eli5: How do sleep apnea machines work?


Do they force air in? Wouldn’t that be super uncomfortable

In: Biology

The CPAP machine delivers a constant flow of air through tubing and a mask and into your airway. The CPAP machine creates enough pressure in your airway to hold the tissue open, so your airway doesn’t collapse. The soft, steady jet of air from the CPAP machine creates enough pressure to keep the airway open.

It feels weird but once you get used to the pressure it’s noticeable that it’s easier to breath.

Depending on the machines, some reduce the pressure when you breathe out to make it easier.

The official term is CPAP (continuous positive airway pressure) machine. They don’t really force air into the nose rather it increases the ambient pressure of the air in the patients lungs and throat like using a full face scuba diving mask. If it’s sealed correctly the patient feels nothing as the pressure in the lungs is the same as the pressure of the air outside their mouth and nose. This slight increase in pressure inflates the throat slightly which will keep the throat from closing and causing the apnea.


They don’t *force* air in.

Air pushes on things. Normal pressure is about 14 psi, meaning that the “weight” of air on one side of a US quarter is 10 pounds! But we don’t notice that because it’s pushing the other side the same amount.

Similarly, your airways get pushed by pressure. If you’re not breathing, the pressure inside and the pressure outside balance each other, and it doesn’t matter. But when you’re inhaling, the pressure in your airway drops, so that the outside pressure tends to squeeze your throat slightly. In obstructive sleep apnea, that can close the airway. And if you can’t breathe in, then you have nothing to breathe out.

Standard sleep apnea machines use CPAP, which means continuous positive airway pressure. They blow air into your throat, so that even when you’re inhaling, the pressure in your airway is greater than the pressure in your bedroom. Therefore, your throat remains inflated even as your lungs are sucking air out of it.

This can, but shouldn’t be, uncomfortable when you’re inhaling.* The problem comes when you’re exhaling, because the machine is working against you. But even so, the airway remains inflated.

Different kinds of machines can mitigate the problems: BPAP can make it easier to exhale, and APAP can reduce/eliminate any discomfort experienced while inhaling.

But none of these machines are ventilators. They don’t force air into your lungs. They only assist.

Footnote/Edit: The machine may be uncomfortable in other ways, e.g., you have to wear a mask over your face, connected to a hose, which itself is connected to a machine, which makes noise.

It’s just some air pressure to not let some tissue at the back of your throat collapse and block the air way. It’s also super-silent in modern machines, surprisingly.

If you have sleep apnea, totally go to to a sleep lab and let them check how bad it is. I’ve probably not have real deep sleep for many years (I didn’t even know you could live like that but lots of mental and other health issues might very much be related). Yeah, it’s kinda annoying at first (it’s not easy to fit the mask correctly onto your face, so you don’t get annoying air leaks), but suddenly I sleep for exactly 7,5 hours every night, get tired like normal people at night and while I fear that over those many years I might have done irreparable damage to my brain, my sleep is just good now.

The best inspiration for doing this (because for some stupid reason I just totally never wanted to have such a machine) was to watch a video of a person suffering from sleep apnoe. Seeing how the half-sleeping body is thrashing about, fighting for its life and imagining this was me several HUNDRED times each night… yeah, not a pretty thought.

It’s not as bad as it seems. My gf has a CPAP and I’ve used it before. It has a ramp up button, so when you first start, it does the lowest air flow, and gradually ramps up to your needed setting as you fall asleep. That way it’s not full flow as you’re trying to settle down.

I just got a CPAP and the other nice thing is that it delivers warmed, perfectly humidified air which also helps keep the nasal passages clear. When I sleep without it, I wake up several times rom very mild apnea. I have come to realize I hadn’t had a good night’s sleep in years before the CPAP because every time my airway relaxes and collapses, I wake up a little. When I wear it, I sleep soundly. So amazing.

Just in case anyone’s holding off on using these machines – in my case it’s been the 2nd most life changing thing of my life. I used to be tired every waking moment, but just assumed “that’s life.” I worked a lot, blah blah, but it wasn’t until I started using the machine that I realized how unnecessary all of that was.

It’s not uncomfortable at all for me these days. It took some getting used to but now it’s completely second nature.

I used to be a sleep tech several years ago. But the sleep apnea machines come in a few different flavors.

Sleep apnea is quite common in the US, snoring, and the lack of airflow cause a significant portion of the US population to have poor sleep. Every time you have an extended apnea, your brain wakes you to take a breath (you probably are not even aware of it) but it takes a toll over time. And eventually it can cause life threatening conditions, such as heart desiese.

The Solution is additional air pressure from machines (or in some cases surgery) to help keep airways open and clear, allowing you to sleep better.

