Thursday, May 30, 2019

Astroskin - Review and Usage during Exercise

Recently I had the opportunity to have a hands on look at the new Astroskin system from the same company that offers the Hexoskin shirt.  I termed this a "system" since it is much more than the previous shirt that measured a single lead ECG, respiration rate and volume.  The Astroskin does that as well as 2 more ECG leads (total of 3), pulse oximetry and blood pressure while one is moving.  This post is meant as a critical review of a ground breaking device as well as a wish list for modifications as well as a hybridization with the Hexoskin in order to incorporate certain features.
First, what is the Astroskin, and where did that name come from.  Carre technologies, the parent company of Hexoskin, evolved the smart shirt into a more complete biometric sensor system for the Canadian Space program.
Before going through with the review, I would like to say a few words on how I came to get my hands on the unit.  As a fan of the Hexoskin and physiologic monitoring in general, I was interested in the Astroskin from the early PR materials.  My son was interested in cutting edge technology and bought a couple of units to evaluate as well as to try personally.  During a recent visit we unboxed and set it up together, then did several sessions of exercise using the device.  I was not given a unit by the company and have no financial ties to them.  

The Astroskin
Here is what it can do from their web site:

And the physical description of the shirt, headband sensor:

The recording module:

Another photo of the recording module:

The shirt
The shirt resembles the Hexoskin with a few modifications.  There are additional sensor pads to enable the extra 2 leads of the ECG, a wire connector near the shoulder to attach to the wire leading to the headband pulse oximetry LED unit and instead of the double elastic straps encircling the chest/thorax it has builtin elastic clasps.  The latter development is extremely welcome for me and hope it makes it way to the Hexoskin eventually.  If you have shoulder range of motion limitation (me), the elastic straps of the plain Hexoskin are difficult to get through the loops of the shirt (the loops are somewhat posterior).  The Astroskin has a couple of elastic short sections built into the front of the shirt and with some adjustment cinching a perfect fit is no problem.  The end result is a better shirt overall.

The control box:
Here things were not so good.  The box needs to be opened to insert 2 AA batteries.  For the life of us, we struggled mightily to open that box.  Although we finally got it opened, with all the tugging it dropped on the floor and a tiny piece of plastic broke off inside.  It worked fine so the plastic was not a critical component.  The other unit was also difficult to open but we didn't break anything opening the second box.  The combination of difficulty opening the device along with the concern with water ingress and durability makes one wonder why they simply did not modify the existing sealed Hexoskin unit.

The headband:
The O2 sensor for both pulse oximetry and blood pressure monitoring is inserted into a nylon headband.  The stability of the band and sensor can be somewhat problematic.  You must make sure the sensor is not obscured by any hair, sits flat and does not turn or twist.  The nylon band is okay for this but a firmer headband (like the one I got with my Moov Sweat) would have been better.  They could also have supplied a few extra nylon headbands, since if you lose the one, you are out of luck using the sensor.  On a couple of the sessions we had a fair amount of BP spikes (artifacts) since the placement was not solid.  If you are careful in the sensor placement, the O2 and BP readings are quite reliable.

Putting it on:
The shirt goes on like the Hexoskin - wet the sensor pads, carefully put it on and snap the front straps of the shirt.  Put on the headband (carefully) and then connect the wire from the shirt to the O2 sensor in the headband.  The connector is of a single orientation and does not lock in well (no feeling of a snap in and can pull straight out).  My advice would be for a small redesign to make it easier to connect, snap in without a risk of loosening during use. Finally the control box is connected to the shirt and you are ready to go.

The Phone App:
Here things get a bit disappointing.  First off, the app is iPhone only.  There is no android version.  Luckily, my son had an iPhone lying around for us to use otherwise we would have been out of luck.  In my opinion this needs to be rectified ASAP or they should provide an ipod touch for us android users.  That out of the way, how does the app look?

