A CPAP machine is a small bedside device that delivers a steady stream of pressurized air through a mask while you sleep, keeping your airway open so you can breathe without interruption. It’s the most common treatment for obstructive sleep apnea, a condition where the soft tissues in your throat relax and collapse during sleep, repeatedly blocking airflow. The machine works like an air splint: the pressure holds your airway open the same way air pressure keeps an inflatable tube from folding in on itself.
How a CPAP Machine Works
The setup is straightforward. A small motor draws in room air, filters it, and pushes it through a flexible tube into a mask you wear over your nose, your mouth, or both. That pressurized air creates a cushion inside your upper airway, preventing the surrounding tissue from collapsing inward each time you relax into deeper sleep. You breathe normally the entire time. The machine simply ensures there’s always enough pressure behind each breath to keep the passage open.
Pressure is measured in centimeters of water pressure (cm H2O), and most machines operate in a range of 4 to 20 cm H2O. The average person needs somewhere around 8 to 10 cm H2O, though your specific setting is determined by a sleep study or a titration test where a technician adjusts the pressure while monitoring your breathing overnight.
The Parts of the Machine
A standard CPAP setup has five core components: a motor that generates airflow, an air filter that cleans incoming air, a length of flexible tubing, a mask, and straps that hold the mask in place. Many modern machines also include a heated humidifier, which adds moisture to the air so your nose and throat don’t dry out overnight. Some have a “ramp” feature that starts at a low pressure and gradually increases to your prescribed level as you fall asleep, making it easier to drift off without feeling blasted by air.
Mask Types and How to Choose
The mask is the part most people have the strongest opinions about, and there are several styles to match different needs.
- Nasal pillow masks are the smallest option. They sit at the entrance of your nostrils with small cushions or soft prongs. These work well if you feel claustrophobic in larger masks, want to read or watch TV in bed, wear glasses, or have facial hair that interferes with a seal around your nose.
- Nasal masks cover your entire nose but not your mouth. They’re a good fit if you need a higher pressure setting or tend to move around a lot in your sleep, since the larger surface area holds a more stable seal.
- Full-face masks cover both your 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 unreliable.
- Hybrid masks combine a mouth covering with nasal prongs or cushions, sealing the nostrils without covering the bridge of your nose. They split the difference between full-face coverage and the lighter feel of nasal pillows.
Getting the right mask often takes some trial and error. A poor fit causes air leaks, which can dry out your eyes, irritate your skin, and prevent the machine from delivering the correct pressure. If your first mask doesn’t feel right, that’s normal and worth addressing with your equipment supplier rather than giving up on the therapy entirely.
CPAP vs. APAP vs. BiPAP
CPAP is the most common type of positive airway pressure device, but it isn’t the only one. All three work on the same basic principle. The differences come down to how they manage pressure.
A standard CPAP delivers one constant pressure all night. An APAP (auto-adjusting positive airway pressure) machine monitors your breathing in real time and raises or lowers the pressure as needed. This is often more comfortable for people whose pressure needs shift when they change sleep positions or move between lighter and deeper sleep stages. A BiPAP (bilevel positive airway pressure) machine uses two separate pressure settings: a higher one when you inhale and a lower one when you exhale. BiPAP machines can reach pressures up to 30 cm H2O, making them useful for people who need very high pressure or who have trouble exhaling against a steady airflow.
Who Needs CPAP Therapy
CPAP is prescribed for obstructive sleep apnea, which is diagnosed through a sleep study conducted either in a lab or at home with a portable monitor. The study measures your apnea-hypopnea index (AHI), which counts the average number of times per hour that your breathing stops completely (apnea) or partially drops (hypopnea) for at least 10 seconds. A higher AHI means more severe sleep apnea, and moderate to severe cases are the clearest candidates for CPAP.
The consequences of untreated sleep apnea go well beyond poor sleep. Each breathing interruption causes a brief drop in blood oxygen, triggers a stress response, and forces your heart to work harder. Over time, this raises the risk of high blood pressure, heart attack, stroke, and heart failure. A meta-analysis published in JAMA found that people who consistently used their CPAP had a 31% lower risk of major cardiovascular events compared to those who didn’t stick with treatment. A sensitivity analysis within the same study suggested the risk reduction could be as high as 45%.
Common Side Effects
Most side effects are related to the mask and airflow rather than the therapy itself. A dry or stuffy nose, dry mouth, and skin irritation from the mask straps are the most frequent complaints. A heated humidifier solves the dryness for most people. If your mask leaks air upward, it can dry out your eyes or cause tearing. Adjusting the straps or switching to a different mask size usually fixes this.
Some people swallow air during the night, which leads to bloating, burping, or stomach discomfort. Feeling claustrophobic in the mask is another common early hurdle. Trying a smaller mask style, like nasal pillows, often helps. The ramp feature, which starts pressure low and increases it gradually, can also make the sensation of pressurized air less jarring when you’re first getting used to the device.
Sticking With Treatment
Adherence is the biggest challenge with CPAP. The clinical standard for “good use” is wearing the machine at least 4 hours per night on at least 70% of nights, and even by that modest bar, long-term adherence often falls below 30% globally. A 2025 prospective study tracking patients over two years found that about 66% were adherent at one month, but that number dropped to roughly 50% by six months and held steady there through the two-year mark.
Two factors predicted whether someone would still be using their machine two years later: how severe their sleep apnea was at diagnosis, and whether they used the machine consistently during the first three months. People with more severe apnea tend to feel more dramatic relief, which reinforces the habit. And early momentum matters. If you’re struggling in the first few weeks, that’s actually the most important window to troubleshoot problems with your mask fit, pressure settings, or comfort rather than quietly abandoning the device.
The learning curve is real, but the payoff is significant. Most people who push through the adjustment period report better sleep, less daytime fatigue, improved concentration, and a noticeably quieter night for anyone sharing the bed.