Last Updated on: 05-APR-2010

Sleep Apnea Information Centre

(OSA, Obstructive Sleep Apnea, Central Sleep Apnea, Sleep Apnoea)

This is a resource created by Sleep Apnea patients with more than 100 years of Sleep Apnea experience. This provides both an introductory level of the various forms of Sleep Apnea including Obstructive Sleep Apnea, Central Sleep Apnea and Mixed Sleep Apnea, as well as providing some very detailed graphs and how to reduce your AHI (Apnea Hypopnea Index).

1. What is Sleep Apnea
2. Why are machines sometimes called CPAP or APAP, BIPAP or VPAP?
3. What kind of machines are there?
4. What is a heated humidifier?
5. What kind of masks are there?
6. Examining Sleep Apnea data
7. Understanding your sleep study
8. Average night of Apneas/Hypopneas when on CPAP
9. How to reduce your AHI (Apneas and Hypopneas)
10. How to change the pressure on your CPAP/APAP machine
11. Where can I get the Clinicians (Doctor) manual for my machine?
12. RLS (Restless Legs Syndrome) and PLMD (Periodic Limb Movement Disorder)
13. Self Help Forums and other information resources
14. Good Discussions around Apneas/Hypopneas
15. ResMed S9 resources

1. What is Sleep Apnea? [top]
Sleep Apnea is a Sleep Based Disorder where you stop breathing characterised by pauses in breathing during sleep. Each episode called an apnea lasts long enough so that one or more breaths are missed, and such episodes occur repeatedly throughout sleep. The standard definition of any Apnea and Hypopnea is to last for a minimum duration of 10 seconds to be classifed as such. There are two types of Sleep Apnea, Obstructive and Central.

Obstructive Sleep Apnea (OSA)
Occurs when a blockage is present in the Upper Airway, usually in overweight people (but not always) where the neck diameter is considered >18 inches. However, this can also occur in normal weight people where their soft palet relaxes too much. The tissue in the back of the throat most often involved in snoring and obstructive sleep apnea is the soft palate. In addition to the soft palate, many people also suffer from obstruction of other parts of the upper airway including the nasal airway, tonsils, tongue, and pharyngeal walls. So you do not have to be overweight or obese for this to occur.

Central Sleep Apnea (CSA)
Occurs when the brain does not send the signal to breathe to the muscles of breathing. The brainstem controls breathing. As a result, any disease or injury affecting this area may result in problems with normal breathing during sleep or when awake. Conditions that can cause central sleep apnea include bulbar poliomyelitis, encephalitis affecting the brainstem, neurodegenerative illnesses, and stroke affecting the brainstem. Under normal circumstances, the brain monitors several things to determine how often to breathe. If it senses a lack of oxygen or an excess of carbon dioxide in the blood it will speed up breathing. The increase in breathing increases the oxygen and decreases the carbon dioxide in blood. Some people with heart or lung disease have an increase in carbon dioxide in their blood at all times.

In central sleep apnea, the basic neurological controls for breathing rate malfunction and fail to give the signal to inhale, causing the individual to miss one or more cycles of breathing. If the pause in breathing is long enough, the percentage of oxygen in the circulation will drop to a lower than normal level (hypoxaemia) and the concentration of carbon dioxide will build to a higher than normal level (hypercapnia). In turn, these conditions of hypoxia and hypercapnia will trigger additional effects on the body. Brain cells need constant oxygen to live, and if the level of blood oxygen goes low enough for long enough, the consequences of brain damage and even death will occur.

When there is a chronic (long term) increase in blood carbon dioxide, the brain starts to ignore the oxygen level and monitors the blood carbon dioxide level to determine when to take the next breath. The control of breathing also becomes slower to respond to changes in carbon dioxide levels; so when a person takes more or deeper breaths and "blows off" carbon dioxide the drive to breathe decreases and the rate of breathing decreases. As a result of slower rate of breathing, the carbon dioxide builds back up in the blood and the rate of breathing increases again. The brain, slow to adjust, continues to signal for more rapid breathing until the carbon dioxide level drops too low. Breathing then slows down or stops until the carbon dioxide level rises again. This pattern of abnormal breathing is called Cheyne-Stokes breathing (after the men who described it). It is characterized by repetitive cycles of fast breathing followed by slow breathing and apnea.

