Leatherman JW, et al. - Herein, the goal was to investigate if heliox (helium-oxygen mixture) could reduce the degree of hyperinflation and hypercapnia in mechanically ventilated patients with severe air-flow obstruction. In this group of patients, no effect of heliox was seen on indices of dynamic hyperinflation (plateau pressure and total PEEP), moreover, administration of heliox led to only a small attenuation in P_aCO2.