Brainwaves

Imagine a brain, like the one in the photo, made from a string of fairy-lights. Imagine billions of lights in the brain, all blinking in a seemingly random pattern, passing electricity onto each other in a pattern that only makes sense to itself. Now imagine that wires can grow directly between bulbs that commonly light at the same time, making a connection between them.

That's pretty much what is happening inside our brain, except the fairly lights are neurons and the wires are neural connections. The power comes via tiny electrical impulses and electro-chemical messengers.

Imagine that, like the one in the photo, your head is made of glass and that it were possible to record how fast and how bright the majority of surface lights in a particular area were flashing.

That's roughly what an EEG can achieve. 

It's complicated in there, and anyone who says that they have a complete grasp of what is going on inside is lying!

...but we have a few clues to guide us.

We can use an EEG to record the voltages that are present near the surface of various areas of the brain.

Essentially, an EEG is a volt-meter recording the voltages that escape to the surface via adhesive electrodes glued to the skin.

Straight away, this is a limitation because we are therefore oblivious to the voltages that are buzzing away in deeper areas of the brain and multi-lead EEGs can look at many areas of the brain at the same time.

However, we are still able to deduce an awful lot from a single site EEG.

These are slowly coming onto the market for consumer use, one that I've had for a while is the X-Wave. It's a large headset with a single forehead electrode and an ear-clip. The voltage from your forehead is monitored and by comparing the signal pattern to a known pattern for either "concentration" or "relaxation" the attached computer is able to deduce whether you are in either of those mental states. 

This is a neuro-feedback system. You can spend ages watching the flicking graphs and wiggling lines playing "trial and error" trying to make them respond as you wish. When you achieve the desired pattern you are given positive reinforcement by the computer, making it easier to achieve that state again. Oddly, being taught what to do is tricky, but given half and hour of experimentation you'll find that you soon pick up what to do.

With a little practice I was able to achieve 100% concentration...

...and around 80% "Meditation" which isn't that easy when you are desparate to grab a screenshot of being "relaxed"...

There are also computer games written for the X-Wave which allow you to control them by either concentrating, or relaxing. A good "real world" example is the "Star Wars Force Trainer" where you wear a similar headpiece and try various thought patterns until you find the one that makes the ball float.

I first purchased the X-Wave because I thought it would help me to determine sleep stages if worn when asleep. It would have been an uncomfortable night as the headset isn't really condusive to a good night's sleep. However, it doesn't (yet) have the ability to record and playback data, nor does it (yet) allow you to see the raw waveform, although I believe that this is something in the pipeline, although this would still leave the user needing a knowledge of EEG interpretation to be able to determine which sleep stage a sleeper was in.

The XWave may be useful for games and biofeedback, but it wasn't able to do what I wanted, nor did the PC interface become available as was available for pre-order on the website.

I then purchased the Zeo Bedside Sleep Monitor which uses EEG technology to do what I wanted (determine and record sleep stages automatically). Then, with updated firmware and a home-made lead, you can connect the Zeo to a computer and see an awful lot of what is going on in your brain. Granted, this is still a single channel EEG, so it is only looking at one area of the brain, but still the amount of activity that you can see is astounding!

First I'll mention some of the different types of brainwave that I've seen with this system. These waves are all recordings taken from my brain whilst I've been asleep. 

Generally speaking, the thing that determines one type of wave from another is its frequency (how many times it cycles per second), although some features jump off the screen at you such as "K-Complexes" and "Sleep Spindles", both features of Stage 2 NREM sleep.

It is possible that some features found in our brainwaves also serve a function, or at least they show when the brain is carrying out a particular function. For example, K-Complexes can be induced in a sleeping person by external noises. It is thought that the K-Complexes are a response to a noise that the sleeping brain has evaluated as not being a threat.

Sleep spindles also seem to be connected to the outside world. They represent when the brain is not consciously processing input from the world outside. In my oversimplified world I tend to think of them as little bundles of barbed wire that sit on the boundary of sleep and wake somehow shouting "La la la, we're not listening".

