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CPAP vs. BiPAP Differences: How To Know if You Need a BiPAP Machine

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BiPAP vs. CPAP - Machine Differences

If you are using CPAP therapy or think you need it, you may already be familiar with Continuous Positive Airway Pressure (CPAP) and the Automatic Positive Airway Pressure (APAP). But, did you know there’s a third type: the Bi-level Positive Airway Pressure (BiPAP)?

In this article, we’ll look at what a BiLevel or BiPAP machine is, how it works, the differences between BiPAP vs. CPAP, and what the benefits and potential drawbacks are of BiPAP therapy.

Let’s dive in!

Related Reading: Best BiPAP Machines Reviewed – Our Top Picks!

What Is a BiPAP Machine, and How Does It Work?

A BiPAP machine is a type of PAP therapy machine that can be adjusted to two different pressure levels: one for inhaling and a different one for exhaling.

This may sound a lot like an APAP machine that auto-adjusts based on the inputs from a person’s breathing, but it’s more complex than that. Because of the complexity, a BiPAP machine is normally reserved for those with a sleep disorder such as Central Sleep Apnea (CSA), Complex Sleep Apnea (CompSA), as well as those with Congestive Heart Failure (CHF) and Chronic Obstructive Pulmonary Disease (COPD).

The experience of sleeping with a BiPAP is almost identical to using a CPAP. Both machines contain a motor and an air compressor (and an included or optional humidifier to moisten your therapy air). The BiPAP brings room air in and is then filtered and pressurized. The pressurized air is delivered to your airway via tubing and a CPAP mask, which you wear to sleep. This air works like a splint to keep your collapsing airway open during sleep.

However, whereas CPAP has a single air pressure setting, a BiPAP allows for a differential in inspiratory and expiratory pressures. This means your doctor may prescribe one air pressure for inhaling—often a higher pressure than a typical CPAP will allow—and a second lower air pressure for exhaling.

This pressure gradient is helpful for people who may need additional assistance with their nighttime breathing. For example, if you have very low blood oxygen, your doctor may recommend a higher inspiratory pressure in order to get more air into your lungs. However, exhaling against that higher-than-average air pressure can be difficult. The bi-level pressure setting allows for a lower pressure when you exhale to make breathing more natural and comfortable.

In addition, if you have too much carbon dioxide in your bloodstream, the lower expiratory pressure means you don’t have to work as hard to exhale and eliminate the excess CO2. The bi-level air pressure settings enhance your body’s ability to take in and remove gases.

What Is the Difference Between BiPAP vs. CPAP?

There is one major difference between CPAP and BiPAP: CPAP machines are set at one single pressure while BiPAP machines are programmed with two distinct pressures—one for inhaling and one for exhaling. CPAP machines are primarily used to treat Obstructive Sleep Apnea (OSA) while BiPAP machines are used to treat Central Sleep Apnea, Complex Sleep Apnea, or COPD.

CPAP Machine: A CPAP machine only delivers therapy air to the wearer at one specific pressure and doesn’t vary unless manually changed by a sleep doctor. A CPAP machine pushes the same amount of air pressure throughout the night and is used to treat most cases of OSA.

BiPAP Machine: A BiPAP can be programmed to have two different values of air pressure: one for inhaling and one for exhaling. These are respectively called Inspiratory Positive Airway Pressure (IPAP) and Expiratory Positive Airway Pressure (EPAP). BiPAP therapy pressures are usually higher for inhale and lower for exhale. The lower pressure on the exhale can make it more comfortable to breathe out.

Why would someone need two different settings?

