If your doctor prescribed BPAP instead of CPAP, or if you have read that BPAP is the “upgraded” machine, you may be wondering whether you are getting something better. You may also have noticed that your CPAP already has a setting called EPR that lowers the pressure when you breathe out, and wondered if that is the same thing.

Here is the short answer. BPAP is not a better version of CPAP for most people with sleep apnea. It is a different tool built for different problems. EPR and BPAP share one idea, but they are not the same thing, and they are not used for the same reasons.

This article explains how each one works, what recent research shows, and the specific situations where a sleep doctor will choose BPAP.

The Bottom Line First

• For most people with obstructive sleep apnea, CPAP works just as well as BPAP.
• A 2026 review of 21 studies found that BPAP and EPR did not meaningfully increase nightly use compared with standard CPAP.
• EPR gives a small, brief drop in pressure when you breathe out. BPAP uses two separate pressures for the whole breath and can actively help you breathe.
• Doctors choose BPAP for specific medical reasons. The most common are high pressure needs you cannot tolerate, high carbon dioxide levels in the blood, lung or muscle diseases that weaken breathing, and some types of breathing pauses that come from the brain.

How Each Machine Works

All of these machines blow air through a mask to keep your airway open while you sleep. The pressure is measured in centimeters of water (cm H2O). The difference between them is how the pressure behaves as you breathe in and out.

Device	What the pressure does	Main purpose
CPAP	One steady pressure all night, in and out	Keeps the airway from collapsing in obstructive sleep apnea
APAP (auto CPAP)	One pressure at a time, but it adjusts up and down through the night	Same as CPAP, with automatic fine tuning
CPAP or APAP with EPR	Pressure dips slightly at the start of each exhale, then returns to full pressure before the next breath	Comfort
BPAP (bilevel)	A higher pressure when you breathe in (IPAP) and a lower pressure when you breathe out (EPAP)	Comfort at high pressures, and active help moving air in and out of the lungs
BPAP ST (with backup rate)	Same as BPAP, plus the machine delivers a breath if you pause too long	People who stop breathing because the brain does not send the signal, or whose breathing is too weak

A simple way to picture it: CPAP holds the door open. BPAP holds the door open and also helps push air through it.

Is EPR the Same as BPAP?

No. EPR (expiratory pressure relief) is a comfort feature. ResMed calls it EPR. Philips uses names like C-Flex and A-Flex. They all do roughly the same thing.

Here is how EPR and BPAP differ:

• Size of the drop. EPR lowers pressure by a small amount, usually 1 to 3 cm H2O. BPAP can set a gap of 4, 6, 10 or more between the inhale and exhale pressures.
• Timing. EPR lowers pressure only at the start of the exhale, then brings it back up before your next breath. BPAP holds the lower pressure through the entire exhale and the higher pressure through the entire inhale.
• Breathing support. EPR does not help you take a bigger breath. BPAP does. The gap between the two pressures, called pressure support, pushes more air into the lungs with each breath. This is what lowers carbon dioxide.
• Backup breaths. EPR has no backup rate. Some BPAP machines (BPAP ST) can give a breath if you stop breathing on your own.
• Pressure ceiling. Most CPAP machines top out at 20 cm H2O. Many BPAP machines can deliver 25 or higher.

So EPR is a small comfort tweak. BPAP is a breathing support device that also happens to feel more comfortable for some people.

Is BPAP Better Than CPAP?

For most people with obstructive sleep apnea, the research says no.

The strongest recent evidence comes from a 2026 systematic review and meta-analysis that pooled 21 controlled studies with 1,462 adults. It compared CPAP with “pressure support” approaches, meaning BPAP, EPR, or both. Here is what it found:

• Nightly use was about the same. Pressure support added about 13 minutes of use per night, and that difference was not statistically meaningful.
• The small benefit faded. The longer people were followed, the smaller the gap became.
• Apnea control was the same. The number of leftover breathing events per hour did not differ.
• Daytime sleepiness was the same. Sleepiness scores improved equally.
• Mask leak was lower with pressure support. That is a real comfort benefit for some people.
• People who struggled with CPAP did slightly better on BPAP, gaining about 40 minutes of use per night. The certainty of this finding was very low, so it is a reason to consider BPAP for some patients, not proof that it works for everyone.

