Black Shadow: A Multi-Channel Sleep Study Device


In my experiments so far I've only looked at a few "channels" of data such as airflow, blood oxygen levels and sleep stage, but when you have a full sleep study in a hospital or sleep-lab many more channels are monitored, all of which provide insights into the cause of your sleep problem.


I've recently been using a hospital-grade multi-channel sleep study device that is new to the market. It's designed to be used at home or in a sleep lab / hospital. I've been using it at home. It's called the Black Shadow and it's made here in the UK by Stowood Scientific Instruments.



The Black Shadow is capable of monitoring:

  • Nasal Airflow (via a nasal cannula)
  • Oral & Nasal Airflow (via a thermal sensor)
  • Respiratory effort (ie breathing movements) (via 2 inductance belts)
  • Pulse oximetry
  • Pulse rate (via pulse oximetry)
  • Plethysmograph (pulse profile)
  • Sound recording and snore detection (from a small microphone on the cannula)
  • Actigraphy body movement
  • Body position: Left, right, prone, supine & upright
  • ECG (one channel)
  • Separate leg movements (via EMG or movement sensors)
  • Event marker (via a patient activated button)

The system also has provision for auxiliary inputs (4). It also has provision for ECG/ EEG/ EOG/ EMG data (via an additional unit).

The prospect of having all the data available in an automated unit really intrigued me. In subsequent blog-posts I'll show how I've used the Black Shadow to verify some of my previous experiments and create some new ones, but this post is really going to be an introduction to some of the things that the Black Shadow has revealed about my sleep.

In many sleep labs and hospitals, you are connected to several bedside monitors by long wires allowing you to move in bed, but making it hard if you need to get up in the night to use the bathroom. The Black Shadow overcomes this by being wearable, so once you're connected, you are free to move around should you need to.



I've no intention of posting a photo of me in pyjamas wearing the device on the internet, so I fitted it to a mannequin to illustrate how it's worn.

The next few photos illustrate some of the sensors in a bit more detail (click for larger images).




Under the shirt the mannequin is wearing three adhesive electrodes which are used to record ECG data.





The microphone and thermal sensor fix to the nasal cannula, which is then worn around the ears:





Heel / Ankle straps are also worn to detect leg movements in the night:



Also an oximeter sensor is worn on the finger which connects via a long lead to the top of the central unit. It's a flexible probe and actually a lot more comfortable than the plastic "crocodile-type" probes that I'm used to. My mannequin's hands are a bit like mittens, so I haven't fitted the oximeter probe to him.

I decided to start from scratch and take a baseline recording of my sleep (no vitamins, no supplements, no Rematee and no alcohol). After connecting myself to the various sensors I pressed the button on the front of the unit, waited for the recording light to flash and then went off to sleep.


The Black Shadow is Bluetooth capable, which allows you to configure the device wirelessly, and to see live data via bluetooth at the beginning of the night in order to check that all the channels are configured correctly. So after pairing with my laptop, and checking that everything was fine, I was ready to sleep.

Analysing the Data

The data is recorded to a high speed SD Card.
In the morning I removed the SD Card from the Black Shadow and downloaded the data to the Visi-Download software.


Not only was there a lot more data than I'd had access to before, but I was able to manipulate it and interrogate it in ways that I've never been able to do previously.



Once downloaded, I was able to see a graph of all the channels on one page along with some additional channels derived from the data: "Pulse Transit Time" (an indicator of intrathoracic pressure and an indicator of autonomic arousals in sleep), "R-R interval" and "Flatness".


The channels are able to be moved up and down the screen so that you can, for example, put the SPO2 (oxygenation) on top of the airflow channel, making it easy to spot correlations.

The software will perform an analysis on the data (using customisable criteria) and display it in a multi-page report. Once the data has been analysed, markers appear on the graphs showing events such as apnoeas, hypopneas, pulse rate changes, oxygen desaturations, snores etc.

Zooming in on an event allows you to verify it, and if necessary disregard it.

Positional Data

As expected, it was easy to spot that I did indeed have respiratory events through the night. Once analysed, my AHI was calculated to be 7.24 which agrees nicely with my previous 5-day mean score of 7

Comparing selected channels with the body-position channel, it was also easy to see that the vast majority of my respiratory events occurred while I was sleeping on my back. (Click for larger image).

The body position channel (3rd down) shows the first half of the screen with me on my back turning onto my right side for the second half.