Like K-Complexes and Sleep Spindles, some wave patterns are closely related to sleep stages, such as Deep Sleep, which takes its correct name, Slow Wave Sleep, from the waves that are associated with it - Delta Waves, or Slow Waves.

Just as measuring the voltage from the screen of your television doesn't tell you what programme it's showing, measuring the voltage from your skull doesn't tell you what thoughts are being thought (although it's becomming ever closer http://www.ibtimes.co.uk/articles/290907/20120201/mind-reading-machine-scientists-computer-program-epilepsy.htm ) Trying to detmine what the person is thinking or dreaming about isn't as simple as looking at the brainwaves they produce and then comparing it to a vast dictionary of known squiggles. For one thing, the brain is capable of producing (and does so) many waves at the same time, in the same area of brain. The relative power of these waves can be separated out using FFT algorithms.

However, thoughts and sleep stages are completely different animals, and the Zeo is able to determine sleep stages with a high degree of accuracy (References Shambroom, Fabregas & Johnstone, also here and here), which is after all what it was designed to do. We are just piggy-backing off its ability to show EEG data.

The following is the raw data from a section of sleep. The bottom is a hypnogram (shows the stages of sleep) for a whole night (top-bottom = wake, REM, Light, Deep); the top is the raw waveform for the current 15 seconds) whilst the line in the middle is a record of about 45 minutes of data.

The middle one is the result of the FFT analysis (mentioned above) and represents the types of waveforms in proportion to each other. From this it is possible to determine which is the dominant waveform. 

A good example of this is observing the transition out of slow-wave sleep. (Note the steep drop in the red line).

Click for larger image

It's also interesting to see what happens to your brainwaves while awake and carrying out various tasks.

Normally, the frequency distributions seems to be fairly scattered (the lines are nicely spaced out), but one night I woke around 3am and couldn't get back to sleep, I kept the headband on. It seems that when I was concentrating on reading Twitter the various frequency brainwaves became more focused, leaving Alpha and Theta as dominant.

These grouped together even tighter when I actually tweeted and a form of Beta wave became dominant (although only slightly). I presume the tight grouping is because typing required more concentration and more focused thought. Oddly I received a phonecall while awake, and this shows another pattern.

  Click for larger image

Through playing around with this set-up you learn to spot patterns. For example if I am disturbed in the night by a sound that wakes me you can see a brief period of concentration before I go back to sleep. it would be fantastic to actually see the change in brainwaves during an episode of sleep paralysis or a lucid dream.

This would make a great neuro-feedback system and I plan to use it to test the claims of various products that they are able to "induce delta waves" or "cause trance like theta waves" etc.

Non-Invasive Ventilation

I could rehash the many excellent write-ups of non-invasive ventilation (NIV) that already exist on the internet, but I thought it would be more personal for me to tell how my son came to use it, explaining NIV along the way...

Bear in mind that these events took place over a period of 10 years and involved many medical professionals from various hospitals and clinics, although it may read as if it took just a few nights. 

A person's breathing might not be enough to sustain them for various reasons including:

• Illness (short term or long term)
• Injury (critical phases)
• Neuro-muscular issues

Sometimes a person will need respiratory support during these times. Sometimes it can be for a short while whilst in intensive-care or a high-dependency unit, other times it can be a life-long need, in which case they will likely have to have a tracheostomy tube fitted in order to leave their face free and unobstructed.

There are also people who only need respiratory support whilst they are asleep.

Due to changes in our respiratory drive and how our muscles respond during sleep our breathing undergoes many changes, this can even vary depending on the stage of sleep we are in. 

The following graphs contain information about how much air I was breathing per minute during the various stages of sleep (as scored by Zeo)...

I won't go into great detail about the why here, instead I want to concentrate on what can be done about the problems that these changes can cause.

