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The number of people in the United States diagnosed with sleep apnea has been dramatically increasing in recent years. Positive airway pressure (PAP) devices, which are the primary treatment for sleep apnea, has thus also surged. For those who are just becoming familiar with this health condition and these devices, the different types of machines can be dizzying.

In this guide, we’ll help to demystify the two most common PAP device types, the CPAP and BiPAP (or BPAP). We’ll review how they work, their similarities and differences, who they may be best for, and all of the other key details that you need to understand which of these machines may be most appropriate for you or your loved one.

CPAPSimple setup / Effective for most sleep apnea cases / Lower-cost optionsSingle pressure / Less useful in treating serious sleep apnea or other conditions
BiPAPVariable pressure for comfort and flexibility / More effective in treating other conditionsMore expensive

How Do CPAP and BiPAP Machines Work?

Both CPAP and BiPAP machines are types of positive airway pressure (PAP) devices. This means that the device filters and pressurizes air and pumps that air into the airway (in the back of your throat). This pressurized air helps to prevent the airway from closing while you are asleep, which can pose various health risks.

PAP devices may be referred to by other names including non-invasive positive pressure ventilation (NIPPV) or non-invasive ventilation (NIV), however, PAP is the most common term.

These devices are composed of three primary parts. The device itself draws in air from your room and pressurizes it. A hose moves this air from the device to a mask, and the mask transfers this air into your windpipe. A water reservoir (humidifier) is included in many devices to help add moisture to the air, and there may also be a heating element to warm this water.

There are two main types of masks that are used with CPAP and BiPAP machines.

Full face

This kind of mask fully covers the nose and mouth and is held in place by straps around the head. It is best for people who breathe at night through their mouth or a combination of their nose and mouth, but it can be more intrusive and uncomfortable for some users.

Nasal pillow or mask

These masks either fit over or under the nose, delivering air through the nostrils. Some may also include a strap under the chin to keep a person from breathing through their mouth.

What is CPAP?

The C in CPAP stands for continuous because these devices offer one consistent level of pressurized air.

How Does a CPAP Work?

The CPAP draws in air from the room, filters and pressurizes it, and then delivers that air to your windpipe. The same pressure of air is maintained the whole time including as you inhale and exhale. In some users, this continuous pressure may make it harder to comfortably exhale.

How is CPAP Pressure Set?

The pressure for your CPAP device will be determined by a sleep expert who monitors your breathing at night while in a sleep study (usually overnight in a clinic). These devices are designed to “ramp up,” which means that they don’t immediately start at full pressure. This can make it less intrusive when you are first trying to fall asleep.

What is an APAP Machine?

The A in APAP stands for autotitrating, which means that the device detects your breathing patterns and then modifies the amount of pressure (from within a given range of levels) automatically through the night.


What is BiPAP?

Bi-level is the key word in BPAP, and it refers to the device having two different pressure settings: one for inhalation and one for exhalation. It may be referred to at times as VPAP for variable positive airway pressure.

BiPAP devices are less commonly prescribed than CPAP. In many cases, BiPAP is only prescribed when a CPAP does not work (such as with obstructive sleep apnea, known as OSA). BiPAP is prescribed ahead of CPAP in patients with central sleep apnea (CSA) or complex sleep apnea (a mix of OSA and CSA).

How Does a BiPAP Work?

The components of a BiPAP are the same as with a CPAP, the difference is just that the airflow generator in the device can pump air at varying levels of pressure.

How is BiPAP Pressure Set?

As with CPAP, the BPAP pressure will initially be determined through a sleep study. However, as with APAP, some machines have the ability to measure and adjust the pressure depending on a person’s rate and depth of breathing.

What is an ASV Machine?

Another device that offers varying air pressure levels is the ASV, which stands for adaptive servo-ventilation. These devices have more nuanced settings to make the delivery of air more tailored to the user including on a breath-by-breath basis.


What Conditions Are CPAP and BiPAP Used For?

The most common reason these devices are prescribed is sleep apnea. Apneas are temporary pauses in breath, and these can pose major health risks including cardiovascular complications. There are three main types of sleep apnea:

  • Obstructive sleep apnea (OSA): this is caused by the blockage of the airway and is often associated with snoring. It is the most common type of sleep apnea.
  • Central sleep apnea (CSA): this is not caused by a blockage but rather by a failure of the muscles that control breathing to adequately receive signals from the brain to function properly.
  • Complex sleep apnea: it is possible for people to have both OSA and CSA, which is complex or mixed sleep apnea.

There are some other health conditions that involve potentially diminished breathing or airflow and that can be helped with the use of PAP devices. These conditions include

  • Respiratory Failure
  • Chronic Obstructive Pulmonary Disease (COPD)
  • Heart Failure
  • Muscular Dystrophy

How Much Do CPAP or BiPAP Machines Cost?

The list price for CPAP and BiPAP devices can range from hundreds to thousands of dollars. As a general rule, BiPAP machines cost a a few times more than CPAP machines, although this can vary based on the brand, model, and features.

Because they require a prescription, both CPAP and BiPAP machines are often covered by insurance. This can significantly reduce the cost, and your doctor or insurance provider can help you understand any out-of-pocket costs that you may incur. These costs can sometimes include masks or replacement parts (if needed).

Which is Better — CPAP or BiPAP?

There is no clear answer to whether a CPAP or a BiPAP is better. Both can be very helpful in addressing breathing problems during sleep. A CPAP works for most people with OSA, but for people who have CSA, complex sleep apnea, or other conditions, a BiPAP usually is a better fit. A BiPAP or device with variable pressure may also be best for people who find the use of a CPAP uncomfortable.

In the end, it’s important to talk to a sleep technician and your doctor as they can work with you to help identify which device would be the best to help you breathe freely at night.