Comparing the supine to side-sleeping data it is clear that (From the top down):

  • My SPO2 (oxygen saturations) are higher and stable with side sleeping
  • My pulse is lower and stable
  • Change in body position from Supine to Right
  • My snoring stops (filtered sound channel)
  • My oral/nasal airflow is stable
  • My leg isn't twitching
  • My body movement is greatly reduced

The improvement is revealed in a table in the report:

It's possible to exclude periods of data from the analysis by highlighting them; so for example, by only looking at the periods when I slept in a supine position (on my back) I could see how my AHI was if I only slept on my back.

All of this is a great indicator that positional therapy such as the Rematee would help my sleep problem.

Obstructive vs Central Apnoeas

The two respiratory effort channels allowed me to see whether my apnoeas were obstructive or central in nature. Obstructive apnoeas are where the body still tries to breathe (ie the intercostal and diaphragm muscles still move as normal) but the airway is obstructed, rendering the effort useless. Central apnoeas are where the brain doesn't signal the muscles to breathe, or the signal is blocked for some reason.

Each respiratory effort graph relates to one of the inductance belts that are worn around the chest and stomach. The graph therefore shows the chest and stomach movements, and hence if an effort to breath was made how strong it was in relation to other breaths.

My graph showed that I still attempted to breathe and yet no airflow was recorded, this makes my apnoeas obstructive in nature. (Click for larger version)

Audio Recording & Snore Detection

The Black Shadow records sounds continuously through the night, so unlike my attempts with a voice-activated dictaphone, you are able to hear sounds leading up to an event rather than just a second or so after the event itself.

Because the microphone is calibrated, the sound channel is graphed according to sound amplitude in dB. The software also creates a second sound-channel of sound that is filtered to highlight snoring. The detected snores are then marked automatically, making it easy to click on the graph and actually hear the snore. Listening to sound can be done at any point of the night, not just snores, so it's possible to hear sleep-talking and other noises.

I'd like to say that I sleep silently, and that the Black Shadow didn't detect any snoring from me, but that would of course be a lie because I snored a lot. The report (above) showed that I snored at a level of above 55dB for 90% of the night! 158 snores were louder than 75dB, which is roughly the noise level generated by a lawnmower!

This is a screenshot of 23 seconds of my sleep. Four snores are shown which were detected and marked automatically, these correspond to the snores that have been isolated on the filtered channel. What I find interesting about this screenshot is that the vibrations caused by my snoring are visible on the airflow channel (top - orange line).

(Click for a larger image)

Again, I was able to see that most of my snoring took place while I slept on my back.

Leg Movements

When I took a look at the leg movement data I saw something that surprised me.

Like most people, as I drift off to sleep, I twitch a bit. If I'm laying on my back I know that my left leg is prone to having the odd twitch (since I injured a disc at L5 in my spine), and this also happens when I'm sitting using my computer late at night, but I didn't suspect it happened when I was asleep. Looking back, I probably should have done.

Sometimes arousals from respiratory events will cause a body or leg movement, but I was seeing these twitches in periods of sleep that were free of respiratory events.

This is what I saw when I looked at a 12 minute section of my data (click for larger image):

At 1:15 am my left leg (leg 1) started to twitch slightly, and as you can see the amplitude increased almost with each subsequent movement over the next 4 minutes. This then caused me to turn from my back onto my left side (shown by the Body Position channel in blue). This happened several times a night, in all sleeping positions and on more than one night. Although I haven't been able to eliminate them, maybe this is an indication of why the Vitamins and Minerals improved my sleep as Iron is thought to be beneficial to Periodic Limb Movements.

Those legs movements and the subsequent turning over could be a problem if it happened often enough because it is yet another thing that can cause a sleeper to awaken briefly. These small awakenings are called micro-awakenings (or micro-arousals). The higher the number of these there are in a given night, the more your sleep is disrupted and the greater the likelihood of waking in the morning still feeling tired. If I want to improve my sleep further then these are the sort of things that I need to be aware of.

Pulse Rate Increases

The Visi-Download software also shows other arousals which are calculated from my heart-rate data.

This section of my sleep shows how a cluster of respiratory events (marked by the blocks under the airflow line) affected my oxygen saturations (top red line). If you look at the other data shown in line with those events you'll see that not only was my heart rate affected, but also my Pulse Transit Time - a very good indicator that I was continuously being woken (brief)y by my respiratory disturbances, causing fragmented sleep.

The Pulse Plethysmograph also shows changes, even on this timescale because the arousals went on for a prolonged period of time. Shorter micro-arousals are able to be seen using the PTT and Pleth channels when looking at a smaller timeframe.

