Unexplained intermittent nocturnal oxygen desaturation events

[Sjakie]

40-year old male, 6'1'' 145 lb., increasing fatigue since 2000, often feels like I didn't sleep all night long.
Underwent a PSG three times: no sleepapnea was found (all revealed a significantly low percentage of deep sleep and lots of tachy-arousals [pulserate between 35 and 110 bpm]).

Then a longer-term pulse-oxymeter study revealed significant nocturnal oxygen desaturation events:
- sometimes SpO2% drops quite suddenly to a low 80 (75-85), sometimes even as low as 60;
- these events last for 5 to 45 minutes and then SpO2% quite suddenly goes up to normal level;
- there are no known eliciting factors, I only suspect that a certain degree of physical exertion in the days before might increase the chances of an event (getting a deeper sleep?);
- estimated frequency: only 1 out of every 5-7 nights (but sometimes several nights at a row) and then (mostly) only 1 desaturation event per night;
- the day after such an event I feel extremely bad and fatigued (with a strong correlation between severety of symptons and the kind of event: how low/how long).

Specialist did several additional tests to rule out problems with lungs etc. and Holter registration revealed no obvious cardiac problems in relation to events.
Test with oxygen-therapy during the night (1l/hr): desaturation events were not prevented, BUT low-point significantly increased to low 90 and intensity of symptoms was somewhat reduced.

So far, the provisional diagnosis is 'idiopathic hypoventilation', but to me that sounds more like a description of symptoms than a diagnosis.
My specialist has never seen anything like this before (at first he thought of artifacts in registration).
Have you ever seen or heard something like this or could you give advise on further examinations?

[Sjakie]

Central sleep apnea is not yet ruled out but it is sure that the desaturations are not due to obstructive apneas.

Would central sleep apnea (or REM-sleep related hypoventilation?) fit in this picture of quite long and deep desaturations (of up to 45 minutes, to 80% SpO2) and that for on average only 1 out of every 5-7 nights?
That would mean very specific conditions must be met before such events can occur.

[Steven Y Park, MD]

Did they rule out central sleep apnea?  Do the periods of desaturation correlate with any breathing pauses? Were they due to central or obstructive apneas?

It's hard to say without looking at the whole picture (physical exam and the sleep study). Honestly, it sounds like a mystery to me. You may want to consider getting a second opinion.

http://www.doctorstevenpark.com