The authors concluded that BPAP and EPR do not justify routine use over CPAP for obstructive sleep apnea, given their similar results and higher cost.

Why lowering exhale pressure can backfire

There is also a physical reason not to assume that less pressure on the exhale is always better. Research from the past few years shows that the upper airway is often at its narrowest near the end of the exhale, just before the next breath. That is the moment the airway most needs support.

When EPR or BPAP lowers pressure during the exhale, it can make the airway less stable for some people. This may explain why some patients have more leftover apnea events after EPR is turned on, and why comfort features have not produced the big jump in CPAP use that many hoped for.

What this means for you: if you are on CPAP with EPR and your machine report shows a higher number of events than expected, ask your doctor whether your EPR setting is part of the problem. Do not change it on your own without a plan.

So Why Would Your Doctor Put You on BPAP?

When a sleep doctor chooses BPAP, there is usually a specific reason. Here are the most common ones.

1. You need high pressure and cannot tolerate it on CPAP

Some people need a high pressure to keep the airway open. Breathing out against that steady pressure can feel like exhaling into a strong wind. It can cause air swallowing, bloating, mask leaks, and waking up to rip the mask off.

BPAP lets the doctor keep the inhale pressure high enough to control apnea while giving you a lower pressure to breathe out against. This is the classic reason for switching someone with obstructive sleep apnea from CPAP to BPAP.

Insurance rules reflect this. Medicare and many private insurers usually cover BPAP for obstructive sleep apnea only after CPAP has been tried and documented as not working. That includes a trial of lower CPAP pressures that still failed to control symptoms or apnea events. If your doctor started you on CPAP first, that is often why.

2. Your blood has too much carbon dioxide

This is the most important medical reason for BPAP. Some people do not just have a blocked airway. They also do not breathe deeply enough to clear carbon dioxide (CO2) from the blood. Doctors call this hypoventilation.

CPAP keeps the airway open, but it does not make each breath bigger. BPAP does. Conditions where this matters include:

• Obesity hypoventilation syndrome. Extra weight on the chest and belly makes deep breathing harder, especially during sleep.
• COPD with high CO2, or COPD combined with sleep apnea (sometimes called overlap syndrome).
• Neuromuscular diseases such as ALS, muscular dystrophy, and myasthenia gravis, where the breathing muscles are weak.
• Chest wall conditions such as severe scoliosis.

The evidence here is stronger than it is for routine sleep apnea:

• A randomized trial in the Journal of Clinical Sleep Medicine studied people with obesity, airway disease such as COPD, and high CO2. After 3 months, BPAP lowered daytime CO2 by about 9.4 mmHg more than CPAP did. Nightly use and sleepiness were similar between the two machines.
• A Cochrane review of 21 randomized trials found that home breathing support with these devices lowered CO2 in people with COPD and high CO2. In stable COPD, it likely lowered the risk of death by about 25 percent.
• A separate meta-analysis of 19 randomized trials in COPD found the biggest survival benefit in people who started with the highest CO2 levels and in those whose CO2 dropped the most on treatment.
• In ALS, recent systematic reviews and an expert panel conclude that home breathing support relieves symptoms, improves quality of life, and extends survival.
• In neuromuscular and chest wall disease, an analysis of individual patient data found that how many hours you use the device each day mattered more than how aggressive the settings were.

A recent meta-analysis of 40 studies also found that this kind of pressure therapy improved sleep itself in people with chronic high CO2. Sleep efficiency, deep sleep, and REM sleep all increased, and arousals dropped.

Not everyone with obesity hypoventilation needs BPAP. Many people do well on CPAP, especially when obstructive sleep apnea is the main problem. Your doctor decides based on your CO2 level, oxygen level, sleep study results, and how you respond.

3. Your breathing pauses come from the brain, not the throat

In central sleep apnea, the airway is open but the brain briefly stops telling the body to breathe. CPAP cannot fix a missing signal. A BPAP machine with a backup rate (BPAP ST) can deliver a breath when you do not take one.

