Fiorelli A, et al. – Study's goal was to find out whether the difference in lung volume measured with plethysmography and with the helium dilution technique could differentiate an open from a closed bulla in patients with a giant emphysematous bulla and could be used as a selection criterion for the positioning of an endobronchial valve. Similar values in lung volumes measured with the two methods supported the hypothesis that the bulla communicates with the airway and thus is likely to collapse when the endobronchial valve is implanted.