From interview with Dr Dr Michael Berthon-Jones ... ResMed chief designer of AutoSet (prior to the S9 AutoSet enhanced algorthim)
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 cmH 2O, 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 10cmH2O, it’s just a good place to put the line in the sand
Read more http://www.resmed.com/au/assets/document...0906r1.pdf