This can matter for people who take long-term opioid pain medicine. A systematic review found that CPAP failed more often in opioid users, while BPAP with a backup rate and another device called ASV (adaptive servo-ventilation) were able to bring breathing events back to normal levels.

Central sleep apnea is complex, and the best device depends on the cause. In some cases, such as central apnea that appears after starting CPAP, ASV may control events better than BPAP. Some heart failure patients should not use ASV at all. This is a decision for your sleep specialist.

4. CPAP failed for reasons that pressure can fix

Sometimes a sleep study shows that CPAP keeps the airway open but oxygen levels stay low, or that you keep waking up struggling against the pressure. In those cases, a BPAP trial in the sleep lab can show whether two pressures work better for you. A mask problem, however, is usually fixed with a better mask, not a new machine.

Signs Your Current Machine May Not Be the Right Fit

Talk to your doctor if you notice any of these:

• You feel like you cannot breathe out against the pressure.
• You wake up bloated or burping, which can mean you are swallowing air.
• You keep pulling the mask off in your sleep.
• Your machine report shows an AHI (events per hour) above 5 most nights, or large leaks.
• You still feel very sleepy during the day despite using your machine every night.
• You wake up with morning headaches, which can be a sign of high CO2.
• Your ankles are swelling, or you are more short of breath than usual.

What to Do Next

• Do not change your settings yourself. Pressure, EPR, and BPAP settings work together. One change can make another worse.
• Bring your data. Most machines and apps show nightly use, leak, and AHI. Bring a few weeks of reports to your appointment.
• Fix the mask first. Leaks and discomfort are often a mask fit problem. Ask your equipment supplier or sleep clinic to refit you.
• Ask about comfort settings before a new device. Ramp, humidity, heated tubing, and EPR can solve many comfort problems on CPAP.
• Ask whether your CO2 has been checked if you have COPD, a neuromuscular disease, severe obesity, or morning headaches. A blood test or overnight CO2 monitoring can show whether you need BPAP.
• If you are on BPAP, use it every night. The benefit depends on hours of use. Even the best machine does nothing on the nightstand.

Questions to Ask Your Doctor

• Why did you choose BPAP for me instead of CPAP?
• Am I using BPAP for comfort, or because my CO2 is high?
• Do I need a backup rate?
• What are my pressure settings, and what should my AHI and leak look like?
• When should we recheck my CO2 or repeat a sleep study?

Final Takeaway

BPAP is not a premium CPAP. For most people with obstructive sleep apnea, CPAP works just as well and is easier to get approved. EPR is a small comfort tweak, not a substitute for BPAP.

If your doctor chose BPAP for you, it is likely because your body needs more than an open airway. You may need help moving air in and out of your lungs, help clearing carbon dioxide, or a backup breath when your brain pauses. In those situations, BPAP is the right tool, and using it every night is what makes it work.

---

Disclaimer

This article is for general education only and is not medical advice. It does not replace a visit with your own doctor or sleep specialist. Do not start, stop, or change any treatment or device setting without talking to a qualified healthcare professional. If you have severe shortness of breath, chest pain, or confusion, seek emergency care right away.

