If you’re having central apnea, your chest and abdomen aren’t moving because your brain’s not telling your body to try to breathe. When you have an obstructive apnea, as a result of an obstruction in the throat and the nose and everything, your chest and abdomen are trying to suck in and create negative pressure to breathe. Itâ’s just that air can’t get through that area. Here you can see that this is the pressure flow transducer at the nose (which measures air flow at the nose) and we just have these repetitive apneas over and over again. There’s no air flow going on here, there’s a drop in the oxygen saturation level that’s pretty severe in this patient, in each one of these. That’s the amount of oxygen in the blood which is obviously important for your body functioning.
Then there’s an arousal – so there’s kind of a snort and a wake up here that opens the airway back up, allows a little bit of breathing, and then the patient falls back asleep and this happens again. This is very insidious, the patient doesn’t usually know that it’s happening unless their bed partner tells them about it or they’re noticing they’re sleepy during the day. Those are the reasons that these people end up coming to see me.
The important relationship between this and Chiari is that some people that have this can elevate because they’re not breathing well, they’re carbon dioxide levels can go up. When that happens, the blood vessels in the brain can dilate and so more blood can go into the blood. That has a tendency to increase intracranial pressure and increasing intracranial pressure is bad for people with Chiari Malformations. So it can make the Chiari Malformations worse so that’s a vicious cycle. The Chiari Malformation is making the sleep apnea worse, and then the sleep apnea with the CO2 and so that’s a concern.
The obstruction in obstructive sleep apnea can be multiple areas, large tonsils, large uvula, which is that thing that dangles down in the back of your throat, blockages in the nose, septal deviations and things like that. Large tongues can also contribute to this. And then also muscle tone in the throat, as I mentioned, those three nerves that can be stretched. When we all fall asleep we actually have about twenty muscles in our throat that have to increase their tone to keep your airway open. If they don’t do that very well you get a collapsible floppy airway which is a real problem for people.
For obstructive sleep apnea the prevalence is actually pretty high, it’s one of the most common diseases known to man. If you just took a random sampling of people off the street and did a sleep study on them and you said that those that had apneas or hyponeas (which are like apneas but not as severe) if they had more than five of those an hour you would diagnose them with this. You would find that about 9% of women and 24% of men would have an apnea/hyponea mix higher than 5. If you ask a second question where you say you also need to have symptoms in order for this to be a disorder; then it’s about 2-4% of the population that has this problem. That’s in the general population, not in Chiari folks and we’ll talk about Chiari specifically in a minute.
The risk factors are, [see Figure 7] in the general population being a man, being older, being overweight, those are the most common ones. Smoking can contribute, having a large neck size. In men, if the neck size is 17 inches or greater you’re at risk for this. In women, if the neck size is 16 inches or greater. The treatments for it are really three – this is for the run of the mill patient, not the patient with the Chiari. CPAP, continuous positive airway pressure, which is a little mask, you can see this gentleman wearing it over his nose. It’s connected by a tube to a small box that pushes pressurized humidified room air. So there’s no additional oxygen or anything like that being put in there, and it’s usually between 5 and 20cm of water pressure and it works like a pneumatic splint to sort of pop the airway open and keep it open when you sleep. In people that have trouble with that or if they have really big anatomic obstructions, large tonsils for instance, we can do different types of surgeries. This is an example of a uvula palatal pharyngoplasty or a UPPP. We trim out the uvula which dangles down here and part of the soft palate. This is not usually curative but helpful and definitely helpful for snoring. Lastly, dental appliances that can be worn at night that move the lower jaw forward can pull the tongue forward and open up this air space.
Central sleep apnea, which only makes up about 5% of the people with sleep apnea that we see [see Figure 8] is shown here with this polysomnogram fragment. This is similar to what I showed you before but what I want you to focus on down here is these chest and abdomen measurements of movement. You can see here, when we have these cessations in air flow right here, now we’re not having any respiratory effort here. This patient is just not trying to breathe when they’re asleep. This is often complicated as to what’s causing this. We divided it into whether or not CO2 levels are up or not. Some people have it, it’s called idiopathic, we don’t know why. Some people can have problems with this because they’re very, very obese. Other people that have neuromuscular diseases can have problems with this. Heart failure can often result in this type of picture. For those people that have central sleep apnea, here are all the different causes.