Backup respiratory rate during noninvasive positive pressure ventilation in obesity hypoventilation syndrome: can this difficult puzzle be resolved?

Obesity hypoventilation syndrome (OHS) refers to sleep-related hypoventilation with repetitive episodes of complete and partial obstructions of the upper airway. 1 Some fi nesse is required to determine the appropriate ventilator settings to prevent such episodes, which can alter the effi cacy of noninvasive positive pressure ventilation (NPPV). In a recent article in CHEST (January 2013), Contal et al 2 analyzed the effects of three strategies: a spontaneous (S) mode, a low backup respiratory rate (BURR), and a high BURR. The S mode was worse than the S/T mode, and changing the BURR from an S/T mode with a high or low BURR to an S mode was associated with the occurrence of a highly signifi cant increase in respiratory events and oxygenation desaturation index events. It is worth highlighting some features of this study, which help place the fi ndings in context. First, the population selected had some interesting characteristics. The prior use of NPPV for at least 42.7 months (duration of NPPV) and a baseline BURR of 14 may have infl uenced the results. Specifi cally, patients who had already been acclimated to NPPV might have adjusted more easily to a range of BURR. Second, a high BMI of 48.5 kg/m 2 could also have reduced the effi cacy of NPPV, making it diffi cult to generalize from these results to the entire spectrum of OHS. 3