At the time of writing, there is a good Wikipedia article about these changes entitled "Sleep & Breathing" 

When he was first paralysed, my son was on full time ventilation. This was considered to be a long-term and possibly a life-long situation and he was give a tracheostomy tube (a tube inserted through an opening in the neck and directly into the windpipe) to allow the ventilator to be connected to him.

10 years on, he is still paralysed but fortunately after several months of being in hospital the tracheostomy tube was able to be removed because the higher part of his spine had partially recovered. He had been slowly weaned off ventilation.

After the tube was removed his oxygen levels were continuously monitored and it was discovered that his oxygen saturations plummetted when he was asleep, but they always picked up again. We left hospital with a pulse-oximeter (a device that monitors pulse rate and blood oxygen saturations via a finger probe).

On some occasions his levels dropped as low as 65% (Generally speaking most people maintain a level of >92%). It was this that prompted me to buy the equipment to record his oxygen saturations so that I could show the relevant doctors involved in his care. Although, not a chart of the lowest that he dropped, this is a chart from early on (right) that is a good guide to what used to happen.

Each row is 4 hours of data (grey parts are when the machine was not monitoring due to him being awake).

Red = heart rate (bpm). Green = oxygen saturations (%) 

 

Left: How the chart should appear (taken from a fairly recent night when he was breathing oxygen via a mask)

 Right: His chart from a typical night

So why not just use oxygen, if it makes the graph all straight and pretty?

Well, oxygen is only one of the gasses involved in breathing, granted it's an important one, but Carbon Dioxide is also involved.

At school we were all taught that we breathe in air, use the oxygen then exhale carbon dioxide, but the carbon dioxide actually serves a purpose. It is used as a trigger to breathe. When the levels rise to a certain level, we breathe to remove the CO2.

If the "sense and control" mechanism in the brain is damaged, or if the muscles are not able to respond to its signal to breathe, then CO2 can build up in a condition known as hypercapnia.

That is what was going on while my son was using oxygen. We were able to see this by the use of a split cannula. It looks like a standard nasal cannula for oxygen delivery, but the tube to one nostril is used to deliver oxygen whilst the other is used to monitor the CO2 using an end-tidal CO2 monitor / Capnograph.

High CO2 can lead to other health issues, and it actually affects the Ph of your blood.

So my son was trialed on a type of ventilation known as Continuous Positive Airway Pressure (CPAP). This involves a constant pressure of air being delivered into your nose (or nose and mouth) via a mask. 

If you ask a child to blow a balloon up, then they will probably struggle, but if you "do the tricky bit" and start it off for them then they will probably be able to top up what you've started and finish inflating the balloon.

That's essentially the idea of CPAP. The airways are kept open by the pressure, leaving the user the task of inflating their lungs.

CPAP can be a great help when people suffer from Obstructive Sleep Apnoea. It can prevent the airway closing off, thus allowing the sleeper to breathe normally.

However, CPAP wasn't preventing my son's apnoeas.

This could have been because he needed much higher pressures, or because the apnoeas were "central" and not "obstructive" in nature.

A central apnoea is where the brain doesn't tell the sleeper to breathe.

Fortunately, the CPAP machine records the overnight data to an SD Card and can decide whether the apnoeas are obstructive (airway closed) or central (airway open but no flow).

It showed that he had mainly obstructive apnoeas with hypopneas, but also the odd central apneoa, along with many apnoeas tagged as "unknown".

The night above shows them towards the end of the night. This didn't fit with the pattern of oxygen desaturation that we saw begin around an hour after sleep onset, even whilst on CPAP, hence we weren't sure how much to trust the detected central apnoeas as they seemed few and far between. However, if someone has both obstructive and central apnoeas, CPAP can reveal those central ones after it has removed the clutter of obstructive apnoeas. 

The CPAP that he was prescribed was "Auto-titrating CPAP" this means that the machine decides which pressures are needed. You can see this in the graph above (the pressure line varies throughout the night). Intriguingly, the when the pressure is the highest there are no apnoeas, but he still desaturated.

