People with chronic sleeping disorders need to have their sleep assessed.
There are two basic locations that a sleep study can take place in. Either at home, where they are called Home Sleep Tests (HSTs) or in specialist settings, such as a sleep clinic or a hospital. These assessments are called in-lab sleep studies.
I have written a very detailed guide to HSTs that you can read here but in this article I want to focus on in lab studies.
For an in lab study you will spend the night away from home in a specialist setting, such as a sleeping clinic.
At the sleep clinic you will be sleeping in a room on your own (and it should have an en suite bathroom) and all for the whole time that you are there someone will be with you.
But don’t worry they monitor via video camera and intercom from a separate room.
This person should be a Registered Polysomnographic Technician (RPSGT). For this reason, in lab studies are called “attended”.
The test that is used to measure different information about your sleep is called a polysomnography (PSG). And the result of all of that collected data is called a polysomnogram.
The test is carried out by connecting a series of sensors or electrodes to different parts of your body.
Wikipedia believes that a PSG will typically record a minimum of 12 types of data (or channels) and each type of data will require at least two electrodes to be attached to be attached to your body.
Exactly how many channels are used will depend on the patient and what information or symptoms you are looking to collect information on.
The Different Channels or Data
Channel 1: EEG Channel
Sensors are attached to your head and they measure brain activity. It helps to monitor the sleep stage.
Channel 2: EOG Channel
These electrodes are placed by the eyes and they monitor the vertical and horizontal movement of your eyes. They provide information about the start of sleep and about Rapid Eye Movement (REM).
Channel 3: EMG Channel
These electrodes are placed around the chin and also on the legs. It provides information about how relaxed the muscle are. The electrodes on your limbs can also help to gather information about Periodic Limb Movements (PLMD.)
Channel 4: Airflow Channel
These sensors are placed around the nose or mouth and provide information about breathing in and breathing out.
Channel 5: ECG
These electrodes record the heart’s electrical activity and help to see if your heart is functioning properly.
Channel 6: Pulse Oximetry
These sensors measure how much oxygen is in your blood. If you are struggling to breathe, it will drop.
Channel 7: End Tidal or Transcutaneous CO2
This detects the level of carbon dioxide in your body. Carbon dioxide increases with any breathing pauses you may have.
Channel 8: Respiratory Effort
A belt is fitted round your upper chest and another may be fitted just above your waist. These measure your breathing effort, which will help to identify any pauses that you might have in your breathing.
Channel 9: Sound recordings of Snoring
This might be recorded with a sound sensor placed around the neck or the RPSGT might just record it manually as mild, moderate or severe.
Channel 10: Continuous Video Recording
And so I have listed 10 different sets of data that a polysomnograph might want to collect.
Although there are 10 different pieces of data to collect, the number of electrodes that you will have connected to your body could be in the dozens.
The good news is that attaching these wires to your body is a relatively painless task. Those that attached to your scalp are “glued” on user water soluble paste whereas most of the others are held on with tape.
In my article on home sleep tests, I explained that they were only to be used to diagnose one sleeping disorder- obstructive sleep apnea. Since a polysomnography is recording so much data, it can diagnose or rule out many more types of sleeping disorders, including narcolepsy, hypersomnia, PLMD and sleep apnea.
Unlike a home sleep test you will have no equipment to collect or familiarisation sessions to attend.
You will have a pre-arranged time to be at the clinic- normally this is about 8pm or 9pm.
You will be given specific instructions about what to do on the day of your test. Some clinics like you to keep to the exact routine as you would do for any other day. This is so that, when your sleep is studied overnight, they get a very typical or real picture of you.
Other clinics ask that you avoid napping in the day, or drinking coffee after lunch. Some physicians might ask you to stop taking your medication during the day.
So you can see that approaches may differ slightly but what is important to remember is that you should be given clear instructions by the sleep clinic about what to do.
One of the things that you would have discussed with the clinic, is the time that they expect you to arrive in the evening. There will be some flexibility here but it is normally between 8pm and 9pm.
Before you leave for the clinic, there are 5 things that you need to do
- Eat your dinner
- Take a shower
- Packed your pyjamas and clothes- you will need to wearing a pyjama top or t-shirt in bed.
- Pack your toiletries, including any make-up remover.
- Pack a book or a iPad if you normally read or surf on the Internet before going to sleep.
When you arrive at the clinic you will be met by a registered polysomnographic technician (RPSGT) who will go over some paperwork with you, get you to fill out a few more forms and talk you through what is about to happen.
They will take you through your health history and take your blood pressure and then you will be connected up to the wires and sensors. This can take about an hour.
Whilst you get into bed, The RPSGT will go into a separate room and talk you via an intercom.
They will test and calibrate the equipment so that it is running perfectly. The video camera will start to record if it hasn’t already been started.
Once this is done, you will be encouraged to read or surf for a little while before going to sleep.
If you need to go to the toilet during the night or one of the electrodes or sensors “falls off” you, the technician is there to help you.
The study will normally finish sometime between 6am and 7am. The technician will come in and help take all the electrodes and sensors off. This should be a fairly painless and has a similar sensation to taking Band Aids off.
The data will be analysed and should be sent to your physician within a few days.
Most people are very nervous because not only are they in a strange bed, but they are connected to lots of equipment and someone is watching over them. People worry that they won’t sleep.
Overall, there is no need to be concerned. People sleep far better in these settings than they think they do and in nearly all cases, ample evidence is collected from the PSG from which to diagnose you and come up with a detailed treatment plan.
The most important thing to consider throughout the whole process is what the information will do for you. You should end up with a very detailed treatment plan that will help you sleep more and by doing that changing your life for the better.
Make sure that you have already eaten.
Remember to take your pyjamas (the ones that you would normally sleep in) and toiletries.
Once you get there, you will be met by a registered polysomnographic technician (RPSGT) who will go over some paperwork with you, get you to fill out a few more forms and talk you through what is about to happen.
They will take you through your health history and take your blood pressure and then you will be connected up to the wires and sensors and then go to bed.
The RPSGT will go into a separate room and talk you via an intercom.
The equipment will be tested and calibrated so that it is setup to run perfectly.
Once this is done, you will be encouraged to sleep.