What Is The Difference Between CPAP, APAP, BIPAP, and ASV?


When it comes to treating sleep apnea, there are a wealth of options available to patients and it can be somewhat confusing when trying to determine which option is best for you.

What’s more, there is so much terminology and so many acronyms relating to sleep apnea treatment that you may find yourself stuck in a word soup and come bedtime, are still none the wiser to the most appropriate treatment option for you.

But these worries can be easily eliminated by gaining an understanding of the different types of machines that are used to treat the condition and in this article we are going to be looking at these in a little more depth.

This will allow you to understand the difference between the APAP, BIPAP, CPAP and ASV options.

How Is Sleep Apnea Treated?

One of the most important things to remember when you are diagnosed with sleep apnea is that not all forms of the condition need to be treated. In some patients with a milder form of the condition, simple lifestyle changes can be the most effective way of treating sleep apnea.

However, for those with moderate to severe sleep apnea, a machine designed to open the airways and make breathing easier is the most common form of treatment. These are known as PAP machines which stands for ‘positive airway pressure.’

These machines come in a variety of forms, usually the first port of call is the CPAP machine and this is what is most frequently used by patients with sleep apnea.

However, there are other types of machine and depending on which type of sleep apnea you have and its severity will play a part in what type of machine you use.

Understanding The Difference Between Types Of PAP Machine

The four machines that we are going to be focusing on in this article are the CPAP, the BIPAP, the APAP and the ASV machines. The original machine was the CPAP but further designs have been developed over time.


Continuous positive airway pressure machines, more commonly known as the CPAP machine is a device which delivers pressurised air through a tube and mask, which is worn on the face.

The machine takes air from the room and pressurises it before delivering it as a continual stream of air. This ensures that the airways remain open and that the patient is able to breathe freely and easily throughout the night.

These machines have the ability to alternate the air pressure, and in many cases patients will start on a lower pressure whilst drifting off to sleep which then automatically increases to the desired pressure for the entire night.

The reason for this is that the CPAP machine can make inhaling a breeze but on exhaling, it can feel somewhat uncomfortable and whilst many patients become used to this, especially when allowing the pressure to increase gradually, others may never get used to this feeling.

With the CPAP being the original form of sleep apnea treatment, it is often the least expensive but can also be much less technologically advanced than the other treatment options that are available.

CPAP is most commonly used to treat patients with obstructive sleep apnea in which the muscles in the throat will relax intermittently, causing a blockage.


Bi-level positive airway pressure is a device which is often used for patients who have struggled to get along with using a CPAP machine. The reason for this is that unlike the CPAP, which delivers one continuous stream of air, the BIPAP machine gives two varying air pressures – one for when the patient inhales and one for when they exhale. This can feel more comfortable and natural.

In addition to this, the BIPAP machine is much more sophisticated since it has the ability to ‘learn’ the breathing patterns of the user, meaning that the machine will adjust if it notices a shift in the breathing but can also be preset to work with the individual patients breaths per minute.

In this case, the machine will usually deliver a slightly less intense pressure on the exhale to further assist in comfort whilst breathing out.  As you can see, this is more technologically advanced than the CPAP, making this one of the clear differences in this piece of machinery.

One of the other common uses aside from treating sleep apnea, is to assist patients with underlying or separate conditions, most commonly COPD or heart failure. This can make breathing easier.

For those with central sleep apnea, which is a form of the condition where the brain cannot send the correct signals to induce breathing, BIPAP treatment is the preferred method.


The APAP machine, which stands for Automated Positive Airway Pressure is the preferred treatment for those who suffer from sleep episodes only during periods of REM sleep. But it can also be used to treat patients who may have an allergy or increased congestion of the airways – this is especially useful for those who tend to sleep whilst lying on their backs.\

The APAP is certainly superior when it comes to technology and provides the user with a wealth of functions which are not found on the CPAP or BIPAP machines.

One of the most notable smart features of the APAP is that it can be set to varying pressures and the machine will fluctuate between these as the patient sleeps. The APAP machine is designed with complex algorithms which enable it to determine even the most subtle shifts in the patient’s breathing which in turn cause it to alter the pressure.

The user also has the ability to set a maximum and minimum pressure level to ensure that the machine never goes outside of these, therefore producing the best effects conducive for safe and comfortable sleep.

Despite its higher technological advances, the APAP machine is still extremely similar in appearance to both the CPAP and BIPAP machines.


The final machine that we are going to explore is the Adaptive Servo Ventilation machine which is most commonly used to treat patients who suffer from either central sleep apnea or mixed sleep apnea. This is a form of the condition in which patients suffer from both obstructive sleep apnea and central sleep apnea.

In addition to this, the ASV can also be used to treat a condition called Cheyne-Stokes respiration which causes the breathing to become abnormal resulting in episodes of sleep apnea. In this condition, the patient’s breathing will act in a crescendo and decrescendo manner.

