How Does a CPAP Machine Work? Key Facts for New Users

How a CPAP Machine Works

What Is Sleep Apnea?

Obstructive sleep apnea (OSA) is a common sleep-related breathing disorder in which a person’s breathing repeatedly stops and restarts during sleep. It occurs when throat muscles relax during sleep and block the flow of air through the upper airway. 

Central sleep apnea is a less common form of the condition that occurs when the brain doesn’t send the correct signals to the muscles that control breathing. This leads to airway collapse and sleep-related breathing problems. 

A continuous positive airway pressure (CPAP) machine is the most common device used to treat sleep apnea with non-invasive ventilation. 

Understanding Continuous Positive Airway Pressure

A CPAP machine delivers a continuous airflow at high pressure through your mouth and/or nose to help keep your airways open during sleep. 

The Role of Pressurized Air in Obstructive Sleep Apnea

In obstructive sleep apnea (OSA), a blockage in the airways interrupts normal breathing patterns. This is because your throat and airways collapse shortly, or there is a temporary blockage, thus preventing air from passing through. Each interruption (or episode) lasts at least 10 seconds. Depending on the severity of OSA, there can be  5 to 30 episodes or more per hour for the entire sleep period.  

This interruption of normal breathing leads to low oxygen levels in the body and increases the risks of other health problems. Untreated sleep apnea can increase the risk of many medical conditions, including:

• Cognitive impairment due to disrupted sleep: daytime sleepiness and problems with thinking and concentration leading to accidents and injuries

• High blood pressure

• Type 2 diabetes mellitus

• Heart disease

• Atrial fibrillation: abnormal heart rhythm  

• Stroke

• Pulmonary hypertension

Continuous positive airway pressure (CPAP) helps to keep your airway open. Positive airway pressure treatment ensures you don’t stop breathing during sleep and prevents low oxygen levels. This constant pressure and forced air delivered by CPAP treatment results in less disrupted sleep, improved daytime sleepiness, and a lower risk of serious chronic health conditions.

In addition to being used to treat sleep apnea, CPAP devices are also used in the neonatal intensive care unit (NICU) in premature infants whose lungs are not fully developed.

Key Components of a CPAP Machine

• A mask that fits over your nose and mouth or only your nose

• Mask straps that hold the mask in place

• A tube that connects the mask to the CPAP device

• A CPAP unit that contains a motor that blows pressurized air through the tube and mask into your upper throat and airways

• An air filter that filters the air before you breathe in

• Additional features like humidifiers that add moisture and heat to the air you breathe

• Adjustable pressure settings

Types of CPAP Masks for Sleep Apnea Treatment

Nasal pillow masks or nasal prongs

A nasal pillow mask fits your nostrils. It is a good choice if a mask that covers more of your face makes you feel claustrophobic, you wear eyeglasses and read or watch TV in bed, or facial hair interferes with the fit of other types of CPAP masks.

Nasal masks

A nasal mask covers your nose. It is a good choice if you need a high-pressure setting, you tend to move around during sleep, or you find a full-face CPAP mask uncomfortable.

Full face masks

A full face mask, also called an oronasal mask, covers your nose and mouth and is a good choice if you have blockages in your nose or you breathe through your mouth. It is recommended for people who do not benefit from a nasal mask or nasal pillow mask. Full-face or oronasal masks may consist of a nasal mask or nasal pillow mask combined with a chin strap to keep your mouth closed and/or a heated humidity feature.

Oral masks

An oral mask, also called a hybrid mask, delivers pressurized air through your mouth. It is a good choice if you wear glasses or breathe through your mouth.

The Functionality of CPAP Machines: How Does a CPAP Machine Know When You Stop Breathing?

Monitoring of Breathing Patterns: How Does CPAP Know You're Asleep?

A CPAP machine knows when you stop breathing because it tracks your breathing patterns. If you have an automatic CPAP machine, also called an APAP machine, it not only provides positive airway pressure but also monitors your breathing patterns. CPAP  machines track a person’s breathing and know they are asleep by monitoring the following:

• Number of obstructive apneas or hypopneas within a fixed timeframe.

• Number of consecutive snore breaths.

• Number of breaths of stable breathing in a fixed time period.

Adjusting Airflow During Sleep

If abnormal breathing patterns are detected, an automatic CPAP machine gradually increases the pressure until it reaches the desired level to maintain stable breathing.

Ensuring Continuous Airway Pressure

A CPAP machine ensures continuous airway pressure by measuring breathing patterns, airway resistance, and oxygen levels. It can also detect changes in sleep quality and adjust the pressure. 

Types of CPAP Machines

Standard CPAP Machines

CPAP (continuous positive airway pressure) is the most common type of device used to provide positive airway pressure. A standard CPAP machine consists of a tube connected to a mask that delivers a constant stream of air at a higher pressure. The CPAP machine takes room air and filters it, and the machine’s motor then blows air to keep your airway open and help you breathe while you’re asleep.

Auto-Adjusting CPAP Machines

Auto CPAP or APAP machines are devices that can provide a range of self-regulated pressures to keep your airways open. These devices measure parameters like breathing patterns, airway resistance, oxygen levels, and sleep quality, and adjust the pressure to ensure stable breathing.

