A large study finds that ASV yields better compliance among obstructive sleep apnea patients who develop treatment-emergent central sleep apnea than does CPAP. Researchers discuss why and what it means in clinical practice.

Presented in April at the Sleep and Breathing conference in France, an abstract comparing two therapy options for obstructive sleep apnea (OSA) patients who develop treatment-emergent central sleep apnea piqued the interest of many sleep medicine professionals. Could there be better therapy for these difficult-to-treat patients?

The retrospective analysis of 198,890 patients’ compliance rates found those with treatment-emergent central sleep apnea (CSA) who switched from CPAP (continuous positive airway pressure) to ASV (adaptive servo-ventilation) used their therapy longer and had significantly fewer apneas during sleep.1 An article summarizing the findings published on www.sleepreviewmag.com in mid-May sparked one of the highest social media engagement ratings on Sleep Review‘s Facebook page in the second quarter of 2017.2 The study was sponsored by ResMed, and patients received CPAP via ResMed’s AirSense 10 or ASV via ResMed’s AirCurve 10 devices. The study used the Medicare definition of compliance.

Adam Benjafield, study coauthor and vice president of medical affairs at ResMed, says, “We expected that ASV would improve adherence rates and were pleased to see how high the adherence rate improvement actually was, as patients who switched to ASV were 76.6% adherent on ASV, and just 62.7% compliant on CPAP before the switch. It was very encouraging to see that ASV therapy had such a significant impact on increasing compliance rates and improving overall usage to such a large degree.”

In terms of clinical implications, Benjafield says, “It’s crucial to identify OSA patients with treatment-emergent CSA and switch them from CPAP to ASV therapy as soon as possible in order to maximize their therapy comfort, outcomes, and likelihood that they remain on therapy. Even those in need of ASV who stay adherent on CPAP aren’t receiving the most effective therapy, affecting their sleep, outcomes, and overall quality of life. This study can shine a bright light on this population, helping them get the attention and the therapy they need.”

Teofilo Lee-Chiong Jr, MD, chief medical liaison at Philips, who was not involved in this study, notes that ASV was developed to care for the more challenging patient population. He says, “Patients with complex sleep apnea, whose unique ventilation needs can vary greatly throughout the night, pose special challenges to healthcare professionals caring for them. Servo-ventilation has been developed specifically for those who require more sophisticated management of central apneas and periodic respiration.” Philips also makes ASV and CPAP devices, and Lee-Chiong notes that the Philips DreamStation BiPAP autoSV is designed to detect and reduce central apneas.

Anita Simonds, Sleep and Breathing conference co-chair and professor of Sleep & Respiratory Medicine at Royal Brompton & Harefield NHS Foundation Trust, United Kingdom, says the questions raised by the research are of interest, but cautions that the work itself may not prove conclusive. “One reasonable interpretation of these results is that those patients who swapped from CPAP to ASV developed treatment-emergent central sleep apnea, or had a degree of mixed sleep-disordered breathing in which central apneas and/or hypopneas were not adequately controlled on CPAP, leading to persistence of symptoms, and therefore worse compliance,” she says. “These central events were then controlled better on ASV. This would indeed be in line with other small trials that have shown patients with treatment-emergent central sleep apnea or mixed sleep-disordered breathing may progress better on ASV than CPAP, so the results are not necessarily surprising and would support this hypothesis. As such, the results presented are of interest and generate questions and useful data for modeling, but as often with big data, it does not produce firm answers.”

The researchers were inspired to investigate this topic “since little is known about the exact prevalence or clinical impact of treatment-emergent central sleep apnea,” Benjafield says. “We hoped the research would shed light on those topics and offer guidance on how to effectively improve care and outcomes for this population.

“Our previous study on 135,000 patients on PAP therapy showed that those with treatment-emergent CSA are nearly two times more likely to terminate.3 With this research, we wanted to learn if switching these patients from CPAP (which treats obstructive events) to adaptive servo-ventilation therapy (which treats both obstructive and central events) can improve patient outcomes and adherence to therapy.”

There is still much to be done. Benjafield says, “We know that 3.5% of CPAP users have treatment-emergent CSA and that ASV can improve their therapy and adherence—but we still don’t know why or how they develop it. Can we prevent it? If not, are there common risk factors or other symptoms besides central apneas to help spot it earlier, further improving patients’ therapy quality and chances of staying on therapy?”

As for the way forward, both Simonds and Benjafield look to big data as the guide.

“Use of big data is a new and innovative approach applied to sleep medicine. The authors used a ResMed company database of individuals started on CPAP and ASV,” Simonds says. Benjafield says, “Connected health solutions aren’t just key to best identifying patients in this study’s subpopulation, but also to liberating the data to conduct this very research. Not only does this connected care solution help clinicians remotely monitor their patients and identify those struggling with therapy; on a broader scale, it enables us to dive into these larger research questions to identify best practices for improving outcomes and adherence.”

Tamer Abouras is a freelance writer and editor from Williamstown, NJ.


1. Pepin JL, Woehlre H, Liu D,  et al. Compliance after switching from CPAP to ASV: big data analysis. ERJ Open Research. 2017;3:45.
2. For patients with treatment-emergent central sleep apnea, switching from CPAP to ASV significantly improves compliance. Sleep Review. 15 May 2017. Available at: www.sleepreviewmag.com/2017/05/patients-treatment-emergent-central-sleep-apnea-switching-cpap-asv-significantly-improves-compliance
3. Woehrle H, Liu D, Armitstead J, Benjafield A, Malhotra A. Trajectories of central sleep apnea during continuous positive airway pressure and association with therapy termination: a big data analysis. Am J Respir Crit Care Med. 2017;195:A2928.