They started tightening things up in the mid-'90s. Previously the standards hadn’t been at all rigorous and there wasn’t much or any national cohesion, but then National Geographic and other popular press started sponsoring major technical expeditions like the Wakulla and Huautla caves, and profiling pioneering cave divers like Bill Stone, and suddenly there was a problem of amateurs thinking they could do these extreme dives at a time when there was no formal training. Also there was the 1994(?) death of Ian Rolland, who was diabetic. He had surfaced, but he passed out in shallow water, his rebreather came out and he drowned. It was always assumed he’d passed out because he was low – interesting what @MichaelS says about “feeling disconnected from the diabetes.” So everybody wanted to ensure nothing like that happened again.
That’s exactly how it was done outside the Navy too. Sheck Exley wanted to figure out why so many divers were dying in Florida caves in the '70s and '80s and started analyzing their dives so other divers could learn from the mistakes. In 1986 he wrote (and typed and photocopied and stapled) “Basic Cave Diving: A Blueprint for Survival,” the first safety manual and the foundation for all safety rules that came after.
A wrist computer that talked to a CGM would be very cool.
The sensors should still work, but the big difficulty there is the signal from the sensor transmitter. Water does a number on any of that type of communication, either RF or bluetooth. Which is one of the reasons why submarines use sonar instead of radar. I imagine it would need to be a wired connection.
Just for clarification @Breacher the disconnect is a result of the nitrogen narcosis. It hits every diver a little bit differently. It is refereed to as Martini’s Law (for every so many feet below 100 is like drinking one martini.) at 109ft is where I begin to feel the nitrogen narcosis. Beyond 110ft I cannot feel where my blood sugar is at, and makes me wish I had a cgm option. I need to see if a sensor would work in a dry suit. I don’t know what I would do about the reader (I’m currently using the Freestyle Libre system).
This is fascinating! I (clearly stupidly) assumed that scuba would be a thing somewhat out of the realm of possibilities for T1. Leave it to FUD to clear that up!
I realized also that @TiaG’s description of claustrophobia in relation to diving is an issue for me. We’ve gone on a number of snorkeling trips which I’ve had trouble with the mask and the snorkel and the water. Didn’t know that was a thing for others.
Also, a friend went last year on a trip across Africa and Asia. She and her boyfriend took a diving course that lasted a week, included pool and boat components, and it sounded like the most dodgy experience ever. I’m fuzzy on the details and location, but she struggled with the equipment and they just laughed it off and told her to do it anyhow. I’m pleased to read stories here about regulations and instructions and how to find a reputable dive shop. I’m sure once you know what you’re doing it seems safe, but her experience made my hair stand on end.
I feel like this was the type of operation I was exposed to when I was in Australia. It was part of an all-expenses included boat trip, and you had a few hours’ training and then jumped in. It was all open-water, warm, low-depth (like less than 20 feet almost)reef diving so maybe the stakes were pretty low, but the whole process of training and going on the dive took less than a full day. SOOOO UNSAFE.
By contrast, my husband’s scuba training was a several week training course in a pool in the city. To be certified you had to do a dive with a trained person and demonstrate several key safety skills. And the instructor, a 75-year-old man who had been diving for half a century, was extremely wary of risk. I still get spooked when my husband dives but I do believe he’s well trained and he is very meticulous and focused on safety. He did get a burst ear drum one time while doing a wreck dive, but other than that has had no close calls.
I got both Open Water and Advanced certs during my teenage years, before Type 1. When I went to university it was just too expensive and too much of a hassle when I didn’t have a car. I’ve been thinking that I want to take it up again some time now that have both a full-time job and a car.
I use the Libre and the IP rating of 30 minutes at one meter isn’t cutting it for diving, though I suppose the pressure itself shouldn’t be a problem if I can protect it from the water. I think the cold waters around here are an advantage since I need a dry suit anyway. I’m sure I could do a dive without being able to read the sensor underwater, but I don’t want to break it. Has anyone tried wearing a CGM at scuba depths?
The IP rating doesn’t give you much confidence that it wouldn’t leak if exposed to water at depth, although a dry suit should remove the water. Wonder if the manufacturer has tested pressure only?
Here is a link to one report that says it works and contains some detailed info:
One report that the Libre survived, but the adhesive didn’t is quoted below:
Hi everyone, I’m back from the scuba diving holiday in Malta (which was awesome) and I’m gonna report back.
I was wearing a Freestyle Libre Sensor on the first day of diving which involved 2 dives. I had the sensor attached for about 10 days before the dive so I wasn’t that worried if something went wrong with it. I had also covered the sensor with Kinesio tape for some added security.
