First, the ASV device used in SERVE-HF allows for only fixed expiratory positive airway pressure (EPAP). Data from Table 2 in the study indicate that at the baseline, on average, 20% of the apnea-hypopnea index (AHI) for both control and ASV subjects was composed of obstructive events. It is known that the phenotype of sleep-disordered breathing (SDB) may change over time from predominantly central to predominantly obstructive events. In a fluid-overload state such as heart failure (HF), the latter may largely be related to shifts in fluid status. Given the variability of the sleep apnea phenotype, the fixed EPAP might at times prove inadequate, with consequent residual SDB events. Evidence that this might have occurred in SERVE-HF is found in the large range of AHIs downloaded from the ASV devices across the months of follow-up (Table S4 in the Supplementary Appendix). Recorded AHI values at 3, 12, 24, 36, and 48 months ranged as high as 72, 51, 46, 61, and 38 events/hour and mean values were all more than 5/hour. Times below an oxyhemoglobin saturation of 90% were as high as 344, 269, 285, 291, and 278 minutes at the same respective time points, and means were all 18 minutes or higher. Clearly, this previous-generation ASV device failed to adequately control SDB in some of the subjects studied, and it is therefore surprising that the authors asserted that SDB was “well controlled.” It is conceivable that patients in whom ASV failed to suppress CSA or obstructive sleep apnea contributed to the negative primary outcome or even the excess mortality. This scenario would be similar to that which was predicted and in fact materialized in a previous unsuccessful trial of positive-pressure therapy. We also note that after the first 12 months, clinic visits with device downloads occurred only annually.