To the Editor:
A recent editorial in the European Respiratory Journal [1] recognises that the fundamental scientific data on lung clearance index (LCI) obtained by sulfur hexafluoride (SF6) multiple-breath washout (MBW) have paved the way for clinical use of LCI. Although the editorial stresses the need for standardisation, it also appears to suggest that SF6 can be replaced by nitrogen (N2) as the washout gas.
We (Innovision ApS, Odense, Denmark) are the manufacturer of the AMIS 2000 medical mass spectrometer system that, using user-specific software and hardware, was adapted to perform MBW. The AMIS 2000-based devices are now considered the “gold standard” device for SF6 LCI measurements in cystic fibrosis patients by opinion leaders in the field [2]. This device has been used in the vast majority of studies demonstrating the clinical value of SF6 LCI in cystic fibrosis patients, with one recent notable exception: the demonstration of the change in LCI caused by Ivacaftor in cystic fibrosis patients with normal forced expiratory volume in 1 s, where a prototype version of our other system, Innocor, adapted for open-circuit SF6 LCI, was used [3].
The AMIS 2000 adapted MBW system is too …