Blog – What is polysomnography?

I currently work as a research assistant in sleep psychology using Polysomnography (PSG). Although the name sounds similar to an ancient Greek curse, PSG is the gold standard of sleep recording equipment. I use PSG on Dementia patients, but it can be used on any healthy, willing participants. PSG can diagnose sleep disorders such as narcolepsy or sleep apnoea by monitoring sleep stages and cycles, to observe when and why your sleep is disrupted. It records brain waves, blood oxygen level, heart, and breathing rate during sleep. This blog will give you an insight into what PSG is, how it is set up, and why so many of my patients look in the mirror at the end of the process and let out a little gasp…

My research work requires Dementia with Lewy Bodies and Alzheimer’s Dementia patients to wear PSG for three consecutive nights in their homes. I will arrive at a patient’s house at around 7pm and begin applying the equipment. Before setting up I prompt participants to get a drink, use the toilet, turn the television on etc, as the process takes between 2-4 hours to set up depending on operator experience. It certainly requires full concentration and brain power. This can be difficult when I am trying to maintain a conversation with my patient about their last holiday in Spain, whilst simultaneously trying to concentrate on which wire goes where.

So, what exactly does setting PSG up entail? Firstly, I get all my equipment out and prepared so I can access each component easily. I ask my patients to sit on a dining chair, therefore it is convenient for me to stand behind them and work on their scalp. This is advantageous as I can use the accompanying dining table as a workspace. There are two starting points you must locate on the head to begin. I will introduce you to two words that before working in sleep psychology had never entered my vocabulary. The inion and the nasion... The nasion is essentially a fancy word for the bridge of your nose. The inion is the projecting part of your occipital bone found in the skull. If you put your hand on the back of your head, you should be able to feel a lump on the skull just above the base of the neck. Some people have very prominent inions and others are barely visible. Using these starting points I then measure the patient’s scalp with a cloth tape. While measuring, I use a red body pencil to mark the points where I will place the electrodes later in the session.

Fun fact: Polysomnography doesn’t just monitor your brainwaves—it also tracks your eye movements, heart rate, and even your leg twitches while you sleep! It’s like a full-body sleep spy.

There is a complicated equation for measuring and placing the red mark on the scalp called the 10-20 system (Jasper, 1958.) Once the scalp is marked, I will begin attaching electrodes one by one. Each electrode is gold plated. I load them with a scoop of electrode conductive paste and then place a small amount of electrode gel on top of the paste, using a needle. I often see my patient’s eyes widening and colour draining when I pull the needle out of my bag, but I quickly reassure them that it will be going nowhere near their skin and won’t be used for injecting or withdrawing blood purpose. I choose a previously drawn red mark and apply the electrode with some light pressure to the scalp. I then place mesh gauze over the top to secure it overnight. The gel and paste harden with oxygen exposure helping the electrodes to stay put. I apply two ECG electrodes (the kind you would see in hospital) to the chest to measure heart rate. I then attach a total of 19 electrodes to the scalp and face. My male patients always manage to get a giggle out of me – which is difficult at 9pm. They often comment that the electrodes are like a set of hair extensions, and they suddenly realise the annoyance that comes with long hair.

Once all the electrodes have been applied, I attach two Velcro straps, one around the waist and one over the shoulder. Two boxes are placed on these straps – the recording box sits on the waist strap. This provides the equipment with battery power and stores the flash card which holds all the data collected overnight. The headbox sits on the shoulder strap higher up on the chest. All the electrodes are plugged into the headbox and then a main lead connects both boxes together to create a comprehensive body kit! When it comes to plugging the electrodes in, I always liken it to the most stressful, dystopian puzzle game in existence. Each relative electrode has a specific slot that it must be plugged into on the headbox. Bearing in mind that each electrode is a different colour, this forms what one of my patients called ‘spaghetti junction’ on the head. Using the recording box, I must then check that each electrode is performing the way it should be by checking its impendence value. The values range from 0-100 with lower impendence values reflecting a better connection. It can be difficult to obtain low values when working with longer hair. The more hair someone has, the harder it is to reach their scalp and get a good electrode-to-scalp connection.

