Treatment-Emergent Central Apnea and Why New Central Events Appear After Starting CPAP
Why treatment-emergent central sleep apnea shows up in your CPAP data and what it actually means
Your machine says central apneas, so here is what that number really measures, how long the events usually last, and the point where it stops being normal.
What Treatment-Emergent Central Sleep Apnea Is and How Common It Is
Treatment-emergent central sleep apnea is the appearance of central breathing pauses after positive airway pressure has already cleared the obstructive ones. Your airway stays open, but your brain briefly stops sending the command to breathe. Older papers call it complex sleep apnea syndrome or CPAP-induced central apnea.
The distinction matters, because the two event types need different fixes, as our guide to how central and obstructive events differ explains. Obstruction is a plumbing problem. A central event is a signalling problem, which is why no mask tweak reliably removes it.
Nigam, Pathak and Riaz reported in Annals of Thoracic Medicine (2016) that 8.37% of patients developed central events during PAP titration, 366 of 4,375 people across nine studies. Study rates ranged from 5.0% to 20.3%.
Everyday use looks milder than the sleep laboratory. A database analysis of 133,066 CPAP users by Liu and colleagues (2017), summarised in the Journal of Thoracic Disease, found emergent central sleep apnea in 3.5%. Older age was a significant risk factor, and affected users showed lower compliance.
- Central events after starting therapy are recognised and studied, not a broken machine.
- Roughly 8% of titrations and 3.5% of real-world users are affected.
- The airway is open during these pauses, so airway-opening fixes do not apply.
Why Positive Airway Pressure Can Unmask Central Events
CPAP does not damage your breathing control centre. It shifts the balance of a feedback loop that was already fragile, and researchers measure that loop as loop gain.
Loop gain has two halves. Controller gain is how hard your chemoreceptors react to a rise in carbon dioxide, also called chemoreflex sensitivity. Plant gain is how far your blood gas actually moves for a given change in breathing.
When treatment opens the throat, ventilation improves and PaCO2, the carbon dioxide level in your blood, can fall. If it drops below your hypocapnic apnea threshold, the drive to breathe switches off until CO2 rebuilds. The gap between your sleeping CO2 level and that threshold is your CO2 reserve, and a narrow reserve leaves little margin.
Two further factors shape the pattern. A low arousal threshold means you wake easily, and each awakening is followed by overbreathing that drives CO2 down again. A long circulatory delay makes the correction arrive late, which can produce periodic breathing.
Settings matter too. High fixed pressures, a wide auto-adjusting APAP range rather than a fixed CPAP pressure, and expiratory pressure relief can each make breaths bigger. So the first step is rarely a new machine, but a careful look at your current settings.
- Central events reflect an unstable ventilatory control loop, not damage from the machine.
- Falling CO2 below the hypocapnic apnea threshold switches breathing effort off temporarily.
- Pressure level, APAP range and comfort settings all influence how often this happens.
How Your Machine Decides an Event Is a Clear Airway Apnea
A clear airway flag means your device tested the airway during a pause and judged it open. Devices commonly use the forced oscillation technique. They send a tiny, imperceptible pressure wobble down the tube and read how it bounces back. A closed throat reflects the pulse; an open one lets it pass.
That is a clever proxy, not a diagnosis. In a sleep laboratory, polysomnography (PSG) scores a central apnea by measuring chest and abdominal effort directly with belts. Your machine never measures effort, so a CA count on a home report and a scored central apnea are not the same number.
The three-part test for treatment-emergent central sleep apnea
Published criteria combine three conditions, not one. Check all three against your own screens.
1Your central apnea index is 5 or more
The central apnea index (CAI) counts central pauses per hour of therapy. Below 5 per hour, the criterion is not met, however alarming the raw event count looks.
2Centrals dominate your residual events
More than half of your residual apnea-hypopnea index (AHI), the events left per hour on therapy, must be central. If obstructive events and hypopneas, partial airway narrowings, still dominate, the problem is unresolved obstruction.
3Your diagnostic study showed a CAI below 5
The events must be new. If your original study already showed frequent central pauses, this is pre-existing central sleep apnea, not the treatment-emergent form.
