How a CPAP Machine Works and What to Expect When Using One

Quick Answer

A CPAP machine delivers a continuous, steady stream of pressurized air through a mask to keep your airway open while you sleep, preventing the pauses in breathing that characterize obstructive sleep apnea. When you begin therapy, expect a ramp-up period where the pressure gradually increases, a break-in phase for mask comfort, and a requirement to demonstrate regular usage—typically defined as at least four hours per night for 70% of nights—to maintain insurance coverage.

A CPAP is only one option among several positive airway pressure (PAP) devices, and not all machines on the market are equal in terms of safety and reliability.

Key Facts

CPAP (Continuous Positive Airway Pressure) works by delivering a constant, prescribed air pressure to splint the airway open during sleep.
The device consists of three core components: a motor/blower unit, a humidifier (integrated or separate), and a mask interface (nasal, nasal pillow, or full-face).
Therapy success hinges on mask fit, pressure titration, and consistent nightly use.
Compliance tracking is typically required every 90 days during the first year of treatment for insurance coverage; patients must demonstrate usage of at least 4 hours per night on 70% of nights.
Philips Respironics issued a recall in June 2021 for certain CPAP, BiPAP, and ventilator devices due to degraded sound abatement foam, later classified as Class I by the FDA.
A re-issuance of a product notification occurred in July 2025, affecting approximately 93 DreamStation Auto CPAP and DreamStation Auto BiPAP units in the U.S. (65) and France.
As of January 2026, Philips reported that over 99% of registered recalled devices have been remediated; the U.S. Patient Portal has closed, but the company continues to accept device returns.
In 2024, Philips Respironics halted sales of CPAP devices; new models are expected in 2025 with updated safety protocols, pending FDA approval.
The 2025 AASM clinical practice guideline update for central sleep apnea (CSA) reopens the door for adaptive servo-ventilation (ASV) with guardrails and adds transvenous phrenic nerve stimulation as a treatment option.

The Mechanics of Positive Airway Pressure How It Actually Works

The Core Principle Splinting the Airway

Obstructive sleep apnea (OSA) occurs when the soft tissues at the back of the throat—the soft palate, uvula, and tongue—collapse during sleep, blocking the airway. Each obstruction event can last 10 seconds or longer, causing oxygen desaturation and frequent arousals from deep sleep.

A CPAP machine addresses this mechanically. The device draws room air through a filter, pressurizes it via an internal blower motor, and delivers it through tubing to a mask worn over the nose, or nose and mouth.

The continuous pressure acts as a pneumatic splint, physically holding the airway open so that breathing remains stable throughout the night. The prescribed pressure is measured in centimeters of water pressure (cm H₂O).

Typical pressures range from 4 to 20 cm H₂O, determined during a titration study in a sleep lab or via an auto-titrating device at home. The pressure must be high enough to prevent airway collapse but not so high that it causes discomfort, mask leaks, or difficulty exhaling.

Device Variations CPAP, APAP, and BiPAP

While CPAP delivers a fixed pressure, related devices offer variations that address specific patient needs:

APAP (Auto-Positive Airway Pressure): Also called auto-CPAP, this device automatically adjusts pressure throughout the night based on real-time detection of snoring, flow limitation, and apnea events. APAP is often used for patients who need different pressures across sleep stages or body positions.
BiPAP (Bi-level Positive Airway Pressure): Delivers two distinct pressures—a higher inspiratory pressure and a lower expiratory pressure. This makes exhalation easier for patients who find fixed CPAP pressure uncomfortable or who have conditions like obesity hypoventilation syndrome or central sleep apnea.
ASV (Adaptive Servo-Ventilation): A more advanced device that continuously monitors breathing and adjusts pressure support on a breath-by-breath basis. The 2025 AASM guideline update re-evaluated ASV for central sleep apnea with specific guardrails, recognizing its role for select patients after earlier safety concerns from the SERVE-HF trial.

The Humidifier Overlooked but Essential

Modern CPAP machines typically include an integrated heated humidifier. Pressurized air, especially at higher flow rates, dries out nasal passages and can cause congestion, nosebleeds, or throat irritation.

Heated humidification adds moisture to the airstream, significantly improving comfort and tolerance. Many machines also feature heated tubing to prevent rainout—condensation that forms inside the tube when warm, humidified air meets cooler room air.

