April 5, 2008
rehydrate in water
on another thread you state "On long dives (runtime over 90mins) you must make provision on open circuit diving to rehydrate in water - do not try this without running through the procedures for this with your instructor - Post me another question on this and i'll run through the very crucial issues of this." I dont think anyone has posted this question so here it is.
| Posted :
April 7, 2008
Rehydration In Water – Some good rules of thumb
It is important to try this with your instructor first and in any case definitely NOT on a Deco dive first.
 you need to select sensible oral isotonic and non-isotonic fluids that are easily drunk. I like using the foil pouches that you get from your large supermarkets in boxes of 10 or 20 – for me tropical juice and black current are a nice combination.
 make sure the foil pack is not the sort that requires you to insert a straw !!! Go for the plastic screw cap versions.
 NEVER drink at depth or at any deco stop below 6m. The minor volume of gas you swallow with the fluid is very very dangerous as it will expand (Boyle’s law) and may be dangerous to your guts…
 Always hydrate well 24 hours prior to a dive and 48 hours after with at least 3L of water a day spread out evenly so the body can absorb and retain as much of this whilst maintaining electrolytic balance of your blood volume.
 This will mean you will (a) need to pee on a 90 mins dive and (b) you will need to hydrate in water on dives with duration of 90 mins or more
 Practice on LAND – put your mask on. Breathe in (not deeply and hold) then Take a foil pack and place the valve in your mouth holding the foil pack in one hand and twist, gripping the valve in your teeth. Squeeze the bag and drink using the least number of gulps possible (minimise air ingestion). Twist the bag and close the valve take the foil pack out of your mouth and breathe out (simulate reg clearing). Master this as an operation that you can comfortably complete in short time span – say 10 seconds.
 Practice in the bottom of a pool or in sea water – with you on the floor or sea bed. You need to get the minimum of sea/pool water in with each gulping and practice so that you make no more than three gulps at any time and no more than three drinks in any 15 mins period.
 When you use this technique on dives that are 90 min + to 400 min run times you need to space the hydration out so I tend to drink 500ml bag every hour and make sure that for every drinking session of 3 gulps I add 2 mins (even though it takes a fraction of that) to my deco stop time. I also switch from one drink flavour to the other for no key reason other than keeping tabs on the drinking regime.
 When drinking – ensure that you are very careful with buoyancy control and do not screw this up as the impact again with Boyle’s law you could over pressure your lungs etc and such would be bad. Long run times are likely to be extreme technical diving with helium so such deviation at the stops will badly bend you (not keeping hydrated will too even if you perfectly performed the deco but failed to hydrate – a cause of a fair number of bends in tech divers).
 On cold dives you may need to be careful with the cold temp these fluids obviously will get to. I use the hand warming packs to gently warm these fluids via a home made neoprene pouch to put the drink + 1 hand warming pack in. On 400 min+ dives you will need to use the walking reservoir and tube system as the number of foil packs will get silly and put this walking reservoir in a long neoprene sleeve with a number of the hand warmers at the start of the dive.
 Although tempting never ever use oral rehydrate fluid – even if this has worked for you and your reading this answer – these fluids are great for isotonic rehydration on LAND, but to use on a dive could bend you in how these work to restore electrolytic balance – even diluted.
Hope this is useful and if you want further information please feel free to post further Q’s or contact me direct.
April 7, 2008 by - The-Lone-Diver
|Thanks for the info, I have in the past drank those type with a straw at 15-20m on no stop dives, sounds like its a DEFINATE NO NO.