Before the first dive I scanned as close to the dive as I could so that just in case the sensor wasn’t working afterwards I still had as much data as possible. Maximum depth of the first dive was 16m and total dive time was about 45 mins, afterwards the sensor was working as before. A pleasant surprise  the sensor was working fine!
The main thing I noticed was that the glue on both the kinesio tape and the sensor was noticibly less than before the dives. I wanted to get home and shower before changing the kinesio tape and unfortunately right after my shower I managed to pull off the sensor and the tape.
All in all I was pleased that the sensor was still working after the dives but the main issue was that the sensor wasn’t really attached properly afterwards.
I think this definitely requires more research and testing. I’m glad to see that I’m not the only one wondering if the sensor would continue to work after being exposed to pressure to pressure.
There is one thing that we need to keep in mind with testing the limits of the sensors. The button battery may be a Lithium Ion button battery. If these are sealed batteries and it is indeed a lithium battery, and if subjected to enough pressure, the lithium layers could get damaged under pressure and ignite.
I will call Abbott CS and see if I can get more details on the battery composition. I will report back here when I find out.
Update: After calling Abbott CS, I was told by the the CS rep that this is outside the range of what this is tested for. They are trying to get information for me(like who the battery manufacturer is, and if they have done any testing that could provide the information I’m looking for).
I think I over whelmed the CS Rep, but I do give him credit, he was willing to run this up the management chain and see if they could get me some answers. The Abbott CS rep said that if they get any more info on this subject, that they will contact me about this.
Manufacturer of the battery is probably your best chance at testing, as you have already surmised. I guess this means that your Nitrox and Heliox dreams are going to have to be put on hold, or only dive on days between sensors.
@Eric would be proud of your diligence I believe. And good for them for looking into it!!!
This sounds like a complex issue that maybe they wouldn’t even have thought of. So maybe it’s helpful you reached out! Someone could get to do a bunch of diving with the device for testing purposes.
Here is my old card. No tricks with the picture, I was actually only a white-boy for 6 months of the year. This is what I looked like during spring and summer.
It’s nice to get some more information from the manufacturer and battery safety seems pretty important for them to consider with a device that’s worn right on the skin. Personally though, I wouldn’t worry too much about it. I haven’t extracted an actual CGM battery for testing, but I looked at a LR44 cell to get some idea of what we’re dealing with, although that one is a lot bigger. The flat sides seem to be at most 1 cm². A deep dive to 30 meters would put about 300 kPa of pressure on it. That’s 30 newtons compressing if, which really isn’t that much. To really test this, and prove to everyone that I’m at least a little bit crazy , I placed a battery on my kitchen scale and applied force until the scale bottomed out, which would means at least 50 N of force applied. I did deform it very slightly right in the middle, but I think that’s because I used the tip of a Phillips screwdriver. I’d say that makes it a worst-case scenario.
Does anyone have a hydraulic press so we can test this out for real?
@Kalle I’ve got a dive buddy from my pro days who is willing to do an experimental dive with me. We are looking at taking a few end of life Libre 14 day sensors on an experiment dive. We are going to use several small cylinders to hold the sensor, and use small cylinders of argon gas to keep the cylinders holding the sensors at ambient pressure. We’ll deploy a sensor testing rig every 25 ft to a dive line anchored in 300ft of water on one end and tied off to a floating dive platform on the surface. This should give us data on the durability of the batteries at depth.
We will deploy the testing rigs for a 24 hour period, and then recover them and examine the sensors and then the batteries of those sensors for any pressure damage.
This will be a fresh water dive test, so the results won’t be as accurate with sea water. I don’t think that will be to much of a problem though, as we will be going far deeper then any sport diver would go.
I do think that your kitchen test is great, and I’m glad you didn’t catch anything on fire. Did you see any deflection in the surface of the battery case (i.e. did it dent)?
That sounds like a really serious test! Does it means that the sensors will be in gas but at ambient pressure, like in a dry-suit? In my test, there was a small visible dent in the battery afterwards, but it was very small, right at the tip of the screwdriver, which can’t have been more than 1 mm² of contact area.
I understand that most wireless communications like Bluetooth are very effectively blocked by water, but the Libre uses NFC. If the reader could somehow survive the pressure, it should be possible to get readings underwater when it’s right next to the sensor with no water in between. For other CGM systems it might be possible to have a Bluetooth antenna inside the dry-suit.
, I placed a battery on my kitchen scale and applied force until the scale bottomed out, which would means at least 50 N of force applied. I did deform it very slightly right in the middle, but I think that’s because I used the tip of a Phillips screwdriver. I’d say that makes it a worst-case scenario.