Noninvasive Mechanical Ventilation in Stable Hypercapnic Chronic Obstructive Pulmonary Disease: Is Restful Sleep a Suitable Distinctive Parameter?

Second, the authors enrolled patients who needed supplemental oxygen during NPPV in minor hypercapnic stable COPD (1.3 ± 1.1). To interpret this hypoxemic condition and the ventilatory modes, it is important to know if there is overlap between obesity hypoventilation and COPD and if this condition shows variations and ventilatory mode influence after 6 weeks [ 5 ; table 1]. There is no clear explanation for this aspect and its relevance for long-term outcome. Third, the ventilatory parameters need more evaluation as (a) the influence and level of expiratory positive airway pressure (5.8 ± 2.1 mbar) and (b) amounts of air leakage during two study ven-tilatory periods and how could be influenced tendency of PCO 2 improvement with iVAPS period [6]. Fourth, although they mainly focused on sleep quality parameters , the authors reported that positive pressure-induced discomfort was higher during iVAPS than during HI-NPPV (p = 0.04), and no other significant differences were found with regard to subjective sleep quality and comfort with NPPV in the hospital. These aspects need more clarification. It would be interesting to know what environmental conditions during home mechanical ventilation were stable before and after the study [ 7 ; table 3]. Further prospective longer-term trials are necessary to consolidate this trend towards a 'restful sleep' quality and to learn more about the mechanisms of sleep improvement in stable hypercapnic COPD. Dear Editor Currently, there is scarce information regarding the potential impact of ventilatory modes on sleep quality over time in stable hypercapnic chronic obstructive pulmonary disease (COPD) in a home noninvasive mechanical ventilation program [1]. The factors and pathways are complex and mainly depending on complex interaction between patient requirements, lung mechanic and ventilator mode capabilities [2]. Intelligent volume-assured pressure support (iVAPS) is a hybrid mode of servoventilation providing constant automatic adjustment of pressure support to achieve the patients' target ventilatory requirements compared to high-intensity noninvasive positive pressure ventilation (HI-NPPV). However , solid data on the influence of long-term impacts of using 'target volumes' and the influence on sleep quality are required [2]. In their original study, Ekkernkamp et al. [3] described potential effects of HI-NPPV and iVAPS on sleep quality during a short period (6 weeks), measured by the visual analog scale, polysom-nography, partial transcutaneous pressure of CO 2 (PtcCO 2) monitoring and blood gas analysis. The main result was a favorable restful sleep score during iVAPS and a greater decrease in …