What are CPAP results or symptoms indicating oxymeter need

What are the CPAP results or health symptoms indicating the that I should add an oxymeter?

If I need one what are good ones?

I would prefer one that does not require a finger sensor, such as the Bodimetrics O2 vibe or the CONTEC CMS50IW

If you had a titration study and it showed you to still have oxygen dips even with effective treatment, that could indicate something to keep an eye on. Same if on CPAP you still have prolonged events. Other than apnea related, having other respiratory issues that merit monitoring could matter. Theoretically, if there are no other issues besides OSA and your CPAP is working as it should, there shouldn't be desats.

My last sleep with titration study was years and arguably pounds ago (2012). It said:

"The baseline waking oxymetry was 95-96%, asleep with CPAP it remained low on 94-95% at lower CPAP and BiPap pressures, but did improve with higher CPAP pressures ranging from 96-97%. Overall oxygen saturation nadir was 90%"

When nurses check my oxygen at doctor visits the results are usually 98-99%. I am unaware of any respiratory issues.

My concern is a mid-afternoon sleepiness at the office but it could be because I eat too much at lunch or I'm bored.

My 6 month Sleepyhead results are:

AHI .84
Obstructive index .26
Hypopnea index .42
Clear airway index .15
RERA index .15
% Cheyne Stroke Respiration .12%
Ave leak rate .89
% above leak threshold 0%
Ave. pressure 12.72
Max pressure 14.36