CPAP - It's well worth taking the time to get it right

Previously I'd used CPAP for a few days to try to get an idea of how my son felt as he started to use it.

Initially I tried it in the hospital where it was prescribed. I used it whilst awake using a variety of masks and pressures to see what high pressures felt like and to see how it responded to me exhaling, holding my breath, trying to talk and opening my mouth etc. Then I used it for a few nights. I wanted to know what problems he could encounter because he isn't able to move to correct them for himself, so I thought that if I were familiar with some of the problems it'd at the very least give me a frame of reference for when he told me what issues he was having.

For practical reasons I purchased an additional CPAP (technically an APAP machine - Auto CPAP). I chose the Resmed S9 Autoset, which to its credit doesn't look like a piece of medical kit; it looks more like a modern bedside clock radio. Yes, the pressures should be set by a professional and you need a prescription to buy one but it looks like a piece of consumer electronics, which is a great thing because it doesn't make your bedroom look like a High Dependency Unit.

Resmed also make coloured "skins" for the device which would be helpful when trying to introduce it to children as part of their therapy.

The S9 has a coloured display screen which allows the user to adjust the comfort settings and climate control and to allow them to see an instant indication of whether the mask is fitted properly along with a morning readout of your AHI (Apnoea Hypopnea Index).

The S9 records overnight summary data and detailed data to an SD card, which via the ResScan software allows you to see the following data: 

• Respiratory Events via flags on the timeline (Central Apnoeas, Obstructive Apnoeas and Hypopneas)
• Pressures chosen by the machine at any given time
• An indication of snoring level
• Flow (allowing individual breathing waveforms to be seen)
• Leak
• Flow Limitation (an indicator of the degree of obstruction)
• Compliance data (how long I used it for)

An example of the data from one of the nights that my son used it is shown below.

All of this is very useful to have access to because it lets you see a record of the choices that the machine makes which helped me to trust that the machine wasn't going to deliver a high pressure unless there was a good reason to. This is all recorded automatically while you sleep at home (or in the sleep lab). Compared to a one-night study in a sleep lab (especially a split night study) the data may be a more realistic representation of your sleep because you'll be sleeping in a familiar place and adhering to your usual routine.

The output that we collected from the ResScan software was viewed by my son's doctors during his initial trials with CPAP before changing over to Bi Level ventilation (BiPAP / VPAP / BPAP)

I chose Resmed's Swift FX Nasal pillows as they left a lot of my face free, they didn't feel trapping and are easy to remove if I really felt like it in the night.

My son uses them with Bi-Level PAP and prefers them over a wide range of masks that he's experimented with, although he can't move below his shoulders he has learned to remove the Swift FX pillows by a head movement, so he feels comfortable using them as he knows that he can take it off if needed.

The S9 has an "AutoSet" mode where it can alter the delivery pressures as it deems necessary. The machine can be forced to work within a range of pressures. I decided to let the machine have a free reign and didn't force it to choose between limits. 

I managed to keep the CPAP on for most of the night, but I remember waking frequently and moving the tubing and to keep checking the machine because... well to be honest... I was nervous. The machine is very quiet which was another reason to check it every time I stirred in the night in case I'd managed to turn it off in the same way that I snooze the alarm clock. 

Over the few days I was tired because, as I said above, I'd been awake due to my own anxiety and the strangeness of it all, also I managed to get caught up in the tubing one night! The following evening I arrived home from work and dived face down into bed without CPAP. Due to my sleep debt over the previous few nights I experienced sleep paralysis and a lucid dream, so it wasn't all bad.

...and that's where my trial with CPAP ended.

However, recently I've fallen in love with CPAP and in particular Resmed's S9 Autoset (the photo above is my S9 beside my bed), and here's how it happened...

There's a lot to get used to with strange tubes and masks on you and your bed plus a new machine on the bedside table - and that's without getting used to the pressures that the machine delivers... considering this, my experience wasn't really a fair trial for CPAP, especially since it is considered to be the "Gold Standard" in treating obstrucitve sleep apnoea.

