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22 million Americans have sleep apnea, a dangerous sleep disorder where the individual stops breathing during sleep. Fortunately, sleep apnea is extremely treatable – through the use of CPAP or BIPAP therapy.

However, many people abandon CPAP therapy or do not use it as directed because they find it uncomfortable. If these people were made aware of the different PAP therapy options they have for treating their sleep apnea, it could improve compliance and relieve their sleep apnea.

Below we’ll explain all the different kinds of PAP therapy used to treat sleep apnea and various respiratory problems, so you can understand the pros and cons of each and which will better serve your needs.

For our unbiased, research-based recommendations, check out our Best CPAP Machines and Best BiPAP Machines pages.

Name What It Treats Pros Cons
CPAP (Continuous positive airway pressure) Obstructive sleep apnea (OSA) Most popular treatment
More affordable option
Simple and easy to use
Best option for people with mild to moderate OSA
Single pressure setting can be uncomfortable for some users
Not effective for CSA or other respiratory or pulmonary conditions
BIPAP (Bilevel positive airway pressure) Central sleep apnea (CSA)
Chronic obstructive pulmonary disorder (COPD)
Congestive heart failure (CHF)
Variable pressure settings can be more comfortable
More customizable settings
Effective at treating a wider range of conditions
More expensive
In cases of OSA, only available as a second option after CPAP fails

What health conditions do CPAP and BIPAP treat?

CPAP (continuous positive airway pressure) and BIPAP (bilevel positive airway pressure) are two types of noninvasive ventilation (NIV) therapy prescribed to treat sleep apnea and other respiratory problems that interfere with sleep:

  • Obstructive sleep apnea (OSA) is sleep disorder characterized by momentary pauses in breathing during sleep (called “apneas”) caused by a collapse or obstruction of the airways, such as from excess fatty tissue in the throat.
  • Central sleep apnea (CSA) occurs when the brain stops telling the lungs to breathe. This type of sleep apnea is due to a neurological communication issue, rather than a physical blockage as with OSA.
  • Mixed sleep apnea or complex sleep apnea is a combination of symptoms from both OSA and CSA. Complex sleep apnea is often diagnosed when the apnea episodes are not effectively eliminated by CPAP therapy.
  • Chronic obstructive pulmonary disorder (COPD) is a progressive lung disease that obstructs the airflow from the lungs.
  • Congestive heart failure (CHF) is a chronic heart condition where the heart fails to pump enough blood to meet the body’s needs.
  • Other pulmonary or neuromuscular conditions such as Cheyne-Stokes respiration, Parkinson’s, or ALS.

People with any of these conditions have to work harder to breathe properly during sleep to maintain appropriate blood flow and oxygen levels. Sleep-disordered breathing disrupts sleep quality and can result in choking, gasping, or snoring. Untreated, it causes chronic sleep deprivation and increases the person’s risk of developing type 2 diabetes or cardiovascular disease.

normal breathing vs snoring vs sleep apnea

How do CPAP and BIPAP work?

The severity of sleep apnea is defined by the patient’s apnea-hypopnea index (AHI), which refers to how many apneic episodes you experience during sleep. The goal of PAP therapy is to reduce AHI below 5, so patients can enjoy more restful sleep and all the health benefits associated with that.

You’ll note that both CPAP and BIPAP finish with PAP. That’s because both are non-invasive therapies that deliver positive airway pressure (PAP). The air pressure creates a pneumatic splint that keeps your airways open and pushes your tongue forward and out of the way. Both machines look fairly similar – a tube connects the machine to a mask you wear over your face or nose.

The main difference between the BIPAP and CPAP is how the flow of pressure is delivered, which is why one can be a more suitable option for treatment over the other in certain cases or patients.

Neither of these therapies takes over your breathing. Rather, they regulate the air pressure you’re breathing in to help you keep breathing steadily throughout the night.

What is CPAP?

Continuous positive airway pressure (CPAP) is the first line of defense for treating OSA, and most people with straightforward mild to moderate OSA will have success with this therapy.

How does CPAP work?

CPAP machines deliver a continuous flow of air at a steady, defined pressure.

All CPAP machines feature a ramp-up setting to help you adjust to the air pressure, starting out at a lower-than-prescribed pressure and slowly increasing as you fall asleep. CPAP therapy does take some getting used to. Normally, within a few weeks of using the device, you will be fully adjusted.

Since CPAP machines use the same pressure setting for both inhalation and exhalation, some people find it tougher to exhale comfortably. That’s why many CPAP machines now include a variability pressure setting known as C-Flex, AFLEX, Bi FLEX, EPR, or SensAwake, depending on the manufacturer. This feature reduces the pressure setting up to 3 cm on exhales.

Some patients will not need to ever use this setting, and some may find this setting provides sufficient pressure relief. Others, however, will need more pressure relief, which often leads them to explore BIPAP as an alternative treatment.

How is CPAP pressure determined?