Who suffers from Sleep Apnea?
Anyone can suffer from Sleep Apnea. Overweight people are more susceptible to Obstructive Sleep Apnea, but likewise a very large amount of the population are not overweight or excessively overweight and can still suffer from Sleep Apnea. It's like most diseases, it can affect anyone in any walk of life.

How do I know if I have Sleep Apnea?
Sleep Apnea is usually diagnosed with an overnight sleep test called a polysomnogram, or a "sleep study". However, in some areas you might not have a Sleep Study. The side effects to look out for with untreated Sleep Apnea can include:-

- Snoring, gasping/choking, stop breathing at night
- Daytime sleepiness or tiredness, wanting to nap in the day time and finding it easy to nap
- Drowsy when driving, you may continue to lose focus and find when you are driving that you are swaying between lanes on the road
- Morning headaches, dry mouth, sore throat
- Waking up often to urinate in the night
- Twitching and jerking of limbs whilst sleeping (this usually also is related to RLS / PLMD)
- Difficulty falling asleep or staying asleep.

What are the danger levels of Sleep Apnea?

It is considered by the medical profession that the AHI figures be rated as follows...


I suffer from some of these symptoms, do I have Sleep Apnea?
It is entirely possible that you might, but at first I would recommend you try the Epworth Sleepiness Scale below. If you still think you may suffer from Sleep Apnea, seek out a sleep specialist doctor. More information for the Epworth Sleepiness Scale can be found at the official site.

Situation Chance of dozing
Sitting and reading  
Watching TV  
Sitting inactive in a public place (e.g a theater or a meeting)  
As a passenger in a car for an hour without a break  
Lying down to rest in the afternoon when circumstances permit  
Sitting and talking to someone  
Sitting quietly after a lunch without alcohol  
In a car, while stopped for a few minutes in traffic  

Enter against each of the situations a number as follows
0 = No chance of dozing off
1 = Slight chance of dozing off
2 = Moderate chance of dozing off
3 = High chance of dozing off

1-6 = Congratulations, you are getting enough sleep
7-8 = Your score is average
9+ = Seek the advice of a sleep specialist without delay

2. Why are machines sometimes called CPAP or APAP, BIPAP or VPAP? [top]
CPAP = Continuous positive airway pressure (CPAP is a fixed pressure, e.g. 10cm H2O)
APAP = Similar to CPAP but also allows for variable pressure so if your Apneas increase over the fixed pressure limit, APAP's can respond and treat and reduce the Apnea events
BIPAP = Bilevel Positive Airway Pressure allows to change the inbound vs outbound pressure independently rather than one fixed pressure, good if you can't exhale against the inbound pressure of CPAP/APAP
VPAP = Variable Positive Airway (similar to a BIPAP)

3. What kind of machines are there? [top]
There are many different machines from different suppliers, I have always gone with ResMed machines as ResMed always seem to be on the cutting edge of technology and have very small and lightweight robust machines.

Below is a list of CPAP/APAP machines although this list might not be up to date shows a good comparison of machines and features and specifications.

These are the machines that I have previously used. I now have the S9 (left in the first image) but have had two S8's (right in the first image). The second image shows the S9 with the H5i heated humidifier that provides Climate Control and a heated hose to reduce rainout.

4. What is a heated humidifier? [top]
A heated humidifer provides heated air. Sometimes the air coming from CPAP or APAP machines can be cold because the room temperature drops over night, probably because you don't run your central heating 24/7. So the air temperature drops coming through the tube to your mask. This can soemtimes give you a cold or sore throat and the heated humidifier will rectify this by heating the air. On newer machines like the ResMed S9 they no tonly include a heated humidifer but also include Climate Control so you can set the temperature that you want to come through the mask and the heated humidifier will keep that same temperature no matter what temperature the room drops to throughout the night.

Heated humidifiers work by having a reservoir / tank of water that you fill nightly and empty in the morning. The humidifer heats this water which gives off steam. The CPAP will blow air into the heated humidifier which is then heated and the air taken out of the humidifer into the tube and down the tube to your mask.

