Welcome to an article we could talk about obstructive sleep apnea and specifically, we’re going to get into the pathophysiology the risk factors the diagnosis and the treatment for obstructive sleep apnea.
Ok, let’s talk a little bit about the pathophysiology thought the physiology is basically how do things go wrong so what is obstructive sleep apnea.
It’s basically literally when you stop breathing because of an obstruction and if you were to look at somebody’s cross-section of their face and I’ll just kind of draw,
I’m not a very good artist but you can kind of see what it is that, I am talking about here and this is the nose here this is the person lying on their back and this is the airway going down kind of a simple drawing yes but gets the point across and here’s the tongue basically in this area.
So you’ve got two areas where air can travel they can go into the nose and it can go into the mouth the problem is back here in this area here this is where the back of the tongue is and this is where fat gets stored and it’s in this area specifically that you can have tissues so big because of fat storage that you can actually get an obstruction in that area.
So typically what will happen is that when you’re awake you can breathe through this area but when you go to sleep your muscles go to sleep and when your muscles go to sleep they become flexible this is not like a PVC pipe.
It’s not rigid and especially with gravity lying on your back your tongue muscle can actually fall back and this area becomes flabby and finally, it can become obstructed so your lungs which are of course connected down here and of course, you’ve got the diaphragm which is contracting in this direction causing the lungs to expand.
Okay that’s going to cause air to try it again and so you’ve got a negative pressure that’s going to try to suck air in but because this area here is blocked you’re not going to have any airflow there’s a blockage of airflow and that’s basically the pathophysiology of obstructive sleep apnea you’re basically sleeping.
When you’re sleeping the lungs are breathing on their own because they’re getting input from the medulla obligation of the brain but because of the issues here in the back of the throat no air can get in because of the obstruction now as this happens since no air is getting in, of course, your pulse ox your saturation starts to drop and the resistance.
Causes of Sleep Apnea:
Starts to increase what that does is it sends a signal up to the brain that says there’s a problem and then what does that do it causes the brain to arouse out of its sleep sometimes completely waking up and what that does is it sends a signal down to these areas to tighten up and then air starts to go in again when the air starts to go in that sympathetic response from the lungs is stopped the brain goes back to sleep and this area once again becomes flabby and it closes off.
And so what you see in terms of oxygen saturation is the cyclical type of a vent where the oxygen drops because there’s an obstruction and then the brain becomes aroused out of its mental state and as it does as the brain becomes rounds out of its sleepy state the airway becomes open again and the air starts to go back in again as it comes back up the brain goes back to sleep again as the brain goes back to sleep again the muscles become flabby and they close off and the oxygen starts to drop.
So you’ll see this type of a wavy oxygen pattern unless the patient gets into a position where there’s not any sleep apnea or the patient goes into and two different types of sleep now the problem here is that and we’ll talk about this over and over again is that there are things that can make this area worse and these are risk factors for sleep apnea.
We’ll talk about that but though two that I’ll bring up here that’s related to sleep and we’ll talk about this later is anything that makes that obstruction worse is going to make your sleep apnea worse and there are two things that I want you to be aware of that can make that area worse the first one is being supplied.
Now, this doesn’t happen in all patients but in some patients being supine can make it worse and this is reasonable if you think about someone’s tongue so one’s tongue can fall back and make this area closed off so being supine is one the second one is being in REM sleep now REM stands for rapid eye movement but there’s something very important about REM sleep and REM sleep you dream and as a result of that the body has a defense mechanism where you become paralyzed.
This is very important because if you weren’t paralyzed you would act out your dreams so most of the muscles in your body are paralyzed and that includes these muscles that are trying to keep your airway.
Open so REM sleep can really make obstructive sleep apnea much worse so being so pine and being in REM sleep can make this worse so this is the pathophysiology of obstructive sleep apnea.
Let’s talk about the risk factors so what are things that make this condition more likely well one of the big ones that we’ll talk about is mail this doesn’t mean that women can’t have it but let me put it to you this way in terms of the prevalence in the population for men in terms of the prevalence.
Now of actually stopping breathing not necessarily having the syndrome of sleep apnea but just stopping breathing at night more than five times per hour it’s 24% of men do that when we look at women it’s 9% now if we actually look and see how many have the syndrome this is where they stop breathing.
More than five times per hour and in addition to that they have excessive daytime sleepiness because they’re not getting good sleep at night because they keep getting aroused then it drops down to about 4% for men and 2% for women so that’s the syndrome there that we’re talking about so how many people in the population have obstructive.
Sleep apnea and have the syndrome associated with it it’s about on average about 3% and that’s in the general population that’s not in your clinic population or in your hospital population or in your sick population.
It’s much higher for that and we’ll talk about that the other thing about male I should tell you is that men tend to store fat more in the neck the other thing.
I should tell you is that women catch up to men after menopause so, after the age of 40, 50, 55, for women and women catch up with men in terms of their risks what about obesity obviously this is a big thing some people think that only obese people get obstructive.
Sleep apnea that’s not the case but it is a big risk factor now if you’ve got obesity it increases your risk by about 10 to 14 times you’ll see in patients with obesity that it’s usually recent weight gain.
And just to give you an idea about how little this can be if you have just a 10% increase in weight that can be about a six times increase over 6 fold increase over four years.
So the things that we’re looking for there is the BMI the neck size and something called the waist to hip ratio interestingly race also plays a role in we have white non-white and the prevalence is about 4.9 percent in white and in non-white it’s 16.3%.
Now in Asians, it also is it increased risk so if you have these patients in your population think about this as well the other risk factors that I would remember is nasal obstruction so think of things like allergic rhinitis this maybe this the case where medication for the allergic rhinitis may actually improve.
Sleep apnea and then finally the last respecter which we’ll talk about are genetic factors so if you have a first-degree relative that increases the prevalence from 22 percent to about 86 percent that’s a huge increase.
So first-degree relatives that would be like mother fathers brothers sisters that would increase the risk of obstructive sleep apnea there is actually one other risk factor that I think is important to go over and that is age and it basically.
If you were to look at a graph it kind of goes up with age until it reaches about 50 or 60 and then it kind of just Peters off and stops so the maximum prevalence is in the 50 to 59 age group.
It just stops kind of about there but in the part, before it, there is a definite increase in incidence some things that also increase it acromegaly testosterone makes.
It worse hypothyroidism has no connection and then we talked about menopause it’s kind of like the equalizer for women good so let’s talk about the diagnosis how do we go about diagnosing it we will talk about that in the next lecture as well as the treatment for obstructive sleep apnea thanks for joining us you.