Event Marker

Pressing this button during recording causes a marker to be inserted into the data. This could be for any event, such as being woken, waking from a nightmare, feeling unable to breathe, or even (as I plan to use it) for marking lucid dreams and sleep paralysis. 


The Black Shadow opens up many additional ways for me to explore and hopefully improve my sleep and I'm looking forward to experimenting further with it.


Additional Links

Non-invasive Monitoring of Vital Signs Utilising Pulse Wave Transit Time

Use of Pulse Transit Time as a Measure of Autonomic Arousals in Patients with Obstructive Sleep Apnea

Pulse Transit Time Improves Detection of Sleep Respiratory Events and Microarousals in Children - Pepin et al

Obstructive Apneic Events Induce Alpha-receptor Mediated Digital Vasoconstriction - Zou et al


Lucid Dreaming - Wake & Back to Bed

A few nights ago I had a spontaneous lucid dream.

The curious thing about this is that I can pin-point when it happened on my hypnogram, so I thought I'd share it on here.

First let's take another look at a near-perfect hypnogram. This is from my son's sleep and is about as near to textbook as I think possible in real-life:

Adults will typically get less REM than this, but the pattern should still be the same. Slow-wave (deep) sleep in the first half of the night, decreasing as the night wears on then increasing amounts of REM into the morning.

In my previous post about Lucid Dreams I mentioned a method of inducing lucid dreams called "Wake and Back to Bed". Essentially it goes like this: 

  1. Go to bed at your usual time
  2. Set an alarm for the early hours (say 4am)
  3. Wake when the alarm sounds
  4. Get out of bed and read for an hour or so
  5. Return to bed

This has the effect of causing your REM sleep to be concentrated in the period when you've returned to bed (the idea being that your body is now screaming out for the REM that it should have had when you were awake for the hour). The period of being awake should also "sharpen" your conscious mind so that it is more likely to be aware of the dreamworld when it next encounters it.

For my lucid dream, this happened by accident as is good evidence that the method works.

I spontaneously woke at my usual weekday alarm-time which was ridiculously early for a Saturday morning, so took off the Zeo headband, flicked through the news and Twitter on my phone (still in bed), then decided to have another go at sleeping.

I didn't get a mass of REM in this second sleep, and most of the "sleep" that I did get was light dozing, but there was an isolated period where I slipped into REM and had a lucid dream. This can be clearly seen on my Zeo hypnogram for the night:

I know that it's boring listening to other people's dreams but to give you an idea of how lucidity evolves I'll outline it...

I was in a restaurant in France. I was sitting with my extended family who took up most of the restaurant. Then I realised that people were "tutting" at me. Somehow I'd managed to offend the restaurant owners. 

It seemed odd. After a while the tutting turned to people talking about me as if I wasn't there. I looked down at my plate and realised that the tables were full of rain. Again, more oddness. Water was actually flowing around our plates as if we were eating in some sort of water feature.

It began to make less and less sense, then I looked at the faces of the people who I thought were family. I didn't recognise any of them. 

Then it hit me: people's faces changing, changed laws of physics, feeling of conspiracy... it was a dream. I still wasn't sure, so I calmly did a "reality check" (Something that I don't get to do in dreams that often)... I counted the fingers on one hand. Five... so it must be real. I looked at my hand again and saw an extra finger! 

Ha! Definitely a dream then. 

I got up to leave and (almost symbolically of the dream trying to re-capture me) found that the people in the restaurant were trying to prevent me from going. I managed to get out of the door which seemed to pull me back like a magnet, but eventually I was in the street outside. 

More symbolism: The world outside was definitely the dreamworld, it was a town mixed with cartoon imagery complete with giant cartoon people using skyscrapers as stepping stones. 

Anyway, I won't go on, but as lucidity came on slowly I was able to stay calm and stay in the dream, rather than waking. Eventually after a couple of periods of forgetting I was dreaming and becoming lucid again, the dream won and settled into a normal dream. The dream covered about 3 days, but as you can see from the solitary green bar on the hypnogram, it lasted not much more than 5 minutes.

This is definitely a method that I think is worth exploring further.


Sleeping Position: Get off your back!

When you have a multi-channel sleep study, one of the "channels" that is examined is the position that you sleep in.

At first this may seem a strange thing to monitor, after all if you manage to achieve sleep, who cares how your inert body is positioned? 

Sleep position affects several aspects of our sleep, for example when I sleep on my back I find that:

  • I experience more sleep paralysis
  • I experience more body twitches as sleep begins
  • It's also known that breathing is harder when sleeping flat on your back (supine), it is for this reason that patients with higher level spinal injuries are recommended to sleep with their head inclined and foot of their bed lowered as this can actually increase their vital capacity
  • GERD / Acid Reflux / Heartburn is affected by sleeping position. Raising the head of your bed can prevent or at least reduce reflux episodes.

