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What are the differences between CPAP and BiPAP?

An overview of non invasive respiratory support for nursing students

Let’s be honest . . .

Ventilation can be a tough subject.  I have said before, but the RT (respiratory therapist) should be your best friend on the clinical floor.  Understanding the various modes of ventilation and which is best for a given patient or disease process can be confusing.

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This episode is designed to give you an overview of the differences between CPAP and BiPAP so that you will be able to walk into a room and feel comfortable with how your patient is ventilating.


First of all, let’s define what these terms stand for:

CPAP – Continuous Positive Airway Pressure

BiPAP – Bilevel Positive Airway Pressure

It’s also important to mention here that both CPAP and BiPAP are NONinvasive modes of ventilation . . . that just means that we are not required to insert a tube (endotracheal tube for mechanical ventilation).  The patient simply requires a snug (very snug) fitting face mask or nasal pillow in order to be on this therapy.

cpap and bipap settings for nurses


Continuous vs Bilevel

The major difference to keep in mind between these two is that CPAP is delivering a set pressure CONTINUOUSLY . . . it never changes.  It doesn’t matter how fast the patient breaths, whether they are taking a breath, or if they stop breathing . . . it will just keep pumping along at the same pressure.

Bilevel on the other hand is much more sophisticated.  BiPAP will deliver a DIFFERENT pressure depending on whether the patient is taking a breath or exhaling.

These two pressure differences are known as IPAP and EPAP.

IPAP – Inspiratory Positive Airway Pressure

EPAP – Expiratory Positive Airway Pressure

This is important for nurses and nursing students to understand because this is the KEY difference between these two therapies and is the foundation for their uses.

nursing cpap bipap settings

Uses for CPAP

Because CPAP only delivers one pressure setting it is important to understand that it helps best in situations of hypoxemia as it will aid with oxygenation.

CPAP will do the following:

  • ↑O2
  • ↓ Work of breathing
  • ↑ Intrathoracic Pressure which will ↓ preload thereby ↓ cardiac workload

Due to these effects of CPAP it can be useful in situations of sleep apnea and CHF exacerbation.

The only real settings for CPAP that the nurse needs to keep in mind is the initial pressure setting . . . measured in cmH2O.

Remember . . . CPAP is spontaneous . . . which means the patient does not receive any ventilatory support.

Uses for BiPAP

Due to the key difference between CPAP and BiPAP ( one pressure vs two pressures) , BiPAP is a great tool for ventilation (removal of CO2) in conditions like COPD exacerbation or other situations where the patient needs ventilation support.

Settings for BiPAP written by the physician will look like this:

Bipap 10/5 rate of 12 FiO2 of 60%

Notice the two pressures (IPAP vs EPAP).  The difference between these two numbers is called PRESSURE SUPPORT.

In the order above PS is 5 . . . IPAP – EPAP or 10-5.

Notice also that they physician has ordered a RATE.  This is a big difference between BiPAP and CPAP.  With BiPAP a specific rate is programmed in the machine and whether or not the patient is breathing, the machine will deliver the programmed pressure at the set rate.

Also, notice the order has a set FiO2 . . . this is the % of O2 to be delivered.  Normal room air has an FiO2 of about 21%.  The FiO2 will be titrated to keep the patients SpO2 (pulse ox) or SaO2 (blood gas) at or above 91%.

If the patient continues to have difficulty maintaining appropriate SpO2 or SaO2 . . . the FiO2 can be adjusted.

If CO2 levels are high then IPAP and EPAP can be adjusted accordingly.

As Pressure Support increases (difference between IPAP and EPAP) the lungs will be able to expand more to allow increased ventilation (clearing of CO2).

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As I mentioned above . . . we have RTs and Practitioners for a reason. . . . this can become very  complex very quickly.  However, it is VITAL that you understand the basic settings and differences between CPAP and BiPAP.

You should know exactly what your patients settings are and if/when adjustments have been made.  It is also important to know WHY the patient was placed on ventilatory support as this will help you assess you patient and notify providers for any possible needed changes in settings.

As the nurse . . . are at the bedside . . . you are with the patient . . . it is your job to know what it going on with your patient.  It isn’t required to have a complete, indepth understanding of all of this . . .but as you begin to understand better what is going on you will be able to better take part in the patients care.

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Podcast Transcription

So head over to, go ahead and sign up there and every Friday we will email you a free worksheet, cheat sheet, however you want to call it that’s going to help you in your nursing school journey. Today, what I want to talk about is, I want to talk about the difference between CPAP and BIPAP, what they are, and really what the differences are and maybe some situations where they would be helpful, where they’re going to be useful for your patient’s. This is a question we get a lot and it’s something that you are going to encounter because you can encounter CPAP and BIPAP anywhere in the ED, on the MED/SURG floor, and in the ICU even.


