CPAP 101: understanding sleep apnea therapy

Being diagnosed with obstructive sleep apnea can be overwhelming. This is doubly true if you (or your loved one) have been recommended a CPAP machine. It’s understandable to wonder, “What does a CPAP machine do?” You might be nervous about the machine and the mask, fearing discomfort or claustrophobia.

The good news is CPAP machines have come a long way in recent years. They’re also the gold standard treatment for obstructive sleep apnea, says certified clinical sleep health professional Karla Thompson. “Not only is CPAP the least invasive treatment, it also begins working on the first night of sleep,” she says.

In this article, we'll explore what CPAP does and why it works, so you can start your therapy informed instead of anxious.

What does a CPAP machine do?

A CPAP machine keeps your airways open while you’re sleeping by delivering air into your mouth and/or nose.

CPAP stands for continuous positive airway pressure. It’s the first-line treatment for obstructive sleep apnea because it directly addresses the condition’s mechanical cause. “It is highly effective at preventing the airway collapse," says Thompson. 

According to the National Heart, Lung, and Blood Institute, a CPAP machine, sometimes known as a sleep apnea machine, includes the following parts:

1. Mask or other device: This fits over your nose, or nose and mouth, so air can enter your upper airway.

2. Straps: Straps position the mask on your face and keep it stable.

3. Tube: The tube connects the motor and the mask so the air can pass through.

4. Motor: The motor blows air into the tube.

How does a CPAP machine work?

A CPAP machine moves air from a motor into your upper airway to prevent pauses in breathing (also known as apneas).

If you have obstructive sleep apnea, blockages develop in your upper airway. Often, this is due to tongue muscles, soft palate, or parts of your throat relaxing too much. A common example is your tongue falling backwards. In any case, this collapse obstructs your airway and prevents enough air from getting through, says the National Heart, Lung, and Blood Institute. This causes your breathing to pause at least five times an hour.

CPAP therapy addresses that problem directly. It provides a consistent stream of air into your mouth and/or nose, keeping your airway open. “This pressurized air keeps the airway from collapsing during sleep,” says Thompson. That way, you can keep inhaling and exhaling without a problem.

So, if you’re wondering what a CPAP machine does when you stop breathing, the simple answer is that it prevents this from happening in the first place.

“When pressure is optimal and CPAP is used consistently, there is a significant decrease in breathing events during sleep,” says Thompson. “In some cases, the events are completely eliminated.”

What does CPAP do for your body?

By preventing pauses in breathing, CPAP treatment reduces snoring, improves sleep quality, and reduces the risk of health issues linked to OSA. 

“CPAP works on the upper airway rather than the lungs,” says Thompson. It doesn’t force air into your lungs, but exerts pressure into your upper airway to prevent it from collapsing. This enables you to breathe on your own. 

Breathing pauses due to untreated OSA lead to lower oxygen levels in the blood. This deprives your brain, heart, kidneys, and other essential organs of oxygen. Carbon dioxide also tends to build up in the body, says the U.S. Food and Drug Administration.

When your brain notices this, it wakes you up briefly so that you can take a few breaths. This can happen many times in one night. You may not remember it the next day, but it’ll still lead to symptoms such as excessive daytime sleepiness.

“When CPAP is effective and thus stops apneas from occurring, breathing and oxygen levels stabilize,” says Thompson. “This can make sleep more continuous."

As a result, you may feel more alert and energized, and a lot less sleepy during the day. Your memory and cognitive function may also improve, reports a 2024 study in Clocks & Sleep. With consistent use, CPAP may also help lower blood pressure.

Research suggests that consistent CPAP use may lower cardiovascular risk. In two analyses of randomized trials, people who used CPAP regularly — generally at least 4 hours per night — had about a 30% lower risk of major cardiovascular events, with much of the benefit linked to fewer cerebrovascular events such as stroke. However, CPAP did not reduce these events overall when researchers analyzed everyone assigned to CPAP, regardless of how consistently they used it. These findings are encouraging, although they do not prove that CPAP alone caused the lower risk.

If your loved one is receiving CPAP therapy, you’ll likely notice a lot less snoring, often none at all.

What to expect when you start CPAP

When you first get started, you can expect some discomfort as you get used to the mask, but you may enjoy the benefits of CPAP rather quickly.

Expect an adjustment curve

The first nights of using a CPAP machine can feel strange. You may notice side effects like congestion, runny nose, nosebleeds, dry mouth, and skin irritation. The National Heart, Lung, and Blood Institute suggests stopping use of CPAP and calling your healthcare provider immediately if you experience bloating or stomach discomfort.

In any case, Thomas notes that side effects are manageable for many people. 