In hindsight, I suspect it would have been better to begin by choosing a low pressure and just wearing it to get used to the mask and tubing - almost a dress rehearsal before the therapeutic pressures are used.

My CPAP experience was well over a year ago and before the time that I started this blog and before the time that I realised that I had mild to moderate obstructive sleep apnoea. Now that I have a better understanding of my own sleep and have found various ways to reduce my AHI without CPAP I decided to give it another go and compare the results, after all we now had my son's "old" (barely used) S9 Autoset sitting in a cupboard doing nothing because he actually needed Bi-Level PAP.

This time I paid a lot more attention to my own AHI.

I also decided to eliminate the uncertainty of whether the machine was going to wake me with a high pressure during the night, so I did a gradual titration over several nights using the "Straight CPAP" setting of my son's backup Respironics BiPAP S/T.

I found myself making slow deliberate breaths while I tried to sleep. This wasn't particularly helpful, because (even if you aren't wearing CPAP) when you think about your breathing you find yourself consciously taking over, and to be honest this is something that our bodies do better if we don't let consciousness interfere with it.

However, I found myself calmly waking up every now then wondering why I wasn't breathing and finding that I had to consciously take a breath, I listened to machine respond, then dropped back off to sleep. This happened maybe 5 or 6 times that I remember during the night and wasn't anything like waking with a snort or a choke, in fact it felt quite strange. 

In the mornings I took a look at the data (the BiPAP S/T also records data to an SD Card that is readable via the Respironics Encore Viewer or Encore Pro software. 

I found an explanation for the breathless awakenings...

Whilst the obstructive apnoeas were few and far between, the machine had detected "Central Apnoeas". These are when the airway is open yet no air flows. This can be from a variety of causes, but from my own baseline sleep studies I know that my apnoeas are usually obstructive in nature, so I knew that these new Central Apnoeas were because my chosen pressure was too high.

If breathing is too effective at clearing CO2 from the bloodstream then central apnoeas can occur because during normal breathing the brain sends a signal to breathe when CO2 in the bloodstream reaches a certain trigger level. We then breathe causing gas exchange, (taking oxygen in and exhaling CO2), after which our bodies produce more CO2 which reaches the trigger level and the cycle begins again.

If the CO2 level is too low then the brain doesn't need to clear it, so doesn't send a signal to breathe. Our oxygen levels then drop which wakes us up and allows us to consciously take a breath.

I adjusted the pressure down by 1 cmH2O the following night, but I still wanted more data. Were these really "centrals"? A night wearing the Black Shadow Sleep Monitor whilst on CPAP confirmed that they were.

I switched machines back to the Resmed S9 Autoset because it allows you to see a lot more data as opposed to the trend data given by the Respironics BiPAP S/T. It actually allows you to look at the data at a much higher resolution (you can see every breath taken) so I could then verify any detected apnoeas for myself.

Along with the lower pressure setting, I set the S9's EPR (Expiratory Pressure Relief) to full (3) which drops the pressure down by 3cmH2O (or 1 or 2 cmH2O, depending on your chosen setting) when it detects that you are exhaling. This is very helpful, even for psychological reasons as not only does it help you to exhale, but it provides a form of tactile feedback letting you know that the machine is "listening" to you and not trying to force a gale into your nostrils whether you like it or not.

One interesting thing that the S9's additional data allowed me to see was the moment that I stopped doing those forced breaths I that I mentioned above. This is the moment that I fell asleep. 

I fell asleep fairly quickly, and woke once when I turned onto my side and found that I needed to adjust the nasal-pillows slightly.

The following morning I checked the data and found that the central apnoeas had cleared and my AHI was a very respectable 0.4 which varied over the next few nights but still remained under 1.0.

