scholarly journals Elucidating the roles of solubility and ventilation-perfusion mismatch in the second gas effect using a two-step model of gas exchange

2020 ◽  
Vol 128 (6) ◽  
pp. 1587-1593
Author(s):  
Ben Korman ◽  
Ranjan K. Dash ◽  
Philip J. Peyton
Keyword(s):  
Gas Exchange ◽  
Theoretical Analysis ◽  
Constant Volume ◽  
Gas Solubility ◽  
Gas Uptake ◽  
Volume Correction ◽  
Step Model ◽  
Gas Effect

Gas exchange in the lung can always be represented as the sum of two components: gas exchange at constant volume followed by gas exchange on volume correction. Using this sequence to study the second gas effect, low gas solubility and increased ventilation-perfusion mismatch are shown to act together to enhance second gas uptake. While appearing to contravene classical concepts of gas exchange, a detailed theoretical analysis shows it is fully consistent with these concepts.

Importance of oscillations in alveolar gas concentrations in the analysis of rebreathing data

1986 ◽  
Vol 61 (3) ◽  
pp. 1104-1113 ◽  
Author(s):  
K. H. Weisiger ◽  
G. D. Swanson
Keyword(s):  
Time Course ◽  
Continuous Process ◽  
Inert Gases ◽  
Accurate Estimation ◽  
Gas Solubility ◽  
Estimation Errors ◽  
Gas Uptake ◽  
Cyclic Model ◽  
Low Solubility ◽  
Cyclic Data

Cyclic rebreathing of a soluble inert gas can be used to estimate lung tissue volume (Vt) and pulmonary blood flow (Qc). A recently proposed method for analyzing such cyclic data (Respir. Physiol. 48: 255–279, 1982) mathematically assumes that ventilation is a continuous process. However, neglecting the cyclic nature of ventilation may prevent the accurate estimation of Vt and Qc. We evaluated this possibility by simulating the uptake of soluble inert gases during rebreathing using a cyclic model of gas exchange. Under cyclic uptake conditions alveolar gases follow an oscillating time course, because gas concentrations tend to increase during inspiration and to decrease during expiration. We found that neglecting these alveolar gas oscillations leads to the underestimation of soluble gas uptake by blood, particularly during the early rebreathing breaths. When continuous ventilation is assumed Vt and Qc are overestimated unless rapid rebreathing rates, large tidal volumes, and gases of moderately low solubility are used. Under these conditions the amplitude of the cyclic oscillations is minimized, the alveolar time course more closely resembles that expected from continuous ventilation, and the resulting errors are minimized. Alternatively, when the effect of oscillating alveolar gas concentrations on mass transfer are considered, these estimation errors can be eliminated without restricting rebreathing rate or gas solubility. We conclude that failure to consider the effect of cyclic rebreathing on the time course of alveolar gas concentrations may result in significant errors when evaluating rebreathing data for Vt and Qc.

Breath-by-breath variation of FRC: effect on VO2 and VCO2 measured at the mouth

1979 ◽  
Vol 46 (6) ◽  
pp. 1122-1126 ◽  
Author(s):  
H. U. Wessel ◽  
R. L. Stout ◽  
C. K. Bastanier ◽  
M. H. Paul
Keyword(s):  
Steady State ◽  
Gas Exchange ◽  
Gas Flow ◽  
Co2 Gas ◽  
Mean Values ◽  
Gas Uptake ◽  
Source Data ◽  
Alveolar Level ◽  
Age Range

We examined breath-by-breath (B-B) variations of FRC (delta FRC) and their effect on measured O2 and CO2 gas exchange in 52 2- to 4-min segments of continuous air breathing obtained in 29 patients (age range 6--50 yr). Respiratory frequency ranged from 13 to 43 breaths/min, VE from 6.7 to 22.5 l/min (BTPS), and expired VT from 234 to 1,370 ml (BTPS). Computer analysis was based on the following source data measured at the mouth: inspired (VI) and expired (VE) gas flow, FN2, FO2 and FCO2. The analysis provides B-B evaluation of VI, VE, delta FRC in terms of VN2, and VO2 and VCO2 at the mouth and at the alveolar level, i.e., after correction for delta FRC. Significant B-B variations of FRC were found in all studies. delta FRC ranged from +360 to -360 ml (BTPS). For single respiratory cycles VI - VE is primarily a function of N2 exchange at the mouth (VMN2). VO2 and VCO2, uncorrected for delta FRC, are significantly more dispersed about mean values than the corrected gas uptakes (P less than 0.0005). The data support the view that the assumption of VIN2 = VEN2 is invalid for single respiratory cycles. Determination of breath-by-breath VO2 and VCO2 should therefore, not be based on steady-state gas uptake equations. It requires measurement of both inspired and expired breath volumes and evaluation of N2 gas exchange.

Intertissue diffusion effect for inert fat-soluble gases

1965 ◽  
Vol 20 (4) ◽  
pp. 621-627 ◽  
Author(s):  
William Perl ◽  
Herbert Rackow ◽  
Ernest Salanitre ◽  
Gerald L. Wolf ◽  
Robert M. Epstein
Keyword(s):  
Adipose Tissue ◽  
Gas Exchange ◽  
Human Subjects ◽  
Compartment Model ◽  
Inert Gases ◽  
Gas Uptake ◽  
Model Generalization ◽  
Capillary Exchange ◽  
Uptake Measurement ◽  
Kinetics Of

