Low O2 Levels During Sleep with Low AHI

[cmpman1974]

Is it common to have nights without patterns like this?  Most of my nights this doesn't happen.  There are no clusters of apneas, but this was definitely an exception.  My doc lowered my pressure the day before and I figured that was an issue.  However the following night at the same pressure, my AHI went down to 3.0.  `

[Jeff8356]

... I am going to invest in some form of a continuous oximeter ...

Please have a look at the list of OSCAR supported oximeters here: http://www.apneaboard.com/wiki/index.php..._Oximeters
Their data can be imported into OSCAR. The Contec units have software for Windows, and the Wellue/Viatom units have both Mac and Windows software (as well as iPhone and Android apps).

I also have pulmonary hypertension, interstitial lung disease, and severe asthma. Breathing can sometimes be a chore.
I have both a Contec CMS50F and a Wellue SleepU. Both are recording oximeters and are OSCAR compatible.
My daytime SpO2 can range from 92-96. My nighttime SpO2 varies from 87 to 91. But every day is different. Most days it's rather normal. Some nights it's just terrible. But I use these devices as a guage, not as a precise instrument. If I see my SpO2 has been unusually low for 4 or more days then I speak to my Dr. If it's low for one or two nights I don't worry about it.
And to answer your question...YES...I have had nights of 0.0 AHI and have had lower than normal SpO2. Then I have had nights of 7 AHI with my SpO2 at 95. So it changes like the weather. But that is MY normal. Yours may vary, but don't get trapped into chasing those numbers. See what your average is over days or a week.

[cmpman1974]

Thanks for the insight.  This was very helpful.  Do you notice your nights with lower O2 levels for whatever reason correlate to feeling worse the following day(s)?   

On a different note, my sleep doc changed my settings again y-day by moving EPAP from min of 5.0 to 10.0.  Looks like there were very few apneas/hypopneas.  15/10 seems to be a decent pressure for me based on these results unless I'm missing something glaring, which I very well could be.

[Sleeprider]

Your additional details and charts have really helped to clear things up. You are using the ST-A in iVAPS mode which is a pretty sophisticated algorithm to maintain the minute vent rate. Your doctor's modificaiton to increase EPAP really cleaned up the events and settled down the need for pressure support. Both the older and newer chart have identical median tidal volume and minute vent, but the more recent one looks far less disruptive and stable. Higher EPAP pressure would also be consistent with using PEEP (positive end expiratory pressure) to recruit lung volume to increase oxygenation and improve ventilation to reduce CO2. With this increase in pressure, the pressure support is nearly constant at 5.0. I assume this was more comfortable and less disruptive for your sleep, correct?

[cmpman1974]

The most difficult part is I rarely feel 'disrupted' sleep in the form of waking up many times a night.  I usually wake up once per night meaning physically get up and out of bed for whatever reason (often to use the bathroom or due to discomfort in my spine - stiffness).  Last night was no different.  Strangely there is little to no correlation between how I feel for the day and number of times physically awake during a night so it's difficult to answer your question  My performance the next day is my only indicator as to success.  I have no good days in my eyes, but certainly some more tolerable than others.  I always feel groggy, head tension, eye strain, and eyes and nose draining clear fluid throughout a day. 

All that said, I feel like last night was a better night than others. I was trying to determine if IVAPS is what I truly needed, but I assume these numbers show it is.  I'm trying to understand all these charts in the context of my breathing patterns assisted vs unassisted by the machine, if even possible. Are you saying my average tidal volume would be much less without the help of this machine? My Respiratory Rate seems lower than average based on the reading I have done (normally 15+). I'm trying to put together the big picture and comprehend where/how this device kicks in the help my specific issue the doc feels I'm dealing with.

