology ◽

10.1016/0034-5687(81)90125-0 ◽

1981 ◽

Vol 46 (3) ◽

pp. 247-259 ◽

Cited By ~ 19

Author(s):

Michael P. Hlastala ◽

Peter Scheid ◽

Johannes Piiper

Keyword(s):

Inert Gas ◽

Inert Gas Retention

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Fission Gas Bubbles in Fractured UO2

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100101177 ◽

1968 ◽

Vol 26 ◽

pp. 286-287

Author(s):

O. M. Katz

Keyword(s):

Electron Microscopy ◽

Thermal Gradient ◽

Gas Bubbles ◽

Inert Gas ◽

Thermal Gradients ◽

Fission Gas ◽

Beam Heating ◽

Limited Application ◽

Bubble Characteristics ◽

Electron Beam Heating

The swelling of irradiated UO2 has been attributed to the migration and agglomeration of fission gas bubbles in a thermal gradient. High temperatures and thermal gradients obtained by electron beam heating simulate reactor behavior and lead to the postulation of swelling mechanisms. Although electron microscopy studies have been reported on UO2, two experimental procedures have limited application of the results: irradiation was achieved either with a stream of inert gas ions without fission or at depletions less than 2 x 1020 fissions/cm3 (∼3/4 at % burnup). This study was not limited either of these conditions and reports on the bubble characteristics observed by transmission and fractographic electron microscopy in high density (96% theoretical) UO2 irradiated between 3.5 and 31.3 x 1020 fissions/cm3 at temperatures below l600°F. Preliminary results from replicas of the as-polished and etched surfaces of these samples were published.

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Correlation of γ-radioactivity and Scanning Electron Microscopy in measurement of retention of 111Indium-labeled canine endothelial cells on synthetic vascular grafts

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100156419 ◽

1989 ◽

Vol 47 ◽

pp. 886-887

Author(s):

E.J. Prendiville ◽

S. Laliberté Verdon ◽

K. E. Gould ◽

K. Ramberg ◽

R. J. Connolly ◽

...

Keyword(s):

Blood Flow ◽

Ex Vivo ◽

Vascular Grafts ◽

Retention Data ◽

Vascular Prostheses ◽

Group 4 ◽

Human Fibronectin ◽

Insufficient Time ◽

Group 3 ◽

Group 2

Endothelial cell (EC) seeding is postulated as a mechanism of improving patency in small caliber vascular grafts. However the majority of seeded EC are lost within 24 hours of restoration of blood flow in previous canine studies . We postulate that the cells have insufficient time to fully develop their attachment to the graft surface prior to exposure to hemodynamic stress. We allowed EC to incubate on fibronectin-coated ePTFE grafts for four different time periods after seeding and measured EC retention after perfusion in a canine ex vivo shunt circuit.Autologous canine EC, were enzymatically harvested, grown to confluence, and labeled with 30 μCi 111 Indium-oxine/80 cm 2 flask. Four groups of 5 cm x 4 mm ID ePTFE vascular prostheses were coated with 1.5 μg/cm.2 human fibronectin, and seeded with 1.5 x 105 EC/ cm.2. After seeding grafts in Group 1 were incubated in complete growth medium for 90 minutes, Group 2 were incubated for 24 hours, Group 3 for 72 hours and Group 4 for 6 days. Grafts were then placed in the canine ex vivo circuit, constructed between femoral artery and vein, and subjected to blood flow of 75 ml per minute for 6 hours. Continuous counting of γ-activity was made possible by placing the seeded graft inside the γ-counter detection crystal for the duration of perfusion. EC retention data after 30 minutes, 2 hours and 6 hours of flow are shown in the table.

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