Series dead space for inert gases in healthy subjects

Guénard, H.; Manier, G.; Castaing, Y.; Varene, N.

doi:10.1007/bf00589250

Cited by 5 publications

(2 citation statements)

References 6 publications

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“…In figure 2. t.~e e1evated values of the exchange ratio at the beginning of expiration should reflect tpe yery high but non-infinite value of series dead space VA/Q ratio [24].…”

Section: Resultsmentioning

confidence: 98%

Estimates of mean alveolar gas in patients with chronic airways obstruction

Giannella-Neto¹,

Paoletti²,

Fornai³

et al. 1989

Eur Respir J

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Alveolar to arterial differences (AaD) may be computed from representative alveolar gas pressures (PA). These are particularly difficult to obtain in patients with chronic airways obstruction (CAO) and severe inhomogeneity of the ventilation/perfusion (VA/Q) ratio. In 25 such patients, using a computerized mass spectrometer, representative values of alveolar gas were obtained: 1. as end-tidal concentrations (ET); 2. using the alveolar air equation with PACO2 derived from Bohr's equation (BE); 3. putting PACO2 = PACO2 into the alveolar air equation to compute ideal O2 alveolar pressure (ID); 4. applying Rahn's definition of "mean" alveolar gas (RD), i.e. taking within each jth breath, the alveolar pressures corresponding to the moment when the instantaneous gas exchange ratio R(t)j equals the overall exchange ratio for that breath Rj. During quiet breathing, the point where R(t)j equals Rj occurred at 71% of tidal volume (VT). Alveolar pressures by BE and RD resulted in similar values (115.5 +/- 6.9 and 115.5 +/- 6.6 mmHg for O2 and 30.3 +/- 5.7 and 30.8 +/- 5.7 mmHg for CO2, respectively), but they were significantly different from those by ET and ID (106.2 +/- 9.5 and 95.6 +/- 13.5 mmHg for O2 and 36.3 +/- 7.7 and 48.2 +/- 11.2 mmHg for CO2, respectively). These findings may be explained considering that PA(BE) and PA(RD) represent both high and low VA/Q units, whereas PA(ET) and PA(ID) represent mainly low VA/Q units. AaDCO2 by RD and BE appeared proportional to the severity of CAO as estimated from VT. Automated techniques make it possible to substitute end-tidal determinations with more accurate estimates either by measuring anatomical dead-space and using Bohr's equation or by applying Rahn's definition.

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“…In figure 2. t.~e e1evated values of the exchange ratio at the beginning of expiration should reflect tpe yery high but non-infinite value of series dead space VA/Q ratio [24].…”

Section: Resultsmentioning

confidence: 98%

Estimates of mean alveolar gas in patients with chronic airways obstruction

Giannella-Neto¹,

Paoletti²,

Fornai³

et al. 1989

Eur Respir J

View full text Add to dashboard Cite

show abstract

“…The arguments contesting this assumption are more diffuse but integrate both experimental and theoretical results. In some experimental studies, the excretion of acetone in relation to ether does not follow the MIGET predicted trend 9,12,55 and dead space as predicted by inert gases decreases as the blood solubility increases 20,41 . Additionally, theoretical studies showed that acetone exchanges predominately within the airways during tidal breathing and these predictions were used to explain inert gas data from humans and dogs 1,56 .…”

Section: Introductionmentioning

confidence: 83%

Impact of Airway Gas Exchange on the Multiple Inert Gas Elimination Technique: Theory

Anderson

Hlastala

2010

Ann Biomed Eng

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The multiple inert gas elimination technique (MIGET) provides a method for estimating alveolar gas exchange efficiency. Six soluble inert gases are infused into a peripheral vein. Measurements of these gases in breath, arterial blood, and venous blood are interpreted using a mathematical model of alveolar gas exchange (MIGET model) that neglects airway gas exchange. A mathematical model describing airway and alveolar gas exchange predicts that two of these gases, ether and acetone, exchange primarily within the airways. To determine the effect of airway gas exchange on the MIGET, we selected two additional gases, toluene and m-dichlorobenzene, that have the same blood solubility as ether and acetone and minimize airway gas exchange via their low water solubility. The airway-alveolar gas exchange model simulated the exchange of toluene, m-dichlorobenzene, and the six MIGET gases under multiple conditions of alveolar ventilation-to-perfusion, V̇A/Q̇, heterogeneity. We increased the importance of airway gas exchange by changing bronchial blood flow, Q̇br. From these simulations, we calculated the excretion and retention of the eight inert gases and divided the results into two groups: 1) the standard MIGET gases which included acetone and ether and 2) the modified MIGET gases which included toluene and m-dichlorobenzene. The MIGET mathematical model predicted distributions of ventilation and perfusion for each grouping of gases and multiple perturbations of V̇A/Q̇ and Q̇br. Using the modified MIGET gases, MIGET predicted a smaller dead space fraction, greater mean V̇A, greater log(SDVA), and more closely matched the imposed V̇A distribution than that using the standard MIGET gases. Perfusion distributions were relatively unaffected.

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Inert Gas Transport in Blood and Tissues

Baker

Farmery

2011

Comprehensive Physiology

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This article establishes the basic mathematical models and the principles and assumptions used for inert gas transfer within body tissues-first, for a single compartment model and then for a multicompartment model. From these, and other more complex mathematical models, the transport of inert gases between lungs, blood, and other tissues is derived and compared to known experimental studies in both animals and humans. Some aspects of airway and lung transfer are particularly important to the uptake and elimination of inert gases, and these aspects of gas transport in tissues are briefly described. The most frequently used inert gases are those that are administered in anesthesia, and the specific issues relating to the uptake, transport, and elimination of these gases and vapors are dealt with in some detail showing how their transfer depends on various physical and chemical attributes, particularly their solubilities in blood and different tissues. Absorption characteristics of inert gases from within gas cavities or tissue bubbles are described, and the effects other inhaled gas mixtures have on the composition of these gas cavities are discussed. Very brief consideration is given to the effects of hyper- and hypobaric conditions on inert gas transport.

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Series dead space for inert gases in healthy subjects

Cited by 5 publications

References 6 publications

Estimates of mean alveolar gas in patients with chronic airways obstruction

Estimates of mean alveolar gas in patients with chronic airways obstruction

Impact of Airway Gas Exchange on the Multiple Inert Gas Elimination Technique: Theory

Inert Gas Transport in Blood and Tissues

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