Although most who live with any level of OSA can use CPAP, some conditions related to someone’s ability to regulate their breathing in their sleep are better treated with BiPAP:

  • CSA or CompSA. The primary reason for using BiPAP is if you have one of these forms of sleep apnea. These two of the three types of sleep apnea require your therapy device to be able to prompt you to breathe in case you stop breathing, which only a BiPAP can do.
  • Higher CPAP pressures. The pressure of PAP machines is measured in centimeters of water column or cmH2O for short. CPAP and APAP machines can only be dialed up to 20 cmH2O. BiPAP machines can be set to as high as 25. If you have low oxygen levels, it’s likely you require higher PAP air pressures to treat your sleep apnea effectively.
  • Obesity Hypoventilation Syndrome (OHS). This form of sleep-disorder breathing is commonly found in those with a high body-mass index (BMI). They may breathe too shallowly or slowly during sleep, which can lead to hypoventilation—also known as respiratory depression. It can also lead to a high level of carbon dioxide (CO2) in the bloodstream, causing hypoxia, which can lead to heart or respiratory failure if left unchecked for more than a few minutes in the case of complete oxygen deprivation.
  • COPD/Overlap Syndrome. Overlap syndrome is a term referred to when someone has any type of sleep apnea as well as COPD. COPD prevents your body from finding an optimal balance of CO2 and oxygen in your bloodstream when you’re awake, and your body never gets a chance to correct this imbalance when you’re asleep. Overlap syndrome leads to a number of potentially serious health complications that can be treated by using a BiPAP. Most recent estimates suggest that as many as 65 percent of those with OSA also have COPD. With its higher inspiratory pressure and lower expiratory pressure, BiPAP can help rebalance the blood oxygen and CO2 levels while you sleep and improve your overall breathing throughout the night.

Here are a few other key differences between the machines:

  • There is no ultra-portable BiPAP machine, while there are portable travel CPAP machines.
  • Unlike CPAP, BiPAP machines can deliver pressure settings up to a setting of 25.
  • A BiPAP device may be more comfortable because of the two different pressures.

Benefits of BiPAP Therapy

What are some of the benefits and advantages of using a BiPAP to treat sleep apnea?

  • BiPAP Is a Better Treatment for Those With Breathing Restrictions. People with breathing restrictions may have trouble getting enough oxygen and expelling enough CO2. A BiPAP device can improve your gas exchange, which helps your body function more efficiently. Clearing the body of CO2 can also prevent a dangerous and sometimes deadly condition called hypoxia.
  • BiPAPMakes Exhaling Easier—Which Is Good for Those With a Need for a Higher Inspiratory Pressure. If your doctor recommends a higher-than-average air pressure to help keep your airway from collapsing, then you may find exhaling against that pressure to be challenging and uncomfortable. Working to exhale is no fun, and it may actually lead to a higher blood CO2 level. Many people with a need for higher pressure end up switching from CPAP to BiPAP.
  • BiPAP Includes an Optional Breath Timing Feature. This setting can measure your sleep respiration rate and set an “ideal rate” for how often you should inhale and exhale over a set period of time. When you’re asleep, if you go too long without inhaling, the BiPAP will increase air pressure temporarily. This forces you to take a breath. Once you resume breathing at your normal rate, the automatic setting returns to the previous air pressure level.

Downsides of BiPAP

BiPAP has many pros, but also a few cons:

  • Cost Factor. A BiPAP will cost more than a CPAP. On average, they can cost anywhere from two to four times as much. If you can get your BiPAP covered by insurance, the cost may be reduced, but you may have trouble getting insurance coverage unless you can prove you need a BiPAP for medical reasons.
  • Adjustment Period. Getting used to using a BiPAP may take some time. Although the mask and tubing will feel the same as using a CPAP, the need for higher pressure variations can be challenging at first for some wearers.

Uses and Indications for BiPAP Therapy

How do you know if you need BiPAP therapy? Your doctor will tell you which to use, based on the results of your sleep study, your titration study, and your general health history.

Common reasons to use BiPAP include:

  • CPAP Intolerance. If you cannot tolerate a CPAP machine, BiPAP can be approved as an alternative. However, a BiPAP is traditionally more expensive than CPAP. Because of this, for your insurance to cover the change, your inability to use a CPAP machine will need to be documented during your sleep study.
  • A Need for Increased Ventilation. If you have a pulmonary disease or any other condition that requires assistance with both inhaling and exhaling, BiPAP may be a better choice for you than a CPAP machine. If you have an obstructive and restrictive component like Central Sleep Apnea, obesity hypoventilation, COPD, or Overlap Syndrome, then talk to your doctor about using a BiPAP.