Important to understand and we’re just going to give you a high level breakdown of what it is just so that when you walk into a patient who’s either on CPAP or BIPAP or a patient who is struggling to breathe or a patient who is coming off intubation that you’ll be able to understand what’s going on and possibly even be able to help out with the decision making process with that. Let’s talk really quickly, CPAP BIPAP, I know you’ve heard of it because CPAP is often used for patient’s with sleep apnea, maybe you have a CPAP or BIPAP at home or maybe you have family members who do or a dad who snores of has sleep apnea and is now on CPAP.


Let’s talk really quickly about what it is. The first to understand what is going on here, we need to understand that CPAP and BIPAP are both non-invasive methods of ventilation assistance or respiratory assistance. So, what does non-invasive mean? That means we don’t need a tube, we don’t need to intubate in order to provide this but it is a step up from a face mask or a Venturi mask or nasal cannula. It’s a step up from just oxygen in the nose but it’s definitely a step down from mechanical ventilation. It’s kind of our next step. So, what is the difference then between CPAP and BIPAP?


What CPAP stands for is continuous positive airway pressure ventilation where BIPAP stands for bi-level non-invasive positive airway pressure. Just those two names give you a basic overview of what it is. CPAP, continuous positive airway pressure. What that means is we have this tight face mask on our patient or a tight nose pillow and what we’re doing is we’re providing one airway pressure to that patient continuously. We’re just delivering 10 centimeters of water of airway pressure, 5 centimeters of water or whatever it is without stopping.


It’s just continuously giving that during inspiration and expiration. Where with bi-level positive airway pressure we have 2 pressures, we have an inspiratory pressure and an expiratory pressure. That’s the basic overview. Let’s talk a little bit more about CPAP. What CPAP is really good for is it’s generally used for oxygenation problems for hypoxemia, low oxygen in the blood. What we can do is we can pump them with oxygen with our CPAP. We’re supplying them with oxygen through one continuous pressure setting. Our CPAP would just be a CPAP of 10 where they’re going to be getting this continuous pressure whether they’re breathing in or they’re breathing out.


What it really does is it helps improve oxygen which is going to hopefully decrease the work of breathing. We’re just going to pump their lungs with this continuous level of pressure. What that’s going to do is that can increase our intrathoracic pressure. As we pump them with this pressure setting, with this oxygenation with this level it’s going to increase intrathoracic pressure and that’s going to decrease our preload. That’s going to decrease the ability of our ventricles to stretch. A couple weeks ago we did a podcast about preloaded afterload so to help this make sense you might go back and listen to that one but what this is going to do is it’s going to, as we fill their lungs, that’s going to exert a pressure, that intrathoracic pressure, it’s going to exert a pressure back on the heart.


That’s called transmural pressure but it’s going to exert that pressure on the heart and it’s going to decreased stability to preload. What that’s going to do it’s going to decrease cardiac work load and to an extent that can help with CHF because the heart won’t have to work as hard. We decrease our cardiac work load which can help with CHF with a certain extent. We don’t want to overdo it by any means but by increasing this pressure and they’re decreasing preload we’re decreasing cardiac work load. CPAP can help with the CHF exacerbation’s and it can also help with pulmonary edema and it can help with sleep apnea.


We’re just delivering one set pressured level. No difference whether they’re breathing in or breathing out and that can cause a lot of patient’s frustration’s in that as they’re trying to breathe out they might have to be working against a higher pressure. That is why we have BIPAP. BIPAP is bi-level positive airway pressure. We have several settings on our BIPAP. Like I said we have our iPAP which is our inspiratory pressure and we have our ePAP which is our expiratory pressure. Now the interesting thing about BIPAP is that we can also set a breathing rate.


We can set it breaths per minute and then we can have an FIO2 so we can deliver additional oxygen with it. For example, the physician might write BIPAP settings of BIPAP 10/5, rate of 12, FIO2 60%. All of these can be adjusted. We basically have 2 pressure settings, we can set a rate, and then we can also have our FIO2. It’s generally used for issues with ventilation. What we’re trying to do is we’re trying to remove CO2. A setting where this might make sense would be like a patient with COPD and we’ll get into this a little bit here. Again, 2 pressure settings. That’s the biggest thing to remember.