[Sleeprider]

Your last chart actually suggests that you have good spontaneous breathing rate and effort, but need the higher EPAP and steady PS 5. I believe you would do just fine on VPAP-S mode or Vauto with the same settings. You have VPAP-S and ST available on that machine if you ever want to try it. What we don't know from Oscar are what the full suite of settings are on your particular machine if there is a backup rate or iBR enabled, alveolar target volume and some other settings. Your respiration rate was 13.0 BPM on 2/7/23 with the lower pressure and 13.60 bpm on 2/9, so I would characterize your spontaneous rate as being mostly in the range of 13 to 16. The more remarkable thing to note is that the mask pressure chart shows very few instances of pressure support above 5.0, and your PS was mostly constant that the set minimum.

[Jeff8356]

...  Do you notice your nights with lower O2 levels for whatever reason correlate to feeling worse the following day(s)?   ...

Short answer: No

On some rare occasions I may wake up with a headache on a night I have low SpO2 levels, but nothing consistent enough that I can say low O2 numbers are the definitive cause. Could just be a bad allergy day for me.

YMMV...

[cmpman1974]

Your last chart actually suggests that you have good spontaneous breathing rate and effort, but need the higher EPAP and steady PS 5. I believe you would do just fine on VPAP-S mode or Vauto with the same settings.  You have VPAP-S and ST available on that machine if you ever want to try it.  What we don't know from Oscar are what the full suite of settings are on your particular machine if there is a backup rate or iBR enabled, alveolar target volume and some other settings.  Your respiration rate was 13.0 BPM on 2/7/23 with the lower pressure and 13.60 bpm on 2/9, so I would characterize your spontaneous rate as being mostly in the range of 13 to 16. The more remarkable thing to note is that the mask pressure chart shows very few instances of pressure support above 5.0, and your PS was mostly constant that the set minimum.

I was just looking at the info you were asking about.  My machine does have a back-up rate enabled.   It appears the machine shows expected vent rates based on a person of my height that has Ideal Body Weight.  I sure do not.  Those numbers are:  RR: 15; MV: 6.4 L/min; Vt: 428 mL and Vt/Kg: 5.8 mL/Kg.  The machine is set to a target Va of 4.5L min.  Upon more thought, I'm guessing this target level is indicative of the findings on a spirometry test that showed my max volume for a breath is approximately 65% of 'predicted' value of someone my height.   I know weight doesn't factor in to predicted levels, but absolutely plays a huge part in one's lung output.  4.5 L/min divided by 5.8L/min = 78% of target. 

I don't fully understand IVAPS, but I assume somehow the machine tracks the volume output and if mine under the minimum EPAP/IPAP pressures do not meet the 4.5L/min goal, the machine kicks in to provide additional air flow to reach that target?  Maybe if I forget to breath at all, the machine provides the full 4.5L/min breath?  98% of my breaths were labeled spontaneous so the other 2% would come from the machine?

[quiescence at last]

yes. the 2% is the machine triggering the breath, and why Master Sleeprider noted you may do just as well on other settings, due to the very high spontaneity. before your doc raised your EPAP, I was going to chime in that the amount of hypopnea suggested you needed a higher support pressure, although I might have suggested pressure of 7 or 8 instead of 10. But, the chart really looks great on your latest setting.

QAL

[cmpman1974]

Does this flow pattern depict flow limitations of any sort?  I was reading through the OSCAR section titled Examples of respiratory wave form abnormalities including flow limitations.   Some youtube video from a guy on SleepHQ talked about flow limitations still existing with great AHI numbers leading to all kinds of oxygen instability.  What he did not say is whether the patient actually felt better once they stabilized their O2 wavelength all night by increasing CPAP pressure. At the end, that is what truly matters. i have no idea how medically qualified the presenter is. He seemed to know his stuff, but I'm certainly not a doctor to confirm!

I am very much a mouth breather and have been my whole life. My tonsils/adenoids are quite large. I should've had them removed when I was very young, but unfortunately my parents didn't go that route so not much choice now. I also have a lot of environmental allergies that probably do not help much.