Using the threshold of residual CAI ≥ 5/h, 3.5% of the patients had CSA at day 1 or day 90 of CPAP therapy:
• Patients with OSA had an average CAI that remained consistently well below the threshold of 5 CSA events per hour.
• Patients with transient CSA began above the threshold but then gradually normalised over the 90-day period.
• Patients with emergent CSA began below the cut-point of 5, but rose gradually over time.
• Patients with persistent CSA remained consistently well above the cut-point.
Similar trends were observed when day-by-day values of CAI and AHI over the first 2 weeks of therapy were analysed.
The initial analysis was done according to the US definition of residual or persistent CSA, which is ≥ 5/h.The recent European Respiratory Society (ERS) task force states that patients with persistent CSA with a persistent AHI ≥ 15/h should be switched to ASV.* The investigators also performed a post-hoc analysis using this definition to look at any differences.
When using this more restrictive ERS task force criteria, the prevalence of residual CSA differs slightly (1.2%). However, all other findings are similar.
Only one of the terms, emergent CSA, is currently recognised as a new category of CSA by the International Classification of Sleep Disorders-Third Edition2 and the ERS task force document on central breathing disturbances.3 However, this study seems to show that we can indeed identify 3 categories.
• Average daily usage hours in the first 90 days were lower in those with any kind of CSA during CPAP therapy than in those without.
• Patients with any CSA during CPAP were significantly more likely to terminate therapy after 90 days than those without CSA. Patients with emergent CSA were nearly 2 times more likely to terminate CPAP therapy than OSA patients on day 90..
• Compared with the OSA group, patients with any CSA during CPAP therapy were less likely to continue using therapy. The estimated probability of continuing CPAP therapy on day 300 was: 83% for OSA, 79% for transient CSA, 76% for persistent CSA, 72% for emergent CSA.
All forms of CSA negatively impact CPAP therapy, decreasing compliance and increasing therapy drop-out risk.
The same trajectories impact compliance or therapy termination risk similarly whether identified using ERS task force criteria or US criteria.