pressure versus leaks

I have questions on how to interpret some of the information I am getting about pressure and leaks.

I am trying to figure out the chicken and egg question so far as pressure and leaks go. Which is cause and which is effect? I have read that increased pressure will result in increased leaks. Is it also true that increases in leaks will cause increase in pressure?

When I am aware of mask leaks at a particular time at night, I can see that the graph showed increased leaks, and at the same time line, I sometimes see the pressure has increased. Usually there are no obvious apnea or hypopnea lines that would have called for the pressure increases. If there were, then increased pressure to control them could show that increase of pressure equals increase in leaks. So, my question is - if my mask is leaking, will the machine compensate by increasing pressure to maintain what it thinks is airway restriction? I have only had the software record a single time of large leak, and there was no corresponding increase in pressure. Perhaps the machine can recognize a large leak for what it is and not increase the pressure. I do not appear to do any mouth-breathing.

Several people kindly explained flow limitation to me, so I have an understanding of the progression of flow limitation, to hypopnea to apnea. I am not sure how snoring relates to the progression, if at all. I think my numbers are pretty good for a beginner. For the last 20 days of data, my AHI averages 1.8, with a range of 0.5 to 3.4. Snoring average is 0.8. I have used different masks, so the leak numbers are hard to average. Pressure ranges from 8 to 13 for the 90% calculation with 10.2 cm as that average. The average pressure is 8.14cm. My PSG study said 13 cms for treatment, but they started me with a CPAP of 15 cm “just in case”. I am not really sure what all that tells me, but maybe someone can tell me what to look for to better interpret these numbers and improve my treatment.

Thanks in advance.
the Catnapper

You are off to a good start, many would be glad to trade success with you.

You are correct about the Chicken and the Egg, Although in most cases the Chicken (Leak), comes first, The leak lowers your real treatment pressure and events and snoring comes in. The machine tries to apply more treatment pressure, which causes even more leaks.

Like a dog, in the middle of the room, trying to catch it's tail. One solution is to lower the high end pressure to the lowest you need to keep a good AHI, there by letting the dog catch his tail. The other is to try different masks, maybe one will leak less.

It just takes extra work, and we never seem to get to the end of it. You are on the right track, Good Luck! Jim

If your mask is leaking, the machine will blow more air, so that the pressure it detects in the circuit remains steady, despite the leak.

I have no idea if, when the machine is blowing stronger, to supply enough pressure despite the leak, it will report the pressure as higher... or as the same, but with more of a leak.

Beyond a certain point, the leak becomes unmanageable, and then the machine reports nothing but that big leak.

A rise in pressure will always raise the vent leak rate, and consequently the reported leak rate - even if you seal is perfect. I believe those Australian company's machines - you know, those who limit internet sales - will report 0 leak rate if you tell them which kind of their own masks you're using, and they don't detect a leak above the vent leak rate.

O.

The sleep lab will titrate you for the worst scenario and give you that pressure. If you then use an autopap it may give you a much lower 90% pressure. If that 90% increases then it means it seen something that needed the higher pressure if still lower than your PSG titration I wouldn't worry about it. Your 90% can change if you change and sleep on your side or have a glass a wine with dinner or even allergies.

The higher your pressure goes the harder it will be to stop leaks, more noisy mask and machine will be. As long as the leak doesn't exceed the limitiation of the machine to deliver pressure you should be fine.

Comparing leaks: Your mask should have come with a flow chart. If you look up on that chart your 90% pressure you should find the flow rate or intentional leak rate in Litres per Minute (L/m). If the chart shows 30L/m at 10cm pressure then any report by your machine should be the same. If the machine says your leak rate is much higher, then that leak is external or leaking from the cushion-face contact or via hose.

Cats like to poke holes in the cpap hose with their claws.

Its not that easy for me to figure out even w/the flow chart that came w/my ComfortLite 2.

I have the Resemd S8 Elite (only because I didn't know about their new policy regarding online sales of their software and Reader). With the CL2 nasal pillows I use the Resmed's Swift setting. When using the CL2's nasal cushions I'm not sure which Resmed mask setting I should use.

It looks like (as near as I can read this CL2 chart) the nasal cushion has a 15 L/pm leakage at 6 cm pressure whilst the nasal pillows and the direct seal have a 20 L/pm leakage at 6 cm pressure.

I have looked at the leak chart that came with the CL 2 mask. The chart has a data point for each increase of 5 cm H2O with a line connecting the data points which are indicated by a diamond for the simple cushion and a square for the pillows and direct seal. It is a tiny graph that is not easy to read and with the way it is presented and its size, it is hard to get good information from it. The lines do not seem to represent data between the 5 cm markers.
At 5 cm, the SLPM for the cushion is maybe 8, at 10 - maybe 26, at 15 - maybe 32 and at 20 - maybe 38. I could make a graph based on those points. I probably don't need specific numbers anyway, just ball park numbers should do for the purpose. The cushion has lower SLPM than the other two types.

Thanks for the help. I worry too much.

Catnapper