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Reliability of oximetry for dx?
My primary doc told me I have sleep apnea because an overnight pulse oximetry test came back abnormal. I was referred to a pulmonologist for a CPAP.. who said the oximetry tests are very unreliable and I need to do a sleep study first. How likely that a sleep test will be normal? Why is a pulse oxietry test done?
Follow-up
I'll try to answer your questions very directly: 1-Your pulmonologist is quite right: abnormal oximetry doesn't rule out all the other possible sleep disorders, or tell him/her anything about your apnea in terms of treating it. It only tells the doctor that something is wrong, but not what exactly and to what degree, or what it needed to treat it. That's why he/she is suggesting a sleep study before CPAP (it's also good medical practice for him/her to do so). 2- You already know (via the oximetry) that your sleep is not "normal", therefore your question about how likely it is that your test will be normal is moot. (This isn't like trying to find a squeak in a car that goes away when you take it in for repair to the dealer!) The sleep study will tell the doctor what is happening that is causing your blood oxygen to drop, which is already a known fact. Then, the technicians can find what level of CPAP pressure is needed to treat you. 3- The pulse oximetry is done for screening purposes (it is the tell-tale sign of apnea). It is also relatively cheap and quite painless. Of course, the doctor may charge a bunch of money to interpret the test, making it far from cheap. (Loaning you the equipment for a night, or having someone take it to you, is cheap.) I hope this info helps clear up your anxiety. Write to me directly if you have more questions. -Tom PS--The other response (from Susie) mentioned some concerns over the oximetry test itself (including the doctor's suggestion that she was having hallucinations about it). I recommend you don't let her experiences keep you from having a sleep study (which will include an oximetry test). By the way, I had hypnopompic hallucinations, too.
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