One night I found that the S9 data showed that I'd been quietly snoring, it was also on this night that my AHI was the highest that I've had so far whilst on CPAP (0.9), although this is still a fantastically low AHI.

So the next night I crept the pressures up by 0.4 cmH2O, only to find that the snoring cleared but some central apnoeas returned, so I dropped the pressures again. It became obvious that finding a pressure that was perfect for every night was going to be a challenge.

Of course I realise that there is going to be some "natural variation" from night to night due to factors such as body position and time spent in each sleep stage but wouldn't it be good to be able to pin down what the other less obvious variables are?

My main factors are related to body position (apnoeas are more likely and frequent when I sleep supine) and REM sleep (when muscle tone is decreased in the airway), but I suspect that other factors during the day play a part.

This is where the S9 Autoset excels: In AutoSet mode it adjusts the pressure it delivers based on your need at the time, so where "Straight CPAP" is limited because it can only give me one pressure throughout the night meaning that 8cmH20 may be too much for me at some parts of the night (causing Central Apnoeas), yet not adequate for other parts of the night) where 10 or 11 cmH2O is more appropriate.

I set my S9 to "Autoset" mode and adjusted the settings so that the machine would work within fairly restrictive limits just to get me comfortable with the idea. In the morning I could see from the ResScan software that the machine had delivered the maximum permitted pressure at some points in the night, so I gradually extended the pressure range over a few nights until the machine didn't reach my ceiling limit and was able to deliver the necessary pressures.

The following graph of the pressure that the S9 delivered over one of the later nights illustrates how my requirement varies through the night. 

On the night above I woke myself up snoring after several hours (just before the red vertical line), so I raised the lower limit and went back to sleep, this is why the graph above shows the delivery of pressure that is lower than permitted minimum pressure at the start of the night.

Had I been prescribed straight CPAP based on the pressures titrated on this night then I would have had to have a constant pressure of between 10 and 11 cmH2O to eliminate all my obstructive apnoeas. However, the chances are that I would have then had more central apnoeas occurring. A compromise pressure of 9 cmH2O would have removed the majority of apnoeas but would have been inadequate when my obstructions were at their most severe. There could also have been central apnoeas occuring at this pressure for some of the night.

The textbook, "Sleep Medicine Pearls" by Richard Berry MD describes this well with a case study of a patient unable to tolerate the high pressures needed to treat his obstructive apnoea. If you have access to the book you can find the details under Patient #43. In fact the whole book is packed with case studies that provide a unique insight into treating sleep issues.

If high pressures can't be tolerated it may be preferable to have a lower than optimal pressure setting just to ensure that some benefit is obtained, although it is likely that these patients would benefit more from Bi-Level PAP which allows a much lower expiratory pressure.

In Autoset mode, the S9 allows low pressures but can deliver the higher pressures when necessary, giving you the flexibility (and comfort) of both in one setting. 

Some good news: my nose isn't as big as I thought...

I found that I woke up several times in the night and had to adjust the nasal pillows but each pack of Swift FX nasal pillows come with three sizes of pillows. I found that when I decreased the size of the nasal pillows to the medium size (although the large were comfortable and the leak minimal) the medium pillows were more comfortable and needed a lot less adjusting when I first put them on and hardly any throughout the night.  

I slept really well and took a look at the display screen on the S9 when I woke.

I was greeted by an AHI of 0.0 and a green smiling face telling me that the nasal pillows were a good fit and weren't excessively leaking.

The ResScan software also confirmed the Zero AHI. 

Now that I use the Autoset mode, my AHI is always under 1.0 regardless of what position I sleep in or even if I've had a glass of wine.

It actually feels good to sleep on my back again, I'd been using the Rematee side-sleeping belt for a while and found that I missed sleeping on my back. With CPAP I didn't ache when I woke up. CPAP was surprisingly unrestrictive and I soon learned a manoeuvre to clutch the hose and move it with me if I wanted to turn in the night.