The Philips Recall What It Means for Current and Prospective Users

The 2021 Recall and Its Aftermath

In June 2021, Philips Respironics voluntarily recalled certain ventilators, BiPAP machines, and CPAP machines due to potential health risks from degraded sound abatement foam. This polyester-based polyurethane (PE-PUR) foam was designed to reduce machine noise, but under certain conditions—including exposure to high heat and humidity, and use with ozone-based cleaning products—it could break down and release particles or volatile organic compounds into the airway.

The FDA classified the recall as Class I, its most serious designation, indicating that use of the affected devices could cause serious injury or death. Potential side effects reported to the FDA include asthma, dizziness, headache, hypersensitivity, and respiratory irritation, as well as more serious risks such as inflammatory responses and potential carcinogenic effects from inhaling degraded foam particles.

The scope of this recall was massive. It affected millions of devices worldwide across dozens of models, including the DreamStation series, SystemOne series, REMstar SE Auto, and Trilogy ventilators, among others.

The recall triggered multiple investigations, government agreements, and years of litigation.

The July 2025 Re-Issuance and Current Status

In July 2025, Philips issued a customer notice for certain DreamStation Auto CPAP and DreamStation Auto BiPAP devices—a re-issuance of an October 2023 product notification to customers who had not yet responded by phone to prior outreach. This affected approximately 93 units total: 65 in the U.S.

and the remainder in France. The small number reflects the tail end of a long remediation process rather than a new, large-scale safety issue.

As of January 2026, Philips reported that over 99% of registered recalled devices have been remediated—meaning they were either replaced, repaired, or returned. The company closed its U.S.

Patient Portal, which previously allowed patients to register devices and track remediation status. However, Philips continues to accept device returns and process remediation for any remaining affected units.

Legal and Financial Ramifications

The recall generated substantial legal activity. As of July 2026, there were 623 individual Philips CPAP lawsuits pending in a multidistrict litigation (MDL).

A settlement has been reached covering economic losses—the cost of the devices and related expenses—but it does not cover personal injury or wrongful death claims, which remain in litigation. In 2024, Philips Respironics halted sales of CPAP devices in the U.S.

market as part of its restructuring. New models are expected to launch with updated safety protocols, but FDA approval is still pending as of this writing.

This has created a market dominated by other manufacturers, including ResMed, which now supplies the majority of new CPAP devices in the U.S.

What This Means for Patients

For anyone using a recalled Philips device, the message is clear: check the model number, register if you haven't already, and pursue remediation. The Philips website maintains an up-to-date list of recalled devices.

Other resources include the Sleep Foundation and Sleep Doctor websites, both of which maintain comprehensive recall lists and guidance. More broadly, the recall serves as a cautionary tale about the importance of researching device safety and staying informed about recalls.

It also highlights the role of the FDA in monitoring medical devices and the reality that even established manufacturers can face serious safety failures.

What to Expect in Your First Weeks of CPAP Therapy

The Initial Setup and Prescription

Starting CPAP therapy begins with a prescription, typically written after a sleep study confirms OSA. The prescription specifies the device type (CPAP, APAP, or BiPAP), the pressure setting, and the mask type.

A durable medical equipment (DME) provider supplies the machine and fittings, and a respiratory therapist or technician explains the setup. The first night at home can be disorienting.

The mask feels foreign, the noise of the machine—though much quieter than older models—may be noticeable, and the sensation of pressurized air can be uncomfortable. This is normal.

Most patients require a 1- to 3-week adjustment period before therapy feels natural.

Mask Fit The Single Most Important Variable

Mask selection and fit are the primary determinants of CPAP success. A poorly fitting mask causes air leaks, which reduce therapy effectiveness and cause eye irritation, dry mouth, and disruptive noise.

Conversely, a well-sealed mask that distributes pressure evenly allows for restful, uninterrupted sleep. The three main mask types are:

Nasal masks: Cover the nose, sealing around the bridge and upper lip. Good for patients who breathe through their nose at night.
Nasal pillow masks: Insert small silicone cushions into the nostrils. The least obtrusive option, ideal for patients with facial hair, claustrophobia, or a preference for minimal contact.
Full-face masks: Cover both the nose and mouth, recommended for mouth breathers or patients with nasal obstruction.

The ResMed AirFit series and the Philips DreamWear line are among the most commonly prescribed options. However, mask fit is highly individual—what works for one patient may not work for another.

Most DME providers offer a 30-day mask fit guarantee, allowing patients to try a different style if the initial choice doesn't work.