You have a pressure that is delivered on inspiration which is going to be a little bit higher, that would be our 10. As the patient is breathing in we’re delivering more pressure and then when the patient is expiring we deliver a lower pressure to keep the alveoli open. Like I said, it would be 10/5, iPAP of 10 ePAP of 5 and the difference between that iPAP and that ePAP is known as pressure support. With our setting of 10/5 with our BIPAP we have an iPAP of 10, ePAP of 5, our pressure support would be a 5. Pressure support is 5. As pressure support increases the lungs expand more and allow for increased ventilation which that then allows for clearing of CO2.


That’s where that can be really good for COPD. It allows for extra CO2 to be eliminated. For example, if we had iPAP of 15, ePAP of 5, that makes our pressure support 10 and that allows the lungs to expand even more and allows for CO2 to get out. That’s a big difference there between BIPAP and CPAP. One more thing that we can do here, we talked about we can set a rate. We can set our BIPAP at a rate of 12 and we’re generally going to keep this between normal breathing rates but set a respiratory rate of 12 and then what that’s going to do is the BIPAP can sense if the patient is breathing.


If the patient takes no breath it’s automatically going to deliver that increased level. It’s going to deliver that pressure level of your iPAP. Every time the patient does take a breath it’s going to deliver that pressure as well. It can sense the patient’s breathing. If you have a rate of 12 every few seconds to be 12 breaths per minute it’s going to deliver that iPAP pressure. If the patient does take a breath on their own it’s going to deliver that iPAP pressure as well. Every time a breath is taken it’s delivering that iPAP pressure.


This is good for a patient who might not be as awake and things where they might be a little bit of a slower respiratory rate where you can set a timed rate for breathing and every few seconds it’s going to deliver the higher iPAP and then it’s going to back off and have that lower ePAP level. Does that make sense? I hope that’s making sense. We can set our rate and we’re going to deliver our iPAP every single time our breathing rate is reached. What we can also set with this we can set our FIO2. Our FIO2 is our percent of oxygen delivered. Our room oxygen FIO2 is basically about 21% or so.


If our patient is having difficulty keeping their SpO2 at an appropriate level or for getting our ABG’s or SAO2’s where they need to be what we can do is we can titrate this FIO2 up or down to keep the patient’s SpO2 of SAO2 at 91% or above. We will be monitoring our patient’s … If we’re continuously monitoring their SpO2 just on a pulse oximetry or whatever then we will be able to watch closely what they SpO2’s are and if we have it set at 60%, if our FIO2 on our BIPAP setting is 60% and the patient is still at 82 or whatever on their SpO2 then we’re going to up our FIO2 to try to get our SpO2 to where it needs to be.


If we have it at 60% and the patient is 100% we could start backing off on our FIO2 try to to get them closer to a room level FIO2. Is any of this making sense? I hope this is making sense. I realize I’m rambling a little bit but this is really important stuff to understand and it’s really going to help you see what the difference is and where a good situation for CPAP versus BIPAP would be. I like BIPAP because there’s a lot more manipulation that can occur but again it’s going to depend on the physician’s how comfortable they are with either CPAP or BIPAP and the patient’s condition.


Biggest difference, we can have 2 pressure settings with BIPAP, bi-level positive airway pressure or we can have one setting with CPAP which would be just one continuous pressure. A lot of times CPAP is going to be used for situations of hypoxemia where BIPAP is going to be used more for ventilation which would be to remove the CO2 from the blood. The biggest things with BIPAP, remember we have our iPAP and our ePAP which are inspiratory pressure versus our expiratory pressure and then we can also set a timed rate for breathing.


That’s really the biggest things that I want you to keep in mind. I know that’s kind of throwing it out there and kind of just getting it out there for you guys but I hope that helps you. If you need to review this, what I would do is I would take a sheet of paper and I would just write down all of these things. I would write down CPAP on one side, a line down the middle, BIPAP, and just start writing out on CPAP it’s one pressure and on BIPAP it’s two pressures and the under that write iPAP/ePAP what those mean and then you know what your pressure support is which is your iPAP minus your ePAP and where that would come into play.


That’s really what I would do. I hope this really helps you guys. Thank you so much for checking out the show. For those that are new, thanks for coming. Thanks for checking us out. Be sure to listen to some of our older episodes and remember we have several new episodes every single week. I’ve got some really exciting episodes coming up in the next couple days and got some awesome announcements coming up as well. For the time being, you guys are awesome. Be sure you go to where we give out cheat sheets, reference sheets, over cardiac, neuro, pediatrics, and everything that you’re going to need to excel on the clinical floor.


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