Like any facet of life, there are downsides to using PSG. Imagine you have just spent two hours delicately constructing this equipment, you’re on the cusp of going home… when you check an electrode, and it has an impendence value of 100. Horror has stuck and it’s time for some late-night troubleshooting. Usually, the end of the electrode has come loose at the box and just needs pushing in more firmly. Other times it can be a problem with the electrode wire, meaning I must remove and replace the entire electrode. When my patients are wearing PSG, I must be on call overnight. This is for instances like if they wake up at 3am and think ‘I need all this equipment off me right now!’ or another medical emergency. I would have to roll immediately out of bed, drive to their house, and remove the equipment. It’s slightly less exhilarating than receiving a call as a specialist doctor or firefighter, but nonetheless, the same adrenaline is released, and I treat the responsibility equally. Although being on call is project specific- I think if PSG is used in a home setting, a researcher needs to be nominated to act as an emergency point of contact. This gives participants a feeling of safety knowing they aren’t ‘trapped’ in a frenzy of wires. A personal negative outcome of the equipment is the anxiety I feel leaving a patient wearing it overnight.

I often find myself worrying if they’re okay, or panicking if I pressed record on the box leading me to have a bad night’s rest. Something everyone who works in sleep will agree with is that your sleep will be the one that’s impacted.

Do you remember when headphones had wires? You would pull them out of your pocket to find a ball of tangled, knotted mess? That is what the equipment can sometimes look like when I remove it in the morning. I must then commence on an untangling mission (again, quite difficult to do so at 8am.) Summer is a big disadvantage for setting the PSG up, summer heat makes the conductive gel / paste a lot softer meaning it’s more difficult to apply the electrodes to the scalp and get them to stay in place! However, living in the UK I don’t face this particular problem too much…

Once the patient is connected and resembling something out of a sci-fi movie, I run through some simple bio-calibration tests for the PSG equipment. This involves asking the patient to complete a range of tasks like closing their eyes for 30 seconds, wiggling their big toe five times, or mimicking a yawn (usually by night three they don’t need to mimic them anymore!) It’s common at this point that the patient’s partner will insist they get a photograph of their other half kitted up. I can’t imagine how many have ended up on the family Christmas card. I have become accustomed to partners whipping out their mobile phones and taking action shots of me working on their significant other. Once the photo shoot is out the way, I will then ensure they have my number for overnight contact, hope that they have a good night’s sleep, and leave their house. Before leaving I will also agree on what time I will return the following morning.

Most patients ask me to return between 7am and 9am. When I return the next day, I will stop the recording, begin removing each electrode and subsequently the rest of the body kit. Each patient will complete three consecutive nights wearing the equipment for this research, but it can be worn for one night only for other projects. Similarly, PSG can be used and set up in a clinical environment instead of a home setting. The process would be the same with slight alterations depending on research hypotheses.

I hold great respect and admiration for patients who welcome me into their homes during unsociable hours, often disrupting their normal nightly and morning routines.

I frequently think of a quote that has sharp become my favourite, ‘upon the hours of waking one is not at one’s best’ highlighting the delicacy of my role. No one likes the idea of a stranger entering your home when you have just risen and are often the worst version of yourself. I am thankful to those who like to break the normalcy of their midweek lives and live life on the polysomnography edge. My advice to anyone working with novel, complex equipment is to remain confident. Understand that mistakes can happen due to human error but use these mistakes as learning lessons. Your best teacher is your last mistake. I love to use acronyms to help me recall equipment instructions. For example, I must remember the letters ‘F, C, O’ in that order for the electrode positions.

Each time I work on a patient I repeat, in my head ‘fluffy, cuddly, octopuses’ and this method hasn’t failed me yet. I advise that you find a mnemonic device that works for you to help aid information retention and retrieval. Practice and time are two wonderful principles that will ease the difficulty of working with new equipment and provide you with the strong, integral skills you need to perform. After all, I didn’t spend hours practicing on glass model heads for nothing! Funnily enough, they never had as much to say as my patients do…

Amelia Robson

Author

Amelia Robson is a Research Assistant at Northumbria University supporting delivery of NHS Clinical Trials, particularly in working with Dementia with Lewy bodies and Alzheimer’s disease patients. This work currently involves visiting patient’s homes and applying polysomnography sleep equipment on their face, scalp and body. Amelia graduated in Psychology in 2021 and is passionate about supporting people living with the dementia, and providing help for care givers. Her top tip…. Trust your Gut to stay on the right path.

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