(08-08-2015, 08:16 AM)SleepSailor Wrote:
(08-07-2015, 01:08 AM)vsheline Wrote: Also, I suggest lowering the Max Pressure setting. Setting the Max Pressure all the way up to 20 is not uncommon even by doctors but I think a Max Pressure higher than about 10 would be slightly risky, since you haven't had a sleep study. A small percentage of patients have serious problems at high pressures, so I suggest setting the Max Pressure to perhaps 10 and not raising it until you see from the data that you're having obstructive apneas which are not being prevented by a Max Pressure of 10 (or whatever) and you are not having more central apneas than obstructive apneas.
.... In reading the SleepyHead graphs, how would I identify an OSA event that is "not prevented by a Max Pressure of 10 (or whatever)"?
If an OA (Obstructive Apnea) had occurred while the pressure was 10, it would have been an OA which was not prevented by a pressure of 10.
For patients who are seeing CA (Central Apnea) events in their sleep data, they often find that if the pressure is increased this will cause the number of CAs to increase.
If you see that an OA occurred while the pressure was max'ed out at the Max Pressure and the CA Index (the average number of CA per hour of sleep) was not higher than the OA Index (the average number of OA per hour of sleep) and you did not notice anything else happening which would have indicated that the pressure may already be going too high - like ear trouble (dizziness or hearing trouble) or eye trouble or aerophagia (an excessively troublesome amount of air swallowing), or the mask perhaps needing to be uncomfortably tight to control leaks (with mask straps pulling more strongly than necessary on our teeth or jaw, perhaps leading to misalignment of teeth or temporormandibular joint problems) - then raising the Max Pressure setting would seem appropriate.
Over time, some patients learn that they need to make trade-offs between having the pressure high enough to completely treat Obstructive Sleep Apnea versus limiting the pressure in order to not aggravate or cause other health issues.
(08-08-2015, 08:16 AM)SleepSailor Wrote: e.g., last night I had an AHI of 2.78. However, I see 10 CAs, 11 OSAs and 10 Hypopneas. In zooming down on the OSAs and the CAs, I notice periods of non-existent flow rate that last about 10-13 seconds long. To me, these are events that were not prevented. The By Pressure chart shows that .8 minutes were spent at a pressure of 9 and .2 minutes were spent at a pressure of 10.
Your numbers of CA and OA are already low and about equal. No problem there. And typically, during the initial weeks of therapy, the number of CA we get tends to decrease as we become accustomed to CPAP therapy.
By the way, the Max Pressure setting acts merely as a limit. Last night, had the Max Pressure setting been 11 instead of 15 it would not have had any effect on the pressures used during the night, if the pressure never reached as high as the Max Pressure setting.
(08-08-2015, 08:16 AM)SleepSailor Wrote: So, are you suggesting that the APAP machine is able to "Prevent" the OSAs altogether? I guess I am not understanding the basic theory behind blowing air into one's face all night and exactly how that works. Does the machine increase pressure in real time to break up a specific OSA or CA? Or, does the constant pressure reduce the events?
Higher pressure may have been able to avoid all OA events. For example, if your Min Pressure had been 11 you might not have had any OA during the night. But a Min Pressure of 11 may have been very uncomfortable and may have prevented you from being able to fall asleep. After a few weeks of gradually working the pressure higher you might not have any problems falling asleep with a Min Pressure of 11, but it might be unnecessarily high, perhaps causing too many CA events or aerophagia or whatever.
Nonetheless, some Apnea Board members have reported that they do best when their Min Pressure is very close to their highest pressure, so that they are essentially receiving fixed-pressure therapy all or most of the night.
Incidentally, I suggest the Min Pressure setting should not be lower than 2 or 3 cmH2O below your 90% or 95% pressure. The 95% pressure is the pressure the machine was at or below at least 95% of the time. The 95% pressure is also the pressure the machine was at or above at least 5% of the time.
A ResMed machine treats the Min Pressure as a target which the machine is always slowly trying to return to. The higher the pressure is above the Min Pressure setting, the faster (less slowly) the pressure will drop toward the Min Pressure. Therefore the lower the Min Pressure setting is, the faster the machine will lower the pressure between obstructive events, lowering the average pressure and likely allowing more obstructive events than if a higher Min Pressure setting had been used.
Unless you use an Adaptive Servo Ventilator (ASV) or similar ventilator class of CPAP machine with a "backup" respiration rate, your machine will not immediately respond to apneas or hypopneas. According to the set-up manual (clinical guide) for your machine, after an obstructive apnea has ended your machine will take into account how long the OA had lasted when deciding how much to raise the pressure. The machine also proactively raises the pressure in response to Flow Limitation and snore. Flow Limitation is a partial collapse of the airway during inhalation. Higher pressure tends to reduce Flow Limitation but higher pressure only during inhalation (which bilevel therapy can provide) is the optimal prevention for Flow Limitation. ResMed EPR (pressure relief during exhalation) is a limited form of bilevel therapy and can be helpful in lowering Flow Limitation.
(08-08-2015, 08:16 AM)SleepSailor Wrote: .... Also, I see that you are using an S9 with a separate humidifier. My S10 has a "humidifier" integrated into the machine (a pan of water over which the air blows). The climate in Utah is VERY dry and I have woken up with a very dry mouth at times. I wonder whether people with integrated humidifiers will sometimes get an external humidifier and why and how helpful that is.
The S9 humidifier can be removed but when it is used it is not quite separate. The S9 blower unit can electrically sense whether the humidifier is present and whether the heated hose is attached to the humidifier.
Adding a second humidifier between the built in humidifier and the mask would somewhat degrade the accuracy of the machine's estimate of the pressure reaching the mask (which is the therapy pressure), particularly during periods of high airflow through the hose and second humidifier. If your mask is leaking and causing high airflow the machine wouldn't know about the pressure being dropped across the extra humidifier so it would overestimate how much pressure is reaching the mask, and the delivered mask pressure would be too low, perhaps increasing the number of obstructive events.
There is no easy way to add a humidifier at the air intake into the machine. Some have found it helps to use a small room humidifier.
The amount of mask leaking we have can hugely affect the amount of water used by the humidifier. So try to keep leaks low so that the humidifier will not run out of water.
I use a mask liner between the mask and my face, which greatly reduces leaks and how tight I need to adjust my mask to achieve low leak rates.