Tandem pump and SCUBA / other off-pump activities

Pumpless activities: how do you do it? I started this as an answer to a different topic but realized I was hijacking the whole conversation.
Everybody is different. For me to do vigorous exercise sans pump (like hockey), I give 1/2 my usual basal as a bolus for one hour and can keep an eye on my sugar via Dexcom/phone when I’m on the bench. I have an orange juice box for use if required. I’d rather be a bit high than low when going in. This should work for swimming as well. Maybe you can swim with Dexcom and tandem in place, as long as you don’t go too deep. I wonder how waterproof this tandem pump is.
I used to scuba dive but not since Covid and haven’t tried with the pump. I’d like to try again. In the past, it was easier. With MDI I’d have extra OJ before going down and reduce my long acting the night before. That meant I’d be running slightly high during the dive.
My plan with the pump will be the same as hockey or maybe just disconnect for the hour with no little pre-bolus at all. The other problem is the CGM. I don’t think you can wear Dexcom at great depths (100 feet) so I’ll have to reconsider that part. perhaps just remove the transmitter?
I tried diving down in the lake to about 12 feet to pick up something with the CGM attached and got bleeding into my Dexcom sensor pad, possibly due to the additional pressure / lower pressure inside the sensor/transmitter attachment housing. (The transmitter continued to function however).
All a bit complicated for me.

I can tell you what I do to snorkel for 2-3 hours, but I don’t scuba dive and I don’t have a Tandem. So…not sure exactly how much it will help.

First I always have a quick hypo treatment with me to use I shove into my bathing suit.

I have an Omnipod and while you are only “allowed” to be in the water a certain amount of time, my pod has had no issues for even 4 hours. But I know it has depth restrictions too and have never tried depth, that might be a problem. You might have to disconnect and remove the Tandem especially since it’s also the PDM. I have a feeling a lot of things won’t cope with the extra pressure of depth.

I have a Dexcom, but again I really haven’t had depth of more than 10 feet and lasting only a few seconds. I have free dived to pick something off the floor and have had no issues doing that. One of the things that was aggravating for me is I can’t get the Dexcom to read 95% of the time in the water. And if you try to hold up your arm above water , it wants to download data and takes forever to give you a reading. Fairly impossible to count on for a reading out in the ocean. I had heard Scuba divers have worn a Libre so I gave that a try. Sure enough you can have the reader in a waterproof pouch and scan your Libre underwater and it gives you a reading…but I’m not sure at what depth it will do so. I also don’t know if SCUBA divers have tried to do so at depths? I wear a Dexcom now and self fund a libre solely for snorkeling.

Originally without knowing what my numbers were I would reduce my basal starting 30 minutes before for 2 hours. I would also start out higher. Most of the time I would drop but it was okay, a few times I dropped quite a bit, so I would keep my snorkeling to about 60 minutes because I knew that was a safe time period. Once I got the Libre, it was a game changer. I could stay out longer (2-4 hours) because I knew what my BG levels were doing. So now I can stay out as long as I want and can track my BG levels and eat some gummy bears if I need to. Now I have gotten some gels to try if needed. But this is for snorkeling, not diving.

I don’t have to use anything extra to keep my Omnipod on, but it is under my swimsuit and that probably helps. But my Dexcom I had issues with it staying on past 2 days not even getting wet. So I use Skin Tac on it. I also keep my Dexcom on with restarts longer so would have to touch up under the edges with a Qtip.

The overpatches hadn’t helped me until I ran across someone that said they used Skin Tac on the overpatch. So now I use Skin Tac on the Dexcom adhesive and Skin Tac on the overpatch adhesive and it works great. I still have to touch up the edges a little but not for at least 20 days.

I use Stash Waterproof Pouches for my iphone and Libre scanner. They have worked great.

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For something like recreational diving, there is no big downside if your BG is a little high while you are under. It isn’t going to affect you too horribly for a rec dive.

It depends on the dive. For 100 feet the NDL is only 20 minutes! Longer times of course for shallower depths. But there is no reason you need a pump or basal during this time.

My 6 keys for diving are:

  1. Unplug all pump stuff. Zero basal during the dive and a little bit of zero basal time leading up to the dive. For MDI, cut your basal dose in half for the dive. (If you are on Tresiba…switch to a different basal! :grinning:)
  2. Check BG a lot leading up to the dive so you can see your BG trend. Don’t rely only on your CGM because there is a lag. Do a lot of BG checks.
  3. Make sure you have ZERO IOB. Repeat that, ZERO! If that means skipping breakfast, skip it!
  4. Make sure your BG is trending up!
  5. Take some safety carbs before you go over the side if your BG is at all questionable. If it is flat, take some carbs, because your BG will drop from the exercise while you are under.
  6. A high BG at depth won’t kill you. A low BG might. Play it that way!

I was diagnosed in 1972, and certified for Open Water in 1987. And that was before pumps or CGM.

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@Eric2 has helped me a lot. And the fact that he has SCUBA dived. Experience is the best!!!

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Thank you both very much for your thoughtful replies.
And agree that it’s better to go down at a higher level and depending on water temp and exertion, glucose can go down a fair bit even with no insulin on board (from bolus) only residual from basal.

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According to Tandem the pump is only good for 3 feet deep for a maximum of 30 minutes. There is a case by Aquapac but they only suggest it for swimming, bathing and showering.

Part of the problem is that the pressure increases really fast with depth. I was wondering that even if the pump electronics and motor are safe from water, if the increased pressure would interfere with insulin delivery.

This link is about hypoglycemia in children and adults with pumps during air travel. That makes me think that the increased pressure underwater would cause less insulin to be delivered.

https://care.diabetesjournals.org/content/34/9/1932

Here’s an Aquapac link, I understand it is available on Amazon.

The discussions I’ve read on diving and swimming with a pump are to put the pump in a cool place, to use injections of long for basal and rapid for bolus.

The Dexcom G6 sensor and transmitter are only rated for about the same depth and length, plus there is likely no way for the G6 Bluetooth to be received by the pump as water is not a favorable medium for radio waves.

Thanks for this experiential wisdom!