APAP vs. CPAP and BiPAP: What’s the Difference?

Doctor demonstrating difference between CPAP and BiPAP

If you have obstructive sleep apnea, positive airway pressure therapies can help you treat your sleep disorder and reclaim your night. 

These treatment options deliver room air through a mask and hose to keep your airway open during sleep. But what are the differences between each type of positive airway pressure therapy and how do you decide which one is right for you? 

This blog post will compare and contrast APAP, CPAP, BiPAP, and new PAP devices to make choosing a therapy much easier. 


Auto-adjustable positive airway pressure therapy, or APAP, provides different pressure levels throughout the night to treat your sleep apnea. 

How It Works

By setting a pressure range on an APAP machine, you allow the device to adjust to your unique sleep apnea requirements. The APAP machine monitors your breathing and adapts the pressure based on an internal algorithm. 

This type of positive airway pressure therapy typically has a pressure range of 4 to 20 cmH2O. The machine’s algorithm is designed to provide you the right amount of pressure to keep your airway open, so you can breathe normally. This can make the therapy more comfortable and catered to your specific pressure needs on any given night.


APAP might be the right positive airway pressure therapy for you if you need variable pressure during sleep. This may be due to:

  • Deeper sleep cycles
  • The use of sedatives
  • A tendency to sleep on your stomach
  • The position of your head on your pillow
  • What you had to eat or drink that evening  

The device will reduce pressure to the lowest effective level, based on your breathing patterns, to ensure a more comfortable sleeping experience. 

Some health providers will start you on an APAP device with a range of pressure to eliminate the need for an in-lab titration study. These studies are normally used to determine the precise pressure you need to keep your airway open during the night, but can be an inconvenience to schedule and complete..


APAP delivers airflow whether you’re inhaling or exhaling, and getting used to this can be difficult. Because of the constant airflow, APAP devices usually require humidification units which increases the size of the device and adds to the maintenance requirements. You could end up spending hundreds of dollars on a CPAP cleaning device to prevent the accumulation of moisture and bacteria in the hose, device, and humidifier. 

Because APAP is typically set at a wide pressure range, there is also a greater chance of air leaks when the APAP device titrates to the higher pressures. These leaks can decrease the effectiveness of your positive airway pressure therapy, cause discomfort, and disrupt your sleep.


Continuous positive airway pressure therapy, or CPAP, provides you with the same pressure all through the night. 

How It Works

You can adjust the pressure of a CPAP machine between 4 to 20 cmH2O. Unlike APAP, you will receive that same pressure level for the whole night. The same pressure is applied on both your inhalation and exhalation. 


Fixed positive airway pressure therapy is thought to be more effective for obstructive sleep apnea. CPAP therapy can also be more precise if you’re able to conduct an additional in-lab titration study after your diagnosis. If you can adjust to the constant airflow and pressure, CPAP can be an excellent treatment for sleep apnea.


Just because CPAP is the most common type of positive airway pressure therapy doesn’t mean it’s the best option for you. 

Breathing against a strong and continuous pressure can cause discomfort or make you feel like you’re choking. Most CPAP users need a humidifier to counter the drying effect of continuous airflow, which increases the size and cleaning requirements of the device. You may also have to wear the headgear very tightly to get the proper mask seal against the constant airflow. This can cause impressions and redness on your face in the morning.   

Read more about why it can be difficult to adjust to CPAP here.

Man using positive airway pressure therapy


Bi-level positive airway pressure therapy, or BiPAP, has two distinct pressure settings, which is the biggest difference between CPAP and BiPAP.

How It Works

BiPAP devices have one setting for inhalation positive airway pressure (IPAP) and one setting for exhalation positive airway pressure (EPAP). EPAP allows for a lower pressure level during exhalation. The switch between IPAP and EPAP is either timed or determined by your breathing patterns, depending on the device.

You can usually adjust the devices between 4 and 25 cmH2O, which means BiPAP can offer higher peak pressure than APAP or CPAP. 


Because of the two different pressure settings, BiPAP can make breathing easier, especially if you have lung or heart disease. That’s because you don’t have to exhale against the high pressure of incoming air.

The higher peak pressure is also advantageous if you need a moderate to high-pressure range for your treatment.


While BiPAP can be used to treat obstructive sleep apnea, it is more commonly used for central sleep apnea or pulmonary, cardiac, and neurological disorders that require the airway to be supported during sleep.

The BiPAP experience is also very similar to using an APAP or CPAP machine. Every night, you will need to wear a mask that’s attached to a machine with a hose. BiPAP uses continuous airflow, so the devices have a humidifier to make the therapy tolerable. As a result, BiPAP devices can be very loud, bulky, and difficult to clean, which can make them uncomfortable to use and difficult to take on trips. 

BiPAP machines are usually much more expensive than other positive airway pressure therapy devices. You may also still feel the need to purchase costly cleaning devices to prevent the buildup of moisture and bacteria.   

Somnera: A New Positive Airway Pressure Therapy

This simple yet effective new technology delivers airflow on demand while allowing you to breathe in room air. 

How It Works

The Somnera® System uses positive airway pressure therapy, or PAP, to deliver treatment. Proprietary SmartValve™  technology and advanced software algorithms regulate the airflow based on your breathing effort. The device provides airflow during inhalation and you do not breathe against any airflow during exhalation.

As you inhale, you draw air from the room through the valve, which is supplemented by airflow from the flow generator. The SmartValve provides expiratory positive airway pressure (EPAP) at the end of every breath to keep your airway open. Sensitive membranes inside the valve prevent any spikes in pressure to maintain your prescribed settings. Just like CPAP or APAP, you can program the device between 4 and 20 cmH2O. 

You need an obstructive sleep apnea diagnosis and a physician’s prescription for positive airway pressure therapy to purchase the Somnera System. This is the same type of prescription as for APAP or CPAP.

PAP vs. CPAP, BiPAP, and APAP: What Sets It Apart 

Although the Somnera System provides the same therapeutic pressure as CPAP, BiPAP, and APAP, it delivers much less airflow. Somnera’s airflow is also cyclical instead of continuous. This is the first sleep apnea treatment that provides positive airway pressure therapy without the continuous high airflow of CPAP. This low-flow technology may be more comfortable.

Low-Flow Technology

While CPAP relies on additional airflow to blow your exhalation through the holes in the mask to prevent CO2 rebreathing and suffocation, the SmartValve efficiently channels 100% of your exhalation out into the room. You don’t need to put up with the annoying yet intentional leak that is required with CPAP masks   

Because of the lower airflow, your airway is unlikely to get dry with the Somnera System. This eliminates the need for a humidifier and reduces the blower size. That means you don’t need to keep any distilled water on hand and you can say goodbye to that bulky hose. At 9mm, the Somnera hose is the smallest, lightest, and most flexible hose in the industry. If you’re prone to bloating and dryness, you can use the no-airflow GoToSleep™ setting so you only start receiving airflow after you’ve fallen asleep.

Easy-to-Use Device

It’s impossible to breathe down the Somnera hose, which makes the components easier to clean and maintain with soap and water. You don’t need to buy an expensive CPAP cleaning device or worry about checking another bag for bulky CPAP equipment when you travel.

The Somnera System is a great option if you’re suffering from obstructive sleep apnea, but don’t want to deal with the continuous rushing airflow associated with traditional CPAP devices. To compare more obstructive sleep apnea treatment options, read our blog post on alternatives to CPAP.