This article was originally published with the sentence “Thank you for the opportunity to respond to the correspondence by J.G. Nielsen from Innovision about our recent paper”. The authors have since been made aware that J.G. Nielsen sold Innovision ApS (Glamsbjerg, Denmark) prior to the submission of his correspondence and, at the time of writing, has no financial interests in any business relating to lung clearance index technologies. This sentence has now been changed to “Thank you for the opportunity to respond to the correspondence by J.G. Nielsen about our recent paper” in the article itself.