Hilling and colleagues1 present the results of a physiological evaluation of a lightweight ventilatory assist device designed to be powered by different sources for oxygen delivery. They mainly demonstrate a frank physiological benefit in a group of 15 severe to very severe subjects with COPD, attested by a longer exercise duration as compared with continuous supplemental oxygen alone. They also reported improvements in Borg dyspnea score, pulse oximetry, breathing frequency, and leg fatigue score.

These are very interesting results, mainly confirming and extending in some parts previous results from Porszasz et al2 in a reference study using a similar design, although including broader investigations. Accordingly, previous results from Porszasz help with interpretation of the present study. This is particularly true for the delineation between the effects of rising FIO2 during inspiration for one part and the effects of rising inspiratory flow for another part. Referring to the …

Correspondence: Jean-Luc Diehl MD, Medical Intensive Care Unit, Hopital Européen Georges Pompidou, Assistance Publique-Hopitaux de Paris, 20 Rue Leblanc, 75015, Paris, France. E-mail: jean-luc.diehlaphp.fr