Pressure With Oxygen

I've been wondering if added O2 at 2 liters has any effect on pressures CAs,OAs? It's occurred to me that might be why Mike's data seems to be more erratic these days, sometimes his usual AHI 2-2.5 and then up to 5-6 some nights with higher CAs. Leaks are minimal. Does additional oxygen have something to do with breathing patterns and do adjustments have to be made accordingly? Thanks.

You keep the XPAP pressure the same. Can it cause changes, everything you do can cause changes, that doesn't mean that changes are bad, just different. If you do nothing, you will still have changes. Only with a pacemaker and iron lung will things remain the same. Jim

Even then you will have changes, life is changes!

Hi Dori,
I don't know it the added oxygen changes the pressure at all - I doubt it. However, even if it does so, the machines are built to supply constant pressure - even though the pressure if the mask / hose varies - as it migh - due to leaks, changes in inhalation etc. In other words, I doubt very much slight change caused by the added of 2 L oxygen necessitates a manual pressure tweak.

That said there may be other reasons for a change in Mike's AHI pattern -- if indeed it is a change.

1. There was a reason Mike was given extra oxygen. Was his breathing pattern truly stable, when this issue cropped up, and did it change only when oxygen was added? Could it be that the present change is related to whatever made oxygen necessary, and not to the oxygen itself?

2. I can also imagine added oxygen changing a person's breathing pattern because it effects gas exchange / blood oxygenation, etc. Did he have a sleep study with CPAP and oxygen? Do you have systematic (numerical, night by night) data for the time periods you're wondering about?

Hi Ozji, you're posing some good questions that I'm still thinking about. He had 3 episodes of unconciousness, one while eating breakfast, one at midnight while sleeping, one in the rehab when he couldn't be aroused in the morning. I don't think anyone's absolutely sure of what caused them, but his pressure and pulse were almost absent and he was dehydrated. One test showed Afib during a 24/hr period but never showed up again in any further testing. His BP med was changed and RNs made notes that his breathing was "erratic" during the night a few times but otherwise he did well for 6wks of treatment except for that one rehab incidence. Cpap therapy in rehab was a nightmare because the nurses didn't have a clue about mask fitting, leaking,etc. It was ME who suggested supplemental oxygen because of my instinct and because I wouldn't bring Mike home without some reassurance that oxygen might prevent those episodes again. The Drs went along with me but I'm not sure if that was their conclusion too or if they believed "it couldn't hurt". He did well after I brought him home and settled his therapy but lately he's more restless, AHI's higher and since I'm trying him on PR S1 again his RERAs are very high, last night 11.4. I've been trying different settings, auto and straight, probably not giving each setting enough time, I know, I know... He's feeling OK, no deterioration, good vitals,etc. I may have to bug Pugsy again with an email of his PR reports. RERAs were an eye opener because S9 doesn't show them. I've got to go now but if I think of anything else that's pertinent, I'll post later. Thanks.

The O2 will change the pressure by a small amount 2L/min with an average leak of 20L/min means the pressure from the O2 could be at most 10% higher (at very low pressures).

A bigger concern is that the assumption that 2L /min O2 is fine for someone off CPAP works the same as O2 being added to the normal flow. 2L/min into a cannula is much different than 2L/min into an injection port of a CPAP hose because of leak rates which makes the same flow rate less effective with the CPAP machine. I can take the leak rates and flow rates and figure out how to get the same as 2L/min but that just tries to get you back to a guesstimate. Use an SpO2 sensor and run the O2 at the rate where it gets as close to 99 as you can get it. You could go for 100% but you can't reach 101% so its wasting O2 so the goal is 99.9 or whatever the 2nd highest rating your o2 device will give.

cpap is very low psi pressure but higher volume. o2 is higher pressure, but real low volume. if it wasn't higher pressure it wouldn't be able to force its way ino the pressurized cpap system. but with the very low volume it doesn't change the cpap pressure of if it does it would be very very minor and of no consequence. 2L of o2 is a volume, not pressure measurement. 4 - 20 cm/h2o is a pressure, not volume measurement. it's somewhat like comparing apples to oranges.

