(09-12-2014 09:32 AM)Galactus Wrote:
(09-12-2014 05:51 AM)vsheline Wrote:
(09-11-2014 08:35 AM)Galactus Wrote: I guess what I don't understand here and the reason for my confusion is what exactly is PS? Is it how much added pressure the unit will add in the event of an apnea? Like if set at 13 for Min EPAP and PS=1 when it senses an event will it raise to 14 and then by 1's? Or am I misunderstanding what PS is?
Edit -- I'm reading and reading and I have come to the following; Seems to me the settings should be;
Max IPAP 20 (I am now fixed at 18 so +2 should be more than enough)
Min EPAP 13 (Seems like a good starting point)
Max PS- 7 (This is the max difference allowed between IPAP & EPAP and is 20-13=7)
Min PS- 1 (This is the min difference allowed between IPAP & EPA)
Rise Time- 1 (0 is off 1 is 200 msec, 2 is 300 msec and 3 is 400 msec, just seemed like a place to start though maybe 0 is better)
Flex- BiFlex at 3 (Same as my current CFlex setting)
I think your revised settings are fine as a starting point, but please note the points below.
If Min EPAP is 13 and if Max IPAP is 20, the Max PS setting CAN be set as high as 7, but the Max PS setting does not necessarily need to be set that high. The reason I suggested 4 as a Max PS limit was to be cautious, so that PS could not get higher than 4, in case you may find that a high value of PS increases the number of CA apneas or increases the severity of the Periodic Breathing episodes. With a minority of patients, the larger the value of PS, the larger the number of central events they get.
One result of setting the Max IPAP to 20 and setting the Max PS higher than 2 is that sometimes EPAP may not be able to go as high as 18 (which was your fixed CPAP prescription). The AutoB settings which were originally suggested would have guaranteed that the machine would always be able to raise EPAP at least as high as 18, if needed. With the original suggested settings, even if PS is at its maximum limit, the Max IPAP setting is high enough to allow EPAP to raise itself to 18 if needed.
I think this really confirms that I don't get the PS situation. PS must be different from the unit raising and lowering pressure. Maybe you can explain what I am missing, will try and look it up myself as well.
Your first paragraph here warning on CA's I understand a little. The second paragraph I'm lost on. I don't understand how Max EPAP is unable to reach 18 with a Max PS setting of 7. I thought that if Min EPAP =13 and Max EPAP = 20 with a Max PS of 7 that 13+7=20 and that with a Min PS of 1 that Max IPAP could =20 and Max EPAP could =19 which left both numbers above my original script. Did I misinterpret something?
Regarding your question, "what exactly is PS? Is it how much added pressure the unit will add in the event of an apnea? Like if set at 13 for Min EPAP and PS=1 when it senses an event will it raise to 14 and then by 1's?"
On your machine, during an apnea PS would not be increased or decreased at all.
Unlike your machine, ASV (adaptive servo ventilator) machines do react immediately to an apnea or hypopnea, to interrupt and counteract apneas and hypopneas. On ASV machines, within a few seconds the PS might skyrocket from very low to very high if the machine is suddenly faced with an apnea, or the PS might be changed by less than 1 if faced with a small increase or decrease in how much air we are breathing.
Even if we are not making any effort to breathe, an ASV machine will (on its own) cycle between EPAP and IPAP at a "backup respiration rate", unlike CPAP and BiPAP and BiPAP Auto machines which will not try to counteract the present apnea or hypopnea.
In general, an ASV unit reacts immediately to boost or lower PS however much is needed to end the apnea and to keep the volume of air being breathed steady.
The PRS1 BiPAP Auto does auto-adjust PS, but only very slowly: Every few minutes the machine decides whether to leave PS unchanged or whether to increase or decrease PS by 1 cm H2O.
Below is an excerpt from my earlier post #52. It discusses the how slowly PS is adjusted on your machine.
- - - BEGIN EXCERPT FROM POST #52 - - -
Min EPAP: 13 (about 5 less than now)
Max EPAP: 18 (about the same as now)
Min Pressure Support: 1
Max Pressure Support: 4
Max IPAP (or perhaps called Max Pressure): 22 (set to the sum of Max EPAP plus Max Pressure Support, unless you start to experience problems from high pressure.)
Ramp: same as now
Bi-Flex: same as C-Flex now
The above settings would make the EPAP pressure start at 13, so the pressure whenever exhaling would be 13 until the machine [slowly] automatically raises the EPAP pressure when it senses obstructions or partial obstructions.
The above settings would make the Pressure Support start at 1. The IPAP would start at IPAP = EPAP + PS = 14, so the pressure whenever inhaling would be 14 until the machine automatically raises the EPAP pressure when it senses obstructions. If PS remains unchanged and EPAP is raised in response to obstructive events, then EPAP and IPAP would be raised and lowered together the same amount.
But also, occasionally, the machine will do a slow dance to see whether to raise or lower PS, based on how this affects Flow Limitation. In brief, PS is occasionally raised a little (causing IPAP to be raised because IPAP = EPAP + PS) and if this causes Flow Limitation to be reduced then PS will stay at its new higher value for the next several minutes, until the next test to see if PS should be raised or lowered. Also, PS is occasionally lowered a little (causing IPAP to be lowered because IPAP = EPAP + PS) and if this does not cause Flow Limitation to start then PS will stay at its lower value for the next several minutes, until the next test to see if PS should be raised or lowered. But PS will always stay within the limits set by the Min PS and Max PS settings.
In this way the machine will [slowly] raise the pressure only as much as needed to avoid obstructive events and any signs of Flow Limitation.
- - - END EXCERPT FROM POST #52 - - -
Regarding, "I don't understand how Max EPAP is unable to reach 18 with a Max PS setting of 7. I thought that if Min EPAP =13 and Max EPAP = 20 with a Max PS of 7 that 13+7=20 and that with a Min PS of 1 that Max IPAP could =20 and Max EPAP could =19 which left both numbers above my original script."
Yes, in your example, EPAP could be as high as 19, but only if PS happens to be 1. EPAP and PS are separately getting raised or lowered in accordance with their separate algorithms, and I think the EPAP algorithm is not allowed to change PS and the PS algorithm is not allowed to change EPAP.
Keep in mind that whenever EPAP is adjusted IPAP is adjusted by the same amount, so that PS will be unchanged.
Let's take the case that Max IPAP is 20, and EPAP has been adjusted to 15, and PS has been adjusted to 4. (EPAP is 15 and IPAP is 19, which is 1 less than Max IPAP.) In that scenario, if your machine senses that a higher EPAP is needed, it can adjust EPAP to 16. (EPAP raises to 16 and IPAP raises to 20, which happens to be Max IPAP.)
If it so happens that your machine later senses that a still higher EPAP would be beneficial, I think the EPAP could not go to 17, because if EPAP were to be raised any higher, IPAP would also need to be raised by an equal amount, which is not allowed because IPAP is already at its limit.
Later, if the algorithm for adjusting PS happens to lower PS (to 3, say) then EPAP could be raised to 17 at that time (if the algorithm for adjusting EPAP still indicates that higher EPAP would be beneficial).