Understanding the Different BiPAP Modes (BiPAP ST and AVAPS)

BiPAP machines have typically operated on the simple principle of assigning an IPAP and an EPAP value to generate what’s called tidal volume, which is the difference between the two figures. Over time, the spontaneous timed (ST) mode was also introduced. This means that while your sleep medicine physician will still assign you an IPAP and EPAP prescription he also has the ability to assign a breaths per minute value (BPM) that enables the machine to monitor how many breaths a wearer takes per minute. If the machine detects the person has not taken that number of breaths it will prompt them to take a breath.

For example, a BiPAP might be set at the following:

  • Inhalation Pressure – 10
  • Exhalation Pressure – 5
  • In this case, a BiPAP will provide an IPAP of 10 and an EPAP of 5.

A BiPAP ST might be set at the following:

  • Inhalation Pressure – 10
  • Exhalation Pressure – 5
  • 12 BPM (Breath Per Minute)

Similar to the regular BiPAP, the BiPAP ST will provide an IPAP of 10 and EPAP of 5, and will additionally monitor if you inhale 12 times within the minute. Please Note: The ST will not breathe for you, rather it will prompt the user to take a breath.

Another BiPAP mode introduced more recently is average volume-assured pressure support (AVAPS.) AVAPS BiPAP machines are able to automatically adjust the IPAP and EPAP values as it detects changes in the person’s breathing patterns by measuring the inputs and calculating the best value based on a time interval.

This now gives BiPAP wearers the same flexibility that their CPAP counterparts previously had of being able to choose a machine with fixed pressure settings or one that adjusts accordingly. Akin to CPAP or APAP, choosing between AVAPS and ST isn’t necessarily a matter of choice but rather a matter of which one is best for your treatment.

If someone requires frequent changes that are larger than 2.5 cmH2O, using BiPAP ST would be best.

What Is a VPAP and Is It the Same as a BiPAP?

A VPAP is not the same thing as a BiPAP. The two are very similar in how they work, but the main difference between a VPAP and a BiPAP lies in how the pressures for inhale and exhale are selected. Like a BiPAP, the VPAP uses a higher pressure for inhalation and a lower pressure for exhalation.

While a BiPAP is preprogrammed with two distinct pressures for inhale and exhale, the VPAP is an auto-adjusting bilevel breathing device. Unlike a CPAP, which provides continuous flow, the VPAP machine studies your breathing and chooses the correct pressure based on individual therapy needs. VPAPs can treat Sleep Apnea, but can also treat other pulmonary and lung diseases as well.

Why Are BiPAP Machines More Expensive Than CPAP Machines?

One thing those looking to buy a BiPAP machine will quickly notice is how much more expensive they are compared to CPAP and APAP machines. BiPAP machines are complex and have more parts and features that need to come together for the wearer in comparison to CPAP and APAP machines. Its motor and air control technologies must be able to regulate two pressure levels for your every breath with little room for error. Therefore, not only is the underlying technology more expensive to produce, but it must also be made of more durable material to withstand the constant ebbing and flowing of air pressure.

You may be surprised to learn it might be cheaper to buy the machine outright instead of going through your insurance. In some cases, insurance companies will mark up the price of machines in order to make more money or to simply cover the costs associated with getting you the machine (e.g.: reviewing and processing claims or negotiating deals with vendors). In some plans, including Medicare, you may not even end up owning the actual machine, meaning you’re required to pay a certain amount upfront and rent the equipment from them. In addition to that fee, you also need to factor in the cost of your mask and cleaning supplies, which your insurance is unlikely to cover.

This is why CPAP.com does not work with insurance companies; it’s why we’re able to offer lower prices for purchasing your sleep apnea machine outright instead of renting it in perpetuity. Another benefit of this is that you also do not need to worry about other insurance-related items, such as working with a new provider if your employer changes plans or if you switch jobs and get on a new health insurance plan.

Do I Need a Different Mask for my BiPAP Machine?