To be fair I could have just let the S9 go on full unrestricted auto from day one and it would have delivered the same pressures, but from mine and my son's previous experience with Non-invasive Ventilation, a large factor in whether it is successful is down to whether the sleeper (patient) feels comfortable with it, yes the numbers are important (after all that is the whole point of the therapy), but the patient experience is also key as that alone will probably be the biggest factor in whether they are "compliant" with it (ie use it for 4 hours or more a night), after all many PAP machines don't allow the user to see their AHI data so they can only judge based on how it feels.  

Another part of the experience is the mask that is used. There is a wide choice of masks available, and it's important to find one that is right. Also humidification can help people feel more comfortable with PAP therapy, this is something else that should be available to them along with all manner of accesories such as hose holders - really anything that will prevent someone giving up. That said, CPAP therapy isn't right for everyone as my son's situation shows, so good communication with a committed Sleep Consultant is vital in order that the right treatment be offered. 

I think looking into things in this detail was necessary for me, although it was a rather involved way of getting used to CPAP and trusting it, it has been well worth it. I feel a lot more awake in the mornings (generally only sleeping for 7.5 hours now) and my AHI has been consistency the lowest it has been in probably 20 years.

I think the graph below speaks for itself.

CPAP is a clear winner and one that is likely going to be impossible to beat but that's not going to stop me trying out other apnoea remedies to see if they can come close.

CPAP has also made a huge difference to my snoring, the results of which I'll post in a few days. 

For the future: 

• I'd like to see if the pressure requirement decreases if I take a dose of 5-HTP at bedtime.
• Although I don't intend to change my nasal pillows, I would like to see what difference other masks make to the experience.

Useful Links

Michael F. Fitzpatrick, Christi E. D. Alloway, Tracy M. Wakeford, Alistair W. MacLean, Peter W. Munt and Andrew G. Day
Can Patients with Obstructive Sleep Apnea Titrate Their Own Continuous Positive Airway Pressure? 
(full text PDF available to non-subscribers via the link)

Gao W, Jin Y, Wang Y, Sun M, Chen B, Zhou N, Deng Y. 
Is automatic CPAP titration as effective as manual CPAP titration in OSAHS patients? A meta-analysis.

Sleep Onset Apnoeas / "Throat Closing"

One of the search terms that people find this blog with surprised me by how frequently people search for it, there are several variations but these two sum things up well:

• Throat closes as I go to sleep
• Choke as I fall asleep

I hadn't really considered this before but I really should have done because it happens to me, and one of my parents. Normally when I experience those throat-closing moments they are accompanied by the first snore / cluck / snort of the night, a flash of whatever broken dream images were going through my mind and the knowledge that I'll soon be asleep. I guess it's something that a lot of us experience but don't really talk about it because it sounds a little strange.

Polite and usual "sleep chat" is usually along the lines of "Did you sleep well?" and not much deeper than that which is a shame because it's such a fascinating subject that few of us speak about because many (wrongly) consider sleeping to be a waste of 8 hours and some even see it as a weakness ("Sleep is for wimps" etc etc).

I've been using CPAP for a month or so now and have been adjusting my own pressures based on the sleep study data that I record each night. When I reviewed each night's data, one of the things that stood out about breathing as we drop off to sleep was how it changes at sleep onset (the moment that a sleep lab would declare that we are now asleep).

This becomes more pronounced with CPAP (or at least for me as a relative newcomer to using CPAP for myself) because when I first switch the machine on at night I instantly become aware of my breathing and try to control it. Oddly, consciously controlling our breathing is something that we don't do very well and it is best left when our bodies do it for us automatically. Can you imagine the chaos that would result if we had to consciously take every breath or control every heartbeat?

The following is a few minutes of data representing my breathing as I was dropping off to sleep whilst wearing CPAP. It's taken from Resmed's ResScan software (click for a larger version).

The breathing on the left is when I was awake, it is clearly different to the smooth regular breaths on the right side of the graph. Falling asleep is what brought about the change as I "forgot" to consciously breathe and my body took over.

