Near-real-time pulmonary shunt and dead space measurement with micropore membrane inlet mass spectrometry in pigs with induced pulmonary embolism or acute lung failure
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The multiple inert gas elimination technique (MIGET) using gas chromatography (GC) is an established but time-consuming method of determining ventilation/perfusion (VA/Q) distributions. MIGET—when performed using Micropore Membrane Inlet Mass Spectrometry (MMIMS)—has been proven to correlate well with GC-MIGET and reduces analysis time substantially. We aimed at comparing shunt fractions and dead space derived from MMIMS–MIGET with Riley shunt and Bohr dead space, respectively. Thirty anesthetized pigs were randomly assigned to lavage or pulmonary embolism groups. Inert gas infusion (saline mixture of SF6, krypton, desflurane, enflurane, diethyl ether, acetone) was maintained, and after induction of lung damage, blood and breath samples were taken at 15-min intervals over 4 h. The samples were injected into the MMIMS, and resultant retention and excretion data were translated to VA/Q distributions. We compared MMIMS-derived shunt (MM-S) to Riley shunt, and MMIMS-derived dead space (MM-VD) to Bohr dead space in 349 data pairs. MM-S was on average lower than Riley shunt (− 0.05 ± 0.10), with lower and upper limits of agreement of − 0.15 and 0.04, respectively. MM-VD was on average lower than Bohr dead space (− 0.09 ± 0.14), with lower and upper limits of agreement of − 0.24 and 0.05. MM-S and MM-VD correlated and agreed well with Riley shunt and with Bohr dead space. MM-S increased significantly after lung injury only in the lavage group, whereas MM-VD increased significantly in both groups. This is the first work evaluating and demonstrating the feasibility of near real-time VA/Q distribution measurements with the MIGET and the MMIMS methods.
KeywordsPulmonary embolism Intrapulmonary shunt and O2 therapy Respiratory function: dead space VQ mismatch: causes Level of hypoxemia: factors impacting
The authors thank Daniel Mettler and Olgica Beslac of the ESI, Experimental Surgery Unit, medical faculty of the University of Bern, Switzerland, for providing the infrastructure and very helpful support and assistance. We would also like to thank Lukas Häller, Master’s Student in Medicine at the University of Bern, for assistance with data acquisition, sample collection, handling and transport. The authors thank Jeannie Wurz for her proofreading and English language editing support. This research was supported by SNF Grant 320030_133046.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
All procedures performed in studies involving animals were in accordance with the ethical standards of the cantonal ethics committee of Bern, Switzerland.
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