Abstract
The measurement of ventilation distribution is currently performed using inhaled tracer gases for multiple breath inhalation studies or imaging techniques to quantify spatial gas distribution. Most tracer gases used for these studies have properties different from that of air. The effect of gas density on regional ventilation distribution has not been studied. This study aimed to measure the effect of gas density on regional ventilation distribution.MethodsVentilation distribution was measured in seven rats using electrical impedance tomography (EIT) in supine, prone, left and right lateral positions while being mechanically ventilated with either air, heliox (30% oxygen, 70% helium) or sulfur hexafluoride (20% SF6, 20% oxygen, 60% air). The effect of gas density on regional ventilation distribution was assessed.ResultsGas density did not impact on regional ventilation distribution. The non-dependent lung was better ventilated in all four body positions. Gas density had no further impact on regional filling characteristics. The filling characteristics followed an anatomical pattern with the anterior and left lung showing a greater impedance change during the initial phase of the inspiration.ConclusionIt was shown that gas density did not impact on convection dependent ventilation distribution in rats measured with EIT.
Highlights
Regional ventilation distribution in human and animal studies is currently determined by measuring the distribution of an inhaled tracer gas
Gas density did not impact on regional ventilation distribution
It was shown that gas density did not impact on convection dependent ventilation distribution in rats measured with Electrical impedance tomography (EIT)
Summary
Regional ventilation distribution in human and animal studies is currently determined by measuring the distribution of an inhaled tracer gas. Inhaled tracer gases with different gas density (i.e. helium and SF6) are used to measure ventilation distribution in lung disease such as cystic fibrosis [8,9]. In order to investigate the impact of gas density on regional ventilation distribution per se, a measurement technique independent of gas composition and density must be used. Since the commonly used tracer gases such as helium and sulfur hexafluoride (SF6) have negligible electrical conductivity, as does air, EIT assessment of regional ventilation distribution is independent of gas composition and density [8]
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