If you've recently been diagnosed with obstructive sleep apnea (OSA), your doctor has almost certainly recommended CPAP therapy. For many people, learning they need to sleep with a machine attached to their face is an unwelcome surprise — and the initial adjustment can feel daunting. But CPAP is also one of the most effective treatments in all of sleep medicine, with documented improvements not just in sleep quality but in cardiovascular health, cognitive function, and mood.

This guide explains how CPAP machines work, the key differences between machine types, how to choose the right mask, and practical strategies for adjusting to therapy successfully.

How CPAP Works

CPAP stands for Continuous Positive Airway Pressure. The machine works by drawing in room air, filtering it, and delivering it at a constant, pressurized flow through a hose to a mask worn over the nose or face. This continuous pressure acts like a pneumatic splint — it holds the soft tissues of the throat open throughout the night, preventing the collapse that causes obstructive apnea events.

The pressure setting is measured in centimeters of water pressure (cmH₂O) and is determined during a sleep study titration. Most people with OSA are prescribed pressures between 6 and 14 cmH₂O, though ranges extend beyond this for severe cases.

The American Academy of Sleep Medicine identifies CPAP as the first-line treatment for moderate to severe OSA, and the evidence supporting it is extensive. Studies consistently show that effective CPAP therapy reduces apnea-hypopnea index (AHI — the number of breathing interruptions per hour) to near-normal levels and significantly improves daytime alertness, cognitive function, and quality of life.

CPAP vs. APAP vs. BiPAP: Understanding the Difference

CPAP (Continuous Positive Airway Pressure)

Delivers one fixed pressure all night. The most common and least expensive type. Works well for most OSA patients once the correct pressure is identified. The limitation is that optimal pressure may vary throughout the night (more may be needed during REM sleep or in certain body positions), and a fixed setting doesn't adapt to those variations.

APAP (Auto-Adjusting Positive Airway Pressure)

Also called Auto-CPAP or AutoPAP. The machine monitors airflow in real time and automatically adjusts pressure within a prescribed range to provide the minimum pressure needed to prevent apnea at any given moment. More comfortable for many patients because pressure is lower during periods when apnea events aren't occurring. Now the most commonly prescribed type for newly diagnosed OSA patients. Often slightly more expensive than fixed CPAP.

BiPAP (Bilevel Positive Airway Pressure)

Delivers two separate pressure levels: a higher IPAP (inhalation) pressure and a lower EPAP (exhalation) pressure. This makes exhalation easier — useful for patients who find CPAP pressure uncomfortable to exhale against, or those with central sleep apnea, COPD, or other conditions requiring respiratory support. Prescribed by a physician when CPAP or APAP is insufficient. More expensive.

Mask Types: Finding the Right Fit

Mask fit is one of the biggest factors in CPAP adherence. A leaking or uncomfortable mask is the primary reason people abandon therapy. The three main types:

Nasal Pillow Mask

Small, lightweight inserts that seal at the nostrils. Minimal facial contact, good for claustrophobic patients, compatible with glasses, and easiest to use with higher pressure settings. Requires breathing through the nose — if you're congested or a mouth breather, not appropriate without a chin strap.

Nasal Mask

Covers the nose from bridge to upper lip. More contact than nasal pillows but still significantly less than a full face mask. Handles a wider range of pressures well. Most common starting point for new patients.

Full Face Mask

Covers both nose and mouth. Required for mouth breathers. Creates more surface area for potential leaks but allows breathing through either nose or mouth. Generally used when nasal masks prove insufficient.

Adjusting to CPAP: Practical Strategies

The first 1–4 weeks of CPAP therapy are the hardest, and adherence during this period predicts long-term success. Research shows that patients who use CPAP for at least 4 hours per night during the first week are significantly more likely to become consistent long-term users.

Start During the Day

Wear the mask while awake — watching TV, reading — before trying to sleep with it. This desensitizes you to the sensation and builds comfort before you need to sleep.

Use the Ramp Feature

Most CPAP machines include a ramp setting that starts at a low pressure and gradually increases to your prescribed pressure over 5–45 minutes. Starting at a lower pressure makes falling asleep easier before reaching therapeutic pressure.

Address Dryness with a Humidifier

Dry mouth, sore throat, and nasal dryness are common complaints. Most modern CPAP machines include an integrated heated humidifier — use it. Increasing the humidifier temperature setting usually resolves dryness within a few nights.

Track Your Data

Modern CPAP machines record nightly data including AHI, leak rate, and usage hours. Most connect to apps (ResMed's myAir, Philips Respironics DreamMapper) that give you a nightly "score." Reviewing this data helps you identify mask fit issues and track improvement — and is motivating once you see your AHI drop.

Be Patient

Research shows that many patients don't experience the full cognitive and energy benefits of CPAP for 2–4 weeks after achieving consistent adherence. Don't judge the therapy by the first few nights. The benefits accumulate with consistent use.

CPAP Machine Maintenance

For more on sleep apnea symptoms and next steps, see our guide on signs of sleep apnea. And for a full picture of your sleep health, take our free Sleep Score assessment.

Medical disclaimer: CPAP therapy requires a prescription and should be initiated under the guidance of a licensed healthcare provider or sleep medicine specialist. Do not self-prescribe pressure settings.

About the author: Morgan Wells is a certified sleep analyst and wellness writer with over a decade of experience in behavioral sleep health. Learn more about Morgan.