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Interpretation of Apneas Tied to Mask Leaks
#1
I just completed my second night of therapy on my ASV machine after being diagnosed with mixed apneas and an AHI of 50 (after 3 sleep studies and 3 months of arguing with insurance...). The numbers look great but I have a question. Some of the apneas seem associated with mask leaks. Are these apneas real, or simply bad data tied to the leak.

Thanks in advance, Ron


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#2
It appears to me that the mask leak caused the machine to reduce the pressure to try and get the mask to reseal (which worked) and this reduced pressure allowed the apnea to happen. The leak is not large enough to affect the machine's detection of the apnea, it is (was) real.
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#3
Ok, I appreciate your help in interpreting the data. Glad to know that the machine is working properly.
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#4
My memory could be faulty but what I remember is that PR machines will reduce pressure temporarily in an attempt to correct leaks but Resmed machines do not.

The leak might have caused a temporary reduction in pressure that allowed the airway to collapse somewhat causing the hypopnea. That would be my interpretation.

Best Regards,

PaytonA
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#5
(06-26-2016, 11:18 AM)PaytonA Wrote: My memory could be faulty but what I remember is that PR machines will reduce pressure temporarily in an attempt to correct leaks but Resmed machines do not.

Yes, the Philips Respironics APAP algorithm includes 1 cmH2O reduction in pressure in presence of Large Leak (see Table 2 in article linked below).
http://www.ncbi.nlm.nih.gov/pmc/articles...rt=classic

But this was ResMed, and this was a rather small leak, and the normal EPAP pressure of 7 cmH2O was not reduced at all. Instead, the transition to IPAP was strangely delayed/halted and then stepped slightly higher.

The scored Hypopnea may have been an obstructive Hypopnea/Apnea or perhaps might have been a change in sleep position. Not clear what could have caused these pressure and Flow waveforms during the fairly small leak, but probably nothing to worry about.

However, judging from the general unevenness and roughness and jaggedness of the Flow waveform, it looks to me like the EPAP is simply set too low.

In a month or two, when you next see the doctor, he may look only at the good AHI numbers and may see no reason to change anything.

Most new users may be too shy to email a SleepyHead report to the doctor and ask whether the EPAP should be raised. Also, a doctor would likely say, no, the AHI is fine, no need to change anything unless you have a problem to report, so let's keep everything unchanged until your follow-up appointment.

However, I recommend that (at some point in future) instead of ASV mode, ASVAuto therapy mode should be used to perform an at-home titration of EPAP. No harm in asking the doctor why not change to ASVAuto therapy mode.

Either that, or if remaining in basic ASV mode instead of ASVAuto mode, I would recommend that EPAP should be increased by about 1 cmH2O per week or two (or more gradually) until the Flow waveform is more smooth and regular, but not so high that problems occur, such as excessive air swallowing.

Pretty much everyone who is prescribed an ASV machine was previously started out on a CPAP or standard BiPAP, and there are guidelines which say if using standard ASV (not ASVAuto) the EPAP setting should be the same as the EPAP pressure which was previously found (on a CPAP or BiPAP) to be needed to treat obstructive events.

Take care,
--- Vaughn

Membership in the Advisory Member group should not be understood as in any way implying medical expertise or qualification for advising Sleep Apnea patients concerning their treatment. The Advisory Member group provides advice and suggestions to Apnea Board administrators and staff on matters concerning Apnea Board operation and administrative policies - not on matters concerning treatment for Sleep Apnea. I think it is now too late to change the name of the group but I think Voting Member group would perhaps have been a more descriptive name for the group.
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#6
(06-26-2016, 11:18 AM)PaytonA Wrote: My memory could be faulty but what I remember is that PR machines will reduce pressure temporarily in an attempt to correct leaks but Resmed machines do not.

The leak might have caused a temporary reduction in pressure that allowed the airway to collapse somewhat causing the hypopnea. That would be my interpretation.

Best Regards,

PaytonA

I am going to be forced to eat my words. The information that I was given was incorrect. I have seen concrete evidence in the form of Sleepyhead curves, that at least the A10 Autoset does reduce pressure temporarily in an attempt to correct leaks when they get bad enough. I do not know how many of the other Airsense and Aircurve models do the same but I would bet that at least some of them do.

Best Regards,

PaytonA

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