Analysis of factors affecting gas exchange in intravascular blood gas exchanger

1994 ◽  
Vol 77 (4) ◽  
pp. 1716-1730 ◽  
Author(s):  
S. C. Niranjan ◽  
J. W. Clark ◽  
K. Y. San ◽  
J. B. Zwischenberger ◽  
A. Bidani
Keyword(s):  
Gas Exchange ◽  
Hollow Fiber ◽  
Gas Flow ◽  
Coaxial Cylinder ◽  
Co2 Removal ◽  
Transfer Resistance ◽  
Factors Affecting ◽  
Unit Structure ◽  
Alternating Direction ◽  
Flow Through

A mathematical model of an intravascular hollow-fiber gas-exchange device, called IVOX, has been developed using a Krogh cylinder-like approach with a repeating unit structure comprised of a single fiber with gas flowing through its lumen surrounded by a coaxial cylinder of blood flowing in the opposite direction. Species mass balances on O2 and CO2 result in a nonlinear coupled set of convective-diffusion parabolic partial differential equations that are solved numerically using an alternating-direction implicit finite-difference method. Computed results indicated the presence of a large resistance to gas transport on the external (blood) side of the hollow-fiber exchanger. Increasing gas flow through the device favored CO2 removal from but not O2 addition to blood. Increasing blood flow over the device favored both CO2 removal as well as O2 addition. The rate of CO2 removal increased linearly with the transmural PCO2 gradient imposed across the device. The effect of fiber crimping on blood phase mass transfer resistance was evaluated indirectly by varying species blood diffusivity. Computed results indicated that CO2 excretion by IVOX can be significantly enhanced with improved bulk mixing of vena caval blood around the IVOX fibers.

Constant-flow ventilation in pigs

1986 ◽  
Vol 61 (6) ◽  
pp. 2238-2242 ◽  
Author(s):  
P. Webster ◽  
A. S. Menon ◽  
A. S. Slutsky
Keyword(s):  
Steady State ◽  
Gas Exchange ◽  
Gas Flow ◽  
Blood Gases ◽  
Maximum Flow ◽  
Constant Flow ◽  
Catheter Position ◽  
Flow Rates ◽  
Co2 Partial Pressure ◽  
Flow Through

Constant-flow ventilation (CFV) is a ventilatory technique in which physiological blood gases can be maintained in dogs by a constant flow of fresh gas introduced via two catheters placed in the main-stem bronchi (J. Appl. Physiol. 53: 483–489, 1982). High-velocity gas exiting from the catheters can create uneven pressure differences in adjacent lung segments, and these pressure differences could lead to gas flow through collateral channels. To examine this hypothesis, we studied CFV in pigs, animals known to have a high resistance to collateral ventilation. In three pigs we examined steady-state gas exchange, and in six others we studied unsteady gas exchange at three flow rates (20, 35, and 50 l/min) and three catheter positions (0.5, 1.5, and 2.5 cm distal to the tracheal carina). During steady-state runs we were unable to attain normocapnia; the arterial CO2 partial pressure (PaCO2) was approximately 300 Torr at all flow rates and all catheter positions, compared with 20–50 Torr at similar flows and positions in dogs studied previously. The initial unsteady gas-exchange experiments indicated no consistent effect of catheter position or flow rate on the rate of rise of PaCO2. In three other pigs, the rates of rise of PaCO2 were compared with the rates observed with apneic oxygenation (AO). At the maximum flow and deepest position, the rate of rise of PaCO2 was lower during CFV than during AO. These data suggest that flow through collateral channels might be important in producing adequate gas transport during CFV; however, other factors such as airway morphometry and the effects of cardiogenic oscillations may explain the differences between the results in pigs and dogs.

scholarly journals Diffusivity of CO2 and Water Vapors in `Gala' and `Granny Smith' Apples

HortScience ◽  
1996 ◽  
Vol 31 (4) ◽  
pp. 590b-590
Author(s):  
Theophanes Solomos ◽  
John C. Bouwkamp
Keyword(s):  
Diffusion Coefficient ◽  
Gas Exchange ◽  
Gas Flow ◽  
Prolonged Storage ◽  
Water Vapors ◽  
Flow Through

Previous observations have shown that the diffusivity of water vapors is much larger than the value that is predicted theoretically from the magnitude of the diffusion coefficient of CO2, C2H4, or both. This has been ascribed to the ability of water to diffuse through the cuticle and to the transport of water via the capillaries of cellulase micorfibrels to the surface of the lenticels, where it evaporates. We measured the diffusivity of CO2 in `Gala' and `Granny Smith' apples. The former are more permeable to CO2 than the latter cultivar, in particular after prolonged storage at 2°C. The diffusivity of H2O was 10- to 20-fold larger than that of CO2. Furthermore, the ratio of D(H2O)/D(CO2) was similar for both cultivars. Infiltration of dyes and gas flow through apples submerged in water show that in `Gala' apples, the number of open lenticels is larger than in `Granny Smith'. Thus, the data indicate that lenticels are the main avenue of gas exchange in apples.

