What Is a CPAP Machine? A Plain-Language Guide

Last verified: October 6, 2026. A CPAP machine, short for continuous positive airway pressure machine, is a small device that blows a steady stream of mildly pressurized air through a hose and mask to keep the upper airway from collapsing while a person sleeps. It is the most common first-line equipment for obstructive sleep apnea and is also used, in other forms, in hospitals. This guide explains what a CPAP machine is, its parts, the main variants, how it differs from related devices such as a ventilator, and what supply teams should know.

This page is general information, not clinical or safety training. Always follow your institution’s procedures and the manufacturer’s instructions for any device.

What Is a CPAP Machine?

CPAP delivers a constant level of air pressure during both breathing in and breathing out. The pressure acts like an air splint: it holds the soft tissues of the throat open so that breathing is not repeatedly interrupted. The person still does all of their own breathing. The machine does not breathe for them; it simply provides a steady pressure that makes the airway easier to keep open.

A home CPAP system is a compact bundle of components. A flow generator (the machine itself, containing a blower), a hose, and a mask are the essentials. Most systems also include a humidifier, which warms and moistens the air to reduce dryness, and a filter to clean incoming air. Many machines record data such as hours of use and mask leak, which clinicians can review to assess how the therapy is going.

Why CPAP Machines Exist

In obstructive sleep apnea, the muscles of the throat relax during sleep and the airway narrows or closes repeatedly, interrupting breathing and fragmenting sleep. A device that holds the airway open from the inside directly addresses that mechanism without surgery or medication. CPAP became a standard approach because it is non-invasive, adjustable, and effective for many people when used consistently. It is also used in certain hospital and neonatal situations where gentle sustained pressure helps keep the lungs or airway open.

Who Uses a CPAP Machine

Most users are adults with sleep-disordered breathing who have been diagnosed by a clinician, often after a sleep study, and who use the machine at home every night. CPAP is also used in some hospital settings for people with certain breathing difficulties, and in neonatal units for premature infants, using specialized equipment. Pressure settings are individual and are set or adjusted by a clinician, not chosen by the user from a general guide.

Main Parts of a CPAP System

• Flow generator: the main unit containing the blower, controls, and display.
• Hose (tubing): carries air from the machine to the mask, and is sometimes heated to reduce condensation.
• Mask or interface: connects the air to the user. This is the part that most affects comfort and adherence.
• Headgear: straps that hold the mask in position.
• Humidifier: a water chamber that adds moisture to the airflow.
• Filters: disposable or washable filters that clean the incoming air.
• Power supply: a mains adapter, and in some cases a battery option for travel or outages.

Types of CPAP Masks

Mask choice is a major part of CPAP practice, and the main families are:

• Nasal pillow masks: small cushions that seal at the nostrils, with minimal facial contact.
• Nasal masks: cover the nose only.
• Full-face masks: cover the nose and mouth, and may suit people who breathe through the mouth.

Each comes in multiple sizes and cushion styles, and the right one depends on face shape, comfort, and breathing habits. For a broader look at mask designs used for both CPAP and oxygen, see our guide to CPAP and oxygen mask types.

CPAP Variants

Fixed-Pressure CPAP

This delivers one prescribed pressure throughout the night. It is the simplest type.

Auto-Adjusting (APAP) Devices

These adjust pressure within a range, in response to the user’s breathing during the night. They are common for home use.

Bilevel (BiPAP-Style) Devices

Bilevel devices deliver one pressure while breathing in and a lower one while breathing out, which can be more comfortable for some people or suited to certain conditions. Because “BiPAP” is a brand name used informally for the whole category, the generic terms are bilevel or two-level positive airway pressure. These are separate equipment categories with their own specifications, and the choice is made by the clinical team.

Getting Used to CPAP: Why Adherence Is a Practical Issue

CPAP only works when it is worn, and many people find the first weeks difficult. Common complaints include a leaky or uncomfortable mask, a dry or stuffy nose, pressure that feels strange when breathing out, and difficulty sleeping with a hose. Much of the practical work around CPAP is therefore about fitting, not just supplying: trying different mask styles and sizes, adding or adjusting humidification, using a gradual pressure ramp at the start of the night, and follow-up with the clinic or equipment provider. Because the machine can record its own usage, clinicians and programs often review that data to see whether a person is using it consistently and whether the mask is leaking.

