Increasing Hypopnea's

Should I be concerned that my hypopneas have been increasing over the last few weeks while nothing has changed with my pressure? My AHI this morning was 6.04, and in the mid to high 5's the last few days. The only thing that stands out was my hypopnea index which used to be below 1, but now is right around 2 - 3. My AI has been averaging below 2.0 most nights.

Pressure currently being used is 13 - 17cm.

Thanks,

John

IMy hypopnieas keek raisng and clustering as soon as I raise the pressure above 15 cm. But I don't pay attentioin to them as the designer of the Resmed chief designer of the Autusets said:



From an interview with Dr Michael Berthon-Jones, in 2002:

Why is it important for an automatic CPAPdevice
to respond to flow limitation, snore and apnea?

The characteristic flattening of the flow-time
curve caused by flow limitation is the very best
signal for fine-tuning the pressure, once you have
eliminated apneas and snoring. But if you are just
falling asleep, you can go very quickly from having
a totally open airway to snoring very loudly, in a way
that produces somewhat chaotic or messy flowtime
curves, without seeing the characteristic
flattening. So the best approach is to respond very
quickly to loud snoring, and then fine tune using
flattening. Rarely, you can go straight from awake
and unobstructed to asleep and apneic, and so it
can be useful to increase pressure in response to
apnea as well. However, actual apnea is pretty rare
on AutoSet, because in most cases the responses
to snoring and flattening get the pressure up
quickly enough to prevent apneas.


Why doesn’t ResMed's AutoSet respond to
hypopnoea?

When you are lying quietly awake, or when you
first go to sleep, or when you are dreaming, you
can have hypopneas (reductions in the depth of
breathing) which are nothing to do with the state of
the airway. For example if you sigh, which you do
every few minutes, you usually have a hypopnea
immediately afterwards. This can also happen if
you have just rolled over and are getting settled, or
if you are dreaming. And the annoying thing is that
when you are on CPAP, this tendency to have what
are called central hypopneas - hypopneas that are
nothing to do with the state of the airway - is
increased. If you make an automatic CPAP device
that responds to hypopneas, you will put the
pressure up to the maximum while the patient is
awake.

Do you think there is a misconception clinically
that all hypopneas should be treated ?

For simple obstructive sleep apnea, central
hypopneas should not be treated. They are not a
disease. Everyone has them. And they don’t go
away with CPAP.

There is a rare and important exception: central
hypopneas due to heart disease. This is called
Cheyne-Stokes breathing. CPAP does help with
that.

Why doesn’t ResMed's AutoSet respond to
apnea above 10 cmH2O in pressure?

I mentioned before that the higher the pressure,
the more central hypopneas you will have. At a
pressure somewhere around 10 cmH2O, the central
hypopneas become central apneas. On the other
hand, the vast majority of obstructive apneas are
already well controlled by 10 cmH2O, and we are
only fine tuning using snoring and flattening. So it
is a pretty good bet that if the pressure is already
above 10 cmH2O, any apneas are most likely
central, and you should leave them alone (except
in patients with central apneas due to heart failure).
But if the pressure is below 10 cmH2O, most
apneas will be obstructive and you should put the
pressure up. There’s nothing magical about 10
cmH2O, it’s just a good place to put the line in the
sand.

Can you over-treat apnea?

You can’t over-treat obstructive apnea. You
really don’t want the patient having unresolved
obstructive apneas. And we want not just to prevent
apnea - we also want to keep the airway sufficiently
open for the subject to breathe easily and regularly
and stay asleep.

But you can use too much pressure. The higher
the pressure, the greater the side effects. Although
this has never been proven, it is rather obvious - no
pressure, no side effects! So you want to use the
lowest pressure possible while keeping the airway
nicely open.

Likewise can a device that responds to
hypopnea over-treat it ?

The funny thing is that it can both over-treat and
under-treat. It will put the pressure up through the
roof in some subjects, who have lots of central
hypopneas. And it can completely miss repetitive
severe silent inspiratory flow limitation that is totally
disturbing the patient’s sleep without there being
any hypopneas. If this occurs without CPAP, it is
called upper airway resistance syndrome. It is just
as bad for you as obstructive sleep apnea. But a
CPAP machine that responds only to hypopneas
will treat your obstructive sleep apnea, and give
you upper airway resistance syndrome instead.

How can Automatic CPAP devices help
optimise treatment ?

CPAP devices, whether automatic or not, can
tell us - the clinician, the technician - about what is
going on when we are not there. Is the patient using
the device? Is there a leak, and if so, when and how
much? If it is an automatic device, what is the
pressure doing? How well is the patient breathing?
How steadily, how much? This might be particularly
important if the patient also has heart disease or
lung disease, or has had a stroke, and has other
reasons, apart from sleep apnea, for having
abnormal breathing during sleep.
********************************************

So as Dr Brethon says, as long as I dont suffer from CSAS I leave the hypos alone and even remove them from the AHI on my list (the top portion of the HAIs in the ResScan summary graphs).

Awesome article... thanks.

A couple of questions though. What does he mean when he says

The characteristic flattening of the flow-time
curve caused by flow limitation is the very best
signal for fine-tuning the pressure,

Also, you say you remove the hypopneas from your summary graph... how? I have never seen a option to hide that.

Lastly, if 5 is the magic number for AHI, what is the magic number for AI which is just the apnea's without the hypopnea's?

Thanks,

John