Bi-Level Positive Airway Pressure (BiPAP) Machines

Bilevel positive airway pressure (BiPAP machines) are devices that use two pressure settings, a higher pressure during inhalation and a lower pressure during exhalation, to regulate breathing.

Auto Bilevel Positive Airway Pressure (Auto BiPAP) Machines

An auto-bilevel CPAP machine includes a range of self-regulated pressures during breathing in and breathing out. 

Adaptive Servo Ventilation (ASV)

Adaptive servo-ventilation (ASV) is a positive airway pressure device that monitors breathing and adjusts the pressure. It is used in people with central apneas and can also deliver a breath if needed.

Pros and Cons of CPAP Therapy

Benefits: What Happens to Your Body When You Use a CPAP?

The most important benefit of CPAP therapy is that it treats sleep apnea. Untreated OSA can cause repeated episodes of stopped breathing during sleep, which are associated with an increased risk of many serious health conditions, including heart disease, stroke, high blood pressure, diabetes, and cognitive impairment. 

In addition, treatment of sleep apnea with CPAP can reduce sleep disruption (waking up multiple times during the night, gasping for breath). Sleep apnea treatment can therefore result in decreased daytime sleepiness and improved functioning. 

CPAP therapy can also improve overall sleep quality in the bed partner of the person being treated due to reduced snoring.

Possible Side Effects and How To Manage Them: What Is the Downside to CPAP?

Many people find the mask interface uncomfortable. There are many types of CPAP masks available and you may need to try a few different ones before you find one that best fits your face shape and preferences. To ensure comfort and performance, a proper size and fit is key. Remember, sizes can vary across brands, so if you take a small in one brand, you may need a medium in another brand. 

Another possible side effect of oral appliances like CPAP is a dry mouth because the device blows air continuously through the night. CPAP machines that have heated humidifiers can resolve this problem.

As noted, the airflow from CPAP can be drying. This can cause the nose to react to dryness with an inflammatory reaction similar to nasal allergies. It can cause nasal congestion, runny nose, and sneezing. Again, a CPAP machine with a heated humidifier can help.

Using a CPAP device can cause you to swallow air, leading to gas, bloating, and stomach discomfort. Adjusting the pressure on your device may help.

How to Get and Set Up a CPAP Machine

Prescription for CPAP

You will need a formal diagnosis of sleep apnea and a prescription from your doctor to obtain a CPAP machine. Your primary care provider may refer you to an expert in clinical sleep medicine who can diagnose sleep apnea or other sleep disorders and give you a medical device prescription for a CPAP machine if needed.

Learn more about your options for treating sleep apnea.

Cost and Insurance Coverage

CPAP machines can cost anywhere from $250 to $1,000 or more. Most insurance plans cover CPAP machines and their accessories, at least partially. Some plans may not cover replacement parts or place a limit on how many replacement parts you can get in a year. Most insurance companies require you to meet your annual deductible before they start contributing towards your healthcare costs, including the cost of CPAP equipment.

To check your eligibility for insurance coverage of CPAP, your insurance provider will likely ask for a sleep test called the apnea hypopnea index (AHI). AHI is the average number of episodes of stopped breathing per hour. You have to undergo a sleep study in a sleep lab or use home testing equipment to find out your AHI number.

Setting Up Your CPAP Machine at Home

To set up a CPAP machine at home, follow these steps: 

1. Place the CPAP machine on a stable surface at your bedside.

2. Make sure the air filter is in place. 

3. Attach the hose to the back of the machine at one end and the mask at the other end. 

4. Set up the humidifier, if your machine has one, by filling it with water up to the marked line. Insert the humidifier into the slot on the machine. 

5. Put the mask on and adjust it so it fits snugly but not too tightly. 

6. Plug in the mains and switch on the machine.

Tips for Comfortable Use

• Work with your healthcare provider to find the right CPAP mask style, size, and fit that works for you.

• Get used to wearing the mask by wearing it for short periods of time while you’re awake, for example, while watching TV in bed.

• If you have difficulty tolerating forced airflow, use manual titration to start with a low air pressure. The machine can automatically ramp up the air pressure after you fall asleep. Your healthcare provider can set up a timed pressure escalation.

• Use machines with heated humidifiers if you have problems with a dry mouth or a stuffy or runny nose. Humidification helps reduce dryness caused by the continuous positive airway pressure.

• If the mask makes you claustrophobic, try holding the mask on your face without using the mask straps. Do this a few times while you’re awake to get used to it. If the feeling continues, talk to your healthcare provider about using a different type of mask, such as nasal pillows masks.

• If your mask is ill-fitting, it may cause skin irritation (if it’s too tight) or air leaks and undertreatment of your sleep apnea (if it’s too loose). Work with your CPAP supplier to find a mask that fits snugly and is comfortable.

• If you find you accidentally remove the CPAP mask during the night, consider trying a different type of mask. If the problem continues, consider setting an alarm during the night so you can wake up and re-wear the CPAP mask, if needed.

• Most modern CPAP devices are near-silent. If the noise from your CPAP machine bothers you or your bed partner, check the air filter and call the supplier to make sure the machine is working properly. You can also try placing the CPAP as far away from your bedside as possible.