Oximetry, synchronization with CPAP results

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Oximetry, synchronization with CPAP results

Postby am0665 » Fri Mar 04, 2011 4:47 pm

For those of you with a more than average interest in the sleep apnea with home data analysis, I'd like to launch a review of using oximetry data.

1. oximetry as a measure of sleep disordered breathing
The basic assumption is that oxygen desaturation is not good. Not just in connection with apneic events closing off the upper airways, but also hypopneas reducing O2 saturation by more than 4%. I see my and other people's PSG studies and home oximetry report ave O2 and lowest O2, but have no good indication of how much cumulative desaturation (or what measures of the time distribution) are considered pathological.

2. oximetry and saturation level are just one indicator of sleep disordered breathing; apnea events are a 2nd indicator, sleep fragmentation a 3rd. They aren't necessarily correlated: I hear of high AHI without O2 problems, low AHI with O2 desaturations and fragmented sleep , etc.

3. on-CPAP vs off-CPAP oximetry: generally CPAP blows air into the lungs, so that should provide more O2. Still, I'd like to see a good guideline for on-CPAP results; and a correlation to sleep fragmentation

4. how does one get around the tyranny of receiving sloppy and useless automatic printouts from a nightly report, reducing the data to 2-3 numbers (Sao2 mean and lowest %saturation)? Upon requesting more, I got the raw plots: time scale resolution is 1”/hr; the vertical resolution is 2” per 50% saturation, so a 4% desat or an apnea-related desat are hard to notice; the full night statistics didn't separate on- from off-CPAP results.

After searching the forum, here are a few random quotes (hopefully not taken out of context):

- Todzo: "home testing helped me to see that AHI 7/h measured by my CPAP machine was the tip of an iceberg of awakenings. The pulse oximetery confirmed the AHI"
- Mrs Rip Van Winkle: "oximetry should be standard with the home equipment....integrated into it"
- Sharppointy1: "in home pulse oximetry showed my sats for the night <90 90%, <88 75% of the time... So I have been sleeping with 2 liters of oxygen for 2 weeks now."
- Janknitz: "something was not right. I didn't do an overnight oximetry during that episode: it might have shown some de-sats even though my AHI's were good"
- Beerman:
"StarDust Home Sleep Test results: ... Oximetry distribution = < 95% 332.5 < 90% = 5.5 Total Duration <97 = 483 ... Lowest
SpO2 (>2 sec)= 84 # Episodes (> 5min) <88% 0 Longest dur (min) SpO2 <88% = 0.4 Can somebody translate this?"
- mahen56: "Resmed ApneaLink Plus results:... Ave O2 sat 93%, lowest 83% once, O2 ave 95% lowest desat 76%,
Why does this lowest desaturation event up to 83% occur even with CPAP ? Is this a clinically significant to seek an opinion ?
I wake up sometime with my heart rate increasing 100 and sometimes scary very unstable feeling, subsides in next 2-3 min..."
- CrohnieToo: "I have Resmed VPAP Auto + S8 ResLink for oximetry data... not compatible w/the S9s."
Moderate / Severe OSA (2 tests offCPAP).
CPAP ResMed S9 AutoSet EPR, Hi5 Humidifier.
ResMed Masks tried: nasal pillows Swift FX, nasal mask Mirage Activa LT, FF mask Mirage Quattro or FX.
Home CPAP data analysis: ResScan 3.16 sw, oximeter, pulsemeter
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Postby Vicki » Fri Mar 04, 2011 5:35 pm

1. How much one desaturates is dependant on several factors such as the length of apneas, the frequency of apneas and the residual volume of air left in the lungs during an apneic event. This comes from personal communications I had with one of the ASAA board members who is a prominent physician in the field of OSA and who also said OSA should be followed by AHI not pulse-oximetry.

2. If you have normal lung function and your airway is open, then you will not desaturate. Therefore, AHI is the primary indicator of an apneic event, not the secondary indicator which may be, depending on the individual, O2Sat. People who have a low O2Sat and an AHI below 5 generally have primary lung dysfunction (COPD, asthma, etc.) and received supplemental O2 along with their CPAP therapy.

3. I personally know people whose OSA was missed as a diagnosis because they did not desaturate.

Vicki
Being defeated is often a temporary condition. Giving up is what makes it permanent.
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That which does not kill you makes you stronger-Friedrich Nietzsche
Friedrich must of had apnea.
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Postby Daniel » Fri Mar 04, 2011 5:40 pm

Based on your questions/findings, I think you might misunderstand SAHS.

Apnoea events do not necessarily bring about desaturations (ie not everyone with SAHS desaturates).
Hypopnoeas (to be identified) require a desaturation of 4% or greater.

Associated with the condition are RERAs, Spontaneous arousals, limb movements.......all of which have a great input to our sleep architecture.

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Postby am0665 » Sun Mar 06, 2011 12:12 am

Thank you Vicki and Daniel for your comments. Before I get misunderstood and criticized on my concepts: let me admit being on a learning curve of this multi-faceted issue. My forum strategy: thought I’d pose the problem, raise interest, and start the ball rolling with a few questions and forum quotes; hope to see those farther along pitch in, building up a knowledge base.
I am concerned with the high variability in my results from one night to another; getting better sleep off-CPAP than on-CPAP, I am more concerned with the consequence of my hidden desats than with my visible AHIs.

