What Is Continuous Positive Airway Pressure (CPAP) Therapy?

CPAP Treats Sleep Apnea with Air Pressure Delivered Via a Mask

What is CPAP? Learn how the therapy effectively treats sleep apnea with a mask, tubing, and machine
What is CPAP? Learn how the therapy effectively treats sleep apnea with a mask, tubing, and machine. Brandon Peters, M.D.

For nearly everyone who has been diagnosed with sleep apnea, the conversation quickly turns to possible treatment options. The most effective and commonly used one is continuous positive airway pressure (CPAP), but what is CPAP? Take a moment to learn about the basic components of CPAP, including the  mask, tubing, and humidifier. Discover how CPAP effectively treats sleep apnea by delivering air pressure via a face mask.

What Is CPAP?

CPAP is the gold standard treatment for obstructive sleep apnea. How does CPAP work? It is a machine that provides a constant flow of pressurized air that helps to maintain an open airway by preventing its collapse. This air is delivered via a fitted mask. CPAP has been used to treat sleep apnea since 1981 with few side effects. It is also effective in eliminating snoring, which usually occurs due to the vibration of the tissues in the throat. Although there are many different manufacturers of CPAP equipment, each unit consists of the same basic components.

CPAP Machine

The CPAP machine is the workhorse of your treatment. With a small motor, it takes in room air, filters it, and generates the air pressure that is the mainstay of treating sleep apnea. Newer units are small, often smaller than a loaf of bread, and relatively quiet. The newest ones make little to no noise. Most run on electricity, but battery units are also available.

The prescribed pressure level is often determined through a sleep study called a polysomnogram. However, it can also be set with an autotitration function (AutoCPAP or APAP) that automatically determines the pressure needed to keep your airway open. The pressure settings are determined by your sleep physician and set by your equipment provider.

In addition, there is often a feature that makes it possible to set a pressure ramp, which allows you to fall asleep at a lower pressure that steadily increases to the therapeutic pressure that you need either after a set period of time has elapsed or after your breathing becomes more regular, indicating that you have fallen asleep.

Most models have sophisticated methods of tracking your use with an internal memory card. This data can also be shared via an internal or external modem to cloud-based data storage that can be remotely accessed by your provider. This can help your doctor to assess your compliance to the treatment. It also may determine whether insurance will pay for your continued therapy.


As a comfort measure, it is possible to add humidity to the air that is delivered with an attached humidifier. This is integrated into most newer models. There is a water chamber that generally consists of a plastic reservoir that can be filled with distilled water. Heated humidifiers include a small hot plate that increases the amount of evaporation and moisture put into the inhaled air.

As the air passes over the water, direct evaporation occurs and the humidity of the air increases.

It is very important to keep this water reservoir clean, as it can rarely be a source of recurrent respiratory infection or even mold. This will generally only occur if the water is left unattended in the tank for an extended period of disuse.

CPAP Hose or CPAP Tubing

The next component that is standard to all CPAP machines is the CPAP hose or tubing. The CPAP tubing is typically made of a flexible plastic, allowing some degree of movement. Frankly, it resembles the extension hose on a vacuum cleaner. It is typically about six feet long. However, with an adapter or connector, it is possible to have two lengths of tubing linked together. You should be cautious about extending the hose too much as it may decrease the pressure that is ultimately delivered to your face mask. The tubing connects the main output of the machine to the mask. It may be heated and have a temperature setting that you can control to prevent condensation of water into the tubing.


The CPAP mask is, undeniably, the most important part of your experience with CPAP. It is where the "rubber meets the road" and it will make you fall in love with your CPAP machine – or hate it. There are three basic styles of CPAP masks: nasal pillows that sit in the nostrils, an over-the-nose nasal mask, and a full-face mask that covers the nose and mouth. There are dozens of CPAP mask styles available, which makes it all the more important in how to choose one. Work with your physician or equipment provider to find the best mask for you, especially in the first 30 days of CPAP use or any time that you are struggling with leak issues or discomfort from your mask.

CPAP can be an effective treatment for obstructive sleep apnea, but it only does you good if you use it. If you struggle, speak with your sleep specialist about other options, including bilevel or ​BiPAP therapy.

Kryger, MH et al. "Principles and Practice of Sleep Medicine." Elsevier, 5th edition, pp. 1233.

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