[CPAP] How much extra O2 is too much?

[justMongo]

Because my PsaO2 levels were low throughout my sleep study, in addition to a BiLevel machine, my doc prescribed 2 LPM of O2 be injected into the CPAP flow from a concentrator.

He admonished me not to set the O2 levels too high.

From strictly an engineering standpoint I see good reason not to -- The O2 flow will raise pressure as needed to maintain flow (its maximum pressure to try to achieve flow compliance is 5 PSI = 310 cm-H2O). That fights a fixed pressure CPAP device that will try to set flow to maintain pressure. To an electrical engineer that's like connecting a constant current source to a constant voltage source.

I'm wondering if his admonition is in regard to equipment or to physiologic effects of an atmosphere too rich in O2.

Physiologic effects could be decreased RBC or ??????

In the hospital where they have more sophisticated machines, they set my O2 to 30% (compared to the approximate 20% O2 at sea level.)

Thoughts????

[vsheline]

Because my PsaO2 levels were low throughout my sleep study, in addition to a BiLevel machine, my doc prescribed 2 LPM of O2 be injected into the CPAP flow from a concentrator.

He admonished me not to set the O2 levels too high.

… I'm wondering if his admonition is in regard to equipment or to physiologic effects of an atmosphere too rich in O2.

Hi justMongo,

Too much O2 in the blood can create problems -- more oxidation, more free radicals, can render prescription medications ineffective, things like that. At many hospitals they are careful not to give too much O2 to patients nowadays, because of the problems too much O2 was causing years ago.

If you are using O2 nightly then I would recommend wearing occasionally a recording pulse oximeter (like perhaps weekly, and also whenever you are sick or changing medications), so you can see (and keep your doctor informed) what your O2 levels are throughout the night.

This year one member of Apnea Board reported she was able to get her insurance to pay for a prescribed Pulse Oximeter setup for her ResMed S9 machine. But I've heard most insurance companies do not cover it unless there is a special reason, so most people will need to pay out of pocket, so we buy more economical ones, such as are available from Supplier 19 on our Supplier List. You won't need a prescription to buy one, unless insurance is paying for it.

Since you are actually on O2 therapy, I think your insurance should cover a prescribed oximeter. I suggest starting by giving your doctor the exact description: "ResMed S9 Complete Oximetry Kit" (in the USA this would be ResMed product code 369100). If insurance coverage is denied I suggest appealing the denial. Be sure to get your insurance to pre-authorize it before buying, because it is about $1,400 if buying the ResMed kit.

I use a wrist-mounted Pulse Oximeter, because it can be worn more loosely and more comfortably all night, than one where the whole thing (including batteries and display) clips onto the finger. I have very sensitive skin.

Regarding what would be a good target range for SpO2, perhaps 94% to 96%, according to the article linked below, but when we are asleep, I would think it would be okay to go down to 90% or so. 88%, even if asleep, is widely considered too low.

The following is is a quote from the article linked below.

"… administer oxygen to keep saturations between 94 and 96 percent. No patient needs oxygen saturations above 97 percent and in truth, there is little to no evidence suggesting any clinical benefit of oxygen saturations above 90 percent in any patient."

http://www.ems1.com/columnists/mike-mcev...ygen-hurt/

About the author: Mike McEvoy, PhD, REMT-P, RN, CCRN is the EMS Coordinator for Saratoga County, New York, a paramedic for Clifton Park-Halfmoon Ambulance, and Chief Medical Officer for West Crescent Fire Department. He is a clinical specialist in cardiac surgery and teaches critical care medicine at Albany Medical College. Mike is the EMS editor for Fire Engineering magazine, a popular speaker at EMS, fire, and medical conferences, and lead editor of the Jones & Bartlett textbook, "Critical Care Transport".

[justMongo]

My VPAP S is an S8 machine -- so, I doubt the kit for an S9 would be usable. I could get a wrist recording PsaO2 meter. I do have a spot check meter; and I run around 90% awake off O2. I'm only prescribed O2 as an adjunct to xPAP -- however, I'm sitting here now with a nasal cannula at 4 LPM and I am at 95%. Since I'm not feeling well, I tried the cannula; and I feel better.

Part of my O2 sat problem is Pickwickian -- the rest is cardiac. My LV EF is 50%. I'm likely at the end of the Frank-Starling cardiac effect.

[vsheline]

My VPAP S is an S8 machine -- so, I doubt the kit for an S9 would be usable. I could get a wrist recording PsaO2 meter. I do have a spot check meter; and I run around 90% awake off O2. I'm only prescribed O2 as an adjunct to xPAP -- however, I'm sitting here now with a nasal cannula at 4 LPM and I am at 95%. Since I'm not feeling well, I tried the cannula; and I feel better.

Part of my O2 sat problem is Pickwickian -- the rest is cardiac. My LV EF is 50%. I'm likely at the end of the Frank-Starling cardiac effect.

Hi justMongo,

What types data are you managing to get from your machine?

Do you have the custom "Smart Card" reader for the S8 series proprietary data cards?

Left ventricular ejection fraction (LVEF) is the measurement of how much blood is being pumped out of the left ventricle of the heart (the main pumping chamber) with each contraction.

Ejection Fraction Measurement, What it Means
55-70%, Normal
40-55%, Below Normal
Less than 40%, May confirm diagnosis of heart failure
<35%, Patient may be at risk of life-threatening irregular heartbeats

I think low LVEF is associated with Periodic Breathing and Cheyne-Stokes Respiration. It would be good for you to be using a machine which can monitor central apneas and can handle CSR, if you need it. An Adaptive Servo Ventilator (ASV) machine can do this.

