Thursday, March 10, 2011

What's Happening in my PSG/Sleep Study?

A patient came in and brought a CD with a prior sleep study and based on their symptoms I took a look at it later and I thought this might be a good chance to take a screen shot and then show it here so you can see what an average screen looks like so you can see what I review after you get your overnight study.
This screen shot represents 30 seconds, and the average person sleeps about 6.5 hours during their sleep study, so I review on average 780 of these screen shots each time I review a study. It goes quicker than you think, mainly because I've looked at so many now.
---First, at the bottom, you can see a time-of-night bar which shows you where you are in the night. You can see on here that we are early in the night (23:10:38 to be exact if you look closely there or in the upper left corner).
---Next, you can see see the "SaO2" which shows blood oxygenation. This person is averaging 94 and 95%.
---Above that you can see "Abdomen" and "Thorax"  which are from the bands around your stomach and chest. They show movements which help characterize your breathing since there are different type of abnormal breathing patterns (i.e. obstructive apneas, central apneas, hypopneas, mixed apneas, Cheyne-Stokes... etc.)
---The "Flow" above that also helps us via assessment of airflow in your upper airway.
---Next are the "RAT" and "LAT" which assess your leg movements at night... periodic limb movements (PLMS) which can be associated with restless leg syndrome (RLS) or independent, but other abnormal movements of the limbs can be evaluated by these leads as well.
---The "ECG" checks your heart with one lead, and checks basic rhythm and gives a gross view of any premature beats/missed beats/how they may change during the night. Some people have sudden changes associated with their respiratory events.
--- "ROC" and "LOC" tell us what your eyes are doing and helps immensely with staging of your sleep such as slow wave sleep versus REM (dreaming) sleep.
--- "Snore" is self-explanatory. It's a little mic that picks it up.
--- The "Chin" lead tells us if you're having muscle movements in your chin and helps us stage sleep and look at other things like bruxism (clenching/grinding of your teeth at night)
--- The top 6 lines: "Cz-T4" "T3-Cz" "Fp1-O2" "O1-A2" "C3-A2" are the EEG electrodes placed on your head during the study. You don't have to have all the ones we have here, but because I'm a Neurologist, I pay closer attention to EEGs and often get referrals for things that happen at night concerning for possible nocturnal seizures versus other things which a few more EEG leads help you differentiate. This is the most interesting part of this particular Polysomnogram (sleep study) actually: You can see about 2/3rds of the way across that these leads show some large amplitude waves. If you look at them closely, you can see that there is a "wave" and a jagged "spike" component to each of them (maybe 8 or 9 of them total). We call these... "spike and wave" complexes. These are actually consistent with a generalized seizure this patient had during this study. Now I would need a full EEG with many more leads to characterize better... but this person didn't have breathing problems, but instead was feeling awful during the day because they kept having small seizures throughout their night.
I hope you found this interesting. I sure do.