On first glance this is very similar to the Hexoskin app, with the addition of the extra metrics.  Of course, we have the same issue as discussed in another post, this is not easily readable on a bike (or running).  It is certainly fine at rest with your glasses on but not practical in the field.

Sensor live view:



Pulse oximetry:

  • The sensor output is certainly pretty and nice to know before an important session.  Poor quality would be a hint to readjust the sensor pads or headband.

The next issue is probably the most annoying quirk of the entire Astroskin system - the "Done" button.  

The button is there but takes many tries to trigger it's action.  You simply can't get out of this screen back to the main part of the app - there is no back button as in android.  After 10 to 20 tries we got back to the home screen, but this behavior was not a unique occurrence, it happened every time.

Back at the main screen you may choose an activity (just like the Hexoskin), but the module will record from the moment of connect to disconnection. 

Data uploading:
After the session, just disconnect the module and plug it into ...... a Mac.  Unfortunately the module can only interface with a Mac and if you only have a PC, you are out of luck.  I hate to be overly critical but this is not acceptable.  I don't own a Mac (nor iPhone) and should not be forced into the Apple ecosystem. However, we had a Mac laptop that downloaded the data with no issue.  The upload to the companies' website was also less than elegant.  With the Hexoskin, there is an automatic synchronization of your data once you plug in the module to the PC cable.  With the Astroskin, you must manually drag and drop your session into the Mac app window to get it uploaded.  Yes, a bit a of a minor detail, but still something to point out especially if you are accustomed to using the Hexoskin.

The Web App:
The Hexoskin web app has been upgraded recently but still lacks common features seen in exercise web sites such as custom interval averaging and data field composites.  The Astroskin is no different and in some respects even more disappointing.  Let's go through some screens and see why:

Here is the top of the main screen:
I circled the important fields such as heart rate, ventilation, O2 and BP.  However, an important field was missing - calorie burn.  This must be an oversight since it is present in the Hexoskin display.  We did compare the blood pressure output of the Astroskin to a calibrated cuff several times and it was close on each occasion.

Unlike the Hexoskin, each sensor group is present on it's own graph.  Although this could be an option, it is not helpful if you are tracking an exercise session and want to observe simultaneous BP, HR, O2 and respiration.  In addition, the zoom scroll bars are all independent, so if you find an area of interest you will need to figure out the exact zoom and session time to get the other fields to line up:

For instance, here I was interested in looking at systolic BP at the moment of a 10 sec, 800 watt sprint.  I have the actigraph on one graph (top in red) and the BP on the graph below.  Zooming in on one does not zoom the other and using the horizontal scroll bar only moves the one tracing.  They are independent which could be an advantage I suppose, but not as the default:

Here are some other tracing examples during the intense interval and body motion:

ECG (2 out of 3 leads)

The ECG tracing is remarkably free from noise.

Raw abdominal and thoracic respiration

There is a temperature field which could be very interesting for athletes exercising in the heat.  Incidentally, the rise in temp occurred as a ramp was done and peaked at the 800 watt section:

The forehead O2 graph stayed flat except at the end of the ramp and final sprint, where a drop occurred (red oval).  Certainly a parameter of potential interest:

Downloading data:
The data that can be downloaded is immense and easily opened as a .csv file.
Basically, all the data fields, as well as derived data such as RR and NN intervals are potentially accessible.  They have time stamps for easy alignment. 

Here is an example using disparate data from the ramp we did.  We started at a low power near 100 watts and as noted, with increasing power came an increase in heart rate as well as BP.  I took the liberty of taking out a few artifactual readings in BP:
  • There is a heart rate spike at the end corresponding to the 800 watt sprint.
  • BP rise was present but is not out of the realm of what can be seen with exertion.  Monitoring of BP can be a informative piece of data as will be discussed below.

Here is the muscle O2 with the Hex sensor on the RF:
  • There is relative stability until about 200 watts which is probably the MLSS zone and then a final drop in saturation with the sprint.  The large rebound is seen after finishing the session.