The auto-pressure function can be set to choose between limits, or forced to give a constant set pressure. After many nights of alarms. We obtained a chart from a night at 6cmH20 (left) and a night at 15cmH20 (right) to see what was going on.

 6cmH20 had little effect. 15cmH20 was better, but still unacceptable and uncomfortable for him.

He would wake in the middle of the night and not be able to call out due to the mask over his nose and mouth. His heart rate would then increase and his alarm sound to alert me. I'd have to turn the CPAP off and it would have to be re-ramped again (start at a low pressure and build up over time, hoping that he was asleep before it delivered high pressure again). 

Because his blood-oxygen only dropped at certain times of the night rather than be low ALL night it was suspected that it had something to do with a particular stage of sleep. Below is a picture of a normal hypnogram (a graph detailing the stages of sleep, as shown on the Zeo entry of this blog) overlaid with a graph of his oxygen levels from one night.

Seeing this was a goosebump moment...

The pattern of his oxygen desaturations matched up really well with a standard hypnogram, so it was pretty certain that his condition was REM related. However, this wasn't a graph of his REM.  A way of working out and recording when he was in REM was needed.

New equipment was also needed...

Due to the possible presence of central apnoeas, it seemed unlikely that CPAP was going to be an effective solution, afterall there is little point in keeping the airway open if the brain isn't initiating a breath (or the muscles aren't able to respond to the signal to breathe). It was suspected that he would need Bi-level ventilation. Well known brand names for this are BiPAP and VPAP.

These are both Bi-level Positive Airway Pressure devices. Bi-level delivers two alternating pressures. The higher one is the IPAP (Inspiratory Positive Airway Pressure) and the lower one is the EPAP (Expiratory Positive Airway Pressure). The IPAP is essentially the breath, while the EPAP is the amount of pressure required in order to keep the airway open. Usually the breaths are triggered by the sleeper's breathing efforts, but to cover the possibility that he did indeed also have central apnoeas we used a BiPAP machine that could also be set to deliver "backup breaths" if my son didn't breathe a certain number of times a minute.

The CPAP / BiPAP was delivered via nasal pillows. These are fantastic as they allow the user to speak whilst using them. However, this left us with no way of being able to reliably monitor his CO2 using a capnograph.

CO2 monitoring is essential, without this it would be too easy to adjust the ventilator so that there were no oxygen desaturations, but actually be hyperventilating him, or worse causing trauma to his lungs and airways; so unless we could find a way to reliably monitor his CO2 we couldn't go any further. A different type of CO2 monitor was bought in...  A transcutaneous CO2 monitor.

The transcutaneous CO2 monitor gathers its data by way of a probe that is attached to the skin of the chest or arm. It then heats up the skin and evaluates the gasses given off. The probe needs to be removed after several hours and placed on a new site in order to reduce the risk of probe burns to the skin.

The titration process wasn't a one night affair, so we had the luxury of being able to record readings at home between appointments. However, at home we didn't have an EEG machine to record brainwave data, so we couldn't tell what stage of sleep he was in.

We needed to see when (and if) he achieved REM sleep while his settings were adjusted over the course of several nights. We also needed to make sure that the pressures weren't waking him up. Afterall, if he didn't have much REM (or his REM was disturbed) then his oxygen levels would look good and give the false impression that the settings were working. The Zeo was perfect for this.

This graph is from one of the first nights of BiPAP (when the settings were good but not optimal) and it shows a great correlation between his oxygen desaturations and Zeo's calculations of REM sleep. (The dips in the green oxygen line are a near perfect match for the green chunks of REM from Zeo), as are the rises in pulse rate and CO2.

This gave me a lot of confidence in the Zeo's decisions as REM is probably the hardest state to detect due to its similarity to being awake. In fact I'd even feel confident enough to say that the piece of missing data from the Zeo (headband was too loose) would have shown REM.

The result of a few nights adjustments during REM was that BiPAP at the correct pressures eliminated his oxygen desaturations completely and allowed him (and me) to sleep all through the night for the first time in a very long time.

