
Mammalian diving reflex - Smaug123
https://en.wikipedia.org/wiki/Mammalian_diving_reflex
======
jimothyhalpert7
David Blaine: How I held my breath for 17 minutes -
[https://www.ted.com/talks/david_blaine_how_i_held_my_breath_...](https://www.ted.com/talks/david_blaine_how_i_held_my_breath_for_17_min)

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junto
I don't know why, but reading that video transcript makes me feel a bit
physically sick. The thought of deliberately holding ones breath for so long
goes against every basic natural instinct I have. An extraordinary
achievement.

~~~
YeGoblynQueenne
Indeed extraordinary, especially considering that the static apnea world
record is 11 min 35 sec.

To clarify: I'm totally calling bullshit on his claim.

[1]
[https://en.wikipedia.org/wiki/Freediving#AIDA_recognized_wor...](https://en.wikipedia.org/wiki/Freediving#AIDA_recognized_world_records)

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underbluewaters
That's the record for static apnea on regular air. After breathing up with
pure o2, you can push the limits quite a bit more:
[https://en.wikipedia.org/wiki/Static_apnea](https://en.wikipedia.org/wiki/Static_apnea)

~~~
YeGoblynQueenne
The accreditation for _most_ of the records with the pure oxygen is from
Guinness. I'm really not at all convinced by that.

The highest record with pure oxygen that's recognised by AIDA is at 16:32.
That's half a minute under what Blaine claims. So, still, not convinced.

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docaholic
Did an experiment on the dive reflex as part of an undergrad course in
university; hooked up a student (volunteered and willing of course)to a heart
monitor and put their face in a bowl of water.

Heart rate plummeted from 72 BPM (resting) down to 39. It was pretty cool to
see

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Smaug123
According to the Wikipedia page, this effect can be used to defibrillate
infants. Really cool. I'm going to have to try this experiment out on myself
now. Wonder if it has to be cold water or will warm water do.

~~~
docaholic
If I recall correctly, it has to be done in cold-ish water! Warm water above a
certain temperature doesn't invoke the dive reflex (I think we used water at
10 degrees Celcius for the experiment), although I'd have to read up on my
experiment again to be sure.

Sounds like a fun Easter activity :)

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jdswain
I get allergy headaches, and I've found that the single best way of reducing
them is to dive into cold water. Works way better than painkillers, but when
you have a bad headache it's not really something you want to do.

I think it's to do with the diving reflex, that's the only reason I can think
of.

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danieltillett
The next time you get a headache can you try just putting your face into cold
water (less than 10C)? If it is the diving reflex then this should work.

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Natsu
You can also see instinct take over when people are drowning. By watching this
series on YouTube, I learned to spot exactly when drowning takes over:

[https://www.youtube.com/watch?v=L0KTqPloUiU](https://www.youtube.com/watch?v=L0KTqPloUiU)

[Side note: DO NOT read any of the comments. They are particularly obnoxious
and there is nothing worthwhile. You have been warded.]