As far as appearance goes, the ASV machine will look very similar to the other machines that we have discussed in this article but there are key differences in the function. Primarily the ASV is used to treat patients with central sleep apnea for whom BIPAP treatment has been unsuccessful.

You might think of this as the last resort when all other treatment options fail. In addition to this, you may find the ASV being used by people who originally were diagnosed with obstructive sleep apnea but have gone on to develop central sleep apnea or mixed sleep apnea.

In a technological sense, the ASV is by far the most advanced of all the PAP machines with the ability to not only control air pressure but also can maintain the level of oxygen in the blood ensuring that it does not fall below 90.

The ASV machine delivers assistance in breathing as it detects a reduction in breath and provides just the right amount of air pressure to maintain ‘normal’ breathing. The algorithm within this machine is certainly superior and can provide users with the ability to breathe comfortably and safely at the required level and consistency.

In the video below, Jason (AKA Lankyleft27) discusses when an ASV machine is typically used. Jason is a registered Polysomnographic Technologist (sleep tech) and clinical sleep Educator. You might be familiar with his channels.

This is one of his earlier videos, as you can tell. But this is great info. The part I am talking about starts at about the 5 minute mark. He basically is explaining that about 3 lines on a sleep study. The top line shows breathing. if that line gets weak or flat lines, that could mean an obstruction.

The other 2 lines show effort being made by the brain to send signals to the body for breathing. If those 2 lines flat line, it isn’t obstruction, it is central or mixed sleep apnea. A CPAP, APAP, or even BIPAP would not be good enough. So that is where the ASV comes in.

Side note, Jason’s YouTube channel is really a great resource. You go on YouTube and search Lankyleft27 and you could spend days watching his videos. Very informative stuff by an expert.

Choosing The Right Treatment

When it comes to selecting the right treatment for your sleep apnea, it is of course wise to discuss your options with your healthcare provider who will be able to offer you practical advice on the best method of treatment for you. That being said, there are some certain points to consider.

Most importantly, you will need to think about the type of sleep apnea that you have been diagnosed with as well as whether you are suffering from any other health conditions such as heart failure or COPD – this will reflect in what type of machine will benefit you the most.

In addition to this, your treatment will also be determined on how well you are able to work with the different machines. For example, patients who are unable to use a CPAP machine will likely be given the option to switch to a BIPAP machine.

In short, people who suffer from milder forms of sleep apnea or obstructive sleep apnea, a CPAP or APAP machine will be the most advantageous choice, with some patients moving onto BIPAP if it is needed.

However, those who have more severe types of obstructive sleep apnea, central sleep apnea or underlying health problems such as the ones that we have discussed in this article, may benefit more from BIPAP or ASV machines.

So, What Are The Main Differences Between CPAP, BIPAP, APAP and ASV?

Now that we have taken an in depth look at the functions and uses of each of the treatment options for sleep apnea, we can easily identify the main differences between them.

  • Each of the different machines are used to treat different types of sleep apnea as well as other health conditions.
  • The machines range greatly in their technological abilities with the CPAP machine being the least advanced and providing a simple solution for obstructive sleep apnea and the ASV being the most advanced, giving patients with more complex sleep apneas more effective treatment.
  • In addition to the algorithms employed in each machine, they have different settings. For example, the CPAP has one setting which delivers a constant air pressure but can increase gradually, whereas the BIPAP can be altered according to the patient’s rate of breathing. The APAP allows for pressures to be set at maximum and minimum levels whereas the ASV can also control blood oxygen levels.
  • We mentioned that CPAP is the least expensive option when it comes to sleep apnea treatment, and the cost between machines is a very notable difference with the more complex ASV machines coming in at a much greater price.


Depending on what type of sleep apnea you have will play a very significant role in what type of treatment you will benefit from. There are a variety of different machines which are commonly used in the treatment of the condition but despite being aesthetically similar, what they have in common ends here. The function and use of the CPAP, BIPAP, APAP and ASV machines varies greatly.

Each machine has its own range of benefits which can greatly reduce the amount of sleep episodes experienced by a patient with sleep apnea but it is important to note that each one will only serve its purpose if used for the correct condition.

For example, patients with very severe forms of central sleep apnea and who also have underlying health conditions may benefit more from the use of the ASV machine and may find little relief when using a CPAP. In contrast, patients with a moderate form of obstructive sleep apnea may find that the ASV is far too advanced for their needs and would benefit more using the CPAP.

Aside from treating different conditions, the machines also vary significantly in cost and this is due to the amount of settings and operations that each machine is able to perform.


Dan was diagnosed with sleep apnea in 2017 when he was only 32 years old. He has been using a BIPAP machine for his treatment. He hopes to provide a patient's perspective on the sleep apnea experience. Dan lives in Tampa with his girlfriend and 2 dogs.

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