INVESTIGATION OF THE TIME OF GAS FLOW THROUGH A HOLE IN LONG PIPELINES UNDER HIGH PRESSURE

2020 ◽  
Vol 58 (1) ◽  
pp. 30-43
Author(s):  
N.D. Yakimov ◽  
◽  
A.I. Khafizova ◽  
N.D. Chichirova ◽  
O.S. Dmitrieva ◽  
...  
Keyword(s):  
High Pressure ◽  
Gas Flow ◽  
Flow Through

Free area for gas flow through sieve plates with a bubbled bed

1975 ◽  
Vol 40 (11) ◽  
pp. 3315-3318 ◽  
Author(s):  
M. Rylek ◽  
F. Kaštánek ◽  
L. Nývlt ◽  
J. Kratochvíl
Keyword(s):  
Gas Flow ◽  
Flow Through ◽  
Sieve Plates ◽  
Free Area

scholarly journals A Study on Liquid Leak Rates in Packing Seals

2021 ◽  
Vol 11 (4) ◽  
pp. 1936
Author(s):  
Abdel-Hakim Bouzid
Keyword(s):  
Environmental Protection ◽  
Liquid Flow ◽  
Environmental Protection Agency ◽  
Gas Flow ◽  
Outer Boundary ◽  
Health And Safety ◽  
Toxic Substances ◽  
Packing Materials ◽  
Thickness Change ◽  
Flow Through

The accurate prediction of liquid leak rates in packing seals is an important step in the design of stuffing boxes, in order to comply with environmental protection laws and health and safety regulations regarding the release of toxic substances or fugitive emissions, such as those implemented by the Environmental Protection Agency (EPA) and the Technische Anleitung zur Reinhaltung der Luft (TA Luft). Most recent studies conducted on seals have concentrated on the prediction of gas flow, with little to no effort put toward predicting liquid flow. As a result, there is a need to simulate liquid flow through sealing materials in order to predict leakage into the outer boundary. Modelling of liquid flow through porous packing materials was addressed in this work. Characterization of their porous structure was determined to be a key parameter in the prediction of liquid flow through packing materials; the relationship between gland stress and leak rate was also acknowledged. The proposed methodology started by conducting experimental leak measurements with helium gas to characterize the number and size of capillaries. Liquid leak tests with water and kerosene were then conducted in order to validate the predictions. This study showed that liquid leak rates in packed stuffing boxes could be predicted with reasonable accuracy for low gland stresses. It was found that internal pressure and compression stress had an effect on leakage, as did the thickness change and the type of fluid. The measured leak rates were in the range of 0.062 to 5.7 mg/s for gases and 0.0013 and 5.5 mg/s for liquids.

scholarly journals On factors affecting surface free energy of carbon black for reinforcing rubber

2020 ◽  
Vol 9 (1) ◽  
pp. 170-181 ◽  
Author(s):  
Shangyong Zhang ◽  
Ruipeng Zhong ◽  
Ruoyu Hong ◽  
David Hui
Keyword(s):  
Free Energy ◽  
Carbon Black ◽  
Surface Free Energy ◽  
Surface Activity ◽  
Gas Flow ◽  
Influential Factors ◽  
Chromatographic Column ◽  
Factors Affecting ◽  
Carrier Gas Flow

AbstractThe surface activity of carbon black (CB) is an important factor affecting the reinforcement of rubber. The quantitative determination of the surface activity (surface free energy) of CB is of great significance. A simplified formula is obtained to determine the free energy of CB surface through theoretical analysis and mathematical derivation. The surface free energy for four kinds of industrial CBs were measured by inverse gas chromatography, and the influential factors were studied. The results showed that the aging time of the chromatographic column plays an important role in accurate measurement of the surface free energy of CB, in comparison with the influences from the inlet pressure and carrier gas flow rate of the chromatographic column filled with CB. Several kinds of industrial CB were treated at high temperature, and the surface free energy of CB had a significant increase. With the increase of surface free energy, the maximum torque was decreased significantly, the elongation at break tended to increase, the heat generation of vulcanizates was increased, and the wear resistance was decreased.

scholarly journals Applying a Hydrophilic Modified Hollow Fiber Membrane to Reduce Fouling in Artificial Lungs

Separations ◽  
2021 ◽  
Vol 8 (8) ◽  
pp. 113
Author(s):  
Nawaf Alshammari ◽  
Meshari Alazmi ◽  
Vajid Nettoor Veettil
Keyword(s):  
Gas Exchange ◽  
Hollow Fiber ◽  
Hollow Fiber Membrane ◽  
Membrane Surface ◽  
Artificial Lung ◽  
Hollow Fiber Membranes ◽  
Fiber Membrane ◽  
Hydrophilic Modification ◽  
Protein Fouling ◽  
Time Periods

Membranes for use in high gas exchange lung applications are riddled with fouling. The goal of this research is to create a membrane that can function in an artificial lung until the actual lung becomes available for the patient. The design of the artificial lung is based on new hollow fiber membranes (HFMs), due to which the current devices have short and limited periods of low fouling. By successfully modifying membranes with attached peptoids, low fouling can be achieved for longer periods of time. Hydrophilic modification of porous polysulfone (PSF) membranes can be achieved gradually by polydopamine (PSU-PDA) and peptoid (PSU-PDA-NMEG5). Polysulfone (PSU-BSA-35Mg), polysulfone polydopamine (PSUPDA-BSA-35Mg) and polysulfone polydopamine peptoid (PSU-PDA-NMEG5-BSA35Mg) were tested by potting into the new design of gas exchange modules. Both surfaces of the modified membranes were found to be highly resistant to protein fouling permanently. The use of different peptoids can facilitate optimization of the low fouling on the membrane surface, thereby allowing membranes to be run for significantly longer time periods than has been currently achieved.

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