It turned out that obtaining a machine that could provide additional "backup" breaths was a good investment... Pressures alone weren't enough to prevent his oxygen levels dropping, so a backup-rate was set of 13 breaths per minute.

This meant that if he didn't breathe 13 times a minute of his own accord, that the machine would make up the number of breaths. 

 

The graph on the left is with BiPAP pressures set to 18/10. This was fine for his oxygen requirements, but it still was uncomfortable for him (but tolerable). The high EPAP of 10cmH20 made it hard for him to exhale (remember that he has neuro-muscular issues).

The pressures were re-titrated but this time with a lower EPAP. This seems essential for him to be able to exhale effectively, and provides a more comfortable night.

These settings will be reviewed periodically by the medical professionals that have been involved in his care to see if they are still optimal.

He now loves the BiPAP machine and doesn't like sleeping without it, he doesn't sleep in until noon at the weekends, he doesn't fall asleep at school and can stay awake until long into the evening. He also has a ZQ of 137 which he likes to use to mock my awful average ZQ of 68.

Circadian Rhythms & Temperature

Due to a bit of an erratic week, I haven't been able to reliably measure (and experiment with) my apnoeas, so instead this was going to be a blog post about "Circadian Rhythms" (the daily sleep/wake cycle).

Given that we inhabit a planet with a 24 hour day, it is no surprise that our bodies have become roughly linked with the day/night cycle, with various hormones being released at certain stages in the rhythm enticing us to sleep or wake.  

               (Combined photos from my Sky-Watcher and solar telescopes)        

Not everyone's rhythm is the same, some people have theirs shifted (such as when you are jet lagged). Even a skew of an hour or two can make a huge difference to how easily you are able to wake up for work in the morning, or how late you can stay awake.

There are a couple of online questionnaires to help you determine your own circadian rhythm:

http://www.philips.co.uk/c/circadian/178344/cat/
http://www.bbc.co.uk/science/humanbody/sleep/crt/

Both of these decided that my rhythm was skewed, so I decided to make my own measurements and chart them here but after seeing the first 24 hours of data, something interesting emerged...

This is a normal circadian rhythm taken from the Philips website. 

In fact, this is a simplified rhythm, because it is normal to have a small dip in the energy levels around mid afternoon, hence the reason for many countries having an afternoon siesta, and the reason why we tend to slump at our desks in the mid afternoon and reach for a cup of coffee.

This dip can be seen in my graph from the BBC circadian test.

Core body temperature is a good way of charting your own rhythm because energy levels are reflected by our temperature. Our body temperature is not a static 37.5 C, in fact it fluctuates throughout the day inline with our circadian rhythm. Of course, it is also affected by ambient temperature and how active we are.

So, all it would take to chart my own rhythm would be a decent thermometer.

I decided to get a data-logging thermometer, so that I could see what was happening while I was asleep.

I ordered a thermometer capable of recording every 10 seconds (to weed out anomalous readings), and was expecting the probe to be a small thermocouple-type sensor that I could stick to the skin under my arm, but the probe was more like a bullet and wasn't adhesive plus the logger turned out to be a lot bigger than it looked in the photo!

I'd gone this far, so in the name of science, I shaved under my arm and fixed the probe there with Melonin (low adhesive dressing) and Tegaderm (a clear waterproof adhesive dressing). I then wedged the cables into my suit and went off to work.

After 24 hours (and a few weird looks) I downloaded the data to a computer. I noticed that generally the pattern was the same as that belonging to "normal" people, but that it had a few fairly severe drops in temp during the night.

I repeated this over several days.

On the graph below, the dip is around 1:30pm and again at 4:00pm. I suspect the 1:30pm dip is my normal afternoon energy dip whilst the 4:00pm dip is environmental because I was working outside at 4:00pm. 

I repeated this the following day and the dip was much more pronounced again early at around noon, but I ended the recording early as it was becoming awkward to carry the data-logger around with me, so I can't show a full 48 hour graph.

