Periodic breathing on a CPAP machine means your device detected a repeating cycle where your breathing gradually gets deeper, then shallower, then pauses briefly before the pattern starts again. Your CPAP tracks airflow in real time and flags this specific waxing-and-waning pattern when it identifies at least three consecutive breathing pauses (central apneas) separated by a crescendo-decrescendo change in breath size, with each full cycle lasting at least 40 seconds.
For most stable CPAP users, the amount of periodic breathing is very small. A study of 618 long-term CPAP patients found the median percentage of time spent in periodic breathing was just 0.32%, and only 24% of patients had a rate above 1%. But if your machine is showing a higher percentage, or if the number is climbing over time, it’s worth understanding what’s behind it.
What the Breathing Pattern Looks Like
Normal breathing during sleep is relatively steady. Periodic breathing replaces that steadiness with a rolling wave: your breaths get progressively bigger and faster (the crescendo phase), then progressively smaller and slower (the decrescendo phase), and then stop entirely for several seconds before the cycle repeats. Each full cycle of buildup, fade, and pause typically lasts 45 to 90 seconds.
This pattern is closely related to, and sometimes identical to, a condition called Cheyne-Stokes respiration. Cheyne-Stokes is the clinical name for the most recognized form of periodic breathing, and it’s the specific pattern most CPAP algorithms are designed to detect. During these cycles, your blood oxygen level dips with each pause and recovers during the breathing phase, creating a sawtooth pattern that your machine or a pulse oximeter would pick up.
Why Your CPAP Detects It
Your CPAP has a flow sensor that continuously measures the air moving in and out through your mask. The device’s software analyzes that airflow data for recognizable patterns. When it spots the characteristic crescendo-decrescendo shape repeating across at least three consecutive breathing pauses, it logs those minutes as periodic breathing time. The result shows up in your data as “PB%” or a similar label, representing how much of your total usage time was spent in that pattern.
It’s important to understand that periodic breathing is fundamentally different from obstructive sleep apnea. In obstructive apnea, your airway physically collapses and your chest muscles strain against the blockage. In periodic breathing, the airway stays open but your brain temporarily reduces or stops sending the signal to breathe. That’s why CPAP pressure alone doesn’t fix it: there’s no obstruction to splint open.
Common Causes of Periodic Breathing
The most significant driver of periodic breathing is heart failure. Between 25% and 50% of people with heart failure develop this pattern during sleep. In these patients, periodic breathing isn’t the cause of the heart problem but rather a consequence of it. Sluggish circulation means it takes longer for blood gas levels to reach the brain’s breathing sensors, creating a delay that produces the overshoot-undershoot cycle. The presence of this pattern in someone with heart failure independently predicts worse outcomes, including higher risk of hospitalization and cardiac death.
The large CPAP monitoring study found that the strongest predictors of periodic breathing in CPAP users were atrial fibrillation (especially persistent or permanent forms), wider QRS duration on an EKG (a marker of how the heart’s electrical system is functioning), and a history of heart failure. Male sex, high blood pressure, obesity, and older age also contributed, but cardiac factors dominated.
Other recognized causes include:
- Stroke. Damage to the brain’s breathing control centers can trigger the same cyclical pattern.
- High altitude. Sleeping at an elevation higher than you’re accustomed to commonly produces periodic breathing, even in healthy people. This resolves with acclimatization or descent.
- Opioid medications. Opioids affect the brainstem’s respiratory drive and can make breathing irregular or cause it to stop briefly during sleep.
- Treatment-emergent central sleep apnea. Some people who start CPAP for obstructive sleep apnea develop central apneas and periodic breathing as a new problem. This occurs because once the airway obstruction is eliminated, an underlying instability in breathing control is unmasked.
Treatment-Emergent Central Apnea
This last cause deserves extra attention because it’s directly tied to CPAP use. If you never had periodic breathing before starting therapy and it appears in your data after you’ve been on CPAP for a while, you may be experiencing treatment-emergent central sleep apnea. In many cases, this resolves on its own within the first few months of CPAP use as your body adjusts. In others, it persists.
Pressure settings can play a role. If your CPAP pressure is set higher than necessary, it can over-ventilate you, washing out too much carbon dioxide and dropping it below the threshold your brain needs to keep triggering breaths. The result is a central apnea until CO2 builds back up, followed by a burst of deep breathing, and the cycle continues. This is one scenario where a pressure adjustment by your sleep provider may help.
When the Numbers Matter
A periodic breathing percentage under 1% is common and, based on available data, not typically a concern in stable CPAP users. Most people fall well below that threshold. The number your machine reports represents the fraction of your total device-on time that the algorithm detected the pattern.
Higher percentages, especially if they’re consistent night after night or trending upward, carry more clinical weight. Because the strongest predictors are cardiac conditions like atrial fibrillation and heart failure, a persistently elevated periodic breathing percentage on your CPAP can serve as an early signal of a heart problem you may not know about. If you’re seeing periodic breathing percentages regularly above a few percent and you haven’t been evaluated for cardiac issues, that data point is worth bringing to your doctor. It’s also worth flagging if you’ve recently started an opioid medication, had a stroke, or noticed that your CPAP therapy seems less effective despite good mask fit and consistent use.
How Periodic Breathing Is Managed
The primary approach is treating whatever is causing the periodic breathing rather than the breathing pattern itself. For heart failure patients, optimizing cardiac treatment (medications, fluid management, device therapies) often reduces or eliminates the pattern. For people on opioids, adjusting the medication regimen with a prescriber can help.
When the breathing pattern persists despite treating the underlying cause, alternative devices may be considered. Adaptive servo-ventilation (ASV) is a specialized machine that monitors your breathing cycle in real time and adjusts its pressure support breath by breath, delivering more air when your breathing weakens and less when it strengthens. This smooths out the crescendo-decrescendo waves. Bilevel machines with a backup breathing rate are another option, essentially giving you a minimum number of breaths per minute so your breathing doesn’t pause long enough to trigger the cycle. However, ASV is specifically not recommended for people whose heart failure has reduced their heart’s pumping ability below a certain level, because a major clinical trial found it increased mortality in that group.
For altitude-related periodic breathing, the pattern typically resolves within a few days of acclimatization. If you travel to high elevations regularly and it disrupts your sleep, your provider may discuss short-term medication options to stabilize your breathing drive.
What to Do With Your CPAP Data
Your CPAP’s periodic breathing reading is a screening tool, not a diagnosis. The algorithm is designed to detect the classic crescendo-decrescendo pattern, but it has limitations. It may not catch all forms of central apnea, and occasional brief detections can be meaningless noise. What matters is the trend over weeks and months, not a single night’s reading.
If your periodic breathing percentage is consistently low (under 1%), your machine is telling you this isn’t a significant part of your sleep picture. If it’s consistently elevated or rising, download or print your data and share it at your next sleep or cardiology appointment. The combination of your CPAP’s periodic breathing data with your central apnea index gives your provider a clearer picture of what’s happening during your sleep than either number alone.