if you use cannulas in the nose without cpap you're not neccessarily getting the full 2 liters in an hour because it is constant and the cannulas are not sealed to the nose. so mask leaks if the o2 is inserted in the hose system won't matter as far as total o2 you're getting. this is why the o2 shouldn't really be inserted at the mask where it is concentrated and can run out the vent or tend to lose more in leaks.

both home pulse oximeters and home o2 generators have top limits and +/- error ranges so i personally don't see using a pulse oximeter to fool with the o2 setting as a good idea. discuss this with the doctor if you feel a need to raise or lower anything. my bet is he'll say leave it alone. raising above 2L can be bad for certain conditions.

my wife is currently on o2 with cpap. i previously was on 02 at night when i was between cpap and a new apap. when my wife went on 02 we saw no difference in cpap statistics. of course there was a big change in the SPO2 program.

just my opinions. others have different opinions.

-tim wrote:The O2 will change the pressure by a small amount 2L/min with an average leak of 20L/min means the pressure from the O2 could be at most 10% higher (at very low pressures).

A bigger concern is that the assumption that 2L /min O2 is fine for someone off CPAP works the same as O2 being added to the normal flow. 2L/min into a cannula is much different than 2L/min into an injection port of a CPAP hose because of leak rates which makes the same flow rate less effective with the CPAP machine. I can take the leak rates and flow rates and figure out how to get the same as 2L/min but that just tries to get you back to a guesstimate. Use an SpO2 sensor and run the O2 at the rate where it gets as close to 99 as you can get it. You could go for 100% but you can't reach 101% so its wasting O2 so the goal is 99.9 or whatever the 2nd highest rating your o2 device will give.

Faulty reasoning, the XPAP will control the pressure, that is what it does.... Jim
Not that it would matter. The second paragraph is true, the leak rate will cut down the value of the O2 that's added at night

From a mechanical airflow standpoint, I wouldn't expect the O2 to affect the CPAP pressure significantly, given the way it's mixed into the airflow.

The CPAP will probably affect the amount of oxygen he's getting because it mixes normal air in with the O2. Presumably whoever prescribed the O2 knows he's on CPAP and prescribed appropriate settings.

The oxygen should affect his blood O2 levels and his nervous system and lungs will probably breathe differently in response.

Would you be able to surmise in which way differently?

DoriC wrote:Would you be able to surmise in which way differently?

I'm thinking that with O2, his blood O2 may be better and he may not "fight" so hard against the apnea. He might show a higher AHI, lower breathing rate, minute vent, etc. This wouldn't necessarily be harmful to his health if his O2 levels stay good. If the O2 level is higher, you don't have to breathe as often.

It seems that if the O2 is twice as high, you only have to breath half as much. I would expect you to breathe a little less.

Try this. Hold your breath for a while during normal breathing until you get comfortable. Then breathe heavily for a while until you hyperventilate and get a bit dizzy and then hold your breath. You'll probably last a longer time after hyperventilating because your blood O2 is higher.

There are also a number of feedback mechanisms in your breathing that can cause things to change in unexpected ways, especially temporarily.

In general, I would expect O2 to be good for his health, even though it might change the AHI numbers slightly for the worse.

That's just my thought process. I have no practical experience with AHI vs. oxygen, but I would say not to panic if the numbers change a little.

Have you looked at his waveform data and seen how long and how deep his apneas are? I don't remember what kind of machine Mike has.

DoriC wrote:I've been wondering if added O2 at 2 liters has any effect on pressures CAs,OAs? It's occurred to me that might be why Mike's data seems to be more erratic these days, sometimes his usual AHI 2-2.5 and then up to 5-6 some nights with higher CAs. Leaks are minimal. Does additional oxygen have something to do with breathing patterns and do adjustments have to be made accordingly? Thanks.

