To the Editor:
I read with interest the study by Willson et al. 1 published recently in the European Respiratory Journal. The paper was focused on interfaces, which are one of the most important issues in treating patients with chronic respiratory failure. The study was set up to compare nasal mask (NM) with full face mask (FFM) ventilation, in terms of sleep quality, gas exchange and tolerability. In addition, the authors tried to investigate any differences in pressure settings between the two types of mask ventilation. Although the questions of this study are relevant, I believe that the design of the study was not adequate to answer these questions.
First, all patients were on NM for >3 months and one patient even for 70 months, whereas they trained only for 1day on FFM. In our centre (Dept of Pulmonary Diseases/Home mechanical ventilation, University Hospital Groningen, Groningen, The Netherlands), patients routinely needmore time (∼7 days) to adjust to their specific mask. As a result of this short time of training on FFM compared with a long-term adjustment on NM, it is not surprising thattotal sleep time and sleep efficiency were worse in theFFM group compared with the NM group. As a consequence of their longer experience with the NM mask, the patients also rated less leak and more comfort in the NMnight compared with the FFM night. Secondly, nodifferences were found between pressure settings if NMwas compared with FFM. However, this study will not detect any differences if pressure settings, optimalised during their review night, remained unchanged during the subsequent mask trials.
Due to the previously mentioned issues, I believe that thestudy by Willson et al. 1, with its present design, makes itdifficult to draw strong conclusions. It would have beenpreferable to compare both mask ventilations in aparallel study of naïve patients in whom noninvasive ventilation was started. In this way, it would have beenpossible to compare the time it takes to adjust to eithernasal mask or full face mask. If the patients wereadjusted to the mask, it would be possible to determine differences in terms of sleep quality, tolerability andpressure needed to maintain an effective noninvasive ventilation.
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