Pressure Adjustments and the Ramp Feature

The prescribed pressure is based on the pressure required to eliminate apnea events during the titration study. However, this pressure may not feel comfortable initially, especially when falling asleep.

Most machines include a ramp feature that starts at a lower pressure (typically 4 cm H₂O) and gradually increases to the prescribed level over a set period (usually 20 to 45 minutes). This allows patients to fall asleep before full pressure is applied.

Some patients experience excessive pressure during exhalation, which can cause a sensation of breathlessness. BiPAP devices address this by providing lower expiratory pressure.

For patients on fixed CPAP who find exhalation difficult, switching to a bi-level device may be appropriate.

Compliance Tracking and Insurance Requirements

Insurance coverage for CPAP therapy is contingent on demonstrated compliance. The Centers for Medicare & Medicaid Services (CMS) and most private insurers require:

At least 4 hours of use per night on 70% of nights
Documented within the first 90 days of therapy
Follow-up evaluation to confirm therapy effectiveness

Modern CPAP machines have built-in modems or SD cards that transmit usage data to the DME provider and prescribing physician. This data includes hours of use, mask leak, apnea-hypopnea index (AHI) during therapy, and pressure settings.

The 90-day compliance check is the first major milestone; ongoing coverage may require periodic compliance verification, though the frequency decreases after the first year. The Carelon clinical guideline for sleep disorder management, revised in late 2025, specifies that ongoing treatment with APAP or CPAP is medically necessary for patients who demonstrate compliance.

Importantly, compliance demonstration is required every 90 days for the first year of therapy, after which the requirement may relax. Compliance demonstration is not required for non-adult patients.

Common Challenges and Practical Solutions

Mask leaks: Address by adjusting strap tension, trying a different mask size or style, or using mask liners for a better seal.
Dry mouth: Often indicates mouth breathing; consider a chin strap, a full-face mask, or increasing humidification.
Nasal congestion: Use heated humidification, saline nasal spray, or discuss with a physician whether nasal steroids are appropriate.
Claustrophobia: Start with nasal pillow masks, practice wearing the mask during waking hours, and use the ramp feature.
Aerophagia (swallowing air): Can cause bloating and stomach discomfort. Lower pressure settings, or switching to BiPAP, may help. If symptoms persist, consult a physician—this can be a sign that the pressure requires adjustment.

The Evolving Landscape 2025–2026 Guideline Updates and Market Shifts

The 2025 AASM Guideline for Central Sleep Apnea

The American Academy of Sleep Medicine published a major update to its clinical practice guideline for central sleep apnea treatment in late 2025. The update, published in the Journal of Clinical Sleep Medicine, introduces several notable changes:

ASV reemerges with guardrails: Adaptive servo-ventilation, previously cautioned against due to the SERVE-HF trial findings, is now conditionally recommended for patients with central sleep apnea—provided they do not have heart failure with reduced ejection fraction. The guideline emphasizes patient selection criteria.
Transvenous phrenic nerve stimulation is added: This therapy, which uses an implanted device to stimulate the phrenic nerve and restore normal breathing patterns, is now included as a treatment option for select patients.
Success metrics expand beyond AHI: The guideline shifts focus from the apnea-hypopnea index alone to a more individualized, patient-centered approach, incorporating symptom burden, quality of life, and patient preferences into treatment decisions.

These changes matter for anyone considering PAP therapy for central sleep apnea—a condition where breathing pauses are caused by the brain failing to send proper signals to the breathing muscles, rather than by airway obstruction. While CPAP addresses obstructive apnea, central sleep apnea often requires different approaches, and the guideline update provides a more nuanced framework for treatment selection.

The Post-Philips Market Who Makes CPAP Machines Now?

The Philips recall and the company's subsequent market withdrawal have reshaped the CPAP landscape. With Philips Respironics no longer selling new devices in the U.S.

as of 2024, the market is now dominated by:

ResMed: The Australian manufacturer is now the market leader, with its AirSense 10 and AirSense 11 series being the most commonly prescribed devices in the U.S. The AirSense 11, released in late 2021, features a touchscreen interface, integrated humidification, and cellular connectivity for data transmission.
React Health: A newer entrant, React Health has gained market share with its Luna series, offering competitive pricing and compatibility with a wide range of masks.
Breas: A Swedish manufacturer known for its compact, lightweight devices, particularly the Z2 series, which is popular among travelers.
Apex Medical: A Taiwanese manufacturer with a growing U.S. presence, offering the XT series at budget-friendly price points.

