Soluble gas exchange in the pulmonary airways of sheep

Schimmel, Carmel; Bernard, Susan L.; Anderson, Joseph C.; Polissar, Nayak L.; Lakshminarayan, S.; Hlastala, Michael P.

doi:10.1152/japplphysiol.01272.2003

Cited by 16 publications

(9 citation statements)

References 17 publications

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“…These include inhibition of protein kinase C, calcium release from sarcoplasmic reticulum, and voltage-dependent calcium channels [37-39]. In vivo , such mechanisms require that the anesthetic diffuse from lumen through the airway wall to reach the smooth muscle layer [40,41], as shown in Figure 1. This process is mediated by the relative partition coefficients for these agents, with a larger ratio between airway smooth muscle and gas indicating a greater likelihood of diffusion from airway lumen to ASM [41].…”

Section: Bronchodilation With Volatile Anestheticsmentioning

confidence: 99%

Volatile anesthetics and the treatment of severe bronchospasm: a concept of targeted delivery

Mondoñedo

McNeil

Amin

et al. 2015

Drug Discovery Today: Disease Models

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Status asthmaticus (SA) is a severe, refractory form of asthma that can result in rapid respiratory deterioration and death. Treatment of SA with inhaled anesthetics is a potentially life-saving therapy, but remarkably few data are available about its mechanism of action or optimal administration. In this paper, we will review the clinical use of inhaled anesthetics for treatment of SA, the potential mechanisms by which they dilate constricted airways, and the side effects associated with their administration. We will also introduce the concept of ‘targeted’ delivery of these agents to the conducting airways, a process which may maximize their therapeutic effects while minimizing associated systemic side effects. Such a delivery regimen has the potential to define a rapidly translatable treatment paradigm for this life-threatening disorder.

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Section: Bronchodilation With Volatile Anestheticsmentioning

confidence: 99%

Volatile anesthetics and the treatment of severe bronchospasm: a concept of targeted delivery

Mondoñedo

McNeil

Amin

et al. 2015

Drug Discovery Today: Disease Models

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“…Experimentally, increases in bronchial blood flow in excised and whole animal preparations 38,43 produce increases in soluble gas elimination. Theoretical calculations 1,5,19 align with these experimental findings.…”

Section: Methodsmentioning

confidence: 99%

“…Because neither argument has been proven conclusively, an experimental investigation was performed to directly assess this assumption. That study used a novel aortic pouch preparation to alter bronchial blood flow (a major factor in airway gas exchange) and demonstrated that changes in bronchial blood flow affected the excretion of highly blood-soluble gases (e.g., ether and acetone) more than low blood-soluble gases (e.g., SF 6 and ether) 38 . But this study could not conclusively resolve the effect of airway gas exchange on MIGET.…”

Section: Introductionmentioning

confidence: 99%

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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“…Then, this dissolved fraction flows to the lower digestive tract where it is absorbed into the blood or passed out with the faecal material. Studies have reported diffusion of SF 6 into the lungs from venous blood (Schimmel et al, 2004), suggesting that SF 6 absorption takes places from the digestive tract. As long as the SF 6 is excreted via the breath and not stored in the body, this route of excretion per se could not be responsible for the association between RR of SF 6 and the CH 4 emission estimates.…”

Section: Sf 6 Tracer Technique and Ch 4 Emission Estimatesmentioning

confidence: 99%

Effect of release rate of the SF6 tracer on methane emission estimates based on ruminal and breath gas samples

Martin

Koolaard

Rochette

et al. 2012

Animal

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The release rate (RR) of sulphur hexafluoride (SF 6 ) gas from permeation tube in the rumen appears to be positively related with methane (CH 4 ) emissions calculated using the SF 6 tracer technique. Gas samples of breath and ruminal headspace were collected simultaneously in order to evaluate the hypothesis that transactions of SF 6 in the rumen are the source for this relationship. Six non-lactating dairy cows fitted with rumen cannulae were subdivided into two groups and randomly assigned to a two-period crossover design to permeation tubes with low RR (LRR 5 1.577 mg/day) or two-times higher RR (HRR 5 3.147 mg/day) RR. The cows were fed limited amounts of maize silage (80% ad libitum) split into two meals (40% at 0800 h and 60% at 1600 h). Each period consisted of 3-day gas sampling. Immediately before the morning feed and then each hour over 8 h, ruminal gas samples (50 ml) were withdrawn through the cannula fitted with stoppers to prevent opening. Simultaneously, 8-h integrated breath gas samples were collected over the same period. Ratios of concentration of CH 4 /SF 6 , CO 2 /SF 6 and CO 2 /CH 4 and emission estimates of CH 4 and CO 2 were calculated for each sample source using the SF 6 tracer technique principles. The LRR treatment yielded higher (P , 0.001) ruminal CH 4 /SF 6 (by 1.79 times) and CO 2 /SF 6 (by 1.90 times) ratios than the HRR treatment; however, these differences were lower than the 2.0 times difference expected from the RR between the LRR and HRR. Consequently, the LRR treatment was associated with lower (P , 0.01) ruminal emissions of CH 4 over the 8-h collection period than with the HRR treatment (111%), a difference also confirmed by the breath samples (111%). RR treatments did not differ (P 5 0.53) in ruminal or breath CO 2 emissions; however, our results confirm that the SF 6 tracer seems inappropriate for CO 2 emissions estimation in ruminants. Irrespective of the RR treatment, breath samples yielded 8% to 9% higher CH 4 emission estimates than the ruminal samples (P 5 0.01). The relationship between rumen and breath sources for CH 4 emissions was better for LRR than for HRR treatment, suggesting that tracer performance decreases with the highest RR of SF 6 tested in our study (3.1 mg/day). A hypothesis is discussed with regard to the mechanism responsible for the relationship between RR and CH 4 emission estimates. The use of permeation tubes with small range in RR is recommended in animal experiments to decrease variability in CH 4 emission estimates using the SF 6 tracer technique.Keywords: SF 6 tracer, permeation rate, methane, breath, ruminal gas ImplicationsThe sulphur hexafluoride (SF 6 ) tracer technique is a method of choice to estimate individual methane (CH 4 ) emissions from large groups of animals under production conditions such as grazing. However, the CH 4 emissions estimates appear related to the SF 6 release rate (RR) in the rumen. This suggests the need to use permeation tubes with a small range in RR in animal experiments, and that the RR is balanced across t...

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Soluble gas exchange in the pulmonary airways of sheep

Cited by 16 publications

References 17 publications

Volatile anesthetics and the treatment of severe bronchospasm: a concept of targeted delivery

Volatile anesthetics and the treatment of severe bronchospasm: a concept of targeted delivery

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

Effect of release rate of the SF6 tracer on methane emission estimates based on ruminal and breath gas samples

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