Background: This study aimed to assess the prevalence of complex sleep apnoea (CompSA), defined as central sleep apnoea (CSA) emerging after the initiation of continuous positive airway pressure (CPAP) therapy for obstructive sleep apnoea (OSA), in patients with normal brain natriuretic peptide (BNP) levels, along with assessing the prevalence of CSA persisting in such patients after the onset of CPAP therapy. We hypothesised that the prevalence of CompSA and persistent CSA after CPAP initiation would be low in patients with OSA and normal BNP levels.
Material and methods: Between April 2004 and July 2007, CPAP was initiated for all patients with OSA for two nights using a standardised protocol. The prevalence of CompSA syndrome (CompSAS) and persisting CSA [central apnoea index (CAI) >5/h and apnoea-hypopnoea index (AHI) >15/h with >50% central events during CPAP therapy] was prospectively assessed in patients with normal BNP levels. Patients with CompSAS or persisting CSA upon CPAP treatment received adaptive servoventilation (ASV).
Results: Of 1,776 patients with OSA receiving CPAP, 28 patients (1.57%) had CSA at the time of CPAP therapy and normal BNP levels. Additionally, 10 patients had CompSAS (0.56%) and 18 patients (1.01%) had persisting CSA. In patients with CompSA or persisting CSA, the AHI was significantly lower with CPAP therapy than at the time of diagnosis (34 ± 15/h vs. 47 ± 20/h, p = 0.005). The CAI increased from 10 ± 10/h to 18/h ± 13/h (p = 0.009) upon initiation of CPAP therapy. ASV reduced the AHI to 6 ± 12/h (p < 0.001) during the first night of use.
Conclusion: The prevalence of CompSA or persisting CSA in patients with OSA and normal BNP levels who are receiving CPAP therapy is low (1.57%). ASV is an effective treatment for these patients.