Check your leak figure before you believe your central count
Unintentional mask leak and mouth leak corrupt everything downstream. A leaking circuit distorts the pressure signal the machine uses to classify events, so the central count from a leaky night cannot be interpreted.
Large leaks are also a recognised risk factor for genuine central events during titration, because they cause pressure swings and arousals. Read the leak line first, as set out in our walkthrough of reading your nightly therapy report. Fix the mask, then judge three clean nights.
- A clear airway flag is an algorithm's judgement from a pressure pulse, not a lab-scored central apnea.
- The criterion is CAI of 5 or more, over 50% central residual events, and a diagnostic study under 5.
- A high-leak night makes the central count meaningless, so read leak first.
Telling Central Events, Cheyne-Stokes Respiration and Opioid Effects Apart
Three different problems produce central pauses, with very different urgency. Many devices already flag Cheyne-Stokes respiration (CSR) as its own category.
| Pattern | What the data looks like | Usual driver | What it means for you |
|---|---|---|---|
| Treatment-emergent central apnea | Clear airway events climb after starting or increasing pressure; breathing otherwise regular | Unstable ventilatory control once obstruction is relieved | Usually settles; recheck over weeks |
| Cheyne-Stokes respiration | Long, smooth waxing and waning cycles, often flagged separately as CSR | Circulatory delay, frequently linked to heart failure | Needs a cardiac review, not a mask change |
| Opioid-induced central sleep apnea | Irregular, erratic pauses in someone taking opioid medication | Suppressed respiratory drive from medication | Medication review with the prescriber |
| Residual obstruction | Obstructive events and hypopneas still dominate the apnea-hypopnea index (AHI) | Pressure, mask fit or sleeping position | Optimise the existing therapy first |
The cardiac question matters most. The SPLF (Société de Pneumologie de Langue Française), in guidance accessed in 2026, reports that central sleep apnea syndrome affects 20% to 30% of people with heart failure, with mortality risk doubled in severe forms. If your report shows CSR, read our explainer on the overlap between heart failure and sleep-disordered breathing, then see your doctor.
- A CSR flag points towards the heart, not towards your pressure setting.
- Opioid medication produces its own central pattern and needs a prescriber review.
- Naming the pattern correctly changes both the urgency and the treatment.
How Long Treatment-Emergent Central Sleep Apnea Usually Lasts
Most cases resolve on their own. The CHEST review of physiologic mechanisms (2021) reports spontaneous resolution in 54% to 86% of affected patients within weeks to months, while roughly one quarter have persistent disease.
The largest real-world split comes from that 133,066-user database (Liu and colleagues, 2017): 55.1% transient, 25.2% persistent and 19.7% late-emergent. A systematic review (Nigam and colleagues, Annals of Thoracic Medicine, 2018) pooled 135,283 treated patients and found persistent central apnea in 31.1% of cases, or 0.9% to 3.2% of everyone on therapy.
1Weeks 1 to 6
Expect a noisy CAI. Use the machine every night, chase leaks, and compare weekly averages rather than single nights. A slowly falling trend is the normal picture.
2Weeks 6 to 12
If your CAI is still 5 or more and centrals remain the majority of residual events, request a review. Watchful waiting stops being the best plan here.
3Beyond three months
Persistent cases are recognised. Ask specifically about CPAP re-titration and whether a different device mode suits you.
- Most people settle without any change of device.
- About one in four persists and needs a formal review.
- Week 6 to 12 is the sensible trigger for reassessment.
When Central Events Appear After Months of Stable Therapy
Late-emergent central apnea behaves differently and deserves a proper work-up rather than patience. It made up 19.7% of cases in the 133,066-user data set, and the 2018 pooled review put delayed onset at 0.7% to 4.2% of patients after at least one month of therapy.
If therapy was stable for months and central events are genuinely new, something else has usually changed. Three questions are worth raising at your appointment. Has a new medication started, particularly an opioid or a gabapentinoid? Has anything changed with your heart, such as breathlessness or ankle swelling? Has your weight moved significantly in either direction?
Bring a current medication list and your last three months of nightly data. Older age was a significant risk factor in the 2017 database analysis, so a slow drift differs from a sudden change.
- New central events after months of stability are not the settle-on-its-own pattern.