Hi DoriC,

First of all, I have never used O2 with PAP.

I do know that at my pressure of 15 cm/H2O my basic leak rate is 27 liters per minute (lpm). The leak rate is what keeps me supplied with fresh air rather than re-breathing my own air. The machine, if memory serves, is able to deliver up to 150 lpm and if I am doing well I will only use about 6 lpm that I actually breath. During a breath the instantaneous flow may rise to about 60 lpm (rare!). I guess what I am leading up to is that 2 lpm is not a lot in this environment and I am suspicious that it must be added after the lossy system bleed (where the air comes out just before air enters the mask). If they added it to the stream before that it would be 2 lpm diluted by the leak rate of at least 20 lpm (10 to 1 or so) and would have little effect.

I would expect adding 2 lpm O2 to the system to have negligible effects on pressure.

In the research I have read O2 enrichment tends to quiet CAs. If CAs do not happen in a case where CAs and OAs tend to be mixed (breathing instability) then there will likely be less OAs as well. OAs and the lead up to CAs tend to feed off one another.

Lets say we are doing ok but then have an OA. This will likely increase the over all breathing rate due to the stress hormones released. The increased breathing tends to wash out CO2 which, along with the stress hormones, tends to reduce circulation including to the brain. The thinking these days is that the stress hormones and resultant shutdown of extremity circulation moves fluid toward the head (rostral fluid shift) and along with the extra air making the airway passage irritated another OA occurs, of greater severity. The cycle repeats until the high breathing rates are enough to result in a CA.

Anything that you can do to help reduce his stress levels is likely to help.

May we find good health!

Todzo

Thanks for everyone's input(except for liters,percentages,etc. ). I'm understanding a little better now. My sonThe Dr mentioned that we breathe in about 4 liters of oxygen with every breath normally and more if we're exerting, so 2L added is extremely minimal but he's not sure what difference the cpap would make ( I'm not sure I heard everything correctly, bad phone connection). Our own Dr is very comfortable with the RX. Todzo, you mentioned stress and I notice that when Mike fixates on something to worry about, like not hearing from a favorite nephew for awhile,which happened recently, and I compare those nights with the data ,I begin to see an erractic pattern that develops which then causes me concern. He doesn't verbalize his angst or stress very much but there seems to be a connection. I'll certainly watch for that, thanks.
Arch, I did your experiment, you're right about being able to hold my breath longer the 2nd time and thanks for the headache!!

I plead ignorance, but i do have an oxygen concentrator, and i have used it occasionally with pap.

Im just wondering why the level would be set so low? Especially, as has been pointed out, your already losing some if it
through leak.

My completely inexpert opinion is that a level of 2 isnt going to have much effect beyond placebo reasoning.

DavidCarolina wrote:I plead ignorance, but i do have an oxygen concentrator, and i have used it occasionally with pap.

Im just wondering why the level would be set so low? Especially, as has been pointed out, your already losing some if it
through leak.

My completely inexpert opinion is that a level of 2 isnt going to have much effect beyond placebo reasoning.

My thoughts exactly, that's why I ignored my Dr and reset mine to 4L.
Thank goodness, my teacher's taught me how things really work. Jim

DavidCarolina wrote:I plead ignorance, but i do have an oxygen concentrator, and i have used it occasionally with pap.

Im just wondering why the level would be set so low? Especially, as has been pointed out, your already losing some if it
through leak.

My completely inexpert opinion is that a level of 2 isnt going to have much effect beyond placebo reasoning.

A typical flow rate for a CPAP machine would be 30 L/m. Air is about 20% O2, so this is 6 L/m of O2 in the incoming unsupplemented air. Adding 2 L/m of pure O2 increases the O2 by about 1/4. It would go from about 20% O2 to 26% O2.

The flow rate (leak rate for the mask) varies considerably with CPAP pressure and mask type, so this is just an example.