ResMed S9 - Are We There Yet?

[Ron AKA]

Ron, the chart with all the leaks also shows a high "snore" rate that coincides with the leaks. That snore is often recorded for "mask farts" where air is released around the edges causing noise vibrations.  I think staying with EPR full time is a better more comfortable option, and I would let the results under 1 AHI stand as "mission accomplished".   I'm sure your wife will be glad once you get your own Airsense 10 to play with so you can leave her alone.

I think you are right about the mask leak being picked up as a snore. When I'm done with pressures I will turn the EPR back on. Most nights with small changes I don't tell her what I have changed. She is looking forward to me getting my machine. It will come with a AirFit P10 with the fit pack and I am going to let her try it first to see if she can benefit from a nasal pillow type instead of full nose mask (Mirage FX). Her pressures are quite a bit higher than mine, go I am not so sure it will work, but we will see. What I notice when we are both masked up is how much noisier her mask is compared to mine. I can barely hear mine while air flow exhaust from hers is quite noticeable. ResMed seems to have done something to suppress the noise in the P10. I hear mine when it is leaking, but when it is working normally, I barely hear it. So, I am hoping the P10 works for her... Quieter when I'm not sleeping and she is!

[Ron AKA]

No chance that I'm brave enough to wake her up in the middle of the night to tell her that!

Yep, my hubby attempted to wake me up once to inform me he could hear air and to fix my mask.
Almost instinctively, my left arm flew out over to his side.....I don’t know where it landed.

I old saying came to mind. "Never wake a sleeping baby", or you pay the price!

[Crimson Nape]

FYI: The S9 does not record events while in the ramp mode. The lack of this knowledge may lead to false assumptions based on your data.

[Ron AKA]

The attachment below has the results from last night. AHI is up, but I am not really focusing on that for now. I'm trying to determine the impact and potential value of setting pressure limits that limit the automatic action of the CPAP. Considering that, last nights results clearly show limitations on maximum pressure (15 cm). In the first one at 0:45 or so, there was one hypopnea event, During the later, and much longer, period from 2:40 to 3:40, there were no hypopnea or OA events. I'm ignoring the CA events. The CPAP seems to be responding to Flow Limitation?? Does that make sense? Is flow limitation a measure of how much total air flow is reduced in comparison to what it considers normal flow? Is it a harmful thing? Bump max pressure up a bit? It might prevent one hypopnea event by letting the CPAP respond higher?

On minimum pressure, the only time the 10 cm was a limit was just after ramp up. Seems like there is no point in setting it lower. Minimum pressures for OA events are just slightly over 11. Thinking of setting minimum at say 11.2 and it may prevent an OA event or two? I recall that in an earlier thread I was getting suggestions of 11 to 12, and I was resistant to that high a number. I'm slowly coming to the same conclusion... That seems to be the reality of what she needs.

All comments appreciated...

[Ron AKA]

FYI: The S9 does not record events while in the ramp mode.  The lack of this knowledge may lead to false assumptions based on your data.

Very interesting. I did not know that. I went back over a month or so and found one OA event which looked like it occurred near the end of the ramp, but when I expanded the time scale it was right at the end. As the machine was originally set up I recall ramp was 20 minutes starting at 5 cm and ramping to 6 cm minimum. That does provide a window where an event could occur if one falls asleep quickly. Now I have it set a 10 minute ramp and ramping to 10 or so. Much less chance of an event in that window.

Out of curiosity do you know if the events are suppressed in the Auto ramp mode of the AirSense 10. It can extend out to as long as 30 minutes if you are slow going to sleep. That was the setting I planned to use on my machine when I get it.

[Sleeprider]

EPR has a functional benefit in reducing incidents of hypopnea. Other than that it is mostly for comfort and I think if you took a look at a closeup of the mask pressure graph you would understand that better. I really see not good reason to have it off in this case. As you note, her pressures are pretty high, and EPR makes that more tolerable, whether she complains or not.

The P10 uses a fine mesh diffuser that works well to quietly vent air. That mesh can be damaged by excessive moisture or cleaning contaminates. If you ever notice that venting seems impaired, those are the common culprits. Go easy on any scrubbing or use of soaps that do not fully rinse free, and be sure it has plenty of drying time before the next use. I rarely clean mine, and have no problems. You really don't have contact with the mask frame anyway, so it is the cushion that should get your cleaning attention. It will work just fine at your wife's pressure, just be sure to use the right size nasal pillow, and err on the side of larger than smaller.

[Ron AKA]

EPR has a functional benefit in reducing incidents of hypopnea. Other than that it is mostly for comfort and I think if you took a look at a closeup of the mask pressure graph you would understand that better.  I really see not good reason to have it off in this case.  As you note, her pressures are pretty high, and EPR makes that more tolerable, whether she complains or not.

