Freediving in Monterey and Hypothermia

Or How to Get, Treat, and Prevent Hypothermia

I had my first freediving class last weekend, and we had amazing ocean diving practices in Monterey, CA. I have yet to absorb all the knowledge of physics, physiology, psychology, and skills for efficient diving pouring from Kirk, Hawkeye, and Erin. I had used a 'floating holiday' for this 4-day weekend class, and indeed did a lot floating and even some sinking ;) (with negative buoyancy below -10m).

This post will talk mostly about hypothermia as I am better prepared to analyze everything I did right and wrong putting my wilderness first aid training to use.

The +/- comments are post-mortem analysis with a clearer head, on what to do for proper hypothermia prevention and treatment.

• Fitting freediving wetsuit
  I wouldn't have had to write a posting about hypothermia, if I could find a proper fitting 7mm Yamamoto 45 freediving wetsuit for the conditions in Monterey.

There were two appropriate freediving wetsuits in 4 dive shops in driving distance. They were either too baggy or too short and my head wouldn't fit.
- I put together a layered wetsuit combination, since it was too late to order a custom wetsuit,

• Subcutaneous fat. I have only 9% fat and most of it visceral. I probably need to add some for freediving:
  + I would have some natural insulation. The Aquatic Ape Hypotheses is partly based on the fact that humans have sub skin fat like marine mammals instead of fur like other apes.
  + I would be more buoyant and my legs won't sink like lead;
  + I would also have extra energy reserves for staying for hours in the water.
  + Having average fat would help me fit in stock wetsuit sizes

Too late to fix that even if I wanted to.

Keep in mind that the skin receptors determine whether you feel hot or cold, yet the core is what really needs to be warm.

Similarly skin controls heat loss through skin blood vessel dilation and sweating, or vasoconstriction and shivering.

No need to worry about thermoregulation effects of fat vs blood vessels in my case.

After pool session first day let's get in the ocean.

Day 2 - Monterey, CA
o 8mm suit + 5mm hooded vest inside, 5mm gloves, 7mm booties
- Lots of water sloshing and worse flowing in the suit, especially on dives or surface swimming

o Plenty of excitement from first ocean freedives, big swell, and man-sized jellyfish
o Fin kicking to keep warm with face submerged, it felt like I was warming up.
- Definitely neither of the above is helping my breathholds, as they keep my
heart rate up instead of slowing it down during breath ups.
- Worse this requires higher respiratory rate - and loses more heat
through breathing.
- Swimming is not a very effective way of warming up. Shivering is better!

o I was doing some pushups on the bar to stay out of the water.
+ Indeed good to keep the head and the body out of the water,
unless wind causes more loss from evaporation

Kirk's mentioned his competition wetsuit wasn't even wet the first half hour,

and noticed how violently I had been shaking the float ;)

- High intensity shivering uses glucose that I would quickly run out of,

while low intensity shivering uses fats

o Home care: very aggressive hot fluid intake,
I was trying not to get a cold that would completely screw up my already bad equalization.

Day 3 - Monterey, CA
It was time to make some changes. Next experiment was to put the
hooded vest on the outside.
o 8mm suit + 5mm hooded vest OUTSIDE
+ It did indeed reduce the water flow through the neck and the back zipper,

- I lost some layering on the core though as the vest was baggy.

Overall I believe this was better.

Yet every time I did a 10 count exhale around the 9th when my heart rate dropped I'd shiver from the cold...

I had lost some dexterity but I felt overall good.

Still, I thought I was functioning normally as I was joking around:

e.g. when I had blood in my nose from bad equalization technique. I was laughing that
"I am just chumming for sharks ;)"

This time I checked to know how cold I was,

as I do carry a hypothermia thermometer in the med kit.
Body temperature 34C (93.5F) => mild hypothermia

Water temperature at -7m (23ft) had been 14C (57F) according to the dive computer.

Home care:
o Virgin lilikoi margarita
+ Good choice, alcohol causes skin dilation and you just lose core heat.
Of course, overkill precautions since we are already indoors.

o Hot fish udon soup for dinner

++ Core rewarming plus food to increase heat production

Next morning core temperature 97.2 was a little low but OK.

Day 4 - Monterey, CA
o 1mm neoprene skin + 8mm suit + 5mm hooded vest OVER wetsuit
5mm surfing gloves OVER, 7mm yamamoto boots UNDER wetsuit
+ The extra skin seemed to take some of the slack, and reduce water flow.

• Predive ritual - pouring warm water in the wetsuite.

Sure feels good, but unsure whether effective in the long run.
- Skin gets warmer and will lose more body heat if the water drains out.
+ If the water indeed stays in the wetsuit, should be good: there is
no need to warm up the first batch of cold water.

At least on the first dives I was still warm and getting to the target depths with ease.

Erin: "I was getting cold just watching you there"

Colder morning, water temperature 13C (55F) at -14m (46ft?) - my deepest dive.
Body temperature 33.5C (92.3F) - no protection combination seemed to be working for this deep and long exposure.

I was functioning fine, but I took it more seriously this time.

Hypothermia self-treatment:

1. Alway keep core dry and warm, then head and finally extremities.
   + Bundled up to preserve keep created by core
   + Drank some water and a little food to keep producing heat.
   
   o Mylar wrap (emergency blanket) would have been most effective for core warming.
   -- I usually have a very convenient wrap in my beach bag, but was in the car as I had used it last week...
   
   -- No hat
   
   
2. Warm shower in the 'head' on the boat - tried to focus on core only.
   - Felt good but was definitely not going deep enough,
   may be dangerous to do on the boat if we had a long ride back.
   - Better to be shivering to generate more core heat and trap it in clothes or blanket.
   I'd skip this.
   
   
3. Turned up the heat in the car. Had a good wicking base layer to move sweat away and not get sweaty.
   + Breathing warm air is definitely a good way for core warming.
   
   
4. Tea with lots of honey. My aunt's homemade honey from the Black Sea helped me visualize warm Black Sea waters and beaches.
   ++ Hot and sweet liquids are definitely a double win on core rewarming and energy.
   ? Unclear whether visualizing calming warming will make your skin lose more heat. Can't help it ;)
   
   
5. Signed for the next class in Kona, Hawaii
   + Some excitement definitely should help get the heart rate up and increase heat production!
   
   
6. Went for a hot tub (110F)
   Warming the core through the skin earlier would have been too slow.
   My procedure to get warmed deep to the bone:

• Keep hands and feet out of the water initially.
• Always raise core temperature first. At this stage for me just best practice,
  but if this was earlier in rewarming it is critical not to warm up limbs before core.
  After that,
• Stay as long as possible.
• Once you get too hot - go out, drink some water.
• Stay out until you start shivering!
• Then get back in the tub for iterating to reaching the next level
  + My theory: core should be warming up faster since water heat exchange is faster than air, and skin permeates. Evaporation from the exposed wet skin will create an air insulation layer, so core heat should be preserved while not losing much in the process of cooling off the skin.

• Cooled off my head
  After getting out with a few stumbles and momentary losses of motion control,
  I realized I had a near blackout from overheating.
  
  This was pretty ironic given I didn't get any LMC or blackout fun at any of the dives or the static apneas (4:20 minutes).
  
  Fix: with core bundled, stayed with a wet head out in the cold air till I got back my bearings.
  + Evaporitave cooling at its best. I should write another post on hyperthermia.

What a weekend!