@kalle You are correct about the bluetooth not working in water. The reason is that a molecule of water has a resonant frequency of about 2.4Ghz. This is also the frequency of bluetooth devices and some cell phones.
For the sensors being in gas at ambient, the answer is yes. I looked at Argon and Nitrogen, but I have Argon available. The reason for these as the atmosphere in the test rigs is that if the battery is damaged, and it does start a fire, the sensor won’t be completely destroyed.
After checking the frequency of NFC (about 13.8 Mhz) there is a chance that the scanner for the Freestyle Libre system could be placed in a case, but it would need a means of activating the device by pushing the button. I have not looked into any of the CGM devices, but I suspect they may have some limitations too.
With the Libre, the data can be scanned up to 8 hours later, which would give me the data I’d be looking for. The big question for me is “What happens to my blood sugar at depth while influenced by Nitrogen Narcosis?”.
My first concern is at what depth does the batter in the sensor become compromised. I think having the battery catch fire at depth on my arm would be a really bad thing. Especially since water will not extuingish a lithium fire.
I don’t like the Bahama’s, too cold for me even with 5mm. I love Cozumel; 60 minute drift dives at 25ft, wonderful, I’ll wear a 3mm there.
Wrt the T1D I follow the DAN guidelines; I don’t enter the water below 150mg/dl. I do think they are slightly ridiculous but I follow them anyway. Scuba is an OCD.
I have dived with an Omnipod, but it doesn’t stand repeated immersion. It is fully equalized and each ascent/descent pumps water into the pump which eventually causes it to fail even if you are just spending time in the pool (dive into the pool, 1/4 ATM of pressure change, water into pump).
The main issue I see is the basal. We have to have the basal, so using Lantus makes sense, but too high a basal and if the boat forgets about you have two different hypos to worry about over the next 8 hours. My lantus is set low so I can survive 8 hours with no hypoglycaemia, don’t know about the hypothermia yet.
Like you I do other stuff so my basal is set to the minimum when using a pod; it is 0.5 IU/hour which I know will leave me stable. With Scuba I kill the basal from the pod and swap to lantus at 8+8 (morning and evening; without that lantus is too peaky for me). Ok, so that’s 0.67IU/hour on average and I admit I haven’t tried an 8 hour test but I do carry a couple of tubes of glucose when I dive; enough to counter almost all the basal. So long as it survives I use the pod for bolus; a pod lasts a while if it is full of insulin because that minimizes the displaceable air in the device.
You are correct about the bluetooth not working in water. The reason is that a molecule of water has a resonant frequency of about 2.4Ghz. This is also the frequency of bluetooth devices and some cell phones.
It’s not one of the resonant frequencies, so bluetooth (and wifi) do penetrate water, but as the above article explains, they get adsorped pretty rapidly.
This is why our Dexcom’s skip out when we sleep and our Omnipods don’t respond when we stick them on our backs. We are 90% water so we adsorb the signals. If you don’t believe me sit inside a microwave (2.45GHz - centre of the ISM band we use) and turn it on.
In principle we could dive with our 'phones in a ziplock bag (plus lots of air) and, holding them close enough to our G6’s (totally equalized, no issues under water) it would all work. The only issue I have is that I paid so much for that phone and I rely so much on xDrip+ that the Scuba OCD kicks in. Still, maybe I’ll try it.
@jbowler I love the cold water, I did my open water cert dives in a spring fed quarry in Toledo Ohio. I do a lot of diving in the Great Lakes region.
The last time I was in the Bahama’s we had water temps between 70F and 80F. I only used a dive skin and didn’t need a wet suit.
What was the water temps you liked while diving in Cozumel?
I’ve always been a little nervous about diving around Mexico because I do not trust the water quality. Too many companies have dumped too much pollution and toxic materials in Mexico for far to many years.
@jbowler You are correct, and great catch btw. What I should have said was that the 2.4Ghz frequency is rapidly dissipated by water, making it less useful than a lower radio frequencies.
@kalle I owe you an apology, I was incorrect. Check out @jbowlers link above to get a more accurate picture of why most radio frequency transmissions don’t work well underwater.
I learnt to dive in Oregon, boat dive at 53F or below in the Pacific and diving on the Illinois river in what is basically melt water from around the Oregon Caves National Monument (but it warms up fast in summer). I have an 8mm semi-dry for that, Michelin Man.
Cozumel has some of the best coral in the world and shallow drift dives with it. I’ve seen better in Fiji but those corals were in 100ft or so of water and an hour boat drive away (Namena but staying near Savusavu), bottom temperature of 84F though, toasty, it was mid-summer (mid-January; low season) Cozumel water also tends to be consistently clear, at least in my experience. Last time I was there I logged a bottom temperature of 73F and my wife logged 79F on the same dive, that was a 53minute drift dive to 48ft at the end of March (same time as now, but two years ago!)
Dives from Cozumel (the island) are typically much easier to reach than from the mainland. This is the Atlantic, Caribbean, side of course. On the Pacific side the Sea of Cortez (the south end of the California Gulf) has similar temperatures and I didn’t encounter any significant pollution even though it’s a heavily industrialized area. My personal experiences suggest that the Mediterranean is far worse for pollution; the water off the Greek Islands is amazingly clear, but there’s nothing to see under the surface. Of course the Med is a closed bottle of a sea. If you want a curious counter example try the south of Taiwan; you can dive where the coolant waters of the nuclear reactor enter the sea (“Water Outlet”, Kenting) and the warm water results in massive amounts of life amongst the discarded fishing line and avid jet skiers. That was about the same temperature too.
I think my dive computer reads low on temperature. For comparison I logged a range of 64-70F in the Bahamas. Blue Hole came in at 65F depth 47ft at the edge; too cold in the hole with a 5mm!
@MichaelS, no apology neccessary. You statement was on the right track, and that’s a step in the right direction. Over time, it gets us closer to the truth.
Now, the information from @jbowler would suggest that some transmission of Bluetooth signals is possible. If I ever end up using a CGM with Bluetooth, that’s something I must try
Now, the information from @jbowler would suggest that some transmission of Bluetooth signals is possible. If I ever end up using a CGM with Bluetooth, that’s something I must try
My G6 drops out intermittently when I am in the bath with it submerged, but it does work some of the time. Insulet swapped the frequency they used to the 2.45GHz ISM band (bluetooth, wifi) and claimed the range increased, but it actually decreased (based on personal measurement). I believe the main issue was that the range was drastically reduced if the signal had to pass through the human body; I wear my pod on my back half the time and that causes reception problems.
Lots of mission-critical scuba equipment uses wireless. My dive computer is a watch (Oceanic/Mares OC1) and it uses a pressure transmitter mounted on the tank (first stage regulator) to monitor how much air I have. According to this post they use much much lower frequencies:
It’s the third reply down. The quoted frequencies are long wave, wikipedia has this to say about the lowest:
Very low frequency waves below 30 kHz can be used to communicate at transcontinental distances, and can penetrate saltwater to depths of hundreds of feet, and is used by the military to communicate with submerged submarines.
Of course having our CGM’s transmit transcontinentally has limited application, though I guess some parents of T1Ds might appreciate it Nevertheless scuba tank transmitters work reliably even in locations where there are a great many scuba divers using similar, or identical, kit in close proximity.
Cozumel water also tends to be consistently clear, at least in my experience. Last time I was there I logged a bottom temperature of 73F and my wife logged 79F on the same dive, that was a 53minute drift dive to 48ft at the end of March (same time as now, but two years ago!)
Nevertheless scuba tank transmitters work reliably even in locations where there are a great many scuba divers using similar, or identical, kit in close proximity.