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Multiple inert gas elimination technique by micropore membrane inlet mass spectrometry-a comparison with reference gas chromatography
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Anaesthesiology and Intensive Care.
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2013 (English)In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 115, no 8, 1107-1118 p.Article in journal (Refereed) Published
Abstract [en]

The mismatching of alveolar ventilation and perfusion (V-A/Q) is the major determinant of impaired gas exchange. The gold standard for measuring V-A/Q distributions is based on measurements of the elimination and retention of infused inert gases. Conventional multiple inert gas elimination technique (MIGET) uses gas chromatography (GC) to measure the inert gas partial pressures, which requires tonometry of blood samples with a gas that can then be injected into the chromatograph. The method is laborious and requires meticulous care. A new technique based on micropore membrane inlet mass spectrometry (MMIMS) facilitates the handling of blood and gas samples and provides nearly real-time analysis. In this study we compared MIGET by GC and MMIMS in 10 piglets: 1) 3 with healthy lungs; 2) 4 with oleic acid injury; and 3) 3 with isolated left lower lobe ventilation. The different protocols ensured a large range of normal and abnormal V-A/Q distributions. Eight inert gases (SF6, krypton, ethane, cyclopropane, desflurane, enflurane, diethyl ether, and acetone) were infused; six of these gases were measured with MMIMS, and six were measured with GC. We found close agreement of retention and excretion of the gases and the constructed V-A/Q distributions between GC and MMIMS, and predicted Pa-O2 from both methods compared well with measured Pa-O2. V-A/Q by GC produced more widely dispersed modes than MMIMS, explained in part by differences in the algorithms used to calculate V-A/Q distributions. In conclusion, MMIMS enables faster measurement of V-A/Q, is less demanding than GC, and produces comparable results.

Place, publisher, year, edition, pages
2013. Vol. 115, no 8, 1107-1118 p.
Keyword [en]
MIGET, ventilation/perfusion distributions, inert gases, mass spectrometry, membrane inlet, gas chromatography
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-210589DOI: 10.1152/japplphysiol.00072.2013ISI: 000325869400001OAI: oai:DiVA.org:uu-210589DiVA: diva2:663308
Available from: 2013-11-11 Created: 2013-11-11 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Ventilation/Perfusion Matching and its Effect on Volatile Pharmacokinetics
Open this publication in new window or tab >>Ventilation/Perfusion Matching and its Effect on Volatile Pharmacokinetics
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The mismatching of alveolar ventilation and perfusion (VA/Q) is the major determinant of impaired gas exchange. The gold standard for analyzing VA/Q distribution is the multiple inert gas elimination technique (MIGET), conventionally based on gas chromatography (GC), and, although simple in principle, a technically demanding procedure limiting its use. A new technique based on micropore membrane inlet mass spectrometry (MMIMS) combined MIGET with mass spectrometry, simplifying the sample handling process, and potentially providing VA/Q distributions for a general clinical approach.

The kinetics of volatile anesthetics are well known in patients with healthy lungs. The uptake and distribution of inhaled anesthetics have usually been modeled by physiologic models. However, these models have limitations, and they do not consider ventilation/perfusion matching. Respiratory diseases account for a large part of morbidity and mortality and are associated with pulmonary VA/Q mismatch that may affect uptake and elimination of volatile anesthetics.

The objectives of the studies were firstly to investigate assessment of VA/Q mismatch by MMIMS and secondly to investigate the effects of asthma-like VA/Q mismatch on the kinetics of volatile anesthetics in an experimental porcine model.

Anesthetized and mechanically ventilated piglets were studied.

In study I, a direct comparison of MIGET by MMIMS with the conventional MIGET by GC in three animal models that covered a wide range of VA/Q distributions was preformed. The two methods agreed well, and parameters derived from both methods showed good agreement with externally measured references.

In studies II–IV, a stable method of inducing and maintaining asthma-like VA/Q mismatch with methacholine (MCh) administration was established, and the effect of VA/Q mismatch on the pharmacokinetics of desflurane and isoflurane was investigated. The present model of bronchoconstriction demonstrates a delay in volatile anesthetic uptake and elimination, related to the heterogeneity of MCh-inhalation induced ventilation. The difference in solubility of volatile anesthetics has a significant influence on their uptake and elimination under VA/Q mismatch. The higher blood soluble isoflurane is affected to a lesser degree than the fairly insoluble desflurane.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 53 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1269
Keyword
Anesthesia, Animal models in research, Mass spectrometry, Gas chromatography, MIGET, Ventilation-perfusion, Desflurane, Isoflurane, Bronchoconstriction
National Category
Anesthesiology and Intensive Care
Research subject
Anaesthesiology and Intensive Care
Identifiers
urn:nbn:se:uu:diva-304298 (URN)978-91-554-9732-3 (ISBN)
Public defence
2016-12-08, Enghoffsalen, Akademiska sjukhuset, Uppsala, 09:15 (English)
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Supervisors
Available from: 2016-11-14 Created: 2016-10-03 Last updated: 2016-11-16

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Kretzschmar, MoritzBorges, Joao BatistaLarsson, AndersHedenstierna, Göran

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