~~~
id
For Youtube standards, the comments are pretty normal. You see these kinds of
comments on every video about tragic situations (and, to be honest, in any
other video). It's easily one of the worst communities, probably even worse
than image boards.

~~~
Natsu
I think that simply reinforces the idea that YouTube comments aren't worth
reading :)

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dghughes
> Peripheral vasoconstriction in the extremities ...

I wonder if this is why seals, whales evolved flippers instead of big limbs
less warm blood wasted in big limbs.

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biot
I suspect it's the same reason we use thin propellers for moving boats through
the water rather than strapping a bunch of prosthetic limbs to a motor.

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bruckie
My introduction to the diving reflex was pretty stressful.

Our daughter was born a few weeks early. Her lungs weren't mature enough yet,
so she was in the NICU for a while. One day we were changing her diaper right
before her evening feed, around 8 p.m. She was already fussy because she was
hungry, and then she got really upset because she pooped halfway through the
diaper change, so we had to start over. She was really mad, screaming at the
top of her little lungs.

In the middle of all of this, I looked over at the monitor (babies are always
on monitors at the NICU) and noticed that her heart rate had jumped from ~160
bpm (typical for a newborn) to ~320 bpm. I asked the nurse about it and she
said it was a little high, but that it was probably just because she was
upset. After we wrapped things up, our daughter started eating and quickly
calmed down. Strangely, though, the monitor hadn't budged: still ~320 bpm.

I asked the nurse if the monitor was correct, and apparently it was, because
things quickly turned serious. Double-check with a stethoscope. EKG ordered.
Doctors we'd never met appeared out of nowhere. Pediatric cardiologist called.
Another IV started. 10 people crowded around our tiny daughter.

The neonatologist texted the EKG printout to the cardiologist (at a hockey
game with her daughter, we later learned), and she and diagnosed a
supraventricular tachycardia. Untreated, it would result in organ failure
within hours.

The top priority became getting the heart rate back to normal. I assumed they
would use drugs or some kind of electrical stimulation, but they told me about
their preferred treatment, and it seemed almost like quackery: sticking ice
packs on our daughter's face and forehead.

They got their bags of ice water ready, applied them simultaneously, waited
precisely 6 seconds, and removed them. A few seconds later, still ~320 bpm. It
hadn't worked.

They planned to try once more, and then try with drugs through the IV. Ice
packs ready. Applied. 6 seconds. Again, nothing. Disappointment, anxiety,
fear, worry.

And then it happened: five or six seconds after they removed the ice packs,
our daughter's heart rate instantly dropped back to ~160 bpm. There was no
gradual decline: it was a step function. It almost seemed like magic. The
quackery wasn't so quackish after all.

That was my introduction to the diving reflex.

(Postscript: our daughter has been on medication since that day, but she's
getting old enough that they're starting to taper it off, and soon she'll be
medication-free. The idea is that if she has a reoccurrence, she'll notice and
tell us. Then, guess what the prescribed treatment is? Yep: stick her face in
a bowl of ice water.)

Further reading:

[http://www.ncbi.nlm.nih.gov/pubmed/22389355](http://www.ncbi.nlm.nih.gov/pubmed/22389355)
[http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1544966/](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1544966/)
[http://www.webmd.com/heart-disease/tc/supraventricular-
tachy...](http://www.webmd.com/heart-disease/tc/supraventricular-tachycardia-
treatment-overview)

~~~
jacquesm
Reading this brought back a whole pile of not-so-happy memories. Great to hear
she's doing ok and I'm _super happy_ that you asked the follow up question
about monitor being correct. If I interpret your recollection correctly that
was one very important thing you did there. Very scary that it should hinge on
that.

~~~
bruckie
I think things would have turned it fine even if I hadn't been there.

Monitors beep if things go out of acceptable range, but nurses (and NICU
parents, eventually) learn to not be alarmed by it. Some of the sensors are
noisy, and all of the bodies they're connected to are. Usually the beeping
resolves itself after a few seconds.

In this particular case, the sensor had been temporarily silenced because of
the diaper change excitement, but the override would have expired and been
noticed by a nurse within a minute or two.

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monk_e_boy
I snorkel and free dive a bit. It's amazing that you can train your body to go
further and longer underwater. Just a few sessions in a pool will help. I have
no idea what is actually improving inside me, but some thing is.

And free dive fins are the best. If you've never tried any, try to get hold of
a pair. It's fun zooming through the water like a seal.

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luxpir
To clarify for the downvoters, freediving has many techniques for slowing
heartrate and conserving oxygen. It's one of the best ways to learn to
'control' your body.

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yaacov
Triggering this manually is a pretty good emergency treatment for panic
attacks. Just tilt your head back, hold your breath, and press an icepack to
your forehead.

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sciencerobot
Or perform the vagal maneuver:
[https://en.wikipedia.org/wiki/Vagal_maneuver](https://en.wikipedia.org/wiki/Vagal_maneuver).

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bleachedsleet
How is this reflex in humans affected by beta blockers?

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robbiep
Logically, if your heart is already slow then it is going to have a hard time
going slower (ie you are already blocking sympathetic drive and when
sympathetic drive decreases further via the reflex it isn't going to change
much). Since beta blockers are largely beta 2 selective these days it
shouldn't affect capillary vasoconstriction, although since the article
specifically mentions capillary over arteriolar vasoconstriction I don't know
whether that is accomplished by adrenoceptors or what particular receptor is
responsible.

So: no or minimal change to heart rate, likely unchanged effect to
vasoconstriction

