(03-24-2016 12:51 PM)DonC Wrote: I used Auto CPAP only before the jump to ASV and the settings were 8 to 15. You said "your current settings will of course give you a max IPAP of 24 (max EPAP 14, max PS of 10) which is quite a 'shock to the system'". I thought these were separate pressures and happened when breathing in or breathing out.
IPAP, the pressure during inhalation, is EPAP plus PS.
(03-24-2016 03:34 PM)Asjb Wrote: My understanding ... is that a pressure support max setting of 10 should be enough to 'breathe for you' when you have central apnoeas, and so get rid of those. The PS will also resolve hypopnoeas.
If we have normal lungs, during a prevented central apnea (during what would have become a central apnea if we would have been using a regular CPAP or APAP or BiPAP machine) a Max PS setting of 10 will typically be adequate to keep us breathing very close to our normal amount of air while the machine is doing for us all the work of breathing.
A large Max PS like 10 will also prevent other central events like (in absence of an ASV machine, what would have become) central hypopneas and Periodic Breathing.
Some ASV users have terrible problems with aerophagia which impell them to limit their treatment pressures, or they may have a doctor who unfortunately does not understand how ASV therapy works and prescribes an inappropriately low setting for Max PS. If the Max PS setting is quite low, such as less than around 8, the ASV machine may be able to eliminate mild Periodic Breathing but may be unable to completely eliminate central apneas, perhaps resulting in central apneas being converted into central hypopneas.
A high setting for Max PS would tend to elminate all central events and would tend to help at least a little toward preventing obstructive hypopneas, but obstructive hypopneas and even obstructive apneas may still occur.
Rather than raising Max PS, instead, raising the EPAP settings is what most helps to prevent obstructive events. On a ResMed ASV machine, EPAP cannot be set higher than 15.
Quote:... you also had a noticeable obstructive component in your test night and to treat those you need an adequate EPAP. I think you've previously alluded to the fact that your obstructives were dealt with pretty well with APAP 8-15? Have I got that right? If so, you may well eventually need an ASV-auto EPAP setting of something similar to 8-15.
That is my understanding, also.
Quote:But if you go immediately now to 'theoretically perfect' settings that will mean you having an IPAP max of 25 (i.e. Max EPAP plus PS), and that is quite a jump from your APAP max of 15 and will take a while to get used to, and will likely give you mask leak and adjustment challenges initially.
(03-26-2016 05:41 AM)DeepBreathing Wrote: From the clinician manual: Central sleep apnoea detection (CSAD) is not active in ASVAuto and ASV modes. The ASV algorithm eliminates central apnoeas. Therefore, any apnoeas reported by the device will be obstructive or indicative of a closed airway.
Of course, here RedMed is presupposing that Max PS has been set high enough to completely prevent central apnea events.
Regarding what our Min PS setting should be, if we have normal lungs I suggest adjusting Min PS to at least 2 and using a recording pulse oximeter to monitor our average (not minimum) SpO2, targeting an average SpO2 between 94 and 96, not counting the short dips during obstructive events.
But if we have COPD, an SpO2 of 94 may be way too high and may lead to excessively high CO2 in the blood. If we have COPD, I think a safer target range for SpO2 would be between 89 to 91.