However, in this blog-post I'm going to concentrate on another major effect that supine sleeping has on the sleeper...

Supine sleeping can dramatically increase the number of obstructive apnoeas and hypopneas a sleeper has through the night!

The reason for this is that gravity has a greater effect on the muscles and soft tissues that relax in sleep and cause obstructive apnoeas. If you can lie on your side then gravity doesn't affect them in the same way, and can go some way to keeping the airways open during sleep.

Invariably we move around in our sleep so I needed a way to monitor my sleeping position as my monitor doesn't have this ability.

More sophisticated sleep study devices do this automatically, and there is actually an iPhone app that can do this for you too: Somnopose, after a couple of night of experimenting with the app you should be able to get a fairly accurate reading. You will probably be surprised how many times you actually turn over in your sleep.

This was actually quite easy for me to do manually as I already had my infra-red camera watching me for several nights during sleep. I then analysed the video to determine my sleep position. As well as recording continuously, the camera creates a new file every time it detects movement, so all I had to do was flick through the files and record the position on a chart alongside my oxygen desaturations. I did also plot a chart of body position against detected apnoeas, but the chart below shows things clearly enough.


 s=supine (back), p=prone (front), l=left down, r=right down

It was no surprise to see that the majority of my apnoeas and hypopneas occurred when I was sleeping on my back.

On several nights I deliberately began sleep on my side, but always woke to find myself flat on my back again and with a high AHI recorded. I needed a way to prevent myself from turning over in the night.

Years ago, a solution to positional obstructive sleep apnoea was to "sew a tennis ball into the back of your pyjamas", this had a "Princess and the Pea" type effect on the sleeper and caused them to be uncomfortable if they turned over and slept on their back.

Nowadays there are more sophisticated solutions, and the one that I put to the test is called the "REMATEE Bumper Belt". It's a neoprene belt that velcro fastens around your chest. At the back of the belt are pockets into which you place inflatable "bumpers". Sounds strange?

It may be clearer if I show you a photo of what I'm describing. Rather then subjecting you to a screen-capture from my camera, I'll use a product photo instead (click for a larger version).

It's surprising how quickly you get used to it.

My belt also has shoulder straps to stop it turning round in the night although when it first arrived I was slightly daunted by the idea of being strapped in, so I decided to tuck the shoulder straps into the pouches that held the bumpers.

I found that if the belt was tight enough then I didn't need to use the shoulder straps, but it does take a few nights of trial and error to get used to how tight to wear it and how much air to put in the bumpers.



When the belt first arrived I tried it out for a few nights without monitoring my breathing and found that it did affect my Zeo stats. It increased my REM sleep. It also reduced the number of awakenings that I had through the night.

Initially, it seemed to decrease Deep (SWS) Sleep but this stopped and my SWS actually increased after a few nights of using it. (See graphs below).


Then I began my five nights of recording my breathing...

Again I followed my rules for determining my 5-night mean data with the obvious exception of not beginning the night by sleeping on my back. I also didn't take any of the supplements discussed in this blog, and I stopped the vitamins and minerals on the Friday beforehand to try to eliminate the effects of those on my sleep.

The results were clear:

The REMATEE belt kept me off my back and reduced my oxygen desaturations:


 s=supine (back), p=prone (front), l=left down, r=right down

My AHI each night was dramatically reduced:

This brought my 5-day mean AHI down to 1.70.


This makes the REMATEE the most effective method that I've found so far to reduce my AHI. 

The reduction in respiratory events (reflected by the reduced AHI) also had a positive knock-on effect on my Zeo data...

Considering that most of my respiratory events happen in REM sleep, it makes sense that when the number of events was reduced, my REM increased (because it was not being broken by me waking up to breathe). As already discussed, my Slow Wave Sleep (deep) also increased.

Will I carry on using the REMATEE? Definitely.

As a follow up, I plan to combine the REMATEE belt with my 5-HTP routine as both seem to reduce my AHI through different mechanisms. Maybe their combined effect will be greater than as individual methods.


Additional Links

The REMATEE Bumper Belt is available in the UK from Intus Healthcare:





Actigraphy: Only Part of the Story...

Actigraphy, or the monitoring and charting of the movement that we make, is an established means of monitoring sleep, albeit not a very detailed one.

