robysue wrote: ↑Sun Aug 05, 2012 12:32 pm
rich0 wrote: if the central apneas are bad enough only an ASV machine will fix the problem (it basically is like a combination APAP/BiPAP that automatically adjusts pressures to address both problems).
An ASV machine is NOT "like a combination APAP/BiPAP".
CPAPs, APAPs, BiPAPs (bilevels), and Auto BiPAPs cannot be set up to occasionally act as a noninvasive ventilator. ASV and bilevel ST machines
can be set up to (occasionally) act as noninvasive ventilators. And it is that capability that makes them useful in treating central and complex sleep apnea.
The point behind xPAP for OSA is to provide enough pressure to keep the airway open most of the time. On the OAs that sneak through the defenses, the machine makes NO attempt to force you to inhale. It waits for you to start rebreathing on your own. (APAPs and Auto bilevels increase the pressure
after the OA is over, they do NOT increase pressure in an attempt to get you to inhale.)
ASV and bilevel ST machines, on the other hand, can and do use pressure to force the patient to inhale---that is why they are considered noninvasive ventilators. Their algorthims for "triggering" inhalations are designed to short circuit the overshoot/undershoot cycle of blowing off too much CO2 which suppresses the "urge" to breath which leads to not blowing off enough CO2 (and a central apnea) which triggers a bit of hyperventilation which leads to blowing off too much CO2 which ... Essentially, ASV and bilvel ST machines trigger enough inhalation during the period when the tidal volume is at its lowest to prevent the undershoot (not blowing off enough CO2) part of the cycle from occurring.
The issue you're likely to run into is that your AHI is under 5. For whatever reason this is considered the target for therapy, and it is unlikely your insurance will pay for a $5000 ASV machine if your AHI is under 5 without one. They probably wouldn't even want to pay for a much cheaper BiPAP. You could of course pay cash, but they're still very pricey (maybe you could get it for $3500 from someplace like cpap.com).
In order to purchase a bilevel or a bilevel ST or an ASV machine from a place like cpap.com, you need a prescription for that particular type of machine. A prescription for a CPAP or an APAP won't be enough.
An ordinary old bilevel (a PR BiPAP or a Resmed VPAP) can be prescribed for a number of reasons, including patient comfort. In my case I was switched to bilevel to see if it would decrease my problems with aerophagia and spontaneous arousals caused by my body overreacting to the physical stimuli coming from my APAP/CPAP.
But prescriptions for bilevel ST and ASV machines are going to require some documented evidence of Central Sleep Apnea or Complex Sleep Apnea. And they'll require an in-lab sleep test for determining the appropriate settings---which are more complex than the settings on CPAPs, APAPs, and bilevels.