1st is the CPAP which stands for “Continuous Positive Air Pressure”. 2nd would be the BiPAP, that one is as it says has 2 pressure settings. Higher for inhale, and lower for exhale. 3rd AutoSV, this one changes the pressures being applied on the fly as needed. 4th Auto PAP this one adjusts the pressure about every 15 to 30 minutes depending on what the patient needs.

All of these are used to prevent the airway from collapsing, to prevent you from having Apnea (Apnea just means to stop breathing). Because when you sleep, especially when you get to the REM cycle, your body releases hormones to essentially partially paralyze you. This keeps you from moving to much in your sleep which can lead to injuries if you did. But it also relaxes the muscles in your throat allowing gravity to pull down on the muscles, restricting your airway.

CPAP machines have to be calibrated to each individual, because too little pressure and the machine will do little to nothing, and too much pressure can cause the patient to stop breathing all together. Since it’s only blowing at a single set pressure. This is the most common unit due to cost and it really does help most people.

For BiPAP, the machine will be calibrated with 2 separate pressures, the lower will be for exhaling and a higher pressure to inhale. The pressures do not change and will always be there setting. The BiPAP is normally for people who have weak lungs, obease, or have problems with air being pumped into their stomach.

AutoSV is the top dog, it has an on board computer to analyze in real time the pressure from the patient breathing. It still will need to be setup with a highest and lowest pressure and in some cases a recommended pressure to attempt to keep the patient at. This one is used for people that don’t do well at a set pressure and need to have the scale moved rapidly during sleep to keep them breathing.

Auto PAP machines are calibrated to the optimum pressure, however the machine can make slight adjustments throughout the night depending on the patient needs and give more or less pressure every 15 to 30 minutes. This one is quickly becoming the more popular choice for patients due to machine cost and the faster calibration.

The sleep tech monitors the sleep of the patient using heart rate, breathing rate, nural activity, body muscle movement. Using the data collected, they can determine the level of sleep (scale from N1 to N3 and REM). This helps get the patients on the correct machine and pressure levels. Some only need the basic CPAP, while others need more help from more advanced machines. Once a patient is titrated (breathing properly with the calibrated settings) to a specific system. They are sent home and a new machine will be assigned to them and calibrated to them specifically. No matter what machine you use, it will need to be calibrated and setup for you. Also every couple of years, you will have to have your machine tested to make sure the pressure is correct. So please don’t use your uncle frank’s old CPAP because it will probably not be at the pressures you need.

– Sorry for the format and spelling errors, I’m typing this out on my phone.

Think of the air flow as water through a flimsy hose. The hose is your airway. The air flow/pressure keeps your airway from collapsing/obstructing

I just want to add that CPAP machines aren’t always a fixed pressure. Mine ramps up or down based on whether I’m breathing or not. It’s customisable, starts at 4psi and ramps up to 12 (if needed.) I can hear it increase the pressure if I hold my breath. Additionally, mine backs off a little as you take a breath to make exhaling easier.

In terms of comfort, I can’t sleep without it. Because I can feel my airways collapsing if I sleep somewhere and didn’t take my machine with me. The more difficult part to get used to was not getting the hose wrapped around my neck as I tossed and turned, or not yanking it suddenly because it got stuck. I’ve actually knocked my machine over a few times doing that. And given it has a humidifier filled with water, that’s not good for it lol.

A stent is a tiny wire mesh or plastic tube that it placed inside a vessel to keep it open and maintain a proper flow.

A CPAP machine creates a stent made of air that forces your larynx and pharynx to remain open.

Think of it as a continuous circulation: air at a positive pressure enters your respiratory system, goes into the lungs and returns via the same route. Because it is continuous, there is never a chance for the “breathing” cycle to be interrupted.

With obstructive sleep apnea, some part of that open circuit is closed. When partially closed, you get snoring, much like partially obstructing a balloon that is emptying of air makes a lot of noise. Sometimes, from poor musculature or problems in anatomy, a portion collapses and breathing is interrupted completely. There is no exchange of inhalation and exhalation, something is closed off and it’s not possible.

Thus the air “stent” is created by the positive pressure and keeps everything open and breathing possible.

CPAP stands for consistant positive airway pressure. It’s set at a point that won’t feel like it’s blowing in your airway, but will still keep your airway open. That being said, many people find the mask that fits around the face (while you’re asleep mind you) is extremely uncomfortable. However, it’s really the only good way to control sleep apnea, which kills seemingly healthy young-sih people every year. I have a cousin who lost her 26 year old son to sleep apnea – it’s devastating.

As a user of a CPAP, it is a bit odd, but it doesn’t feel like it’s PUSHING air in, it just feels like you have a cool intake of air.


There is also a BIPAP which is intake and exhaust for people with very weak lungs that can’t push against that air being inhaled.