Keep in mind that you need to wear your mask whenever you sleep, including during naps. That’s because “CPAP only supports your airway while you're wearing it,” says Thompson. “It doesn't cure OSA or change the anatomy of the airway.”

Some people start to feel better after the first night. Others need more time to adjust. “I always tell people to give themselves at least two weeks to adjust,” she says. If you don’t see improvement in that time, reach out to your healthcare provider. Adjustments to your CPAP settings or setup may help.

Become comfortable with CPAP

It’s understandable if you find the idea of CPAP intimidating. Fortunately, both the masks and machines have improved over the years.

Over time, the machines have become quieter, more comfortable, and more user-friendly. Not only that, but there are different masks of various sizes to choose from. 

“Finding the right mask is a bit like finding the perfect pair of shoes,” says Thomas. “You have to keep trying on options until you find the one that fits.”

If you’re apprehensive about trying a CPAP machine, Thompson suggests giving yourself adequate time to learn how to use CPAP and allow yourself to adjust. She notes that most CPAP problems are fixable, and that you should contact your provider if you have any concerns about the mask, humidity, or pressure settings.

If it turns out that CPAP isn't the right fit for you, alternatives such as oral appliance therapy are also available. Book a consultation with virtual sleep clinic Dreem Clinic for support regarding CPAP and other sleep disorder treatments.  

What is the 4-hour rule for CPAP?

The 4-hour rule for CPAP refers to the amount of time you need to wear your mask for Medicare to consider you “compliant.”

At any time within the first three months of using the equipment, you need to wear your CPAP for a minimum of four hours each night on 70% of nights out of a consecutive 30-day period. That’s a minimum of 21 nights.

If Medicare doesn't consider you compliant, it'll deny further insurance coverage, per the Centers for Medicare & Medicaid Services.

The bottom line

CPAP machines are the gold standard sleep apnea treatment. They deliver air into your upper airway, keeping it open to prevent it from collapsing. This allows you to breathe continuously without the pauses that are common to OSA. Not only does this improve your sleep quality, but it may also benefit your memory, energy levels, and physical health.

While many people are nervous about the possibility of using CPAP, the treatment has evolved over the years. Machines are more user-friendly and masks are more comfortable. Even when problems occur, they’re often fixable.

Whether you’re wondering how sleep apnea is diagnosed, or if you know you need treatment, Dreem Health can help. We offer evaluation, diagnosis, and CPAP management from home. We also offer CPAP alternatives — no long referral queue and no in-lab overnight stay required. Book a consultation to discuss further.

Frequently asked questions (FAQs)

What does a CPAP machine do to your lungs?

A CPAP machine doesn’t work on your lungs. Obstructive sleep apnea isn’t a lung issue. It happens because blockages in your upper airway make it hard to breathe in and out. CPAP prevents blockages and keeps the upper airway open by blowing air into the nose and mouth. That way, you can breathe properly.

What is the downside of using a CPAP machine?

Many people who use CPAP machines experience dry mouth, congestion, nosebleeds, or runny nose. The mask might cause skin irritation or pressure marks, and in some cases, it might leak.

Occasionally, people using CPAP machines might swallow air, which can lead to discomfort or bloating. If this happens to you, the National Heart, Lung, and Blood Institute suggests stopping your CPAP machine and contacting your healthcare provider as soon as possible.

“Many of these issues can be fixed with additional support,” says Thomas.

Do you have to use a CPAP machine every night?

Yes. You need to use your CPAP machine every time you sleep, because it only works when you’re using it.

Does CPAP affect your heart? 

Experts are still exploring the effects of CPAP on the heart. A 2025 study in the European Heart Journal studied the frequency of cardiovascular death, stroke, and heart attack among OSA patients who did or didn't use CPAP.

Results suggested patients with high-risk OSA markers, such as larger drops in oxygen levels or greater increases in heart rate, had a lower risk of these events with CPAP. Patients without high risk markers actually had a higher likelihood of cardiovascular events. These findings suggest that the cardiovascular effects of CPAP may differ depending on a person’s OSA risk profile.

Therefore, whether or not to use CPAP therapy is a decision you should make with your healthcare provider based on your symptoms and risk profile. Alternative treatments to CPAP are also available.

Does CPAP reduce the risk of stroke?

Consistent CPAP use may reduce the risk of stroke. A 2021 study in Journal of Clinical Sleep Medicine analyzed older adult Medicare beneficiaries with obstructive sleep apnea. It found that adhering to CPAP treatment lowered the risk of stroke over 25 months, with a 2% risk reduction for every month on CPAP.

Do CPAP machines stop snoring?

Yes, CPAP machines reduce or stop snoring and pauses in breathing. However, it shouldn’t be used for cases of snoring unrelated to obstructive sleep apnea. Not everyone who snores has the condition.