Mathematical Treatment of Inert Gas Clearance Curve as a Method for Studying Regional Inhomogeneity of Alveolar Ventilation in the Lung

Respiration ◽  
1974 ◽  
Vol 31 (4) ◽  
pp. 310-317 ◽  
Author(s):  
M. Heise ◽  
H. Koppe ◽  
K. Schmidt
Keyword(s):  
Alveolar Ventilation ◽  
Inert Gas ◽  
Mathematical Treatment ◽  
Clearance Curve ◽  
Regional Inhomogeneity

Inert gas-exchange theory using an electric analogue

1964 ◽  
Vol 19 (6) ◽  
pp. 1193-1198 ◽  
Author(s):  
W. W. Mapleson
Keyword(s):  
Alveolar Ventilation ◽  
The Body ◽  
Exchange Theory ◽  
Inert Gases ◽  
Inert Gas ◽  
Respiratory Pattern ◽  
Whole Body ◽  
High Solubility ◽  
Systematic Analysis ◽  
Inhaled Anesthetics

When an inert gas of moderate or high solubility in blood is inhaled, the rate at which the alveolar concentration rises toward the inspired concentration increases as the inspired concentration is increased. The only previous systematic analysis of whole-body uptake of inert gases to allow for this effect was restricted to a single, artificial, respiratory pattern and the numerical calculations had to be made on a digital computer. This paper develops the theory for a range of respiratory patterns and shows how the computations may be made on a slightly modified form of a simple electric analogue. It is shown that the rate of saturation of the body increases less markedly with inspired concentration if the inspired alveolar ventilation, rather than the expired alveolar ventilation, is kept constant during the saturation process. Conversely, washout is more rapid with a constant inspired ventilation than with a constant expired ventilation. The theory is extended to show how the uptake of one inert gas may substantially affect the uptake of another, administered simultaneously. uptake, distribution and elimination; induction; recovery; drugs; inhaled anesthetics; nitrous oxide; diethyl ether; halothane; computers; ventilation; concentration effect; alveolar ventilation Submitted on February 13, 1964

Equation for inert gas exchange which treats ventilation as cyclic

1961 ◽  
Vol 16 (3) ◽  
pp. 531-537 ◽  
Author(s):  
Douglas S. Riggs ◽  
Avram Goldstein
Keyword(s):  
Gas Exchange ◽  
Lung Tissue ◽  
Complex Function ◽  
Fold Increase ◽  
Alveolar Ventilation ◽  
Inert Gas ◽  
Approach To Equilibrium ◽  
Constant Concentration ◽  
Practical Advantage ◽  
Residual Capacity

When a constant concentration of an inert gas is inhaled, the rate at which the equilibrium quantity of the gas in blood and tissues is approached depends upon many factors. In previous mathematical descriptions of this process, ventilation has been assumed to be continuous. In the present analysis, respiration is treated as cyclic, and an equation for the time needed to achieve any given proportion of equilibrium is derived. This equation is a complex function of eight variables. However, two of these, the functional residual capacity and the volume of lung tissue, are of negligible importance. Furthermore, an n-fold increase in rate of respiration has almost the same effect upon the calculated rate of approach to equilibrium as an n-fold increase in alveolar ventilation per breath. The assumption that ventilation is continuous is therefore a legitimate simplification, and the complex equation has no practical advantage over a much less intricate formulation. Submitted on October 13, 1960

Quantitative analysis of transpleural flux in the isolated lung

1997 ◽  
Vol 82 (2) ◽  
pp. 545-551 ◽  
Author(s):  
M. H. Li ◽  
J. Hildebrandt ◽  
M. P. Hlastala
Keyword(s):  
Gas Flow ◽  
Compartment Model ◽  
Alveolar Ventilation ◽  
Inert Gases ◽  
Inert Gas ◽  
Buffer Solution ◽  
Rabbit Lung ◽  
Isolated Lung ◽  
Wide Range ◽  
Single Compartment Model

Li, M. H., J. Hildebrandt, and M. P. Hlastala.Quantitative analysis of transpleural flux in the isolated lung. J. Appl. Physiol. 82(2): 545–551, 1997.—In this study, the loss of inert gas through the pleura of an isolated ventilated and perfused rabbit lung was assessed theoretically and experimentally. A mathematical model was used to represent an ideal homogeneous lung placed within a box with gas flow (V˙box) surrounding the lung. The alveoli are assumed to be ventilated with room air (V˙a) and perfused at constant flow (Q˙) containing inert gases ( x) with various perfusate-air partition coefficients (λp, x ). The ratio of transpleural flux of gas (V˙pl x ) to its total delivery to the lung via pulmonary artery (V˙ v), representing fractional losses across the pleura, can be shown to depend on four dimensionless ratios: 1) λp, x , 2) the ratio of alveolar ventilation to perfusion (V˙a/Q˙), 3) the ratio of the pleural diffusing capacity (Dpl x ) to the conductance of the alveolar ventilation (Dpl x /V˙aβg, where βg is the capacitance coefficient of gas), and 4) the ratio of extrapleural (box) ventilation to alveolar ventilation (V˙box/V˙a). Experiments were performed in isolated perfused and ventilated rabbit lungs. The perfusate was a buffer solution containing six dissolved inert gases covering the entire 105-fold range of λp, x used in the multiple inert gas elimination technique. Steady-state inert gas concentrations were measured in the pulmonary arterial perfusate, pulmonary venous effluent, exhaled gas, and box effluent gas. The experimental data could be described satisfactorily by the single-compartment model. It is concluded that a simple theoretical model is a useful tool for predicting transpleural flux from isolated lung preparations, with known ventilation and perfusion, for inert gases within a wide range of λ.

Reduction of lung perfusion increases VA/Q heterogeneity

1989 ◽  
Vol 66 (5) ◽  
pp. 2423-2430 ◽  
Author(s):  
J. Ohlsson ◽  
M. Middaugh ◽  
M. P. Hlastala
Keyword(s):  
Blood Flow ◽  
Standard Deviation ◽  
Lower Lobe ◽  
Lung Perfusion ◽  
Alveolar Ventilation ◽  
Left Lower Lobe ◽  
Inert Gas ◽  
Dispersion Index ◽  
Perfusion Rate ◽  
Anesthetized Dogs

This study addresses the hypothesis that decreases in lung perfusion rate independently worsen gas exchange efficiency in an isolated left lower lobe in zone 2 conditions. In seven anesthetized dogs, the left lower lobe was isolated, leaving the bronchus and bronchial vasculature intact. Blood was taken from the femoral arteries and reinfused at a controlled rate into the pulmonary artery of the left lower lobe. The flow rate was varied between 100 and 400 ml/min. The multiple inert gas elimination technique was used to quantitate the matching of ventilation to perfusion. Reduction in lobe blood flow resulted in a significant increase in perfusion-related indexes of alveolar ventilation-perfusion heterogeneity, such as the log standard deviation of the perfusion distribution, the retention component of the arterial-alveolar difference area, and the retention dispersion index. The increased heterogeneity suggests a worsening of the intraregional matching between the ventilation and the perfusion when perfusion is less than normal.

Fission Gas Bubbles in Fractured UO2

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.

Inert-gas crystals with imbedded impurities

1978 ◽  
Vol 125 (6) ◽  
pp. 331-349 ◽  
Author(s):  
Boris M. Smirnov
Keyword(s):  
Inert Gas
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