Leak Rate and AHI

[Islander99]

I have searched the forum with no luck per se and I am looking for an explanation of leak rate vs AHI.  Specifically, I note that a leak rate less than 24 seems to be acceptable although I have been told that you want no leaks at all.  I have also been advised that some of the events (e.g., hypopnea) are not real and one has to look at the breathing pattern to determine the validity of an event.

Back to leak rate.  Is a leak rate of 24 or less acceptable?  

AHI:  if one's AHI is less than 5, does that imply that one's sleep apnea has been resolved by using CPAP?

Thanks in advance!

[asuter060514]

My understanding is that your sleep apnea isn't resolved if its less than 5 AHI with CPAP, but that the CPAP is effectively treating you.

[Crimson Nape]

Resmed's report leaks as anything over the mask's intentional leak rate.  Evidently, they have determined that their devices will be able to provide therapy pressures up to the 24 L/min. rating.   It has been found that having leaks can mask apnea events.  The goal is to have none.  

The AHI of 5 was a determination made based on studies of persons without sleep apnea and normal breathing disruptions during sleep.  Doctors will use that as a guidepost of therapy effectiveness.   We use OSCAR to fine-tune the CPAP's parameters to help the patient achieve the best therapy that the CPAP can provide.   Before you get too far into this, I want to say that while a 0.0 AHI is possible and does happen, it is the exception and not the normal value to expect.  Some Papers worry more about the numbers more than the quality of sleep.  Don't be one!  Concentrate on lowering your AHI and keep track as to how you feel.  A lot of times there will be a trade-off between the two.  

Please look at the links in my signature for further information on OSCAR and how to best present your Daily screen images, here for help.

- Red

[staceyburke]

We all have leaks, in fact our masks are made to have leaks to get rid of CO2 on exhale.

If you move your mouse to the left side of the chart “leak rate” and right click - there is an option to put in a dotted line (there are several different dotted lines to choose from) I’m not at my computer right now so I can’t give you the exact title.

That dotted line shows the highest your leak can be for your machine to fight apnea. Any leak hurts but over the line your machine can not supply enough pressure to stop apnea.

[Islander99]

Thank you for your reply.  Typical of my results are:  AHI of 1.63 and no large leaks noted but leak rate of 7.20 (95%) and 13.20 (Max). The leak rate where apnea is not controlled is 24.0 on my machine (ResMed AutoSense 10).  I have been advised that I need 0 leak rate even though my AHI seems to be okay.  Pretty confusing to me.  Can't male sense of the advice or OSCAR as they seem to be divergent views/results.

[SarcasticDave94]

The leak rate does not need to be zero, nor is it acceptable to be at 24. My leak rate goal would be as low as possible while maintaining comfortable mask wearing and a well rested sleep state. The closer to 24 your leaks are, the more you need to make adjustments.

[clownbell]

To Islander 99 -

As I understand it, and with regard to a ResMed machine ONLY:
• The "first 24" liters per minute leak is the "expected leak" and is designed into the mask so you can exhaust the CO2 when you breathe out.
• The "second 24" liters per minute is the "excess leaks" which by definition are over and above the "expected leaks." The ResMed machine reports the excess leak (only) and OSCAR dutifully reflects it.
• So if OSCAR reports 7, for example, your total leak is really 31 -- consisting of 24 expected plus 7 excess.
• You can't expect tp get to a TOTAL of zero because then you would have no means to expel your CO2 and would ultimately die.
• You can work on minimizing the "excess leaks", and zero is theoretically possible yet rarely achieved -- but don't chase numbers to the point of being obsessive and uncomfortable and neglecting the quality of your sleep.

I hope one of the experts like Crimson or Sarcastic Dave chimes is on this, because it's complex and I am not the expert.

[SarcasticDave94]

It seems in theory you'd be correct, with one caveat. The first 24, the expected leak, isn't shown on the chart. The second, the excessive leaks, is shown. At least this is how I view it.

[clownbell]

@Dave - That is the way I understand it. ResMed only reports out the large leaks, so that is what OSCAR displays.

[SarcasticDave94]

OK we're on the same page then. Go get a coffee, you've earned it.