The patient wears a movement monitor(s), the data from which is essentially processed as "not moving = asleep" and "moving = awake". As you can see, this can only really tell us the two states and not provide more accurate sleep stage information. 

Actigraphy is not a substitute for a full sleep study, however the data it provides can be used to augment a sleep study.

There are many consumer actigraphy devices on the market today, and also many intended for professional use. I am only concentrating on the consumer devices. The professional devices are a lot more sophisticated.

A few months ago I tried out a couple of the consumer devices myself, and pretty much dismissed them as I found that they didn't really add anything to my existing set-up consisting of nasal airflow, oximetry, capnography, IR camera and the Zeo.


First let's take a look at the devices and the data they provide:

 The first device is the "Wakemate". This consists of a small circuit board that fits inside a wrist-worn sweatband.

The on-off switch protrudes directly from the circuit board, which had me worrying that it would soon break after repeated use, however it seemed secure enough once tucked inside the padded band.

Once paired with your smart-phone, the device uploads its data via bluetooth. 




The second device is the "Lark".

This is similar to the Wakemate, although it felt sturdier and had a nice charger dock with it.

The electronics are encased in a sealed unit which is then inserted into the wristband.


 To give a fair test to these gadgets, I wore them both on the same night, both on my non-dominant wrist. Once I'd downloaded the data I was able to find a chart of time vs movement. Both charts aligned well:

 (Wakemate - top. Lark - bottom)

The Lark's graph is more detailed than that of the Wakemate, and shows some analysis has already taken place on the data. It highlights large movements blue signifying periods of wakefulness and leaves smaller movement orange.

More data is available from both devices, such as total time awake, total time asleep, time in bed etc.

I then compared the above graphs with the Zeo hypnogram from the same night...

By doing this some of the limitations of actigraphy become clear. I was actually awake for an hour between 1:15am and around 2:15am. During this time I was lying still, hoping to fall asleep again. The actigraphy-based devices interpret this period of stillness as sleep, albeit with some movement. Being still does not equate to being asleep. Consequently, if a partner is moving around in the same bed as you, it is possible that the actigraphy would detect their movement. 

However, it was good to have my broken REM (around 4am) confirmed by the actigraphy devices. At this time I was suspecting that the Zeo was detecting some of my REM as wakefuness (a suspicion that I later ruled out). During normal REM sleep muscle atonia prevents us from moving, so seeing that I actually moved during REM added to the growing evidence that I really did wake during REM sleep.


Whilst looking into actigraphy, I also found a popular iPhone app that makes use of the accelerometer in the phone. It's called Sleep Cycle.

The phone is placed at the top of your bed, near your head, it then monitors your movement (based on how the bed moves) in the night.


It's actually very simple, but I found that it was surprisingly accurate when compared to the Zeo. It correctly identified two periods of being awake and one period of deep sleep. I suspect in a healthy sleeper, it would confuse REM sleep and deep sleep.


I have also used the AxBo "SleepPhase" alarm clock. This is a clock that comes with two wristbands which wirelessly communicate with the clock. Each wristband contains a sturdy sealed module that detects movement. The intention is that two people can use this clock.

I purchased the AxBo before I had any other consumer devices. I still had the oximeter and the capnograph, but no Zeo and none of the actigraphy devices mentioned in this blog-post.

However, after purchasing the clock and using it for one night, I realised that it doesn't actually show sleep stages. I probably should have realised beforehand. 

The sensors are actually very sensitive, and show more movement information than anything I've previously discussed here. They can actually show which axis the movement takes place along. However, after a couple of nights of wearing the band and looking at my movement data I thought "Okay, but so what?". I wasn't actually sure where to go from there as I wasn't interested in the clock's ability to wake me up at an optimal time, more in its ability to chart my sleep.

A device for sleep and wake?

As part of a health kick (and weight loss), I have been using a device called "FitBit". It looks like a very slick pedometer, but it is acutally a lot more sensitive. It uses an accelerometer to determine steps taken in day, how many flights of stairs you climb, how many calories burned, and sleep-actigraphy similar to the devices mentioned above.

The difference between this and a standard pedometer is that this can show you, in graph form, when the activity occurred during the day.

The bonus with the FitBit is that the "FitBit Dashboard" lets you link your data with other "Quantified Self" devices such as the Withings bathroom scales, which in turn lets you link your data with your Zeo ZQ. 

This all adds up to a feeling of being part of a bigger programme, a programme that encourages you to look at all aspects of your health see the effect that lifestyle changes have on your data (and on you). You can actually quantify your exercise, which in turn reveals a greater weight-loss which hopefully will have an effect on my sleep quality, which will be seen in the ZQ.

