Leaks vs AHI

[Lowhypopnea]

If I am having leaks with my mask, does this skew the AHI figures??  And if so, does it make the AHI go up or down??
Thanks.

[Walla Walla]

Normally what happens if the leaks are too large is the machines can't sense the air flow correctly. It won't detect apnea event's that may be happening. So you could have a lower AHI reading which would be wrong.

[Sleepster]

If I am having leaks with my mask, does this skew the AHI figures??  And if so, does it make the AHI go up or down??

The AHI reported by a CPAP machine is erroneous when the leak rate is too high. Measurements taken in this way are garbage, you cannot extract any useful information from them. And it doesn't matter anyway because the goal is to optimize therapy and you can't do that when the leak rate is too high.

[mesenteria]

When you think about it a bit, the mask is designed to help in building pressure, or to resist blow-by...to seal an area so that the device can keep air flowing into your lungs as you inspire, and to release it as you expire.  A leaky mask will overtax the machine set at its highest deliverable volume/pressure, or make it sense that the leak is allowing the prescribed pressures set to not be met.  If it can't detect the 'defects', and correct them inside of the specified range of max and min, then how can it also detect that you're having an 'event', and then how can it enter that event into its record for the night?  Instead, it will just register major leaks.  So, the AHI will not be accurate, and it will be under-estimated generally because the machine won't be able to detect at least some of them...the ones where your mask was askew or misshapen.

[SarcasticDave94]

If I am having leaks with my mask, does this skew the AHI figures??  And if so, does it make the AHI go up or down??
Thanks.

Short answer is a yes it will to the first question. If leaks are large enough, AHI numbers would indicate less than reality.

The reason why? The leak will hinder the CPAP in the ability to detect apnea events. If an apnea cannot be detected accurately, that obviously skews the AHI score. If a leak is bad enough, the machine will not be able to build enough pressure to act as the splint to keep your throat open. These machines today can compete with quite a bit of large leakage, but there is a limit that, once crossed, apnea events are missed and are not being treated as they should.

[AliceF]

According to my cpap manual (it's an old machine) it says that the word Leak refers to air coming\going from the mouth while wearing a full face mask.
  But as I read through the replies in this post it seems you are understanding Leak refers to the air mask leaks. 
 Do I understand that correctly, you think Leak refers to leaking face mask ? 
And if yes, would that mean my manual has it wrong ?  And should I be reading leaks from EncoreBasics as leaks on the mask ?

[Walla Walla]

Sounds like there was a misprint in the manual. You can have leaks through your mouth with nasal and pillow masks. It wouldn't be considered a leak with a full face mask.

[pholynyk]

The machines can't tell the difference between leaks from the mouth and leaks from around the sides of the mask. Looking at the leak graphs, we can see that mouth leaks are more or less steady, with a flat top. Mask leaks tend to come and go in spurts. All of them can disrupt your sleep, and, if large and prolonged, affect your therapy.

[AliceF]

The machines can't tell the difference between leaks from the mouth and leaks from around the sides of the mask. Looking at the leak graphs, we can see that mouth leaks are more or less steady, with a flat top. Mask leaks tend to come and go in spurts. All of them can disrupt your sleep, and, if large and prolonged, affect your therapy.

  Ok thanks pholynyk

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Sounds like there was a misprint in the manual. You can have leaks through your mouth with nasal and pillow masks. It wouldn't be considered a leak with a full face mask.

 Ok thanks Walla Walla.   So no matter where the air leak is, mouth or mask, the smart card reader will pick it up as a leak.

[Lowhypopnea]

Just talked to my CPAP tech today.  She says that the manufacturers are saying leaks above 25L/min may or may not affect AHI scoring.  How is that for a definitive answer.