00:01
So moving on to obstructive sleep apnea, this
is one of the commonest respiratory diseases,
it's up there with asthma and COPD, not quite
as common as those conditions but it is very
common. Now, what happens in this is that you
have some degree of upper airways obstruction
when asleep and the reason for that is that
the fat that accumulates, as you get older
in life is deposited, in men specifically,
around the neck, and that compresses the pharynx
and makes it narrowed during sleep. Especially
this is important during sleep because as
you sleep your muscles relax and that allows
the effects of this obstruction to be more
obvious and the narrowed pharynx occurs as
you sleep. And that generates the noise, one
cause of snoring, but in addition, it generates
obstruction to get in the air from the atmosphere
down into the lungs and that leads to cyclical
desaturations in your blood levels of oxygen.
01:04
It's a hypoventilation disorder that occurs
repeatedly throughout the night. This leads
to poor sleep quality not surprisingly, and
as a consequence of that, patients tend to
be very sleepy during the day and could fall
asleep very easily during everyday tasks such
as reading, watching television etc. driving
a car in fact. And the physiological disturbance
at night has bad consequences for the cardiovascular
system, leading to hypertension precipitating
ischemic heart disease and if it is very severe
you might develop type II respiratory failure
and pulmonary hypertension or cor pulmonale
type situation.
01:43
Now this can affect about 1% of men in the
Western world, it's much commoner in men than
it is in women and the reason for that is
not entirely clear but it seems to be about
fat distribution. Most patients will be over
40 years of age and they'll be obese, they'll
have a significant BMI and with that, their
neck circumference will be large, over 43
cm. As I mentioned earlier, sedative drugs
may cause a type II respiratory failure
and hypoventilation worse, so drinking alcohol
before you go to bed would make patients of
OSA have more severe symptoms. Occasionally
they may have an existing pathology of the
upper airways which might make them more likely
to get obstruction, a deviated septum, and
the position of the jaw micrognathia, a small
jaw or a jaw that projects backwards or forwards
would make you more likely to get OSA and
acromegaly disease, a growth hormone production
very rarely is a predisposing factor for OSA.
So the thing about obstructive sleep apnea
is that actually it remains undiagnosed in
lots of people. Many people snore, many of
those will be snoring actually will be having
a degree of OSA as well. The patient actually
might complaint about daytime sleepiness and
feeling un-refreshed after a night's sleep.
03:01
They might have to get up at night to pass
water and they may have a poor concentration
and memory due to this recurrent hypoxia occurring
at night. The patient's spouse might say “I
get scared because he stops breathing in the
middle of the night, and then gives a big
snort and starts breathing again”, that's
a fairly common and that's an apneic episode
where the problem with ventilation, actually
the obstruction completely stops the breathing
for a few seconds. There aren't really many
signs in OSA, you can look at the back of
the throat and there is a is a score that
you can use to see whether the obstruction
is quite likely to present, depending on what's
visible at the back of the throat, but we
don't need to know that in detail.
What are the problems of OSA? Well, the serious
consequences are car traffic accidents; a
classic example would be, a heavy goods vehicle
driver, 45-year-old man, drinks a bit before
he goes to bed, might be weighing 20 stone,
obstructive sleep apnea, chance of him having
an accident is much higher than if he doesn't
have OSA and that can have very serious consequences
clearly. The OSA itself in severe cases can
lead to pulmonary hypertension, cor pulmonale,
and type II respiratory failure and there
are these consequences on the cardiovascular
system with hypertension, ischemic heart disease,
dysrhythmias and there is a relationship between
OSA and diabetes as well.
04:31
The biggest differential diagnosis is just
simple snoring, snoring without obstructive
sleep apnea. You can investigate these patients
to identify whether it's just snoring or OSA,
and the way to do that is by the sleep study,
and I'll discuss that in a little bit more
detail in a while. Other tests we may want
to do, chest X ray,
spirometry, blood tests, and these are all
to look for associated diseases, for example
co-existing COPD is quite common, hyperthyroidism
is a cause of OSA etc. There's something called
the Epworth sleepiness score, which is a method
of marking how sleepy somebody is during the
day and therefore whether they potentially
have OSA, or not. Personally, I don't think
it's particularly helpful, but it does identify
patients who have significant sleep disturbance
and therefore may need to have a sleep study.
Now the sleep study, the simplest one is where
you just record the overnight oxygen saturations
when the patient is asleep and if you have
obstructive sleep apnea, they fall repeatedly
throughout the night. There are more complex
sleep studies that can be done that measure
chest wall movement, a sleep state using EEG,
muscle movement using EMG, carbon dioxide
levels etc. etc., but they're not usually
required for very standard cases of obstructive
sleep apnea.
05:54
This is a sleep study with moderately severe
OSA and you can see the saw tooth pattern
of recurrent hypo apneic episodes where the
desaturation is occurring several times a
minute, several times an hour out during the
night. And you can define how severe OSA is
by how may desaturations occurring throughout
the night, with over 30 an hour meaning severe
disease. How do we treat? Well very simply,
if the
patient can lose a lot of weight that will
make a substantial difference, they need to
stop drinking alcohol while having sedatives
at night. You treat the hypothyroidism the
acromegaly. If people have mild OSA, then
there is a mandibular advancement device that
pushes their mandible forward a little and
that actually improves the obstruction at
the back of the throat, and has substantial
benefits in patients with milder disease.
06:46
Chronic disease needs treatment with continuous
positive airways suppression. This is a small
amount of airways pressure given as the patient
breathes in, and that splints open the back
of the pharynx, and is a very effective
treatment for severe and moderate OSA. Surgery
is not really effective unless there is a
very specific problem of the upper airways
that can be corrected by the surgical intervention.
A very important point is that because of
this risk of road traffic accidents, driving
should be forbidden with patients with severe
disease unless they have been effectively
treated.