well welcome to another MedCram lecture 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 the 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 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 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 and when you're sleeping the lungs are breathing
on their own because they're getting input from the medulla oblongata of the
brain but because of the tissues 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 o2 saturation starts to drop and the resistance 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 a rounds out of its sleepy state the airway becomes open again and 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 and 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's 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 which 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 so being so pine and being in REM sleep can make this worse
so this is the pathophysiology of obstructive sleep apnea okay 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 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 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 can be if 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 may be 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 is 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 and 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