For organizations that supply or study CPAP, this means that the mask and fitting service are as important as the machine itself. A program that provides machines but not enough mask options and follow-up tends to see lower use. In research, adherence is often a primary outcome in its own right, which is why protocols may define exactly how adherence is measured and which devices are used.

Travel, power outages, and cleaning are the other day-to-day concerns. Portable or battery options exist for travel, and daily or weekly cleaning of masks, hoses, and water chambers is recommended by manufacturers to limit residue buildup. Always follow the specific machine’s instructions for cleaning and replacement.

How a CPAP Machine Differs from Related Devices

• CPAP vs. ventilator. A ventilator can assist or fully take over the work of breathing, with pre-set breaths delivered by the machine. CPAP only provides steady pressure while the user breathes spontaneously.
• CPAP vs. oxygen concentrator. A concentrator supplies oxygen. CPAP supplies pressurized room air. Some people use both, with oxygen added into the CPAP circuit under clinical direction.
• CPAP vs. nasal cannula. A cannula delivers oxygen at low pressure and does not hold the airway open.
• CPAP vs. oral appliances. A mouth-worn device that repositions the jaw is a non-pressure alternative that some people use for sleep apnea. It is a different device category chosen by a clinician or dentist.
• CPAP vs. pulse oximetry. A pulse oximeter measures blood oxygen and is sometimes used to monitor sleep, but it is a monitoring tool, not a therapy.

Practical Relevance for Research Administration and Procurement

CPAP is an unusual product category because it combines durable equipment with a steady stream of replaceable supplies, and that structure shapes how it is bought and managed.

First, the machine is a long-life asset, while masks, cushions, headgear, hoses, filters, and humidifier chambers are recurring consumables that are replaced on regular intervals. Total cost of ownership is mostly supplies over time rather than the initial machine.

Second, mask and component compatibility is not universal. Hoses, humidifiers, and masks are often designed for particular machine models, so a procurement list should specify the exact machine family and mask size, and substitutions need to be checked.

Third, coverage and reimbursement rules often apply. CPAP is typically provided as durable medical equipment, and payer rules about documentation, usage, and replacement schedules vary; see our overview of Medicare DME coverage and the sleep clinic supply checklist for related context on how these items are handled.

Fourth, data and privacy considerations arise because many machines record and transmit usage data. Organizations that run sleep programs or studies should think about how that information is stored and who can see it. Cleaning and infection-control rules also apply, since shared or loaner equipment needs facility-approved processes between users.

Frequently Asked Questions

What does a CPAP machine do?

It delivers a steady stream of pressurized air through a mask to keep the airway open during sleep, most commonly for obstructive sleep apnea.

Is a CPAP machine the same as a ventilator?

No. CPAP provides constant pressure while the user breathes on their own. A ventilator can deliver or assist breaths and is used when breathing needs more support.

What is the difference between CPAP and BiPAP?

CPAP delivers one steady pressure. Bilevel devices, often called by the brand name BiPAP, deliver a higher pressure on inhalation and a lower one on exhalation. Which is appropriate is a clinical decision.

Does a CPAP machine give you oxygen?

Not by itself. It pressurizes room air. Oxygen can be added to some circuits when a clinician directs it, but that is a separate prescription and setup.

Can anyone buy and use a CPAP machine?

Pressure settings are individual, and the machine is generally prescribed after a diagnosis. Using one without clinical guidance is not recommended.

Is CPAP loud?

Modern machines are generally designed to be fairly quiet, though the level varies by model and pressure, and a poorly fitted mask can add a hissing leak noise. Noise ratings are typically listed in manufacturer specifications.

Can CPAP be used in hospitals?

Yes. Hospitals use CPAP and related pressure-support devices for certain patients, sometimes with different equipment than home units. Facility policy and clinical teams determine when and how it is used.

Do CPAP supplies need to be replaced?

Yes. Masks, cushions, hoses, filters, and water chambers wear out or accumulate residue and are replaced on a schedule that depends on the manufacturer’s instructions and, where relevant, payer rules.