After you are diagnosed with sleep apnea or another one of the conditions above, your sleep doctor will order a CPAP titration study to properly calibrate your CPAP machine. This test is also performed in a sleep clinic, and may even be done in the same night as your diagnostic exam.

Before calibrating the air pressure, the sleep technologist will fit you for a CPAP mask. CPAP machines can use nasal, full face, or nasal pillow masks. Some people find one more comfortable than others. For instance:CPAP machine masks types

  • People with allergies who tend to breathe through their mouth will do better with a full face mask as opposed to one of the nasal types.  
  • Nasal pillows are the most lightweight option, making them a good fit for people who feel claustrophobic from the other masks or have a lot of facial hair.
  • The nasal mask provides a nice middle ground between these options, less bulky than the full face mask but sturdy enough to stay put even if you move often during sleep.


Once you choose your mask, you will go back to sleep, with sensors attached to your body as they were during your diagnostic polysomnogram. As they monitor your vitals, the sleep technician will change the air pressure while you’re sleeping, in order to find the right air pressure setting.

What is APAP?

Auto-titrating positive airway pressure (APAP) machines function similarly to CPAP. The A stands for automation, as the machine senses and responds to subtle changes in breathing, automatically adjusting the pressure according to a set range determined from your titration study.

APAP is often prescribed for people who experience apnea only during REM sleep, when they have allergies, or from sleeping on their back.

For example, when you sleep on your back, your jaw and tongue fall back and cause an obstruction of your airways, leading to longer and more frequent apnea episodes. If you have seasonal allergies, you’ll need higher pressure to clear your nasal congestion during those times.

What is BIPAP?

Bilevel positive airway pressure (BIPAP) is prescribed for people with central sleep apnea, chronic obstructive pulmonary disorder (COPD), congestive heart failure (CHF), as well as other chronic lung or neuromuscular disorders.

In cases of obstructive sleep apnea, BIPAP is only prescribed after CPAP therapy proves ineffective. This often includes people with extreme OSA, mixed sleep apnea, or who simply don’t respond well to CPAP therapy. For example, because the pressure delivered with CPAP is steady and constant, some patients have difficulty exhaling against it.

You’ll occasionally see BIPAP referred to as VPAP (variable positive airway pressure). Both describe the same therapy, but have different trademarks depending on the manufacturer. Philips Respironics machines have the BIPAP label, while Resmed produces VPAP machines.

How does BIPAP work?

Unlike CPAP, which delivers a continuous flow of pressure, BIPAP machines offer two different flows of pressure – a higher one for inhalation (ipap) and a lower one for exhalation (epap).

Many BIPAP machines include a feature that measures a person’s optimal amount of breaths per minute, and if a person breathes more slowly than that, the machine temporarily increases the air pressure to force them to breathe.

What is ASV?

Adaptive servo ventilation (ASV) is an alternative option for people who don’t respond well to BIPAP therapy, but still require the variable flow of pressure to treat their apnea. These machines are more advanced, able to vary the volume and pressure of the air, as well as the speed at which it is delivered.

ASV may be used to treat CSA, mixed sleep apnea, or Cheyne-Stokes respiration.

How much does CPAP or BIPAP cost?

CPAP masks start at $185, according to the American Sleep Apnea Association, and can range up to $5,000. BIPAP machines are usually more expensive than CPAP. The cost of cleaning supplies and replacement parts can also add up.

Becauses these are medical devices controlled by the FDA, you’ll need a prescription in order to get one. However, that does not mean you necessarily have to purchase directly through your doctor. Depending on your insurance coverage, you may find a better deal online.

Before choosing a model, ask your healthcare team for their opinion and read online reviews from other users. To find a quality PAP machine, look for information on the leak rates, any humidity issues, and additional included features.

Is CPAP or BIPAP better?

The good news is both CPAP and BIPAP are extremely effective for treating sleep apnea – as long as you use it every night as prescribed. You will also need to replace different parts of the machine every few months, and regularly clean everything to keep it working properly.

Ultimately, one type of PAP therapy may be better for you based on your originating health condition and personal comfort preferences, but either is an equally good option.

Additional resources

More from Tuck

Around the web

  • The American Sleep Apnea Association is an advocacy organization focused on furthering sleep apnea research. The site posts educational resources about diagnosing and treating sleep apnea, and hosts an online Sleep Health Forum and in-person A.W.A.K.E. support groups. They also offer a CPAP assistance program to help individuals pay for their therapy.
  • SleepApnea.com, run by Philips Respironics, provides an online directory of local sleep clinics and sleep physicians.
  • The Community for Sleep-Care Professionals offers guidance on the three types of CPAP masks. The article itself is geared towards health practitioners, but patients may find it helpful to learn about the pros and cons of the various mask types.
  • For a visual guide, the Mayo Clinic has a helpful slideshow of the different mask types along with quick facts and features.
  • Sleep Review Magazine shares 9 alternative therapies for OSA besides CPAP therapy, ranging from less-invasive oral appliances to more extreme surgical options.
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