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Continuous Positive Airway Pressure (CPAP)

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Written by

Danielle Pacheco


Medically Reviewed by

Dr. Joel Gould

Fact Checked

Sleep apnea is a sleep-related breathing disorder that occurs when the airway is blocked completely or partially, causing people to wake up choking or gasping for air. The most common type of sleep apnea is obstructive sleep apnea (OSA), which is caused by a physical blockage obstructing the breathing passage. OSA is thought to affect up to 15% of men and 4% of women in the U.S. Another category is central sleep apnea (CSA), which occurs when the brain is unable to properly signal the muscles that regulate breathing.

For many people with sleep apnea, continuous positive airway pressure (CPAP) therapy is the first line of treatment. Other variations of CPAP, such as bi-level positive airway pressure (BiPAP) or adaptive servo ventilation (ASV), may also reduce sleep apnea symptoms. All forms of CPAP require a doctor’s prescription. CPAP is considered safe for adults and children of any age.

What Is CPAP Therapy?

The idea behind CPAP therapy is that pressurized air delivered into a sleeper’s mouth can keep their breathing passages open and decrease choking or gasping episodes during the night.  The optimal pressure setting varies by person, so the first step when prescribing CPAP therapy is to determine a patient’s best pressure level. Breathing evaluations known as titration tests can narrow down this setting.

CPAP therapy involves the following hardware components:

  • CPAP Machine: A CPAP machine is equipped with a fan that draws in air from your bedroom and a filter to purify the air before pressurization can occur. Many machines also feature heated humidifiers. Pressure is measured in centimeters of water pressure, or cm H20. Most machines made today can reach pressure settings of up to 25 cm H20, but for most people, the optimal setting will fall between 5 and 10 cm H20.
  • Face Mask: The face mask seals the nostrils and/or mouth in order to properly administer the pressurized air. Masks today fall into three basic categories. Nasal masks feature small prongs that fit inside the nostrils, and may also fit over the bottom of the nose. Nasopharyngeal masks are equipped with a tube that fits inside the nose and delivers air into the nasopharynx, bypassing the nasal cavity for faster delivery. Lastly, full face masks form a complete seal over the nose and mouth. Most masks have straps for a more secure fit.
  • Connective Hose: A thin hose – typically 6 feet or longer – connects the base of the face mask to the motor of the CPAP machine. A tight seal is needed at both ends to prevent air from escaping.

CPAP machines administer air at a fixed pressure setting that corresponds to the doctor’s prescription. Patients should never manually adjust the pressure level without first speaking to their physician.

BiPAP therapy is slightly different because the pressure setting during inhalation will be different from the setting during exhalation. Both of these settings are fixed, but some sleepers find breathing easier with different levels of pressure for inhaling and exhaling. ASV therapy automatically adjusts the pressure levels to correspond with the sleeper’s breathing patterns throughout the night.

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    Who Does CPAP Treat?

    CPAP has proven effective at treating symptoms of both OSA and CSA. However, some sleep apnea patients may not respond to CPAP. For instance, BiPAP may be better suited to OSA patients who require higher pressure settings, typically 15-20 cm H20. Studies have also found that people with CSA often respond better to BiPAP or ASV therapy.

    CPAP alone cannot be used to treat people who are unable to spontaneously breathe. Additionally, researchers have noted the following contraindications associated with CPAP therapy:

    • Uncooperative or anxious patients
    • People who have reduced consciousness and cannot protect their airway
    • Those who are undergoing respiratory arrest
    • People with trauma or burns to the face
    • Patients who have undergone facial, esophageal, or gastric surgery
    • Those who live with air leak syndrome
    • People who display large respiratory secretions
    • Patients who experience severe nausea and vomiting
    • People who have been diagnosed with conditions characterized by hypercarbia asthma or chronic obstructive pulmonary disease
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