Posted by roy on March 20, 2003 at 23:05:26:In Reply to: stage2 posted by jim on March 20, 2003 at 19:52:54:
It is common to have K complexes and sleep spindles in slow wave sleep. If the epoch is 20% or more slow waves of 75uv or better it is scored 3 or 4 (50% or more). If not it is scored stage 2 using the 3 minute rule with K's and spindles.
For the exam, in the past, they have not asked if a epoch is stage 3 or 4 but have accepted the score SWS for stage 3 or 4 which makes it much easier. So to be consistent I would use SWS even if I felt it was stage 4 unless they ask for the distinction.
I would expect the voltage will not be close to being exactly 75uv or a little above or below. It will be obvious. In the worse case, no clear voltage criteria, I would say this is sws and not say this is stage sws. You can have sws which doesn't meet the 75uv criteria, it is still slow wave sleep but just can't be scored stage sws.
If you were given one epoch of data and asked to describe it and there were a few slow waves but not 20%, no clear K's or spindles, not slow rolling eye movements consistent with stage one, I would try to rule out REM sleep. And if all 3 criteria for REM are not met, low emg, rapid eye movements, low voltage mixed freq eeg, I would call it NREM sleep and note the reason no stage can be given. Points may be given for making this statement without giving an exact stage.
So a short answer to your question. R&K does not say if the slow waves do not meet the criteria of 75uv you score it stage two. But in most epochs it will be scored stage 2 due to the 3 minute rule for stage 2.
Hope this helps,
Roy