There’s actually no such thing as a BiPAP mask. Any CPAP mask will work with a BiPAP machine. The only mask adjustment would be if your prescription is for more than 20 cmH2O. In that case, you should look for a mask that can create a heavy-duty seal. Odds are that if you are going to begin BiPAP treatment then your prescription may be for more than 20 cmH2O and you should look for a mask and hose capable of handling such high pressures.

Aside from that, the right mask for you will come down to your preferred sleeping position. If you feel you picked the right mask but still experience tiredness during the day and other symptoms that should have been made better with CPAP treatment, your CPAP pressure may be too high. If you feel that’s the case, discuss possible adjustments and other potential solutions with your sleep physician.

When Is BiPAP a Better Sleep Apnea Treatment Option Than CPAP?

When it comes to PAP therapy, it’s not a matter of which therapy is best. It’s a matter of which one is right for you. Although most people with sleep apnea use CPAP on the recommendation of their sleep specialist, there are certain conditions where a BiPAP might be a better option such as:

If You Require Higher CPAP Pressures. If you have low oxygen levels and your sleep specialist has determined that you require higher CPAP air pressure to treat your sleep apnea effectively, then you may benefit from a BiPAP machine. Many people who need a higher air pressure prefer the comfort of a BiPAP thanks to its lower expiratory pressure. Exhaling against a high air pressure can feel like a struggle and may make it harder for you to fall asleep or stay asleep. With a BiPAP machine, that struggle is eliminated.

If You Have Obesity Hypoventilation Syndrome (OHS). This form of sleep-disordered breathing tends to affect people with a high BMI. You may breathe too shallowly or slowly during sleep, which can lead to respiratory depression (hypoventilation) and a high level of carbon dioxide (CO2) in your bloodstream.

A dangerous condition called hypoxia can develop, which can sometimes result in heart failure or respiratory failure. However, for people with OHS, a BiPAP, with its restrictive component, can be a better option than a CPAP because of its ventilatory effect. The higher inspiratory pressure and the lower expiratory pressure can help you to get sufficient oxygen while expelling CO2.

If You Have COPD/Overlap Syndrome. If you have both sleep apnea and chronic obstructive pulmonary disease (COPD), you may have what’s termed “overlap syndrome.” This means you experience double the impact of having either a pulmonary issue alone. You don’t have a correct gas exchange of CO2 and oxygen in your bloodstream when you’re awake thanks to the COPD, but your body never gets a chance to correct this imbalance when you’re asleep either.

Your breathing problems last around the clock, leading to a number of potentially serious health complications. However, by using a BiPAP, you may be able to improve the work of breathing when you’re asleep. With its higher inspiratory pressure and lower expiratory pressure, BiPAP can help rebalance your blood oxygen and CO2 levels when you’re asleep.

Whether you’d benefit more from a BiPAP or a CPAP is a decision your doctor makes based on your sleep test results and medical condition. If you have questions about BiPAP and CPAP, ask your sleep medicine physician. It’s important that you understand the specific benefits of the sleep apnea therapy that your doctor recommends for you.

The Bottom Line

A BiPAP for the treatment of sleep apnea and sleep-disordered breathing is very similar to a CPAP device. Both BiPAP and CPAP machines use pressurized air to keep your airway open.

The main difference between BiPAP and CPAP machines is that BiPAP offers bi-level air pressure. This means you can have two different air pressure settings, one for inhaling (inspiratory setting or IPAP) and one for exhaling (expiratory pressure or EPAP). This differential is also known as a “pressure gradient.”

The pressure gradient can be helpful for sleep apnea wearers who have additional breathing-related issues, such as COPD or obesity hypoventilation syndrome. The dual pressure feature enables you to improve your gas exchange by bringing in more oxygen and eliminating more CO2. A BiPAP is also an effective alternative treatment for those with sleep apnea who cannot comply with or tolerate CPAP therapy at higher air pressures.