---

References

1. Ahmad, A., Ahmad, R., Meteb, M., Ryan, C. M., Leung, R. S., Montandon, G., Luks, V., & Kendzerska, T. (2021). The relationship between opioid use and obstructive sleep apnea: A systematic review and meta-analysis. Sleep Medicine Reviews, 58, 101441. https://doi.org/10.1016/j.smrv.2021.101441
2. Centers for Medicare & Medicaid Services. (n.d.). Positive airway pressure (PAP) devices for the treatment of obstructive sleep apnea: Documentation and coverage requirements (MLN Fact Sheet ICN 905064). https://www.cms.gov/files/document/papdoccvgfactsheeticn905064textonlypdf
3. Cunha-Correia, C. D., Gama, M. D. P., Fontana, P. N., Fantini, F. G. M. M., Prado, G. F., Dourado Júnior, M. E. T., & Schwingel, P. A. (2024). Noninvasive mechanical ventilation assistance in amyotrophic lateral sclerosis: A systematic review. São Paulo Medical Journal, 142(1), e2022470. https://doi.org/10.1590/1516-3180.2022.0470.R1.100423
4. Delorme, M., Leotard, A., Lebret, M., Lefeuvre, C., Hazenberg, A., Pallero, M., Nickol, A. H., Hannan, L. M., Boentert, M., Yüksel, A., Windisch, W., Howard, M. E., Hart, N., Wijkstra, P. J., Prigent, H., Pépin, J.-L., Lofaso, F., Khouri, C., & Borel, J.-C. (2023). Effect of intensity of home noninvasive ventilation in individuals with neuromuscular and chest wall disorders: A systematic review and meta-analysis of individual participant data. Archivos de Bronconeumología, 59(8), 488–496. https://doi.org/10.1016/j.arbres.2023.05.002
5. Georges, M., Perez, T., Rabec, C., Jacquin, L., Finet-Monnier, A., Ramos, C., Patout, M., Attali, V., Amador, M., Gonzalez-Bermejo, J., Salachas, F., & Morelot-Panzini, C. (2022). Proposals from a French expert panel for respiratory care in ALS patients. Respiratory Medicine and Research, 81, 100901. https://doi.org/10.1016/j.resmer.2022.100901
6. Messineo, L., Bakker, J. P., Noah, W. H., & White, D. P. (2026). The effect of bilevel ventilation or modified continuous positive airway pressure on treatment adherence in adults with obstructive sleep apnea: A systematic review and meta-analysis. EClinicalMedicine, 97, 103993. https://doi.org/10.1016/j.eclinm.2026.103993
7. Messineo, L., White, D. P., & Noah, W. H. (2024). Positive airway pressure delivery: Overcoming old hurdles, exploring new frontiers. Frontiers in Sleep, 3, 1522635. https://doi.org/10.3389/frsle.2024.1522635
8. Noah, W. H., Messineo, L., & White, D. P. (2026). The Kairos of the upper airway: The critical time of mid-to-late expiration in the treatment of obstructive sleep apnea. Sleep Medicine, 148, 109209. https://doi.org/10.1016/j.sleep.2026.109209
9. Pinto, A. C. P. N., Rocha, A., Pachito, D. V., Drager, L. F., & Lorenzi-Filho, G. (2022). Non-invasive positive pressure ventilation for central sleep apnoea in adults. Cochrane Database of Systematic Reviews, 2022(10), CD012889. https://doi.org/10.1002/14651858.CD012889.pub2
10. Raveling, T., Vonk, J., Struik, F. M., Goldstein, R., Kerstjens, H. A., Wijkstra, P. J., & Duiverman, M. L. (2021). Chronic non-invasive ventilation for chronic obstructive pulmonary disease. Cochrane Database of Systematic Reviews, 2021(8), CD002878. https://doi.org/10.1002/14651858.CD002878.pub3
11. Tankéré, P., Razakamanantsoa, L., Khouri, C., Patout, M., Stauffer, E., Baillieul, S., Petitjean, T., Pépin, J. L., Tamisier, R., & Peter-Derex, L. (2025). Positive airway pressure therapies improve sleep architecture in patients with chronic hypercapnic respiratory failure: A systematic review and meta-analysis. Sleep Medicine Reviews, 84, 102168. https://doi.org/10.1016/j.smrv.2025.102168
12. Wu, Z., Luo, Z., Luo, Z., Ge, J., Jin, J., Cao, Z., & Ma, Y. (2022). Baseline level and reduction in PaCO2 are associated with the treatment effect of long-term home noninvasive positive pressure ventilation in stable hypercapnic patients with COPD: A systematic review and meta-analysis of randomized controlled trials. International Journal of Chronic Obstructive Pulmonary Disease, 17, 719–733. https://doi.org/10.2147/COPD.S344962
13. Zheng, Y., Yee, B. J., Wong, K., Grunstein, R., & Piper, A. (2022). A pilot randomized trial comparing CPAP vs bilevel PAP spontaneous mode in the treatment of hypoventilation disorder in patients with obesity and obstructive airway disease. Journal of Clinical Sleep Medicine, 18(1), 99–107. https://doi.org/10.5664/jcsm.9506