Dear Editor,

Despite much research, Continuous Positive Airway Pressure (CPAP) therapy is still the gold standard in initial treatment for central sleep apneas syndromes (CSAS) related to congestive heart failure (CHF). Additionally, adaptive servoventilation (ASV) may be an option for these patients.1 CPAP emergent central apnea also known as complex sleep apnea syndrome (CompSAS) has been defined as the development of frequent central apneas or Cheyne–Stokes respiratory (CSR) pattern after introduction of CPAP therapy.2

We read with great interest the results of Correia et al. and consider that some aspects could be analyzed for proper extrapolation practice.3 The present study approaches an important subject in the field of sleep disorder breathing (SDB). Various data has been published with the objective of defining which treatment is most appropriate for patients with SDB and CHF. However, some comments should be made about the present study.

First, the readers need a more precise definition when the diagnosis was made in CompSAS, central sleep apnea (CSA) and CSR. In this context, some questions need to be posed, was the diagnosis made during the baseline sleep study and was the baseline sleep study also a split-night sleep study? In relation to patients that were afterwards treated with PAP, should not the second sleep study include CPAP/Auto-CPAP/BPAP titration?

Second, according to Javaheri et al., CompSAS was transitory and eliminated after 8 weeks of CPAP therapy.4 In the study performed by Correia et al. the reader does not know how long the authors waited for CompSAS to disappear with regular CPAP therapy, before performing ASV titration.

Third, as previously stated in the literature, BPAP in the spontaneous mode may intensify central apnea caused by hyperventilation.1 in relation to BPAP patients, the authors did not mention if S/T mode was used and which pressures were necessary for optimal treatment.

Fourth, parameters such as left ventricular ejection fraction (LVEF) and treatment compliance have been used to assess ASV vs. CPAP therapy in patients with both CHF and SDB.5 In the present study the evaluation of LVEF was a limitation, since only 16 out of 33 patients had a cardiac function evaluation before and after PSG therapy titration and decision. An interesting fact was that in the present study no differences were encountered in terms of cardiovascular (CV) mortality.

Future studies should also focus on long-term effects of persistent CSA in asymptomatic patients, as well as alternative pharmacological interventions for patients with CSAS and HF.

Corresponding author. sequeira.telma@gmail.com