The heated humidifier (h5i) can be seen on the right in the image below where as the ResMed S9 is pictured on the list

What do the filters look like and Data card on the ResMed S9?
The filter for the ResMed S9 is on the left, with the filter casing in the middle and the Data card that stores your sleep information on the right

5. What kind of masks are there? [top]
There are usually three kinds of masks shown below

6. Examining Sleep Apnea data [top]
Below you will find a number of graphs that show each type of Sleep Apnea event.

This is usually considered a full blockage of your Upper Airway and must result in a blockage for a minimum of 10 seconds. The one below is measured as exactly 10 seconds. You can see from the graph that the normal sine wave before the Apnea with a reduced sine wave in the blockage (rectangle) and then disrupted sine wave after the blockage (usually relates to abnormal breathing or partial awakening of sleep).

This is usually considered a partial blockage of your Upper Airway which could if left untreated by CPAP or XPAP be regarded as turning into a full Apnea. Hypopneas just like Apneas must result in a partial blockage of the upper airway for a minimum of 10 seconds. You can see from the graph that the normal sine wave before the Hypopnea with a reduced sine wave in the partial blockage (rectangle) and then back to normal breathing after the blockage.

This is usually considered when you have awoken, say in the morning from sleep, or prior to getting off to sleep, the sine waves are more rounded

7. Understanding your sleep study [top]
Here are some Sleep Study slides and Audio from a Sleep Study Seminar that was conducted over the internet by trained sleep doctors.
Sleep Study Slides
Sleep Study Audio from Seminar

8. Average night of Obstructive Apneas/Hypopneas when on CPAP [top]

Obstructive Sleep Apnea - upper airway bockages
Here is what an average night of Obstructive Sleep Apnea events can look like where a patient is being treated very well on CPAP with an AHI of 1.7 (13.6 events in an 8 hour sleep cycle)

Central Sleep Apnea - brain's respiratory control centers are imbalanced
Here is what an average night of Central Sleep Apnea events can look like where a patient is being treated moderately well on CPAP.

Mixed Sleep Apnea - Obstructive and Central Apnea
Here is what an average night of Mixed Sleep Apnea events can look like where a patient is being treated moderately well on CPAP.

Here is what an average night would look like for me, this was an AHI of 1.7 (13.6 events in an 8 hour sleep cycle)

Here is what a night can look like for me if I start to have some Centrals as well as Obstructives and Hypopneas.

How can I tell when I'm sleeping vs awake when I look at my flow graphs from my CPAP/APAP software?
The graphs will look distinctively different however everyone's breathing is different so your graphs may look a little different to these.

Sleeping Waveform

Awake Waveform

Sleeping Waveform
Here's another look at a sleeping waveform vs a brief awakening by rolling over / changing sleep position

Changing sleep position Waveform
Here's a look at what your sleep data can look like when you roll over or simply readjust your sleep position without awakening fully in the same night as the graph above. The spike you see in the center of the graph is where you've paritally awoken to change sleep position and then gone back to sleep again most of the time without knowing you are doing so. This is completely normal in most peoples sleep. Some people can turn hundreds of times int he night.

What constitutes a bad night for me when on CPAP/APAP?
When I get a night where I'm constantly hitting either partial blockages of my upper airway or full blockages like in the graph below. Where the waveform reduces to almost 0 and becomes a squiggle shows that around these times I'm having Hypopneas or Apneas.

Also what constitutes a bad night for me is not only when I have Obstructive Apneas and Hypopneas but also Central Apneas. Although that said, my treatment/therapy is still very good with AHI's of <2, but I do feel a difference when I awaken with a night like this feeling not as good compared to a night with only 1 or 2 Hypopneas and no Obstructive or Central Apneas.

Types of Breathing events and how they are defined

9. How to reduce your AHI (Apneas and Hypopneas) [top]
You need to first understand what your titration level was from your sleep study. For example if it's 10cm H2O and you are still seeing a lot of Apneas like in the above graph then increasing your pressure incrementally can and should reduce your Apneas and Hypopneas, this should be discussed with your sleep doctor first. By increasing the H20 Pressure will result in splinting open the upper airway and this in turn will stop it from collapsing which is the cause of Obstructive Apneas and Hypopneas. However in some patients by increasing pressure can lead to more Central Apneas. So you have to be careful in increasing the pressure.