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15 thoughts on “CPAP vs. BiPAP Differences: How To Know if You Need a BiPAP Machine”

  1. I am very active in sport gym, cycling and power walk. I have suffered with sleep and sleep apnea for a while which has increased my blood pressure during my interrupted sleep evenings. I need to take blood pressure tablets as a result of this.. and causes me not to have a continuous sleep experience. Can you suggest and approach for me? Some this that is compact yet functional.

    1. Hey Ian,

      Lots of CPAP users are very active in sports. I am sorry to hear that you are having to deal with high blood pressure and interrupted sleep. I would suggest to you that the most economical option would be a small travel machine and a mask. Another option that you may consider is Provent Therapy. Either way you will need to speak with your doctor because we will require a prescription. If you would like assistance selecting a machine and mask that would best suit your needs we will be happy to assist you if you give us a call at 1-800-356-5221. Here is a link to the Provent Therapy that I mentioned https://www.cpap.com/productpage/provent-therapy-30-day-starter-kit

      Whichever option you select please remember that we will require a prescription. We are happy to assist you in obtaining a prescription, just give us a call.

  2. In your article, you don’t say what the letters ST in BiPAP-ST means. I understand that type of machine initiates a breathe for the user, but I’d like to know what ST means.

    BTW the machine I’m using now has an APAP mode and also adjustable exhalation relief in both APAP and CPAP mode. I swear my machine, which is not a BiPAP-ST, can initiate a breath on its own. It doesn’t say it has that capability in the user manual. But I think the manufacturer has incorporated the feature without documenting it in the manual. To give the user the best possible experience. This maybe to avoid lawsuits from the legal owners of the ST technology.

    1. Hi Dave,

      The ST actually stands for spontaneous timed. Here is some additional information for you found on our FAQ page https://www.cpap.com/cpap-faq/BiPAP-Machine#what-is-the-difference-bipap-and-bipap-st.

      Perhaps what you are experiencing is the flow rate of the exhalation relief, or flex feature of your machine (all manufactures call this something different. Eg. Resmed=EPR, Phillips=FLEX, F&P=Senseawake, etc.) Here is some more information on flex technology. https://www.cpap.com/cpap-faq/CPAP-Machine#what-is-c-flex

  3. I have a Dreamstation Auto BiPap with settings at 9/13. I had a ruptured brain aneurysm and subarachnoid hemorrhage/stroke in February and they put me on a BiPap machine while I was in the hospital. In the past 2 weeks my AHI has doubled or more from readings of 2 to 4 to 9.3 to 17.6. I don’t know why or what to do about it.

    1. Hi Mary, I would encourage you to speak with your doctor, as they can view your therapy data and make a determination as to if you require a setting adjustment, or what may be causing the increase in your AHI’s.

      If you would like to speak with us further, please feel free to contact us at: 1-800-356-5221.

      We wish you the best!

  4. I am having differculty @ nite sleeping , a lot of moving in my sleep , sleepy during day , taking naps , I stop breathing even though I am using a c-pap machine, please help me the doc keep saying that my sleep reports look ok , I need help

    1. Hey Rachel, i’m sorry to hear about the troubles with your CPAP therapy. How long have you been using your CPAP machine? The symptoms you are referring to sounds like your therapy isn’t working for you. You may want to suggest to your doctor to increase/adjust your pressure setting.

      Also, what type of mask are you using? Have you checked your leak rate? One of the most important factors with successful CPAP therapy, is having a comfortable mask. If you aren’t using a full face mask, you may try switching to one and if you’re currently using a full face mask, you may want to try a different one.

      Please be sure to continue speaking with your doctor about the difficulties you are experiencing with your therapy.

      Also, please feel free to reach us at: 1-800-356-5221, for further assistance.

      Best Wishes!

  5. Hi, If one has complex Apnea, a mix of Central and Obstructive Apnea, can he use a Bipap Biflex without the ST? Without back up rate?

    1. Hi Ricardo, yes you can use a BiPap without the ST. Really, this is something you must speak with your doctor about. The type of machine you get will totally depend on the prescription your doctor writes for you based upon the results from your sleep study.

      For further questions, or concerns, please feel free to reach us at: 1-800-356-5221, or e-mail us at: cpap@cpap.com.

      Have a great day!

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