Personally, I feel (and function) way better since getting an ASV machine.

I suggest asking your doctor(s) for an ASV titration to see if you would benefit from an ASV machine. (Hey, look, we don't know whether they would eventually say "yes" until you ask them and are persistent.) Your condition may warrant a modern ASV, but you may need to be persistent to get the therapy you need.

The Philips Respironics System One BiPAP Auto would be a step up from your present machine. It would automatically (but slowly) adjust EPAP to avoid obstructive events, and automatically (but very slowly) adjust Pressure Support (IPAP) to further reduce obstructive Flow Limitation. And you can get full data reports of every breath during the night, without needing a proprietary card reader. And it would report (but do nothing to treat) central events.

Alternatively, the S9 VPAP ST-A would be a bigger step up from your present machine and may be easier to adjust to than an ASV machine, since its automatic adjustments to Pressure Support (or IPAP) are more gradual, but (like your present machine) the S9 VPAP ST-A does not automatically adjust the EPAP pressure, so someone will need to monitor the data to see whether the EPAP needs to be manually adjusted to better avoid obstructive events. It will automatically start assisting you by using a backup breathing rate during (what would have become) central events, and will automatically adjust (and fairly quickly, in just a few breaths) the Pressure Support (IPAP) to treat central events.

But the true ASV machines are the Philips Respironics System One BiPAP autoSV Advanced and the ResMed S9 VPAP Adapt. These ASV machines automatically (but slowly) adjust EPAP to avoid obstructive events, and automatically (and nearly instantaneously, from min to max in a single breath if needed) adjust Pressure Support (IPAP) to intervene and prevent central events.

Take care,
--- Vaughn

[justMongo]

Hi justMongo,

What types data are you managing to get from your machine?

Do you have the custom "Smart Card" reader for the S8 series proprietary data cards?

Left ventricular ejection fraction (LVEF) is the measurement of how much blood is being pumped out of the left ventricle of the heart (the main pumping chamber) with each contraction.

Ejection Fraction Measurement, What it Means
55-70%, Normal
40-55%, Below Normal
Less than 40%, May confirm diagnosis of heart failure
<35%, Patient may be at risk of life-threatening irregular heartbeats

I think low LVEF is associated with Periodic Breathing and Cheyne-Stokes Respiration. It would be good for you to be using a machine which can monitor central apneas and can handle CSR, if you need it. An Adaptive Servo Ventilator (ASV) machine can do this.

Personally, I feel (and function) way better since getting an ASV machine.

I suggest asking your doctor(s) for an ASV titration to see if you would benefit from an ASV machine. (Hey, look, we don't know whether they would eventually say "yes" until you ask them and are persistent.) Your condition may warrant a modern ASV, but you may need to be persistent to get the therapy you need.

The Philips Respironics System One BiPAP Auto would be a step up from your present machine. It would automatically (but slowly) adjust EPAP to avoid obstructive events, and automatically (but very slowly) adjust Pressure Support (IPAP) to further reduce obstructive Flow Limitation. And you can get full data reports of every breath during the night, without needing a proprietary card reader. And it would report (but do nothing to treat) central events.

Alternatively, the S9 VPAP ST-A would be a bigger step up from your present machine and may be easier to adjust to than an ASV machine, since its automatic adjustments to Pressure Support (or IPAP) are more gradual, but (like your present machine) the S9 VPAP ST-A does not automatically adjust the EPAP pressure, so someone will need to monitor the data to see whether the EPAP needs to be manually adjusted to better avoid obstructive events. It will automatically start assisting you by using a backup breathing rate during (what would have become) central events, and will automatically adjust (and fairly quickly, in just a few breaths) the Pressure Support (IPAP) to treat central events.

But the true ASV machines are the Philips Respironics System One BiPAP autoSV Advanced and the ResMed S9 VPAP Adapt. These ASV machines automatically (but slowly) adjust EPAP to avoid obstructive events, and automatically (and nearly instantaneously, from min to max in a single breath if needed) adjust Pressure Support (IPAP) to intervene and prevent central events.

Take care,
--- Vaughn

I have an S8 card reader and data card. I could not pull data from the machine. So, I looked in the results menu of the S8 and I have an acceptable AHI and AI. During my initial CPAP titration, central apnea was not seen.

I had a recent echocardiogram which estimated my LVEF at 50%. The study was technically difficult due to my weight.

But, I've not been feeling at all well -- so, my heart may be having problems. I do have a benign arrhythmia -- periodic PVCs. Just had a 24 hour Holter Monitor; and am awaiting results.

I cancelled a nuclear imaging study of the heart on 20 December.
I don't think I fit behind the camera any longer. That study also involves artificial stimulation of the heart with Lexiscan (used to be adenosine.)

[archangle]

From strictly an engineering standpoint I see good reason not to -- The O2 flow will raise pressure as needed to maintain flow (its maximum pressure to try to achieve flow compliance is 5 PSI = 310 cm-H2O). That fights a fixed pressure CPAP device that will try to set flow to maintain pressure. To an electrical engineer that's like connecting a constant current source to a constant voltage source.

If your O2 supply is connected correctly, there will be no pressure problems. The O2 will function to always blow x l/m of extra O2 into the mask, and the CPAP will keep the pressure at y cmH2O, even if that means air goes up the hose and out the back of the machine.

The CPAP airflow will dilute the level of O2 you breathe vs. the same rate of O2 without CPAP. Some doctors don't seem to realize this.

Be sure the setup is done right to avoid fire risks. For instance, you need to turn the O2 off before turning the CPAP off.