Anyway, I've lost 9lb so far and I plan to carry on until I get down to my target weight and then I'll blog the combined results.

Quantifying the exercise that I do in terms of steps taken, flights climbed and calories used should allow me to see a correlation between FitBit exercise and Zeo deep sleep, maybe a correlation with sleep and a quantified "power-down hour" in the evening; who knows, it may even reveal a REM correlation too.

How did FitBit do when compared to Zeo for sleep analysis?


Again, it compared well, with the exception mentioned above (that being still in bed does not equate with being asleep), and to be fair, the Zeo 30 second data does show me drifting into and out of sleep at a couple of points in the large period of wakefulness at the end before I eventually gave up and got out of bed, but for the most part I was awake and just being still.

However, none of the actigraphy devices show sleep-stage data, and (as I'm learning from the fascinating "Quantified Self" movement) more data means a greater ability to "hack" yourself or to help yourself.

By using actigraphy as the sole gauge of good sleep you are blind sleep stage data. Having access to my sleep stage data allows me to target specific stages that I think need attention: If your slow-wave-sleep (deep) is too low then you can exercise to increase it. If your REM is broken or too low then you can try supplements and mental exercises to put it right. This is not possible if you can only tell that you were moving when you were supposed to be asleep.

Having easy access to my sleep stage data set me on the road to investigating why my REM sleep was broken. I was easily able to correlate my drop in oxygen levels to REM sleep using a cheap pulse-oximeter, and from there, with the addition of another channel - airflow, discovered that REM-related apnoeas were the cause. From there with the addition of another channel (motion activated IR camera) I was able to add "positional" and "obstructive" to that diagnosis. Giving me the full diagnosis of "Mild REM-related positional obstructive sleep apnoea".

With a correct diagnosis, I was then in a better position able to properly assess treatments (more of those in a later blog).

This would not have been possible had I only known that I moved during my sleep as the correlation with REM would not have been detectable, although, to be fair,I could have gone onto diagnose apneoa without sleep stage data, it would have not given me the full picture. In fact looking at my sleep using only actigraphy (when I only had the AxBo), made me pretty much give up after a couple of nights. Nothing made me want to look into my sleep further until I had the Zeo and Oximetry data.

I continue to use the FitBit during the day, but I eventually consigned the other sleep-actigraphy gadgets to the bottom drawer until I realised that by using these devices slightly differently that I could use them to add additional channels to my setup, in theory anyway...

A cause of poor sleep is Periodic Limb Movement Disorder, in which the sleeper's legs twitch and move involuntarily during the night, causing them to wake up, or partially wake up (micro-arousal), both of which lead to disturbed sleep. 

By fixing the actigraphy devices to the sleeper's ankles it would be possible to detect this. It might even be possible to detect the leg movements as a cause of waking up, rather than as a consequence of it if the devices could be accurately synchronised. The only thing that concerns me about this is that the timescale on the axis of the movement graphs may not be detailed enough to show the movements occuring before an awakening. Oddly, I think the Axbo would be best suited to this, as the software allows the most flexibility in analysing the data. However, this will have to remain a theoretical test as I don't have an issue with PLMD.


(All device photos are from product websites unless indicated)


Lucid Dreaming



Imagine that as you read these words you hear a voice from nowhere telling you "You're dreaming..."

You may even tell yourself that you just imagined it, but what if you listened to the voice?

What if you then looked around and saw clues that all was not as it seemed?

What if you then realised that you were actually dreaming? You'd realise that you were essentially a character in a story that your sleeping brain was dreaming up.


As the author of this dream you'd them be able to control aspects of it. You'd be able to communicate with your sleeping-self and in essence become a god in a universe that you created.

Crazy? Maybe. Impossible? No.

This happens to people, and it happens to me...

I was dreaming. I couldn't remember how I got there but I was trapped in a room with no doors and no windows. There was, however, a large mirror on the wall. 

Something changed: I stopped worrying about getting out and instead tried to work out how I'd managed to get there in a room without an entrance in the first place.

"It's got to be a dream", I told myself.

"Well, if it's a dream then I should be able to walk through the mirror and escape."

So I tried - face first...

... and after a bit of pushing I found myself in a stairwell on the other side of the mirror. "Yep, definitely a dream" I thought as I became aware of the other me - the "real me" asleep in my bed.

"Wow! I'm dreaming". I did the obvious thing and tried to fly my way to safety; slowly I was hauled upwards by the shoulders and flew for about 300 yards. As I get more involved in the story I somehow started to forget that it was a dream and after a few more episodes of realising and forgetting that I was dreaming it settled back down into a normal dream.