It's also interesting that the temperature drops around 8pm. That's pretty much when I start to look forward to sleep! It plateaus at 10pm for a couple of hours in a similar way to the one produced by my answers to the BBC link. This may have been because I was already asleep by then!

The first 24 hours...

Those drops in temperature during sleep are severe. When I first saw them, I suspected that they were erroneous readings, but the probe was stuck so tightly to me that there was no way that these were due to poor contact (after all, if that were the case, why didn't this happen during the day when there was more movement?). However, as the data rate on the logger was so high (240 recordings an hour), these were clearly not erroneous as they slowly crept back up to the plateau level of around 36.5°C.

I wasn't happy with this result, so I repeated it the following night. The drops in temperature were still there.

On the second night, to eliminate the possibility that these variations were due to environmental changes, my room temperature was monitored with another probe, and it was a surprisingly constant 18°C  for most of the night, so there were no corresponding dips in room temperature. I don't like my bedroom to be too warm so I switch the heating off at night.

I took a look at my sleep-stage data using the Zeo, and was surprised that the seemingly random falls in temperature coincided with awakenings from REM! (Shown as orange "wake periods" on the coloured graph, but as REM/Wake on the detailed graph. Light green = REM, Dark green = slow wave sleep, grey - stage 1 & 2 sleep. For the sake of simplicity I won't show the detailed graph, but you can see one on the blog post "My Baseline AHI").

So what's going on?

Along with the muscle paralysis that comes with REM sleep (to stop us acting out our dreams), there is also a decrease in the body's ability to regulate its temperature (thermoregulation). 

So, it seems that my temperature was dropping, causing me to wake in order to regulate my temperature, pretty much in the same way that my apnoeas cause me to wake during REM.

If this is true then it means that in order to be able to stay asleep during REM I now have two issues to deal with: apnoeas AND temperature!

During REM this decrease in ability to regulate our temperature causes us to be largely "Poikilothermic" (meaning that our temperature is governed by the temperature of our environment). So the key to eliminating this issue is to regulate the temperature of my bedroom better.

I repeated this for two more days, and then concentrated on the nights and gathered more data (total of 5 nights). It seems that these overnight drops in temperature aren't always correlated with REM sleep (sometimes they are just before and sometimes just after), so until my more accurate thermometer arrives, I decided to calculate the mean temperature from the week's recordings to get a better idea of my rhythm and to try to eliminate the overnight drops.

This gives a much nicer picture and goes some way to reducing the environmental effects. The data fits well with how I feel throughout the day. I tend to get a bit tired at 1pm, then start considering bed around 8-9pm.

Compared to the BBC graph, it lines up fairly well, although my "energy drop" happens earlier in the day at a more accurate time.

I'm not comfortable with this experiment as there is much that could be improved on:  

• Better temperature sensor (on it's way)
• Eliminate environmental temperature effects (maybe on a day where I stay at home)
• I still am not convinced whether these changes in temperature are an effect of activity. After all, it stands to reason that when we are more active our bodies produce more heat, so it would be interesting to do this on a day where I forced myself to do nothing, stayed at home and forced myself to stay awake past my usual bedtime, that way I could see whether these changes are still evident on the graph. That said, some of the nights were recorded with an 11pm bedtime although my temperature still dropped as usual around 8pm, so it could be accurate.

One thing that it has shown me is that it is essential to have your sleeping environment just right for you...

A good sleep routine involves making sure that your bedroom is the right temperature. It should be cool but not cold. In days gone by, the outside temperature dropping in the evening acted as a cue for our ancestors' bodies to sleep. Of course, in days where our homes are heated, this confuses the body and can lead to poor sleep.

The same is true with light. Nowadays we have artificial light filling our homes and offices, and that also interferes with our sleep/wake cycle as we don't receive the nighttime cues.

So sunlight during the day and a cool, dark bedroom goes some way to remedying this.

