Continuous positive airway pressure, or CPAP, is a breathing therapy that delivers a steady stream of pressurized air through a mask to keep your airway open while you sleep. It’s the most common treatment for obstructive sleep apnea, a condition where soft tissues in the throat collapse repeatedly during the night, blocking airflow and disrupting sleep. The machine doesn’t breathe for you. It simply creates enough air pressure to act as a splint, holding your airway open so you can breathe normally.
How CPAP Keeps Your Airway Open
When you fall asleep, the muscles in your throat relax. For most people, that’s not a problem. But if you have extra tissue, fatty deposits around the airway, enlarged tonsils, or weakened throat muscles, that relaxation can cause the airway to narrow or close entirely. Each time it closes, your brain briefly wakes you to restore breathing, often dozens of times per hour without you realizing it.
A CPAP machine solves this by pushing air into your nose (or nose and mouth) at a pressure high enough to prevent the collapse. Think of it like inflating a flexible tube from the inside: the walls can’t fold inward as long as the pressure stays constant. This works during both inhaling and exhaling, which is what makes it “continuous.” Beyond keeping the throat open, the pressurized air also helps keep the tiny air sacs deep in your lungs from collapsing at the end of each breath, improving oxygen levels overall.
What’s Inside a CPAP Machine
A standard CPAP setup has five core parts: a small motor that draws in room air and pressurizes it, an air filter that cleans particles from that air, a flexible tube (hose) that carries the pressurized air, a mask that fits on your face, and straps that hold the mask in place. Many modern machines also include a heated humidifier, which warms and moistens the air before it reaches your airway. This addition significantly reduces common complaints like nasal dryness and congestion.
Some newer machines have auto-adjusting pressure, meaning they detect changes in your breathing throughout the night and increase or decrease the air pressure as needed rather than delivering one fixed setting.
Types of CPAP Masks
The mask is the part most people struggle with, and choosing the right style makes a real difference in comfort.
- Nasal pillows are the smallest option, sitting just at the entrance of each nostril. They work well if you feel claustrophobic in larger masks, want to wear glasses while reading in bed, 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 a good fit if you move around a lot during sleep, since the broader surface holds its seal more reliably.
- Full-face masks cover both the nose and mouth. These are typically recommended if you breathe through your mouth at night or have chronic nasal congestion that makes nose-only breathing difficult.
Most people start with a nasal mask or nasal pillows. If mouth breathing is a problem with those options, a chin strap or heated humidifier can sometimes help before switching to a full-face mask.
CPAP vs. BiPAP
CPAP delivers one constant pressure level whether you’re breathing in or out. BiPAP (bilevel positive airway pressure) delivers a higher pressure when you inhale and a lower pressure when you exhale. This makes exhaling feel more natural and less like breathing against resistance. BiPAP is generally considered when CPAP pressure needs to be set at higher levels (typically above 12 to 15 cmH₂O) or when a patient has trouble tolerating steady pressure throughout the breathing cycle.
What CPAP Therapy Improves
The most immediate benefit most people notice is less daytime sleepiness. When your airway stays open, you stop cycling through those repeated micro-awakenings, and your sleep architecture returns to something closer to normal. Sleep quality, mood, and concentration often improve within the first few weeks.
Longer-term use is associated with better blood pressure control and improved sleep-related quality of life. In clinical studies, patients using CPAP showed a measurable reduction in their apnea-hypopnea index, the number of breathing disruptions per hour of sleep. One study of patients with severe sleep apnea found that the average AHI dropped from about 33 events per hour at baseline to roughly 29 after two years of use, with the greatest improvements in the most severe cases.
Meeting Compliance Requirements
If your CPAP is covered by insurance, there are minimum usage requirements you need to meet to keep your equipment. The standard set by Medicare (and widely adopted by private insurers) is straightforward: you need to use your CPAP for at least 4 hours per night on at least 70% of nights within a 30-day period. That works out to about 21 nights out of every 30. You typically have a 90-day window after receiving the machine to establish this pattern.
Modern CPAP machines track your usage automatically and transmit the data, so your provider and insurance company can see exactly how many hours you’re wearing it each night. Falling short of the threshold can result in losing insurance coverage for the device.
Common Side Effects
Most side effects are nuisances rather than serious problems, and most are fixable. Dry mouth is one of the most frequently reported issues, particularly among people who breathe through their mouth or have mask leaks. Nasal congestion, runny nose, and occasional nosebleeds also come up regularly, all related to cold, dry air passing through the nasal passages. A heated humidifier resolves these for most people.
Air swallowing is another common complaint. The pressurized air can leak past the airway and into the stomach, especially during swallowing, leading to bloating, belching, and flatulence. In one study, flatulence was the most bothersome symptom, increasing significantly after patients started CPAP. Reducing the pressure setting (if your doctor agrees), sleeping with your head slightly elevated, or switching to an auto-adjusting machine can help.
Skin irritation or pressure marks from the mask, claustrophobia, and noise from the machine round out the common complaints. Trying a different mask style, adjusting the straps, or using a newer, quieter machine model typically addresses these.
CPAP in Premature Infants
CPAP isn’t only for adults with sleep apnea. It plays a critical role in neonatal intensive care units, where premature babies often have underdeveloped lungs that lack enough surfactant, the substance that keeps tiny air sacs inflated. Without it, these babies have low lung volume and have to work much harder to breathe.
Nasal CPAP, delivered through small prongs or a tiny mask, provides gentle pressure (usually between 4 and 6 cmH₂O) that keeps the baby’s airways and air sacs open. This reduces the need for mechanical ventilation, which carries a higher risk of lung damage. Research from the Cochrane Database shows that CPAP in preterm infants with respiratory distress is associated with reduced respiratory failure, less need for mechanical ventilation, and lower mortality. It may also help stabilize irregular breathing patterns common in premature infants by gently stretching lung receptors that regulate the breathing reflex.