Not sure what BiPAP is or need help setting up BiPAP?

BiPAP is a form of positive airway pressure (PAP) used to treat obstructive sleep apnea. It can also be used in other conditions where there is hypoventilation (under-breathing), such as morbid obesity or chronic lung or muscle problems such as chronic obstructive pulmonary disease (COPD). Setting up BiPAP can be confusing, and if often not done well by homecare providers. This video explains what BiPAP is, why to use it in sleep apnea, and gives tips on setting up BiPAP and determining appropriate pressure settings.

Video Timeline:

  • 00:00 – 02:22 What is BiPAP?
  • 02:22 – 03:37 Why use BiPAP?
  • 03:37 – 05:58 Setting up BiPAP

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I’m going to try and explain to you what the difference is between EPAP, IPAP and CPAP. Essentially to try and explain that, I will first talk about what happens in the upper airway and what pressure we need in the upper airway across the breathing cycle because if you can understand that, then it’s pretty self-evident what the difference is between these two settings.

In this part of the diagram, as we’re breathing out, we’re effectively blowing air from the lungs out through the upper airway and it actually inflates or blows open the upper airway. So the pressure we need to keep an airway open when we’re breathing out is less than what we need when we’re breathing in.

The pressure that’s needed while we’re asleep to keep the airway open at the end of breathing out is called EPAP. So think of it as expiratory positive airway pressure but that’s abbreviated to EPAP.

Now when we go to breathe in and draw air in through the upper airway, we actually generate a sucking effect in the upper airway which then closes the airway. So naturally you would expect you need a higher pressure to keep the airway open during the breathing in part of the cycle. It turns out that’s true and that’s called the inspiratory positive airway pressure so the pressure needed to keep the airway open when we’re breathing in.

There’s normally a minimum difference between the pressure to keep the airway open on breathing out and the pressure to keep the airway open on breathing in of three centimetres of water pressure. That difference, the difference between expiratory positive airways pressure and inspiratory positive airways pressure is called pressure support. So in PAP terms, that would be called PS, pressure support, so a minimum pressure support of three.

Now some people, particularly people who are overweight or got very collapsible airways, need a lot more pressure support than that because when they go to breathe in, the airway is very vulnerable to collapse. So the inspiratory pressure has to be quite a lot higher than the expiratory pressure.

That difference can be as high as 15cmH2O. So we will usually have pressure support on an auto BIPAP machine set at a minimum of 3 and a maximum of 15.

So why actually bother? Why look at expiratory pressure, inspiratory pressure and make it more complicated? Well, actually there is some data suggesting it’s a bit more comfortable for patients. So if we’re setting the pressure, most of the time, to be able to cope with this where the airway is most vulnerable to collapse, as we go to breathe out, we’re going to feel the strength of that pressure and find it a bit harder to breathe out against that resistance.

That’s one of the things people describe with CPAP that can be uncomfortable for them, breathing out against that pressure. It’s also one of the things that can lead to air in the stomach, aerophagia. It’s trying to breathe out against a higher pressure coming back in. So that’s one of the rationales for using a lower pressure in expiration, EPAP, and a higher pressure in inspiration.

Hopefully I’ve been able to give you an idea of the difference between EPAP and IPAP but think of it about what’s happening in the upper airway and I think that allows you to get past some of the confusion with the different terms and think of it as we breathe out, we still need some pressure to keep the airway open because people with sleep apnea have a narrow airway. But as we breathe in, we need a higher pressure to keep the airway open. The difference between those two is what we call the pressure support.

So in setting up a BiPAP machine for patients, what are the settings that we want to look at on the machine? Well, the parameters we’re able to set are expiratory positive airway pressure, EPAP, the maximum inspiratory positive airway pressure so that’s IPAP and the difference, the minimum difference or minimum pressure support and the maximum difference, maximum pressure support.

The way I’ve manually determined the EPAP and this is what I do in the sleep laboratory and I will come to what the auto machine is actually going to do in the home which is more relevant to what you’re doing. Manually in the laboratory what we will do is gradually increase – we will have IPAP and EPAP exactly the same. So we’re using it like CPAP. We will increase the pressures until we get to enough pressure that even at the end of breathing out, the airway is nice and open, so that apnea is controlled.

Then we will set that as our EPAP and then we’re gradually increasing the pressure support, so the difference between EPAP and IPAP. So until we get to a point where when people are breathing in, there’s no snoring, there’s no flow limitation, and then we know what our ideal IPAP is and we know the difference between our set EPAP and our set IPAP and that gives us our pressure support.

Now when you’re using a BiPAP auto in the home, it actually does all that work for you. But at least if you understand how I do it manually, it gives you an idea of what it’s actually doing.

So a BiPAP auto will increase the EPAP until apnea is managed. Then it will gradually increase the difference between EPAP and IPAP to manage hypopnoea, flow limitation, subtle airway narrowing and snoring.

The difference that you need between these is going to differ between the types of sleep you’re in, what stage of sleep, what body position. So it’s not always the same.

That’s where with the auto machines we set these parameters. The minimum pressure support, 3, maximum pressure support, I usually keep that default at 15.

So don’t be intimidated by a BiPAP auto. It’s actually pretty simple to set the parameters and try and think of it in this type of framework of what’s the minimum expiratory positive airway pressure, what’s the maximum IPAP, the minimum pressure support and the maximum pressure support.

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