Update on Friday, December 9, 2011 at 8:46AM by Hypnagogia Blog

My new monitor arrived. It's able to record temperature, blood pressure, ecg trace, heart rate and oxygen saturations together.

I still saw temperature drops, and they still correlate with REM sleep.

The following screenshot (combined with the Zeo hypnogrm) shows the temperature drop along with changes in heart-rate during a REM period.

Key

Zeo hypnogram
Oxygen saturations
Pulse rate
 Temperature

Zeo & CPAP / BiPAP

I've posted on a couple of CPAP boards (and read at more) and it's clear that there are a lot of us who like to see what the ventilators are doing overnight and how many apnoeas & hypopneas there are. Quite a few of us own pulse-oximeters too, so this data can also be included.

One problem is that each device has it's own printout making comparing them tricky.

I created an A4 page in Photoshop and found that it was then easy to align all the graphs as long as all the monitors were were started and stopped at the same time (or as close as you can manage).

You can either print all the various outputs to PDF files using either Adobe or the free CutePDF then open them in Photoshop or you can take a screenshot from each piece of software.

Then cut and paste each graph onto your A4 blank and stretch them so that the start and stop times align.

Below is an example of one from a night of my son's BiPAP data. 

It includes: 

• BiPAP output (Pressure, RR, flow rate, triggered breaths, apnoeas etc)
• Transcutaneous CO2 (actually a reprocessed photo of the onboard graph)
• Oximetry trend
• Pulse rate
• Zeo 30 second resolution hypnogram
• Zeo 5 minute resolution hypnogram

I then pasted bits of relevant data from Zeo and the oximeter around the edge.

This is from a night of making adjustments to the backup rate of breaths and is a good example of what aligning the data can reveal.

Take a look at the highlighted strip and work down from the top...

• The backup rate had been increased a couple of hours before. 
• Then in the highlighted part you can see that the number of breaths increased even more.
• However, there was a much higher increase in the number of breaths he was doing for himself

Why?

When you look down to the Zeo hypnogram it becomes clear. The extra breaths were waking him from sleep, hence his spontaneous respiratory rate increased even more.

The backup rate was too high, so I reduced it.

I have also tried the Zeo with CPAP on myself.

Here is a simple overlay of the Zeo hypnogram onto the ResScan report. (I pasted the hypnogram into a new layer in Photoshop and then made it semi transparent).

A correlation between minute ventilation and periods of being awake (actually broken REM according to the 30 second hypnogram) is easy to see.

Also the apnoea flags point to me losing deep sleep due to apnoeas.

More about that and what I plan to do about it in another post though.

Zeo Sleep Monitor

In many blog-posts I'm going to be talking about some devices that I use to monitor my sleep. So I thought it best to explain a bit about them. The first one is the Zeo.

There are two flavours of Zeo, a bedside unit and a new mobile version that pairs with your smartphone.

 

 Both devices consist of a wireless headband containing fabric electrodes which are used to measure your brainwaves using EEG technology. Previously EEGs were confined to sleep laboratories and hospitals. They involved gluing electrodes onto your scalp and connecting them to a computer in order to detect the voltage changes that take place in your brain. Interpreting these EEGs is a skill in itself.

During a full polysomnography sleep study, a sleep technician will manually look at each 30 second chunk of data (epoch) from the EEG (then combine it with data from what your eyes were doing and how tense your muscles were) in order to determine which stage of sleep you are in. Zeo is much neater and doesn't involve glue or wires.

A typical night with Zeo goes something like this:

• When you are ready to sleep, remove the headband from it's magnetic dock/charger
• Place the headband on your head with the block roughly central on your forehead
• Wait for the little symbol of a head to illuminate (that means it has detected a brainwave pattern - always a relief)
• Sleep
• Wake, remove and re-dock headband

Both versions allow you to instantly see how you slept last night but you can also upload and view the data via the Zeo website. The site allows greater analysis of how you slept; you can also complete a sleep journal detailing coffee and alcohol intake, your "morning feel" and various other factors to help you see a cause-and-effect relationship between them and how you sleep.

