I am going to put forward what I believe are immutable facts that we can work from then add opinions
IMMUTABLE FACTS SECTION:
1) Primary: Respironics state that the Bipap SV can address OSA using a Bilevel titration (OSA being
Obstructive sleep apnea)
2) Secondary: Respironics state that the Bipap SV can address
Central Sleep Apnea - using timed mode (as does the Bipap S/T)
3) Secondary: Respironics state that the Bipap SV can normalize
Periodic Breathing by applying pressure support (PS) using an algorithm that tracks peak-flow over a 4-min window.
#2 (covers when the Bipap SV is used where the sleeper has no OSA)
4) SV only mode. This is where Epap is set the same as IpapMin. And, IpapMAX gets set higher than IpapMIN. Then the machine is primarily in PS mode. This allows the Timed Mode & PS to normalize Periodic Breathing where the sleeper may have little to no OSA symptoms.
Item 1) covers vanilla OSA and uses a Bilevel titration to set the Epap and Ipap values.
Item 2) covers Centrals and uses Timed Mode to switch from Epap to Ipap if the sleeper stops breathing. The machine assumes OSA is taken care of with a proper bilevel titration.
Item 3) is the new bit and the big bonus and the eye of much contention. What it looks for is waxing and waning of breathing (it does not look at zero airflow, that is the Central Time Mode component) - if airflow drops to zero after
exhalation, the Timed Mode kicks in (Epap to Ipap switch). But if airflow (peak volume) drops below the expected target during
inspiration, of any breath the machine will raise pressure within that breath. The PS mechanism merely boost the air intake within a breath so as to match the target.
Item 4) Uses Timed Mode and PS to keep the sleeper breathing to a target airflow (Peak Flow).
At this point the Timed Mode & Centrals should be clearly understood. This mechanism has been with us for years.
The Bipap SV machine can be set as a straight Bilevel (s/T) by setting ...
1) Epap (less than IpapMIN)
2) IpapMIN (greater than Epap)
3) IpapMAX = IpapMIN
4) BPM (a fixedrate or AUTO)
The Bipap SV machine can be set as a Servo Ventilator by setting ...
1) Epap (less than IpapMIN)
2) IpapMIN (greater than Epap)
3) IpapMAX = (greater than IpapMIN - thus adding PS)
4) BPM (a fixedrate or AUTO)
The Bipap SV machine can be set to focus on Servo Ventilation by setting ...
1) Epap (equal to IpapMIN)
2) IpapMIN (equal to Epap)
3) IpapMAX = (greater than IpapMIN - thus adding PS)
4) BPM (a fixedrate or AUTO)
OPINION SECTION:
PS is the difference, the magic that the SV introduces. Now if we look at what triggers PS it is when the airflow drops which can be due to any number of normal and abnormal events.
It is arguing about these events that has been driving this thread of late.
SWS very astutely looked at the Patient Triggered Breaths data & using plain math said that this statistic shows that for 68 times each hour, the machine switched from Epap to Ipap because it decided it needed to. But then the speculation disagreement began. DSM says that yes, this machine is tracking my BPM which averages 14 & if I roll over or switch from mouth to nose, my BPM will be impacted & the SV's Timed Mode tracking will kick in - but that is normal. SWS says this is abnormal.
What we need is another pure vanilla OSA person (DANMC ?) to do a night with an SV and to see if he/she achieves 100% patient triggered breaths or gets a result like DSM (approx 99+0.x %). If other pure vanilla people achive similar numbers to DSM then the data reflects a normal nights sleep & DSM is correct. If the other Vanilla OSA sleepers always score better than DSM then SWS is correct but then we would need to work out what causes the difference. DSM might assert that nasal congestion is the only other probability. But if someone else with nasal congestion and vanilla OSA scores like DSM then DSM is correct else there is some other respiratory problem and that I believe is SWS's assertion.
The other issue is what DSM calls smoothing out residual events. If we agree that the airway is correctly held open with Epap, then there are two types of events that can occur that will trip off the SV PS mechanism (we should agree that a central will be managed by the Timed Mode) ...
1) A looming obstruction (hypopnea, flow-limitation) + what can be called a central hypopnea or flow-limitation.
2) Periodic Breathing irregularity
(which manifests itself to the machine as a hypop or flow-lim)
Now PS will activate and boost pressure in response to either event - as stated above it samples peak air-flow & if the target flow for a given breath looks like it won't be met the machine boosts pressure to a higher setting than IpapMIN (and up to IpapMAX) & based on how far off target the sleeper is and how many breaths this has been going on for (PS will be increased if the 1st pressure boost (in one breath) didn't bring the sleepers air flow back to the target).
So DSM has stated that based on his observations, he believes PS sorts out residual OSA events (hypopneas and flow-limitations) & does it very well. This has triggered comments from SWS and Rested Gal who appear not to accept this observation. They believe there are other irregularities that are not normal.
That is all for this post & I just want to add that I really do enjoy the challenges SWS & Rested Gal have thrown up, we give each other curry at times but I greatly admire and respect both of them for their wisdom & commitment to matters related to SA & SDB.
I'll give either more curry if I am convinced either is putting forward less that adequate arguments or proofs & I know they will return the flavour
DSM
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CPAPopedia Keywords Contained In This Post (Click For Definition):
respironics,
bipap,
Titration,
auto
_________________
CPAPopedia Keywords Contained In This Post (Click For Definition):
respironics,
bipap,
Titration,
Hypopnea,
auto
_________________
CPAPopedia Keywords Contained In This Post (Click For Definition):
respironics,
bipap,
Titration,
Hypopnea,
auto