By increasing the pressure gradually over time you can see by the graphs below that the Apneas and Hypopneas also reduce to an ideal AHI = 0.0. Not everyone will be able to reach an AHI of 0.0, the lower the AHI the better. Anything <5 is considered good for CPAP treatment.

It should also be said that I also have my up and down days, and this is only normal. Not everyone can be 100% perfect in reducing their stats every night.

Click to enlarge the images below.

10. How to change the pressure on your CPAP/APAP machine [top]

Am I allowed to change my pressure?
There's no law saying that you cannot change your pressure. You may want to check with your Sleep Doctor, GP or DME first before doing so. You would have been titrated at a pressure rating in your sleep study, and that usually is the pressure that you should use. However that said, you and your body and circumstances change throughout the course of a year with different seasons. You may have lost weight, you may have gained weight, you might have a cold or be suffering from some new allergy or hayfever. All this means that the original titration in your sleep study was good for then but not necessarily good for now.

Will my Sleep Doctor, GP or DME know that I've changed your pressure?
If they look at the data from your machine and have a previous record of either your titration pressure or previous recordings from your machine then yes, they will see a difference and may ask you why you have increased the pressure.

If I am asked the question as to why I changed the pressure, what should I say?
Just tell the truth. Some people increase their pressure because they feel that they are relapsing and starting to feel more tired. Some people find that the pressure is too intense and have to reduce the pressure. Most Sleep Doctors appointments can take anything up to 6 months to book so you don't want to wait 6 months to see the doctor again.

How do I get into the Admin menu to change the pressure on my machine?
ResMed S8 - hold down down and right buttons for 3 seconds
ResMed S9 - hold down the SETUP and dial/tuner button for 3 seconds

11. Where can I get the Clinicians (Doctor) manual for my machine? [top]
There's a number of manuals below that you can download

   - ResMed
          - ResMed S9 AutoSet
          - ResMed S8 AutoSet Spirit
          - ResMed S8 Vantage
          - ResMed S8 Compact
          - ResMed S8 Escape
          - ResMed S8 Elite II
          - ResMed Sullivan V

          - ResMed SmartDiary - how to make a diary with your machine

   - Respironics
          - Respironics REMstar Basic M Series
          - Respironics REMstar Plus M Series
          - Respironics REMstar Pro M Series
          - Respironics REMstar Auto M Series
          - Respironics REMstar Plus (not the PR System One, non-C-Flex / not the M series)
          - Respironics BiPAP Pro (not the PR System One)
          - Respironics REMstar Auto M with A-Flex
          - Respironics REMstar BiPAP Auto SV

   - Fisher & Paykel
          - Fisher & Paykel SleepStyle600

   - ProBasics
          - ProBasics ZZZ-PAP

Where can I get the software manual for my ResMed machine?
          - ResScan Manual 3.10

12. RLS (Restless Legs Syndrome) and PLMD (Periodic Limb Movement Disorder) [top]

RLS (Restless Legs Syndrome)
Restless Legs Syndrome is a condition that is characterized by an irresistible urge to move one's body to stop uncomfortable or odd sensations. It most commonly affects the legs, but can also affect the arms or torso, and even phantom limbs.

Moving the affected body part modulates the sensations, providing temporary relief. RLS causes a sensation in the legs or arms that can most closely be compared to a burning, itching, or tickling sensation in the muscles. Some controversy surrounds the marketing of drug treatments for RLS. It is a 'spectrum' disease with some people experiencing only a minor annoyance and others experiencing major issues.

The sensations—and the need to move—may return immediately after ceasing movement or at a later time. RLS may start at any age, including early childhood, and is a progressive disease for a certain portion of those afflicted, although the symptoms have disappeared permanently in some sufferers. May Sleep Apnea patients do also have Restless Legs Syndrome and/or Periodic Limb Movement Disorder. There are some circles that believe that the oxygen deprevation and starving the brain cells could be what causes brain cells to die and to bring on other neurological and muscular disorders like RLS and PLMD but it still has not been proven.

