spO2 and AHI

[drmaestro]

Hi,

Can we say that spO2 is the ultimate parameter to prove that CPAP therapy is working? I am asking this question because, some nights I have a relatively high AHI (around 3-4), however my saturations were stable around 92-95%, so technically even if I had obstructive and/or central events, they didn't affect my oxygenation. Of course, I assume that I haven't been woken up constantly, which would probably ensure a higher saturation due to breathing consciously. The reverse can also be true: Low AHI but lots of desaturations would mean something went wrong or the device couldn't effectively tag events (considering there are no additional diseases like heart or lung disease which would affect saturation). 

The question can also be asked as follows: If you had lots of mask or mouth leaks but your saturations were normal, does it prove you are doing fine OSA/CSA wise and the leaks are probably not affecting the therapy?

Thanks...

[SarcasticDave94]

I do think you could build a case for SpO₂ being a better parameter of measurement. I also can see all the docs and RTs balking at change like this.

Going along with this thought, should we consider a way to measure sleep disruptions/arousals and give these a higher consideration?

On the leak/desat question: maybe yes but maybe no. It may prove nothing, because on any given night I'd think you can have lots of leaks and have low events. You can also reverse that, having low leaks and high events. And this could be just proof that event counts can be variable from one night to the next. Personally, I think leaks above the manufacturer of the CPAP machine threshold can skew data results, making it unreliable. I know there is a certain level of leak expected, because the air must vent out. Beyond that value, I think it lowers therapy efficiency.

[Sleeprider]

I think looking at SpO2 is a starting point, but the measure of success is to eliminate sleep disordered breathing in its many forms to enable a good night of sleep without respiratory event disruptions. Do that and SpO2 should follow, but looking at SpO2 alone is over-simplified and does not account for individuals that do not maintain good oxygen levels in spite of normal respiration, or those that may not experience desaturation in spite of events.

A low number of events, even absent desaturation is not a measure of good therapy. As you point out, leaks and disruptions from the therapy may result in very poor sleep. We see people that are intolerant of pressure fluctuations in CPAP or even ASV that have very low RDI, but poor sleep quality. So SpO2 is simply a metric, but is not the measure of effective therapy which is the sum of many factors.

[optimalsleep]

94 to 96% SP02 during Rem sleep is an important factor..... but effective therapy included would be the whole night.

As Sleeprider mentioned alot of other factors are involved. ASV if needed would manage OA and CA....during REM sleep stages and would maintain SP02 during the time it's needed. AHI, even low you could still have an event an hour... after 6- 8 hours of sleep, CA's wouldn't be good.

[fejsbukpejdz]

Before I got Dreamstation APAP, my brother used to pull my mandible forward so that my anxiety attacks at night do not kick in...

Guess what? My O2 was okay...

He woke me up often that way tough lol...

so when I enter good nice deep sleep, I nticed my o2 are dipping more.

So... hmm..

I do not think O2 is an appropriate measure of your sleep.

A good cluster of Obstructives will knock you out of your deep sleep and then you will have good O2 saturation maybe for some time.

Not a perfect indicator of how good or bad was your sleep

[Geer1]

SpO2 is good but only tells part of the story.

Simply put you have to look at the whole picture, no single statistic will ever tell you if treatment is effective or ideal.

Sleep apnea causes two main issues. Low oxygen and sleep disruption. You can check oxygen by SPO2 but checking sleep disruption is harder. A PSG can monitor arousals but obviously that isn't a realistic way of determining if treatment is effective (although a good titration study can be helpful for some). The easiest way to determine effective CPAP settings is a slow arduous process of adjusting settings/equipment and monitoring as much data and how you feel and drawing conclusions on what settings/equipment work best for you. You cant draw conclusions on the numbers but you can draw conclusions by comparing them, in other words your ideal treatment might still result in an ahi of 4 but you wont know that without trying different settings to see what makes this better or worse. Your ahi of 4 may affect you the same way that ahi of 1 or 10 may affect someone else.

Mouth leaks can be signs of ineffective treatment. Many providers sell people on nasal masks because they are for the most part the most comfortable but there are people with nasal congestion etc that have issues with these masks and once you start mouth breathing to compensate your treatment isn't as effective as pressure is not maintained in the airway.

I went through this myself, for whatever reason my mouth breathing was getting worse until I finally broke down and bought a full face mask. It made a noticeable difference on my treatment and I doubt I will ever go back to a nasal mask (unless cause of mouth breathing can be remedied). I actually like the full face mask better, it requires some tight straps and is a bit more intrusive then a small nasal mask but it is far quieter, significantly better venting system and I think the extra humidity helps as well(if I use too much humidity with nasal mask it causes congestion and then mouth breathing but at lower humidity I have issues with dry mouth and throat). On some people a full face mask doesnt help or may make things worse though, no one is the same and only way to find ideal settings/equipment is to try them out.

Back to SPO2, my sleep doctor has stated that my lower nocturnal SPO2 could be a sign of inadequate treatment (nocturnal SPO2 around 1.5-2% lower than awake SPO2) even though I dont have many desaturations. This lower SPO2 is considered just below normal so most wouldnt consider it an issue but it was curious for doctor to say it could be. I havent found a way to increase nocturnal SPO2 to see if that remedies some of sleep/health issues though.

[Gideon]

I havent found a way to increase nocturnal SPO2 to see if that remedies some of sleep/health issues though.

That would be to increase Pressure Support or add an oxygen bleed.

[hegel]

if you're maintaining a high oxygen level by constantly being aroused out of rem sleep in order to catch your breath...that's an issue. 

On nights when I sleep particularly soundly, with lots of rem dreams. my ahi is often higher. But not through the roof. I'll take a higher ahi in exchange for sound sleep anytime.

[Geer1]

I havent found a way to increase nocturnal SPO2 to see if that remedies some of sleep/health issues though.

That would be to increase Pressure Support or add an oxygen bleed.

Yeah that is one of the potential next steps. Been letting the full face mask work for a while and on a wait list for sleep/titration study. If that isn't available soon doctor is willing to do a bipap trial so can try higher PS. 

My SPO2 still always stays decent (rarely under 90%) so low on my priorities. According to doctor nocturnal SPO2 should be same/similar to awake SPO2 though.

I have a feeling it is related to how my nasal congestion etc all get worse at night.

[sleepyp]

I've found that SPO2 sensors are prone to giving erroneous error readings. For example a desaturation score may be given if you're sleeping on the arm where the measurement is being taken.
SPO2 is another good indicator to be used in conjunction with RDI, and maybe sleep tracker detail. The most important measure is how you feel.