- Ask about new medication, cardiac change and weight change before adjusting the machine.
- Take a medication list and three months of nightly data to the appointment.
Treatment Options for Treatment-Emergent Central Sleep Apnea and What Changed in 2025
The first treatment is almost always optimisation and watchful observation, not a new machine. The 2025 American Academy of Sleep Medicine clinical practice guideline, in the Journal of Clinical Sleep Medicine, makes conditional recommendations, on low to very low certainty evidence, for CPAP, bilevel PAP with a backup rate, adaptive servo-ventilation and oral acetazolamide in adults with treatment-emergent central sleep apnea. It suggests against bilevel PAP without a backup rate.
| Option | How it works | Where it fits |
|---|---|---|
| Optimising current therapy | Adjust the pressure or its range, fix leak, review comfort settings | First step for nearly everyone |
| Bilevel PAP with backup rate | Delivers a timed breath if you do not take one | Conditionally recommended, 2025 AASM guideline |
| Adaptive servo-ventilation (ASV) | Varies support breath by breath to smooth periodic breathing | Conditionally recommended, with the cardiac caveats below |
| Acetazolamide | Oral medicine used to stabilise breathing control | Conditionally recommended, specialist decision |
| Supplemental oxygen | Reduces swings in the control loop | Discussed in the CHEST 2021 management algorithm |
| Transvenous phrenic nerve stimulation | Implant that paces the nerve supplying the diaphragm | Specialist option; not among the four in the 2025 AASM list |
Adaptive servo-ventilation carries the most out-of-date reputation online. The SERVE-HF trial (Cowie and colleagues, New England Journal of Medicine, 2015) enrolled 1,325 patients with a left ventricular ejection fraction (LVEF) of 45% or less and predominantly central events. ASV showed no benefit on the primary endpoint (54.1% versus 50.8%, hazard ratio 1.13) and was associated with increased all-cause mortality (HR 1.28, p=0.01) and cardiovascular mortality (HR 1.34, p=0.006).
In Europe that was handled as a medical-device vigilance action rather than a recall: a field safety notice distributed through national competent authorities. The German notice, via BfArM (Bundesinstitut für Arzneimittel und Medizinprodukte), is dated 13 May 2015; France's equivalent authority is the ANSM. Ten years on, the European position has moved.
The 2025 ERS and ESRS statement (Randerath and colleagues, European Respiratory Journal, PMID 40571320) explicitly re-evaluated those restrictions. It concludes that current ASV devices have no negative effect on hard cardiovascular end-points, and describes ASV use after optimal treatment of the underlying disease and an unsuccessful CPAP trial in heart failure with preserved ejection fraction, and in LVEF of 30% to 45% with initiation in expert centres only.
French practice is summarised by LVEF band. The SPLF describes ventilation auto-asservie as recommended above 40%, used with close monitoring between 35% and 40%, and reserved below 35% only where symptoms are disabling and no alternative exists, in an expert centre.
- Optimise settings first; four options carry conditional 2025 guideline support.
- Bilevel without a backup rate is specifically advised against.
- Europe's 2025 ASV position is more permissive than the 2015 consensus.
What a Nasal Stent Can and Cannot Do for Central Events
A central picture rules out a whole category of popular alternatives. Mandibular advancement devices, positional therapy and nasal airway devices are mechanical fixes for a collapsing airway. During a central event the airway is already open, which is precisely why your machine labels the pause clear airway.
Back2Sleep is a CE-certified Class I soft silicone nasal stent that holds the nasal airway open during sleep. It is not a treatment for central sleep apnea, not a substitute for bilevel PAP with a backup rate or ASV, and not a CPAP replacement for anyone with a central component or severe disease.
There is one honest exception, and it arrives later. Once transient central events have settled and your remaining documented problem is snoring or mild-to-moderate obstructive sleep apnea, a nasal stent becomes reasonable to raise with your prescriber, for that obstructive part only.
- Mechanical airway devices cannot correct a ventilatory control problem.
- Do not shop for CPAP alternatives while your central picture is unresolved.
- Revisit obstructive-only options once the data shows central events have gone.
