A CPAP machine delivers a steady stream of pressurized air through a mask to keep your airway open while you sleep. Its primary use is treating obstructive sleep apnea, a condition where the soft tissues in your throat collapse repeatedly during the night, cutting off airflow and disrupting sleep. CPAP is the most widely prescribed treatment for this condition and remains the gold standard after decades of use.
How a CPAP Machine Works
During sleep, the muscles in your throat relax. For most people, this isn’t a problem. But if you have obstructive sleep apnea, that relaxation allows your tongue, the soft tissue at the back of your mouth, and the small flap called the uvula to shift far enough into the airway to partially or fully block it. Each blockage triggers a brief awakening (often so short you don’t remember it) so your muscles can tighten and reopen the passage. This cycle can repeat dozens or even hundreds of times a night.
A CPAP machine stops that cycle by creating a pneumatic splint. It pushes a continuous flow of air at a set pressure into your upper airway, holding those soft tissues in place so they can’t collapse. The pressure is measured in centimeters of water (cm H2O), and most people need somewhere between 4 and 20 cm H2O, with the average prescription landing around 8 to 10. Your specific setting is determined during a sleep study or titration test, where a technician gradually adjusts the pressure until your breathing stabilizes.
Who Qualifies for CPAP Therapy
Sleep apnea severity is scored using the Apnea-Hypopnea Index, or AHI, which counts how many times per hour your breathing stops or becomes dangerously shallow. CPAP is typically prescribed under two scenarios. If your AHI is 15 or higher, that alone qualifies you. If your AHI falls between 5 and 14, you’ll generally qualify when you also have symptoms like excessive daytime sleepiness, impaired thinking, mood changes, insomnia, high blood pressure, heart disease, or a history of stroke.
These thresholds matter because they determine insurance coverage, too. Medicare and most private insurers follow the same cutoffs, meaning your sleep study results directly influence whether your machine is covered.
Benefits Beyond Breathing
The most immediate change most people notice is daytime alertness. In one study of 80 patients with severe sleep apnea (average of 54 breathing disruptions per hour), roughly 86% saw meaningful improvements in daytime sleepiness after starting treatment. The remaining 14% continued to experience excessive sleepiness, which can signal other contributing factors worth investigating.
CPAP also has a modest but real effect on blood pressure. Meta-analyses show an average reduction of about 3 mmHg, with slightly larger drops in people whose sleep apnea is more severe. That number may sound small, but at a population level, even a few points of blood pressure reduction translates to fewer heart attacks and strokes over time.
Speaking of strokes: a study of older adults on Medicare found that each month of consistent CPAP use was associated with a 2% reduction in stroke risk. That effect compounds over time, making adherence especially important for people who already carry cardiovascular risk factors.
Types of CPAP Masks
The mask is the part of the system you’ll interact with most, and choosing the right one is often what determines whether you stick with treatment. There are four main styles.
- Nasal pillow masks are the smallest option, sitting just at the nostrils. They work well if you feel claustrophobic in larger masks, want to wear glasses, or have facial hair that interferes with a seal.
- Nasal masks cover the entire nose and tend to handle higher pressure settings better. They’re also a good fit if you move around a lot during sleep.
- Full-face masks cover both the nose and mouth. These are the go-to choice if you breathe through your mouth at night or deal with chronic nasal congestion.
- Oral (hybrid) masks deliver air through the mouth only, which can work for mouth breathers who also want an unobstructed view for reading or watching TV before sleep.
Most sleep specialists recommend starting with the least intrusive mask that works for your breathing pattern, then switching if needed. It’s common to try two or three styles before settling on one.
Common Side Effects
CPAP side effects are rarely dangerous, but they’re the main reason people stop using the machine. Knowing what to expect makes it easier to troubleshoot.
Dry nose and throat are the most frequent complaints, caused by the constant airflow stripping moisture from your nasal passages. Most modern CPAP machines include a heated humidifier that adds moisture to the air, and adjusting the humidity level usually resolves this within a few nights.
Aerophagia, or swallowing air, causes bloating, gas, and frequent belching. In severe cases, people with aerophagia may belch over a hundred times an hour. This tends to happen when the pressure is set too high or when a mask leak forces you to swallow air to compensate. Lowering the pressure, switching to an auto-adjusting machine, or trying a different mask style can help.
Skin irritation and red marks from the mask are common early on, usually from overtightening. The mask should seal with minimal strap tension. If you’re cranking the straps tight to stop leaks, the mask likely doesn’t fit your face shape and a different size or style will work better. Some people also experience a sense of claustrophobia, particularly with full-face masks, which often improves with gradual acclimation or a switch to nasal pillows.
CPAP vs. BiPAP
CPAP delivers one constant pressure level. BiPAP (bilevel positive airway pressure) delivers a higher pressure when you inhale and a lower one when you exhale, making it easier to breathe out against the airflow. For straightforward obstructive sleep apnea, CPAP is the standard first-line treatment.
BiPAP becomes the better option for central sleep apnea, where the brain intermittently fails to send the signal to breathe, or for complex sleep apnea, which combines obstructive and central patterns. Certain BiPAP modes include a backup breathing timer that delivers a breath if you haven’t taken one within a set window. BiPAP is also preferred for people with lung conditions like COPD or obesity hypoventilation syndrome, where exhaling against constant pressure is difficult. Your sleep specialist will determine which device fits your diagnosis.
Other Medical Uses
While adult sleep apnea is by far the most common application, CPAP has a role in other settings. In neonatal intensive care units, nasal CPAP helps premature babies whose lungs aren’t fully developed breathe more effectively. A study across 26 hospitals in Malawi found that premature newborns treated with CPAP for respiratory distress had survival rates above 60%, even in low-resource settings with nurse-led programs. This has made CPAP an important tool in neonatal care worldwide.
Making CPAP Work Long-Term
Consistency matters more than perfection. Most insurance providers and sleep specialists define “adherence” as using the machine for at least four hours per night on at least 70% of nights. Modern CPAP machines track your usage data automatically and can transmit it to your provider, so you’ll typically have check-ins during the first few months to review how things are going.
The adjustment period is real. Most people need two to four weeks to get comfortable sleeping with the mask, and it’s normal to pull it off unconsciously during the first few nights. Wearing the mask while awake for short periods, like while reading or watching something, can help your brain stop treating it as a foreign object. If the pressure feels overwhelming when you’re trying to fall asleep, many machines offer a “ramp” feature that starts at a lower pressure and gradually increases over 15 to 30 minutes.
Cleaning is straightforward but essential. The mask cushion should be wiped daily and washed weekly, the tubing rinsed weekly, and the humidifier chamber emptied and refilled with distilled water each day. Neglecting this leads to mineral buildup, bacterial growth, and a mask that doesn’t seal properly. Most supplies, including mask cushions and filters, need replacing every few months, and insurance typically covers replacements on a set schedule.