So far so good, but on several nights I noticed that the handover from from awake breathing to asleep breathing wasn't so smooth... 

Notice how there are gaps in my breathing? This is from a night where some apnoeas were still occuring; I remember that as I was falling asleep I experienced at least two of those "throat closing" moments. The apnoea briefly woke me as left me realising that a moment before I was asleep, which also seemed to shift the hypnagogia into my conscious mind and then into my memory because this night was also a night that I remembered a lot of it.

Several different images and phrases came and went as I drifted off to sleep. The Zeo recorded that I briefly entered REM as I fell asleep (possibly causing a loss in muscle tone resulting in apnoeas)...

This is something that I see on many nights when I look at my Zeo data, but in the interest of accuracy, Zeo do point out that if your sleep is generally healthy with 7-9 hours per night and no feelings of tiredness during the day that this brief period of REM could be wake being misinterpreted as REM. It could be that N1 sleep mixed with brief periods of wake (from my respiratory arousals) were interpreted as REM by the Zeo (as wake is so similar to REM). 

The following night my sleep looked very different and I achieved a lot more REM along with no apnoeas or hypopneas recorded at sleep onset, intriguingly the Zeo data doesn't show me passing through REM as I fell asleep. So this could actually be REM, although this could also be because there were no respiratory related arousals during the transition from wake to sleep.

With the Black Shadow Sleep Monitor I've seen that less significant respiratory events are linked with altered REM sleep, in my case a series of hypopneas leading to a Lucid Dream. This raises an interesting issue that may provide some insight into dream formation.

I used to be comfortable with those throat-closures before I knew I had Sleep Apnoea as they had become so familiar to me. I used to use them as a way of knowing that I'd soon be asleep. In a strange way I will be sad if they go because after each "cluck" or snort I'd briefly wake and commit the partial dream or hypnagogic image to memory and would be able to study sleep as I drifted off.

Famously people have used a technique that relies on waking from hypnagogia in order to remember it which involves napping in a chair whilst holding a metal spoon over a metal tray or plate. Once you drop off to sleep you automatically release the spoon, causing a clattering sound which then wakes you allowing you to recall what you saw and heard.

I see my sleep onset apnoeas as such a system, alebit a naturally occuring one. I think that during the times that I want the best of both worlds of having the apnoeas at sleep onset but sleeping safely for the remainder of the night that I will experiment with setting a RAMP on my CPAP which delays the maximum pressure by up to 45 minutes, giving me time to explore the hypnagogic world.

Knowing that I have obstructive sleep apnoea and that the first apnoeas of the night are usually at sleep onset, I would suggest that anyone who experiences these throat-closures at sleep onset should at the very least be aware that they could have Obstructive Sleep Apnoea and look out for other symptoms. The best thing to do it get it checked professionally as it could also be a sign of another condition such as Acid Reflux (GERD) or Laryngospasm.

Lucid Dreaming - Sending a Signal to the Waking World

Lucid Dreaming seems to be a bridge between the waking and dream worlds. You are dreaming, yet you are conscious of dreaming and capable of having rational thoughts during a jumbled dream.

Being lucid doesn't mean that you have full control over your dreams, despite being aware that I'm dreaming I still find that I am compelled to "play along" with the dream that I'm given. So, for example, if I find myself dreaming of a street scene, I can't magically transform it into countryside. In order to change the scenery I have to make the change fit into the story somehow, even if the scene-change is something as crude opening a shop door and "knowing" that it takes me to the countryside.

All this is wrapped in the fact that (for me at least) lucid dreaming is a constant struggle to remain lucid, it doesn't take much to lose lucidity and slip back into a normal dream. 

So when I suggested sending a signal from a dream in this blog-post, I thought it unlikely that I'd ever be able to remain lucid and have the presence of mind to consciously send a signal to the Zeo Raw Data (via ZeoScope) marking the lucid dream.

