How Does a CPAP Machine Work to Treat Sleep Apnea?

If you have been told that you need to use a continuous positive airway pressure (CPAP) machine to treat your sleep apnea, you may wonder how a CPAP machine works. Here, you'll learn how these devices relieve snoring and sleep apnea with pressurized air and what special considerations may be necessary if you have central sleep apnea.

Man with sleep apnea and CPAP in bed
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CPAP machines have been used for the treatment of sleep apnea since 1981. Dr. Colin Sullivan first recognized the potential benefit of a constant, pressurized airflow created with the motor of his mother’s vacuum cleaner. Sleep apnea had previously required tracheostomy to resolve, bypassing the collapse of the throat.

Now, with a fitted mask, tubing, and a machine that could generate air pressure, he found, the disorder resolved. It was a remarkable discovery—and one met with initial skepticism. It would take five years before the devices became more widely available commercially.


Click Play to Learn All About CPAP Machines

This video has been medically reviewed by Sanja Jelic, MD.

How CPAP Works

Modern CPAP machines work based on the same principles as the initial devices developed by Dr. Sullivan. The pressures are now generated with smaller, quieter motors. Nevertheless, room air (not oxygen) is taken in through a filter and pressurized according to settings prescribed by your sleep specialist.

Machines are set to deliver a pressure from 4 centimeters of water pressure (CWP) up to a maximum of 25 CWP. This air is often passed through a heated humidifier and delivered via tubing to the mask interface.

The constant flow of pressurized air creates a cushion along the upper airway. Some have described it as a pneumatic (air) splint that keeps the throat from collapsing. This prevents the soft palate, uvula, and tongue from shifting into the airway. It reduces the vibration that creates the sound of snoring.

It may relieve swelling within the nose and clear out mucus from along the airway. By supporting the airway, breathing normalizes and sleep quality improves as fragmented sleep resolves. Oxygen levels can be maintained. The serious consequences of sleep apnea can be averted.

Automatic CPAP machines vary slightly in that they can detect a collapse of the airway by measuring resistance and react by increasing the pressure as needed during the night to further resolve the sleep apnea. These devices will also test lower pressures and adjust downward if possible.

Side Effects and Risks

Some inevitably worry about the consequences of seemingly artificial or “unnatural” CPAP therapy. Fortunately, there are surprisingly few side effects.

Still, in order to avoid side effects and ensure successful use, it is important that you have support when you first begin using CPAP. Early communication with your healthcare team so they can help you troubleshoot problems is essential.

Two of the most common problems associated with CPAP use are an ill-fitting mask and dry mouth. These can be alleviated with mask shape adjustments and humidification. Similarly, air leaks, challenges for bed partners, and air swallowing (aerophagia) are all commonplace and can be addressed to avoid discontinuation.

CPAP therapy does not worsen asthma or chronic obstructive pulmonary disease (COPD). Rather than causing a stroke, therapy actually reduces the risk of having one.

The nasal sinuses and inner ears are not typically impacted by the treatment, though case reports suggest it is possible for small amounts of pressure to be transduced across the tissues of the face.

There is some evidence that an overly tight or restrictive mask could affect the growth of the mid-face in children, but treatment can be monitored and adjusted to avoid this.

Treatment of Central Sleep Apnea

It is important to review the special case of a related condition. Central sleep apnea is defined by pauses in breathing that are characterized by a lack of effort to breathe, rather than a collapse of the airway. It most often occurs secondary to stroke, congestive heart failure, or narcotic or opioid medication use.

It can also occur in response to CPAP therapy itself, in a condition called complex sleep apnea. In central sleep apnea, it is sometimes necessary to consider other therapy modalities.

In particular, bilevel therapy is sometimes necessary. Bilevel therapy delivers two pressures, one to breathe in and a lower pressure to breathe out, and can adjust pressure on the fly to compensate for breathing pauses. This timed mode inflates the lungs to ensure a minimum number of breaths occur.

In addition, a more sophisticated level of treatment called adaptive (or auto) servo-ventilation can be used. This allows control of breath rate, volume, the timing of the delivered airflow, and other variables in those who have more significantly compromised breathing.

A Word From Verywell

Using a CPAP machine can take some time to get used to and optimize. Overall, you're likely to find that, given the benefits of CPAP therapy, its side effects are minimal and easily overcome.​ Fortunately, you don’t need to know a lot about how your machine works.

Be sure to check in with your healthcare provider if you're uncomfortable in any way: a well-qualified, board-certified sleep specialist will be able to assess your health, review your sleep study, and select the optimal treatment methods to improve your condition.

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8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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