Background: Heliox has a lower density and higher diffusion capacity compared to\r\noxygen-in-air. We hypothesized that heliox ventilation allows for a reduction in\r\nminute volume ventilation and inspiratory pressures needed for adequate gas\r\nexchange in an animal model of an acute lung injury.\r\nMethods: After intratracheal instillation of lipopolysaccharide (10 mg/kg), adult rats\r\nwere randomized to ventilation with either a gas mixture of helium/oxygen (50:50%)\r\nor oxygen/air (50:50%). They were mechanically ventilated according to the ARDSnet\r\nrecommendations with tidal volumes of 6 ml/kg and monitored with a\r\npneumotachometer. Bronchoalveolar lavage fluid was analyzed for markers of lung\r\ninjury, and embedded lung sections were histologically scored for lung injury.\r\nResults: Heliox limited the increase in driving pressures needed to achieve preset\r\ntidal volumes, with a concomitant decrease in loss of compliance. Heliox did neither\r\nallow for reduced minute volume ventilation in this model nor improve gas\r\nexchange. Also, heliox did not reduce lung injury.\r\nConclusions: Heliox modestly improved respiratory mechanics but did not improve\r\nlung injury in this rat model of acute respiratory distress syndrome.
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