An approximately constant 5% difference in alveolar concentration of nitrous oxide and cyclopropane exists when these two gases are administered simultaneously to human subjects. This difference in uptake cannot be fully explained within the traditional framework of a perfusion-limited, multi-compartment model of inert gas exchange. It is proposed that this difference reflects direct diffusion from lean to neighboring adipose tissue through distances of the order of 1 mm. The diffusional rate of cyclopropane uptake into adipose tissue is initially large relative to perfusional uptake. The two rates eventually become and remain comparable as both decrease to zero. Implications of these results for deduction of blood flow to body adipose tissue by gas uptake measurement, and for utilization of capillary exchange surface by fat-soluble gases in adipose tissue are discussed. compartment model generalization; gas uptake in body; inert, fat-soluble gas uptake; kinetics of gas exchange in body; body uptake of inert gases; fat-soluble gas uptake; distribution kinetics of gases in body Submitted on February 3, 1964

Kinetics of absorption atelectasis during anesthesia: a mathematical model

1999 ◽  
Vol 86 (4) ◽  
pp. 1116-1125 ◽  
Author(s):  
C. J. Joyce ◽  
A. B. Williams
Keyword(s):  
Mathematical Model ◽  
Gas Exchange ◽  
Main Parameter ◽  
Important Determinant ◽  
Gas Absorption ◽  
Gas Composition ◽  
Gas Uptake ◽  
Lung Compartment ◽  
Combined Models ◽  
Kinetics Of

Recent computed tomography studies show that inspired gas composition affects the development of anesthesia-related atelectasis. This suggests that gas absorption plays an important role in the genesis of the atelectasis. A mathematical model was developed that combined models of gas exchange from an ideal lung compartment, peripheral gas exchange, and gas uptake from a closed collapsible cavity. It was assumed that, initially, the lung functioned as an ideal lung compartment but that, with induction of anesthesia, the airways to dependent areas of lung closed and these areas of lung behaved as a closed collapsible cavity. The main parameter of interest was the time the unventilated area of lung took to collapse; the effects of preoxygenation and of different inspired gas mixtures during anesthesia were examined. Preoxygenation increased the rate of gas uptake from the unventilated area of lung and was the most important determinant of the time to collapse. Increasing the inspired O2 fraction during anesthesia reduced the time to collapse. Which inert gas (N2 or N2O) was breathed during anesthesia had minimal effect on the time to collapse.

The Separation of Light Gaseous Isotopes by Mass Diffusion Columns II

1964 ◽  
Vol 19 (6) ◽  
pp. 747-755
Author(s):  
W. J. De Wet ◽  
J. Los
Keyword(s):  
Theoretical Analysis ◽  
Mass Diffusion ◽  
Experimental Results ◽  
The Other ◽  
Countercurrent Flow ◽  
Gas Solubility ◽  
Flow Rates ◽  
Mixing Effects ◽  
Other Hand ◽  
Good Agreement

The design of mass diffusion columns operated with partition membranes, for the separation of light gaseous isotopes, is discussed. A theoretical analysis of experimental results obtained indicates that a good agreement between experimental results and theory is only obtained at low column pressures and moderate countercurrent flow rates. At fairly low countercurrent flow rates mixing effects due to viscous dragging and gas solubility by the condensate appear to be considerable whereas excessively high countercurrent flow rates, on the other hand, also seem undesirable. Some suggestions are proposed to obviate impairing effects at least to some extent.

Improving the Performance of a Crankcase-Scavenged Two-Stroke Engine with a Fluid Diode

1982 ◽  
Vol 196 (1) ◽  
pp. 23-34 ◽  
Author(s):  
E Sher
Keyword(s):  
Theoretical Model ◽  
Gas Exchange ◽  
Theoretical Analysis ◽  
Exchange Process ◽  
Engine Performance ◽  
Delivery Ratio ◽  
Engine Torque ◽  
Model Equations ◽  
Gas Exchange Process ◽  
Stroke Engine

A fluid diode was installed at the inlet port of a crankcase-scavenged two-stroke engine. Experiments on the fired engine showed that the engine torque was significantly improved at low engine speeds. A theoretical model to simulate the gas exchange process, including the flow inside the diode, was developed. The model equations were solved numerically. Theoretical analysis showed that with the diode, backflow was prevented, the delivery ratio was increased and the scavenging mechanism and efficiency were improved. It was concluded that a further improvement in engine performance may be achieved by installing an additional fluid diode at the scavenge port.

Metabolic gas effect on phase III slopes of single-breath nitrogen tests

1982 ◽  
Vol 53 (3) ◽  
pp. 789-792 ◽  
Author(s):  
Y. Cormier ◽  
J. Belanger
Keyword(s):  
Gas Exchange ◽  
Respiratory Quotient ◽  
Phase Iii ◽  
Normal Volunteers ◽  
Single Breath ◽  
Relative Contribution ◽  
The Mean ◽  
R Value ◽  
Gas Effect

This study was designed to estimate the relative contribution of gas exchange to the slope of phase III and the mean respiratory quotient (R) during this maneuver. With eight normal volunteers, we studied single-breath nitrogen tests and single-breath reversed tests (SB-N2, SB-R) without and with CO2 added to the test inspiration (SB-N2CO2, SB-RCO2). With an inspired CO2 of about 6% the slope of phase III in SB-N2 and SB-N2CO2 increased from 0.87 +/- 0.24 (mean +/- SD) to 1.03 +/- 0.21% N2.l-1 (P less than 0.01); however, in SB-R an SB-RCO2 the steepness of the slope of phase III decreased from 0.65 +/- 0.13% to 0.50 +/- 0.14% N2.l-1 (P less than 0.01). From these data we can calculate that gas exchange accounted for 13% of the slope of phase III in SB-N2 and SB-R. The mean R value during the slope of phase III for this effect was between 0.6 and 0.7. R was further decreased when CO2 was added, and its influence was increased to 26% of the slope of phase III.

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