Sounds familiar? "The Matrix"? Pretty much, although it's an older idea in the world of philosophy. It's essentially a scaled down version of Gnosticism. In Gnosticism our world is the dream-world and there is a "real world" in which our awareness exists watching us play our parts in the "here and now". Like a set of Russian Dolls, we are also able to create a fake world in which we can lose ourselves in the experiences that it offers.

For some people these dreams happen spontaneously, meaning that they don't have to prepare or practice in order to get to hame them. Others can only dream of having a dream like this (poor choice of words really). The idea of a normal dream is mind-blowing enough when you think about it: every night we go to sleep and lose our sense of identity. We lose sense of the passage of time and we forget that we are The Dreamer Dreaming, we actually feel as if we are the character in the dream...

...but with a lucid dream we adopt a dual consciousness: our real-life identity returns and we can watch the dream from the vantage point of that identity from the comfort of our bed knowing that whatever happens we are safe, we can take more risks in the dream, we can have fun with the story rather than fear it, we can even shape the dream-world, yet we can also simultaneously adopt the vantage point of the dream characters and get involved in the story. You are both the Dreamer Dreaming and the Dreamed.

My first lucid dream was a spontaneous one and it happened on the night that I had three episodes of sleep paralysis. The sleep paralysis was the trigger that told me that I was dreaming. From that moment on I was in the dream, but still able to reason with the dreamer part of me.

Lucid dreaming isn't just an interesting sleeping-habit, it has actually been used to help people control re-occurring nightmares.

How can you make lucid dreams occur?

If you aren't one of the lucky ones that have had lucid dreams spontaneously (or you want to able to increase the frequency with which they occur) then there are a few things that you can do to help turn a normal dream into a lucid one:

Dream worlds seem to be comprised of disjointed scenes with the brain doing its best to link them together in a narrative, as such the rules that govern the dream world can differ from scene to scene, hence if you check, you may have 10 fingers one moment, then the next moment 11 when you check again. This sort of clue should be enough to alert you to the fact that something isn't right and that you are in fact dreaming.

Most people talk of performing "reality checks" where throughout your waking day you constantly check whether you are awake. You can simply ask yourself if this is a dream, or you can perform some checks to see if you are really awake.

These sort of "Reality Checks" don't really work for me, instead I question my surroundings. Do this during the day and it should carry over (sometimes) into your dream.

The big pointer to me is a lack of continuity, such as the night when I entered REM sleep as soon as I closed my eyes (confirmed by Zeo)...

 (Click for larger image)

...I was suddenly in the back of a car that was being driven along a mountain road, I had the sense that we were late for something and possibly being chased but my first thought was, "...but I was in bed a moment ago, how did I get here?". That questioning was enough to shatter the illusion and I became aware that I was still in bed (even what position I was sleeping in), and yet I was still in the dream. So Chitty-Chitty-Bang-Bang style I was able to make the car fly to the meeting that I was late for.

When you wake from a normal dream, you may well kick yourself because something in the dream was so odd that you should have realised that it was just a dream. These are the sort of things that you can look out for to act as a prompt for you to question your surroundings.

Question everything:

  • How did you get where you are?
  • Who are you with? 
  • Why are you there?
  • Is time flowing as it should - were you older a short while ago?
  • Can you fly?
  • Do doors take you where they are supposed to? Actually walk through a doorway rather than assume you have just walked through it. (For me, doors usually take me onto the roof of a building).

Other things to look out for are sounds that don't belong there. I've had several lucid dreams that have been triggered by noises that make their way into the dream. Examples of that are:

  • During the summer I slept with the window open one night. I dreamed that I was standing beside a really busy airport runway with planes rushing by every few seconds or so. As I listened to the noise I realised that they weren't planes but they were actually cars going by my house. This triggered a lucid dream.
  • I was dreaming that I got out of my car, then I heard myself growling... "Oh great, now I'm a werewolf", I thought to myself. I then listened more to the growling that I was making and realised that it was actually snoring, from there it was an easy jump to realise that I was actually dreaming and could hear myself snoring. The dream became lucid from that point.

Several devices make use of this principle.

I've already mentioned Dan's ZeoScope software elsewhere in this blog. This works in conjunction with the raw data from the Zeo Bedside unit. When you have been in REM sleep for a certain time, ZeoScope plays your choice of mp3 to you. This then "leaks" into your dream as a signal to you.