I'd been briefly practicing what sort of a signal to use before going to sleep every night, hoping that it'd stick inside my head if I was fortunate enough to have a lucid dream. Given that the signal has to be based on eye movements I was fairly limited in what I could do, but the practice sessions showed me that flicking my eyes from side to side just seemed to produce a very noisy signal and something that could be interpreted as EMG noise from my forehead, so I settled on eye movements to the right, then centre, which produced a nice peak on the raw EEG data (it is this type of peak that the Zeo filters to use for its EOG signal).

Because the eye movements were forced as far right as I could manage the amplitude of them rose above the normal eye movements of waking and REM. 

(Normal eye movements during a period of REM (right to centre first, followed by left to centre)

On Wednesday night I became lucid in a dream and managed to stop and send a signal using my eyes that was picked up by the Zeo.

The first thing that I remember about the dream was that I was late to get to a party and I still had to stop off and buy a bottle of something to take along. I lifted up and flew along the coast of the Thames Estuary not far from where I live. 

This was the thing that prompted me to become lucid. Flying is such a break from the everyday laws of physics that it jolted me into realising that I was dreaming.

So, I went along with the dream, flying to the party but stopping off at a small stone-clad Welsh off-licence (I have no idea why I ended up in Wales). As I landed and my feet touched the ground I remembered that I was wearing the Zeo headband and recording the raw data, so I darted my eyes sharply to the right and centred them again.

Then I thought, "That's just one, maybe it'll get lost in the other data", so I repeated it 5 more times, then bought my wine and Jaffa Cakes, lifted into the sky and headed for mainland Europe (where the party was apparently).

Shortly after arriving at the party (which turned out to be in a 1970s church hall), I woke up and glanced at the clock before falling asleep again.

In the morning I found it easy to see the signal that I'd recorded. The peaks were a lot larger than my typical eye movements. The first peak is my initial signal, then after a pause I gave 5 more right-eye movements.

So, not as significant as a signal picked up by SETI but still, this is a signal from the dream-world to the waking world. It actually reassures me because several people have asked me, "How do you know that you're not just dreaming that you know you're dreaming?" implying that lucid dreaming is itself a dream. This shows that it isn't. At the time of the signals, I remembered that I was actually asleep in bed and not outside an off-licence in Wales and although I was still standing on the cobbled street and not able to sense the waking world I was able to make an impact on it via this signal.

From the Zeo raw data it seems that a broken night played a part in triggering this dream, and I suspect that respiratory arousals were the cause again as I wasn't wearing the Rematee belt. A rough breakdown of the time surrounding lucidity is as follows...

• 04:34:45 Woke from a long stable period of N1/N2 (light) sleep
• 04:39:15 Entered REM (from wake)

Repeated awakenings and a mixture of N1/N2 and REM until... 

• 05:00:15 Entered stable REM
• 05:03:26 Began to signal lucidity
• 05:03:37 Gave last eye movement of lucidity
• 05:06:14 Woke and looked at the clock before going back into REM again
• 05:11:14 REM ended

So this places my lucid dream within REM, which was the subject of speculation for years until Stephen LaBerge confirmed that lucid dreams are actually REM dreams. 

Jeff Warren also has a good explanation of the technique in this exerpt from his book, "The Head Trip". 

Stephen LaBerge, William Dement, Lynn Nagel and Vincent Zarcone took things a lot further and even recorded morse code signals from a lucid dream via muscle-movements.

I'm still not any closer to seeing a trademark brainwave pattern of lucid dreaming, but I suspect that this is due to the single site EEG. 

I'd like to practice this further and if I'm fortunate enough to be able to do this again I'd like to try to repeat the signal every 60 seconds (as it appears to me in the dream), or at key points in the dream (such as taking off and landing, meeting a person etc etc) it would be interesting to see if these signals can be used as markers to chart the flow of time through a dream.  

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.

Configuration

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

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)