Yes, I will return to testing EPR again after pressures are settled without it. I have been mulling over how OA actually occurs. To take an analogy of a garden hose, you have the pressure on one end of the hose which is like the mask pressure, and you have the pressure at the other end which would be the lung pressure. Then there is a pressure on the outside of the hose which is atmospheric pressure. It kind of acts like someone stepping on the hose. If you have an obstructive apnea when trying to inhale, mask pressure increasing and fighting against the foot on the hose tends to open the obstruction. I think that part is fairly straightforward. But things change a little when it is time to exhale and reverse the flow. The lung cavity has to be squashed down to increase the lung pressure to fight against both the guy's foot, and the mask pressure. The foot pressure never really changes for all practical purposes, but if the mask pressure is reduced with EPR, the pressure differential from lung to mask is increased, and should cause an increase in air flow. But at the same time the differential between the foot pressure and the air passage pressure in the areas susceptible to collapsing is reduced. This will tend introduce a restriction again. I guess the big question is whether or not the so called "air splint" effect of a CPAP is mainly the mask to lung pressure effect, or the mask to outside (guy's foot) effect. 

So my plan is to reintroduce the EPR and see what happens. My ongoing observation of the OA events is that most of the time she can inhale but not exhale, but that is not always the case. Less frequently she can exhale but not inhale. See the graph below, and you can see three consecutive events where inhale is possible, but no exhale. This suggests that the mask is winning against the foot pressure, but the lungs can't win against the mask pressure. In this case increased EPR should help. The second case is the opposite. It suggests there is not enough mask pressure to get air into the lungs.

I will be very interested in seeing how these events look with EPR compared to no EPR. My guess now is that EPR is going to help more than it hurts. Time will tell. 

I have not looked at the hypopnea events very closely yet. My quick looks are that flow is getting restricted in both inhale and exhale directions, but it is not blocked. It will be interesting to see how they are influenced by EPR too. If mask to lung delta P is most important they should be reduced (EPR on). If mask to foot on the hose delta P is more important then EPR could hurt as average delta P will go down.

I'm a retired mechanical engineer, and I find this stuff to be a fun project. Once "we are there" the fun factor will drop off and it will get boring again....

[Sleeprider]

Ron, another analogy that may be closer is to consider using a straw to suck a liquid from a container. Almost anyone can draw water through a straw into their mouth just like inspiration it takes some effort; and if you just hold the water in your mouth, it will flow back out through the straw as in passive expiration. As long as the straw provides an unobstructed channel that can occur easily. Now if we're using an old fashioned paper straw or one that is kinked, the negative pressure caused by sucking water into your mouth may collapse the straw, just like an apnea. Similarly, the straw might kink like what happens in positional apnea. Generally any water in your mouth (air in your lung) can still passively move through that straw, but sucking causes the straw to repeatedly collapse. This is analogous to to your airway. Now let's say you are drinking from a squeeze bottle and by squeezing the fluid you can re-open the straw allowing you to take in liquid again and it would expel with passive effort, because we're not really squeezing very hard . That is CPAP. If we squeeze and then release some pressure, we open the straw to take in fluid, and if we release that squeeze just a bit, the water is expelled even faster and easier, that's EPR.

On the OA events in that chart there is no expiratory flow, so I suspect that we are seeing a combination of flow limited inspiration (the inhale with a downward sloping end curve to zero) and no exhale. It would not surprise me if she is exhaling through her mouth there. Basically there can't be repeated inhales without an exhale, but in this case it is finding a different path.

[Ron AKA]

On the OA events in that chart there is no expiratory flow, so I suspect that we are seeing a combination of flow limited inspiration (the inhale with a downward sloping end curve to zero) and no exhale.  It would not surprise me if she is exhaling through her mouth there.   Basically there can't be repeated inhales without an exhale, but in this case it is finding a different path.

That could be the case. I will watch it further. 

The other interesting issue with CPAP and the pressures used is pressure loss due to flow resistance (other than the obstruction). I have read that the reason CPAP have a minimum pressure of 4 cm is because that is the estimated pressure loss due to flow restrictions in the mask and tubing. In other words a CPAP with a boost pressure of 4 cm just overcomes the pressure lost on inhale due to flow resistance. It should feel like there is no restriction in the mask etc. In actual fact masks and hoses are different and one may still feel some effect. However the issue is that on exhale the flow is in the opposite direction, and you are fighting the 4 cm boost, plus any flow resistance in your body airways. EPR helps reduce that effect but does not eliminate it. Strikes me that exhaling will always be more difficult than inhaling, unless you have a CPAP that can reverse and go negative in pressure - suck instead of blow. Perhaps that is what the ventilator models do?

[Sleeprider]

Exhaling is passive, even with relatively high CPAP pressures. People do not adapt to blow into their mask to exhale, rather the chest just naturally collapses in a relaxed state, and that is sufficient for most expiration. The "relative" difference in pressure between IPAP and EPAP can make that feel easier. It is the inspiratory effort that requires muscles to contract, particularly the tightening of the diaphragm, to impose a negative pressure on the lungs causing inspiration. That effort is made easier with CPAP pressure. Negative pressure is not even used in invasive ventilators.