There are also several iPhone apps that do something similar, although they only guess at when you are likely to be in REM as they have no way of telling. DreamWaker and Dreams Controller are both good examples of this. Dreams Controller also goes to the lengths of prompting you to perform reality checks whilst you are awake. The first time I tried these apps I became lucid, and a certain school of thought says that is likely due to the "beginners luck" effect where your anticipation and expectation of a lucid dream causes it to happen.

To a degree, the principle of a stimulus leaking over from the real world to the dream world also applies to sights as well as sounds.

The NovaDreamer is a device that looks like a sleeping mask, but with red LEDs built into it. An infra-red LED detected when your eyes are moving (hence you are in REM sleep) and then flashes the red LEDs to alert you. In your dream these red lights can become anything from a police car to a volcano. Your job is to realise that anything flashing red in your dream is a signal that you are dreaming. 

I've had limited success with the NovaDreamer and a similar device called the REM Dreamer, although I found that they often woke me up.


Other tips:

  • No alcohol - If you do achieve lucidity then (for me) it is always short lived and usually becomes an episode of sleep paralysis.
  • As you drift off to sleep really be aware of your surroundings. Note your bedroom, your position in bed etc
  • REM deprivation helps. Maybe this is because when you next achieve REM it will be much nearer to the start of sleep meaning that you can carry the awareness mentioned above over to the dream.
  • If you become lucid, don't get too excited otherwise you'll wake up.
  • If you become lucid, keep reminding yourself that you are dreaming otherwise you'll forget.
  • Read about lucid dreaming before you go to sleep, surprisingly this can help as you may dream about lucid dreaming (which will then be a pointer to you in your dream)
  • Set an alarm for around 3am. Wake up and actually get out of bed, don't just doze, you need to be fully awake. You could read for a short while (maybe an article on lucid dreaming would help), then return to bed. This time of the morning is when REM sleep is increasing. This time awake should allow you to enter REM pretty quickly, almost with a vengeance.

Supplements to aid lucidity?

Pills and potions to aid dreaming are nothing new; many works of art such as this fantastic watercolour by John Anster Fitzgerald painted 1857-1858. I have a copy of this on my wall, and yet I am not certain of the name. I suspect that, like Fuseli's work, it is called "The Nightmare", but I've also seen it listed as "The stuff Dreams Are Made Of", although  I think that name may relate to later versions where the bottles (probably containing opium) have been omitted.

Opium aside for obvious reasons, there are a number of nutritional supplements that have an effect on sleep and consequently dreams.

I've tried a few supplements to try to reliably encourage lucidity, with some partial success. It's partial because nothing seems to do this on it's own but with a little preparation they seem to help, but proceed with caution (don't treat anything you see on the internet at automatically safe - my words included. Look both ways before crossing, chew your food etc etc), and research any supplements for yourself before you decide to use them. 

A short word on dosage

Melatonin: the dose given in the BNF is deemed to be the most effective dose. I am well aware that I am taking more th
an that, although singles doses as high as 10mg are on sale and studies of daily doses of up to 75mg have been conducted (MacFarlane et al.).

Vitamin B6: Although 200mg doses are on sale in the UK, it is not recommended to take them on a long term basis as they can cause side effects which appear to reverse when the dose is stopped

Yesterday (in the real world) I was driving for 350 miles and listening to audiobooks discussing consciousness, quantum physics and Gnosticism. I realised that this stuff would be floating around my head during sleep as my brain processed the events of the day, so I thought there would be a good chance of lucidity that night. 

This is the routine that I've found seems to help:

45 mins before bed: 5mg time release Melatonin
30 mins before bed: 200mg Vitamin B6
When in bed:  1mg Melatonin (not time release)

It is known that too much Melatonin will be counter-productive and cause you to wake up. I think my method actually makes use of this effect. The British National Formulary sets 3mg of time-release Melatonin as the correct dose for an adult over the age of 55 (Not usually prescribed for people below 55) Generally 0.25mg of instant release is enough to initiate tiredness and hence sleep - the sustained release version ensures a trickle dose throughout the night. 

I usually find that I wake up fully after a few hours. This is when I then take a further

1mg Melatonin (not time release)...

...which sends me back to sleep within about 20 minutes. That's it. I normally find that will give me lucidity or sleep paralysis (which can be converted to a lucid dream which may even take the form of an OOBE - Out Of Body Experience).

It's not a guaranteed method, but on the nights that I've tried it (a few times a month for several months), usually something has happened, even if the effect was short lived. I suspect that lucidity would last longer if I were calmer when I realised I that it was a dream. 

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