One of my concerns with any dynamic ECG recording method is the presence of artifact in the signal particularly with severe body motion.  In testing the Astroskin we had the opportunity to use it during an intense session with kettle bell throws.  The exercise entails rapidly swinging the kettle bell up to an overhead position, bringing it down and then doing a squat, then repeat.

How does the ECG look in the thick of an interval?  
This was a 4 set session and we will look at a closeup of the ECG during the final set :

The heart rate rises to the 140-150 range on each set.  The motion would be expected to stress the sensor connection to the torso and degrade the waveform.  However, it does not:

Although the tracing amplitude is not auto-scaling properly, we are seeing a clean ECG waveform without artifact.

Looking at the same four sets, how does blood pressure and actigraph look?
  • The actigraph (on top) tracing nicely represents the increased motion (in yellow).
  • Systolic blood pressure rises with each set of exercise (bottom in yellow) but does not exceed about 170 mmHg.  The spikes in BP are artifact.

Summary and Conclusions:
  • The Astroskin is a unique device capable of monitoring respiration (rate and volume), a 3 lead ECG, motion, pulse oximetry, body temp and systolic blood pressure.  In addition, fine details of the ECG such as RR and NN intervals are available.  
  • Although some minor motion artifact occasionally does mar the signals, for the most part the system is largely free from extraneous noise. 
  • The Astroskin shirt has been improved from the Hexoskin with a much more convenient elastic strap setup.
  • A complete menu of recorded data parameters is available in easy to understand .csv files for custom processing  and graphing.

  • The smartphone app as well as the data module upload software is Apple iphone and Mac only.
  • Smartphone app screens are still not able to be customized and difficult to read in the field.
  • Once on the sensor screen, it is very difficult to elicit a press of the "Done" button to escape.
  • The data module battery door is hard to open and the device uses AA batteries, not a sealed rechargeable.
  • Water resistance is unclear given the open nature of the battery door.
  • The headband that houses the O2 sensor is flimsy and needs to be more stable to reduce artifact and noise in the blood pressure signal.
  • The online graphing display places each sensor channel in a separate tracing, making it difficult to overlap data fields during analysis.
  • Each channel tracing also has it's own time scroll bar and zoom level, also making it difficult to follow changes over time in two or more disparate sensors.  For example, zooming in to a heart rate peak does not correspond to a zoom in the blood pressure or respiration graphs. 
  • Poor vertical scaling on the web graphs.  A vertical zoom function would be nice.
  • The connector for the head O2 sensor can be difficult to insert without assistance and does not lock together with it's mate. 

Wish list:
  • A hybrid of the Hexoskin with some Astroskin features.  While the Astroskin is a superior, full featured biometric sensor, many (most) athletes will not be able to afford it.  Instead, a hybrid device consisting of the Hexoskin shirt with the forehead O2/blood pressure sensor would be ideal.  A single lead ECG is adequate for most purposes, respiration data is similar between the two but adding a systolic BP capability would make a huge difference.  
  • Some folks will have exaggerated BP elevation with exercise and may need to take proper precautions to prevent injury.  This situation is also associated with a future risk of developing hypertension.
  • In addition, nocturnal blood pressure rise has been associated with higher levels of cardiovascular disease.  Since this is not routinely checked by physicians, the addition of this ability would enhance the Hexoskin value greatly.
  • Having the O2 sensor would also make the hybrid unit a fairly accurate sleep apnea diagnostic device, capable of sensing hypoxia, BP, heart rate spiking and of course apnea (no breathing).

As a way to help the company monetize the hybrid system (and keeping the base price reasonable), a value added software package or consulting option (especially for sleep apnea) could be put in place.  More enhanced graphics, interpretations, VO2 max, lactate steady state estimation or even feature unlock may be something to think about.  While the Astroskin is a dream device, the bulk of the interested sporting community probably can't afford it.  A lower cost, scaled down unit perhaps with pay per feature may be a reasonable alternative.

I want to thank my son Matt for working with me on this review.
Even at my age, father and son projects are a great experience.

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