Let me also fence in the topic of interest: say we restrict our attention to Sleep Related Breathing Disorders ... of which Obstructive Sleep Apnea is a significant, but not the only symptom… and AHI not the only measure. At this first stage it may be helpful to stay with upper airway dysfunction, leave out O2 / CO2 disorders caused by other cardio-respiratory, cerebro-vascular, or metabolic disorders.
Daniel wrote: Apnoea events do not necessarily bring about desaturations (ie not everyone with SAHS desaturates). Hypopnoeas require a desaturation of 4% or greater. Associated with the condition are RERAs, Spontaneous arousals, limb movements.......all of which have a great input to our sleep architecture.

I agree. Desaturations show up mainly in my off-CPAP time records as oscillatory phenomena barely lagging the apnea cycles. The way I see it, irregularities in the air flow are easiest to measure... while arterial O2 desaturations are a possibly more severe measure, further along the path from external symptom to internal effect on O2 supply to the heart & brain.
We can also include subjective measures of sleep fragmentation and of cumulative sleep achieved.

In the expert literature I see some biomedical engineering experts propose advanced signal processing techniques used in cardiac and other applications ... whereby they see a smooth transition in statistical output over breathing events lasting any duration, linked to airflow from partial reduction (hypopnea) to full blockage (apnea), and can also get cumulative measures ... not just a sleep tech or sw program clicking when an apnea reaches 10 sec duration or a saturation dips by 4%.
Another aspect to include above: which additional home pulse oximetry device and under what home use conditions are covered by insurance.
[edited with a few clarifications]
Last edited by am0665 on Sun Mar 06, 2011 1:14 pm, edited 1 time in total.
Moderate / Severe OSA (2 tests offCPAP).
CPAP ResMed S9 AutoSet EPR, Hi5 Humidifier.
ResMed Masks tried: nasal pillows Swift FX, nasal mask Mirage Activa LT, FF mask Mirage Quattro or FX.
Home CPAP data analysis: ResScan 3.16 sw, oximeter, pulsemeter
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Postby CrohnieToo » Sun Mar 06, 2011 2:57 am

Keep in mind one can "desaturate" w/o reaching the level of needing 02 supplementation, i.e. 98% down to 93% which would register as an apnea or hypopnea if they last long enough. The question then becomes did that 98% to 93% desaturdation cause an "arousal" or disturbance of sleep?

Insurances do not cover home pulse oximeter purchases. Most insurances will cover an occasional night of rented overnight oximeter use.
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Postby Mrs Rip Van Winkle » Mon Mar 14, 2011 9:07 pm

- Mrs Rip Van Winkle: "oximetry should be standard with the home equipment....integrated into it"


I have not taken full time to read through your post or the replies....however I want to clarify here what I meant when posting this. It was in response to a thread asking what would be the ideal xPAP or what the ideal xpap would have. In the present thread(this thread) and without the the text of the thread I posted this in, I do feel it appears out of context....I was NOT commenting on desat nor oximetry testing needs....it was simply stating that it would be nice to have Oximetry testing integrated into the xpap...would be easy enough to do and have at a minimal cost.

Funny how words taken out of a general subject and placed into another thought mean different things...... all's cool though.
I'm only a sufferer, not a medical pro. What I post are my thoughts as a sufferer, not that of the ASAA. As a moderator on these forums I oversee the posting rules. This is the internet, always discuss what you read with your medical team.
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Postby am0665 » Tue Mar 15, 2011 12:14 am

Thanks for all the comments. I certainly didn't mean to put Oximetry up as competitor to Apnea indicators. I consider them both measuring certain aspects of the breathing disorder, and:
- sometime overlapping in their function, like when I see my apneas being followed within a few seconds by O2 saturation dips
- sometime complementary in their function
- and sometime neither measure providing a good indication of what is going on: like currently for my CPAP-induced nasal congestion, or in the case of non-apneic events creating sleep fragmentation

Mrs Rip Van Winkle wrote:I was NOT commenting on desat nor oximetry testing needs....it was simply stating that it would be nice to have Oximetry testing integrated into the xpap...would be easy enough to do and have at a minimal cost.

Point taken. Looks like we both agree on oximetry having some use in home CPAP, but my extract exagerated the degree which you intended.

A counter-argument to my subject: my 2nd opinion sleep dr was in favor of an off-CPAP home oximetry test when he heard of my PSG study having significant 1st night effects. And it confirmed OSA to a moderate instead of severe degree. But once he saw my much better O2 results on-CPAP, he lost interest in oximetry. Still, I had a few nights of AHI ~5, waking up after 3-4 hours, when the only reason I could find was nose congestion and SaO2 at 91%.

I read a number of published articles promoting pulse oximetry as an inexpensive starter diagnostic tool, leading a doctor to recommend sleep testing. A certain correlation between pulse up and O2 down can even indicate going into REM sleep.

Vicki wrote:How much one desaturates is dependant ... the length of apneas, the frequency of apneas and the residual volume of air left in the lungs during an apneic event... a prominent physician in the field of OSA also said OSA should be followed by AHI not pulse-oximetry.

Vicki, I agree ... once I also see the term "cumulative" included, and once I see some numbers assigned. For example:
- one 4% dip of 10 sec duration vs. desats oscillating in sync with apneas and / or hypopneas
- one SaO2 dip below 88% vs. SaO2 drops below 90% cummulating for more than 15 min a night
Moderate / Severe OSA (2 tests offCPAP).
CPAP ResMed S9 AutoSet EPR, Hi5 Humidifier.
ResMed Masks tried: nasal pillows Swift FX, nasal mask Mirage Activa LT, FF mask Mirage Quattro or FX.
Home CPAP data analysis: ResScan 3.16 sw, oximeter, pulsemeter
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