What can bring on RLS in RLS sufferes are things like Iron deficiency, elevated salt intake, elevated caffeine intake, elevated chocolate intake, and the worse cause to bring on RLS is artificial sweetners. Most soft drinks are sugar free or contain artificial sweeteners like Aspartame, Acesulfame K, Saccharin, Sucralose, Stevia, and Tagatose which can be up to 200 times sweeter than regular sugar.

More information for RLS can be found at

PLMD (Periodic Limb Movement Disorder)
Periodic Limb Movement Disorder is a sleep disorder where the patient moves limbs involuntarily during sleep, and has symptoms or problems related to the movement. If the patient moves limbs during sleep but there are no negative consequences, the condition is simply called periodic limb movements of sleep (PLMS). (Most people who have PLMS do not have a disorder, and do not require any treatment). PLMD should not be confused with restless leg syndrome (RLS). RLS occurs while awake as well as when asleep, and when awake, there is a voluntary response to an uncomfortable feeling in the legs. PLMD on the other hand is involuntary, and the patient is often unaware of these movements altogether.

Patients with PLMD will complain of excessive daytime sleepiness (EDS), falling asleep during the day, trouble falling asleep at night and staying asleep throughout the night. Patients also display involuntary limb movements that occur at periodic intervals anywhere from 20-40 seconds apart. They often only last the first half of the night during non-REM sleep stages. Movements do not occur during REM because of muscle atonia.

More information for PLMD can be found at

13. Self Help Forums and other information resources [top]
        British Sleep Apnea Site
        Sleep Apnea Wikipedia
        OSA Online (UK)
        CPAP UK
        The Sleep Apnoea Trust (UK)

14. Good Discussions around Apneas/Hypopneas [top]

        How to reduce your AHI's for OSA [good results]
        An Obstructive Apnea that's not Obstructive? [graph]
        Getting lots of apnea's still
        Why does my treatment pressure not increase(s9)?

        Using the S9 Autoset w/ Centrals... Suggestions appreciated
        Central Sleep Apnea: Pathophysiology and Treatment
        Central Sleep Apnea: Implications for Congestive Heart Failure
        Effective Treatment for Idiopathic Central Sleep Apnea?
        Resmed s9 and central apneas

Mixed/Complex Apneas
        Along comes yet another Newbie...with Complex Central Apnea
        Complex Sleep Apnea: It Really Is a Disease
        The Quest for Stability in an Unstable World: Adaptive Servoventilation in Opioid Induced Complex Sleep Apnea Syndrome
        Complex Sleep Apnea

Lowering your AHI
        How to reduce your AHI's for OSA [good results]
        ResMed S9 and AHI 0.0 - Look Bob no hands!

Restless Legs
        Sleep Apnea and Restless Leg Syndrome

15. ResMed S9 resources [top]

ResMed S9 Photos
        ResMed S9 Autoset - The Unboxing
        Photos of H5i reservoir for the ResMed S9 that comes apart
        One bad thing about H5i humidifier for S9's
        Resmed S9 Auto - 1st night photo summary
        ResMed S9 filters - Standard vs Hypoallergenic [photos]

ResMed S9 Climate Control / Humidifier
        ResMed S9 - ClimateLine and autoset questions
        One bad thing about H5i humidifier for S9's
        Photos of H5i reservoir for the ResMed S9 that comes apart

ResMed S9 ResScan / SD card Problems
        S9 Data Card Capacity
        S9 - How to fix a corrupted S9 data card
        S9 flow skew bug... Anyone else seeing this?
        ResScan 3.10 Nap Bug

ResMed S9 Data Reading
        ResMed S9 and Central Apneas.

By following any of the above information or downloading of Clinician Manuals and changing pressure on your CPAP/APAP/BIPAP you understand that you are personally assuming all risk for using this information on this website and in these documents and will not hold or it's owners, authors or contributors liable for any problems, damages, physical harm (including death), mental harm or any other harm that may come to you, your family members, friends, co-workers or any other persons who may receive this information from you. We highly suggest you seek advice from your Sleep Doctor, GP, DME or qualified physician before attempting any changes discussed in this website.

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