What Happens Next Inside a European Care Pathway
In most of Europe your nightly data is read first by a home-care provider, not by your sleep physician. In France that is the prestataire de santé à domicile; in Germany, the Homecare-Versorger. They receive telemonitoring data, called télésuivi in France, and escalate problems upstream.
This changes what you should do. Contact the provider that delivered your machine, ask for a data export covering the last 30 nights, and ask that it reaches your prescriber. Re-titration or a change of device mode needs a prescription, so buying different equipment cannot solve it. Reassessment may mean a repeat home sleep apnea test or a night of polysomnography, depending on your country.
Vocabulary matters when you search or speak to a clinician. In French, CPAP is pression positive continue (PPC), obstructive apnea is SAHOS, central sleep apnea syndrome is SASc, and the treatment-emergent form is called SAS émergent. German material uses komplexe Schlafapnoe or zentrale Schlafapnoe, and Spanish uses apnea central emergente del sueño.
Your clinician may work from a national document rather than an international one: France has a dedicated Consensus français sur les syndromes d'apnées et hypopnées centrales du sommeil (2023), in the Revue des Maladies Respiratoires. Reporting software differs across Europe too, so if your report shows no clear airway line, ask which label your system uses.
- Your first call is the home-care provider, not the sleep clinic.
- Ask for a 30-night data export, sent on to your prescriber.
- Learn the local term for your condition; it changes what you find.
What Back2Sleep Users Say
Frequently Asked Questions
Does CPAP cause central sleep apnea?
CPAP does not damage your breathing centre, but relieving obstruction can destabilise ventilatory control and unmask central pauses. A 2016 Annals of Thoracic Medicine review found this in 8.37% of patients during titration. Most cases settle within weeks to months without any change of machine or pressure.
Do central apneas from CPAP go away on their own, and how long does it take?
Usually yes. The CHEST review (2021) reports spontaneous resolution in 54% to 86% of cases within weeks to months, and a 133,066-user database (2017) found 55.1% were transient. Keep using therapy nightly and compare weekly averages rather than single nights. If your central index is still high at week 6 to 12, request a review.
What is a normal central apnea index on CPAP?
A central apnea index below 5 events per hour is generally not considered significant. The published definition of treatment-emergent central sleep apnea requires a CAI of 5 or more, plus more than half of residual events being central, in someone whose diagnostic study showed a CAI under 5.
What does clear airway mean on my CPAP report?
Clear airway means the device sent a small pressure oscillation during a pause and judged your throat open, so it labelled the event central rather than obstructive. It never measures breathing effort, unlike laboratory polysomnography. A high leak figure distorts this classification, so always read your leak line first.
Will lowering my CPAP pressure reduce my central apneas?
Sometimes. Excess pressure, a wide auto-adjusting range or strong expiratory pressure relief can lower carbon dioxide and contribute to central pauses, so optimising settings is the recommended first step. Never adjust pressure yourself. In most of Europe your home-care provider must route any change through your prescriber.
Is treatment-emergent central sleep apnea dangerous?
It is usually a temporary instability rather than an emergency, and most cases settle within weeks to months. The real risk is stopping therapy, which leaves your obstructive apnea untreated. Seek review sooner if your device flags Cheyne-Stokes respiration, if you have heart failure, or if central events persist past three months.
Why did central apneas suddenly appear after months of using CPAP?
Late-emergent central apnea made up 19.7% of cases in a 133,066-user database (2017), so it is recognised. It usually signals a change rather than the machine: a new opioid or gabapentinoid, new or worsening heart problems, or significant weight change. Take a medication list and three months of data to your prescriber.
When do I need an ASV machine instead of CPAP?
Only after optimisation fails and a specialist has reviewed you. The 2025 AASM guideline conditionally supports adaptive servo-ventilation, bilevel PAP with a backup rate and acetazolamide for treatment-emergent central sleep apnea. The 2025 ERS and ESRS statement limits initiation in an ejection fraction of 30% to 45% to expert centres.
Do I need a home sleep apnea test or a full polysomnography to confirm central apnea?
Machine data alone cannot confirm central apnea, because devices infer rather than measure breathing effort. A repeat home sleep apnea test may be enough for screening, but polysomnography scores chest and abdominal effort directly. Your prescriber decides which is appropriate, and a suspected cardiac cause is usually investigated before any device change.
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