RE: Machine or operator adjustment?
(02-01-2014, 06:33 AM)drgrimes Wrote: Comatose, i'm certainly not the expert here, but it looks like your events are clustered with major leak problems. When it's leaking that bad, you can't necessarily trust all those event flags. AND i'm thinking that when big leaks are occurring, the Autoset is jacking up the pressure to fix the problem but it can't.
I do not see any "major" or "bad" leak problems in the data Comatose has posted.
The event flags will be less reliable whenever leaks are less steady, but for unintentional leaks below 24 cm H2O I think you can trust the apnea event flags are real events even with leaks which are quickly fluctuating, because the effect of fluxuating leaks would be to cause the machine to miss or under-report the duration of true apnea events.
The machine is adjusting the airflow to maintain the target mask pressure. When we are inhaling the machine needs to supply higher airflow. When we are exhaling the machine needs to supply less airflow. When we look at our data in ResScan or SleepyHead, the Flow plot of airflow into and out of our lungs is based on the machine measuring how much it needs to increase/decrease its airflow so that the mask pressure stays constant.
Varying leaks can look to the machine like a breath has been taken when really it has not, so the machine may not report an apnea (or may report it as being shorter than it really was) if it mistakes varying Leak as being breathing.
I don't know whether very large leaks (far above 24 L/m, I think) may cause the machine to think an apnea is occurring when it is not. I suppose that may be possible, but I have not heard/read anywhere that such a thing may occur. I think it would be likely that at times of very large Leak the machine's software may recognize that measurements have become unreliable and the machine may simply suspend reporting events until Unintentional Leak decreases.
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Correction: apparently the machine continues to record hypopnea and apnea events even during periods of extremely high Leak. I found in my data on nights having exceptionally high intermittent Leak that my ResScan detailed plots show hypopneas and apneas reported for times when the Leak was extremely high. In one case the reported hypopnea was at the very beginning of a 9 minute period when the Leak was a little over 100 Liters/minute. Before, during and after the reported hypopnea my SpO2 was rock steady at 94%. The "hypopnea" "ended" at a time when the Leak happened to dip for several seconds slightly below 100 L/m. Based on the SpO2, I think there was no real hypopnea, and the machine had been fooled. Most of the reported "Apneas" also tend to occur at the very start of a period when the Leak had just increased well above 75 L/m.
END EDIT
At any rate, Comatose's data shows acceptable Leak, below 24 cm H2O, so I think we can be fairly certain that no false apneas (apneas which are not really occurring) are being reported.
Also, the Obstructive Apneas reported by Comatose's machine are accompanied by high Flow Limitation and tend to occur when the pressure is maxed out, which makes sense and confirms these OA's are real.
(02-01-2014, 01:21 PM)PaytonA Wrote: Next we come to the chicken or the egg discussion. Do the higher leakage clusters cause the events or do the events cause the higher leakage clusters?
Flow Limitation and/or Snore cause pressure to be increased, which tends to increase leaks.
Also, events tend to cause arousals which can cause movement, causing increased or fluctuating leaks.
(02-01-2014, 07:29 PM)comatose Wrote: I did toss and turn quite a bit last night and at times found it difficult to breathe so I think that tonight I will change the EPR from 1 to 2.
Can snoring make the leak graph look worse than it actually is?
I was thinking the vibrations from snoring may have a jackhammer effect?
Zonk I had tried to find info on the flow limitation but nothing I found made any sense to me, could you please check out my pickies and enlighten me a bit about the FL please?
Hi Comatose,
EPR can seem bothersome at first but once we get used to it I think most people find therapy more comfortable with EPR than without it, and EPR tends to reduce leaks, and it often leads to improved sleep quality.
On a few patients who are susceptible to having centrals (like me), EPR can increase the number of centrals we are having, but centrals do not seem to be your problem at all, so using EPR of 3 may be better for you than 1 or 2.
However, when you increase EPR you are decreasing the pressure during exhalation (EPAP), and lowering EPAP is associated with making obstructive events more likely. Since your pressure is often limited by your Max Pressure setting, I would encourage you to increase the Max Pressure by at least the same amount that you increase EPR.
When your pressure is maxed out, do you think these could be times that you have rolled onto your back while asleep?
Obstructive Sleep Apnea is usually highly dependent on sleep position, with flat-on-our-back (the supine position) usually being the worst. During sleep studies the technician will not want to miss the worst case, so we are required to sleep in the supine position for at least some time (unless we refuse because we cannot fall asleep in that position or whatever).
I think Snore will not cause Leak to be overestimated, because the snore vibrations do not change the average pressures or airflows.
Regarding Flow Limitation:
An example of Flow Limitation is when we suck on a weak straw trying to drink something. If we suck too hard the straw may partly collapse, limiting how much we can get through the straw. The flow through the straw does not completely stop. Although the flow may have seemed normal at the first instant we started sucking, as we suck harder the flow at first increases but with more suction the flow may actually decrease, because the suction is causing the straw to partly collapse.
The CPAP machine reports Flow Limitation as occurring when the Flow (the rate of airflow entering or exiting our lungs) during inhalation is initially high but decreases and "flattens" (drops and stays at a lower level), as if the suction and airflow during inhalation is causing the airway to narrow.
Take care,
--- Vaughn
The Advisory Member group provides advice and suggestions to Apnea Board administrators and staff on matters concerning Apnea Board operation and administrative policies. 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.