The ComPAS and other non-invasive ventilator alternatives also exist for more complex cases. Notably, the HCPCS billing codes for CPAP devices (E0601) and bi-level devices (E0470) list several manufacturers, including ResMed, Breas, Transcend, React Health, and Apex Medical—a clear reflection of the post-Philips market structure.

Ozone Cleaning The Practice That Worsened the Recall

The Philips recall highlighted the dangers of ozone-based cleaning devices. Products like the SoClean use ozone gas to sanitize CPAP equipment, but ozone can degrade the materials inside the machine, including foam components.

The FDA has received reports of respiratory issues associated with ozone cleaning, and the agency has issued warnings against the practice. The safe alternative is simple: wash the mask and tubing with mild soap and water, allow them to air dry completely, and replace the disposable filter as recommended by the manufacturer.

No specialized cleaning devices are necessary—and their use may void the warranty or damage the machine.

Frequently Asked Questions

How do I know if my CPAP machine is recalled?

Check the model number and serial number against the recall lists published by the FDA and Philips Respironics. The Philips website maintains an up-to-date list of recalled devices.

The Sleep Foundation and Sleep Doctor websites also publish comprehensive recall lists with photographs for identification. If your device is on the list, contact Philips or your DME provider to arrange for remediation—replacement, repair, or return.

Philips continues to accept device returns even though the patient portal has closed.

What is the difference between CPAP, APAP, and BiPAP?

CPAP delivers a single, fixed pressure continuously throughout the night. APAP (auto-CPAP) adjusts pressure automatically within a prescribed range based on real-time breathing detection.

BiPAP delivers two pressures—higher during inhalation, lower during exhalation—which makes breathing out against pressure easier. Your physician will prescribe the appropriate device based on your sleep study results and specific needs.

Can a CPAP machine cause side effects?

Yes, though most are manageable. Common side effects include nasal congestion, dry mouth, sneezing, and eye irritation from mask leaks.

More serious side effects can occur with certain recalled Philips devices due to potential foam degradation, which the FDA has linked to asthma, dizziness, headache, and hypersensitivity reactions. If you experience persistent side effects from CPAP use, consult your prescribing physician—adjustments to pressure, mask type, or humidification can often resolve them.

Does insurance cover CPAP machines and supplies?

Most insurance plans, including Medicare and Medicaid, cover CPAP devices and supplies when prescribed by a physician for a diagnosed sleep disorder. Coverage is contingent on demonstrated compliance—typically 4 hours of use per night on 70% of nights—verified through data transmitted from the machine.

The first compliance check occurs at 90 days. Subsequent checks may be required at intervals determined by the insurer.

DME providers typically handle the billing and prior authorization process.

What happens if my Philips machine is recalled and I haven't received a replacement?

Contact Philips Respironics directly or your DME provider to initiate the remediation process. As of January 2026, Philips reports that over 99% of registered devices have been remediated, and the company continues to accept returns.

If you have not yet registered your device, do so promptly. In the interim, consult your physician about alternative treatment options, including switching to a different manufacturer's device.

Practically speaking, the remediation process can take several months, so starting it early is advisable.

Is CPAP the only treatment for sleep apnea?

No. CPAP is the most common and effective treatment for obstructive sleep apnea, but alternatives exist.

These include oral appliances that reposition the jaw, positional therapy for supine-predominant apnea, weight loss programs, and surgical options such as uvulopalatopharyngoplasty (UPPP) or hypoglossal nerve stimulation (e.g., Inspire). The 2025 AASM guideline update also added transvenous phrenic nerve stimulation for central sleep apnea.

However, CPAP remains the first-line treatment for most patients with moderate-to-severe OSA, and its efficacy at reducing apnea events and improving symptoms is well established.

Reference Notes

Information in this article is based on publicly available sources. Some details may change over time.

Verify with official sources before acting. Key references include the FDA's recall information on Philips ventilators, BiPAP machines, and CPAP machines; the American Academy of Sleep Medicine's 2025 clinical practice guideline for central sleep apnea treatment; the AASM's guidance on evaluation and management of obstructive sleep apnea; the Carelon clinical guideline for sleep disorder management; and updates published by the Sleep Foundation, Sleep Doctor, Drugwatch, and SleepApnea.org regarding the Philips recall timeline and status.

Philips' continuing remediation efforts and the status of related litigation are documented through FDA updates and legal reporting. Reference needed for specific device pricing and availability data.

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