A device that reads your brainwaves... you know you want one. This is where you can get them from in the UK: http://myzeo.co.uk/

So, what does the Zeo actually measure?

As previously said, it uses an EEG, combined with an EOG (eye movements) and EMG (muscle tone) to determine which state of sleep you are in. It then presents this to you in a colourful graph called a hypnogram.

Whereas a sleep technician looks at every 30 seconds, Zeo examines every second of data and makes a decision, it then amalgamates these into 30 second chunks using a proprietary scoring system.

The makers of Zeo have released a special firmware for the bedside unit that allows you to plug a computer into the port on the back and see the actual EEG and play it back in the morning. You can see all the little blips and squiggles and how they relate to your sleep.

 This, for example, is a "Sleep Spindle" it signifies that I was in stage 2 sleep...

Sleep consists of cycles of deep, light, wake and REM (Rapid Eye Movement). On a formal hypnogram you may see these listed as an N and a number. The N simply means Non-REM. N1 and N2 are considered to be light sleep. N3 (and sometimes N4) are considered to be deep sleep.

Early in the night is when you get the most deep sleep, which then decreases through the night and is "replaced" with increasing amounts of REM

 Hence, a normal hypnogram (sleep stage graph) should look something like this:

Graph taken from "A good night's sleep part one: Normal Sleep" by Dr Sue Wilson.
"Nursing & Residential Care", November 2008

Zeo's hypnograms display data at resolution of 5 minutes. The 30 second resolution graph is available by exporting the data into a spreadsheet program.

This is one of my recent hypnograms from Zeo, and as you can see it's a mess...

That's where the Zeo's journal comes in... WHY is it a mess? Too much coffee in the afternoon? Too much wine in the evening? Is the room too warm? Do I always wake up at the same time in the night? Why is that? Could it be the heating making noises? etc etc.

By looking at the patterns, you can aim to work out why your night is disrupted (if it is). If you are one of the lucky ones who seem to sleep normally then you can aim to improve on that sleep to make sure you feel bright and energetic in the mornings.

What's wrong with my graph?

Looking at the the night shown above, there are a couple of things that jump out:

• Deep sleep - not enough of it, and doesn't follow the pattern of decreasing through the night. This is clear because my body obviously tried to catch-up on deep sleep at 7:30am!
• I have WASO (Wake after sleep onset), but it seems that they are not random, they seem to be clustered around what should be solid chunks of REM. 

These REM disturbances are what I believe leads to episodes of sleep paralysis. I will do a blog post on that later, but there is a good article on Wikipedia about it here: http://en.wikipedia.org/wiki/Sleep_paralysis

So all in all, much to improve on.

I did suspect that I had REM related issues. Maybe a small part of my son's condition is hereditary? Maybe not, maybe it's just coincidence.

For the 10 years that it took to get my son's sleep and breathing under control I was forever listening out for his oxygen alarm. He would stop breathing during REM sleep and the alarm would sound to alert me to it.

I'd then wake up, glance at the alarm on the camera that I'd installed and then go in to rouse him from sleep and get him to breathe again.

This would happen many times a night. Children have a lot of REM! 

Maybe in some way my brain had adapted to not be quite asleep, forever on the lookout for my son's alarm that everyone else in the house slept through (including him)!

My son's breathing is now regulated by BiPAP (A breathing machine that delivers alternating pressures of air via a mask - more about that in another post). That started about 6 months ago, so I thought I would have settled down into a decent sleep routine now. 

I decided to explore and used some of the cameras and monitors that I had used for my son on myself. After a couple of nights I now have a fair idea of why I wake in REM. So, I've decided to be a bit more disciplined about collecting data and recording what I'm up to.

This week I'll be gathering data for 5 nights (Mon - Fri) and will post the data and its mean as a baseline for my sleep, then I am going to try a different method of "fixing it" every 5 nights (Mon - Fri) and average for consistency.

I'll blog the results as I'm going along.

Next post: baseline sleep scores.