Breathing

[jimess]

This doesn't really belong here but it doesn't seem to fit in body & soul either.

Question: Our brains need a constant supply of oxygen to function properly. This being so why is it in times of great danger, or when we are really concentrating - we invariably hold our breath (and starve our most vital organ of oxygen when we need it to be operating at optimum level) Doesn't make sense.  

[Clanad]

While there may be a very temporary holding of the breath, I think it's possible that you are assuming such.  Usually, in such times of recognized peril the body, through the release of adrenalin, prepares itself for "fight or flight".  The results is quickened respiration and pulse, as well as numerous other physiological changes. It's possible your experience is otherwise, however...

[Peter Pedant]

One of the functions of lung volume (your lungs have a volume of around 5 li) and the breath being around 700mls - 10mls/kg and oxygen consumption 250 mls/min (4 mls/kg/min) is that the variation in oxygen in the blood from breath to breath is smoothed out.

If you hold your breath from an observational point of view it is a few minutes before your oxygen saturation starts falling. in fact at 250 mls a min, 5 li of air should last 4 mins consdiering that air is 21% O2

 

If you fill the lungs with pure oxygen then the 5 li could last up to 20 mins. Ths simple fact is used in anaesthesia when the doctors anaesthetise you.

[Space]

what is a "mls" ?
what is a "li" ?

[CT]

Those would be li = litres
mls = millilitres
1000 mls = 1 li

[Space]

I've never seen these abbreviations before, where do they come from?
Maybe I should make my own ...
I'll call ounces "ons"
and pounds "pn"

[CT]

'fraid pounds and ounces have already been done
pounds = lb
ounces = oz
Surely you've seen some of these on supermarket (etc) products.

[Space]

CT, my message was a (miserably failed) attempt to be ironic...
litres and mililitres already have proper abbreviations too, and I was (pathetically) trying to take the biscuit out of Peter Pedant's home-made abbreviations...

[CT]

Apologies too for not realising your irony. Not always easy on computers.

[mimififi]

LOL, you guys! Toooo funny.

I think generally people do breathe faster when frightened or sick.  Hence the whole hearing your heart pounding in your ears, and the whole hyperventalating thing when you are crying so hard, you can barely speak for the sorrow.

But I know what you mean, sometimes, you feel as though you are holding your breath, especially if you are bracing yourself for a blow to the head, for example, or are trying to deal with pain, such as child birth, which incidentally, any midwife will tell you not to do: "Breathe Mrs Tomlinson, breathe!"

But when I am anger managing, or if I am trying NOT to cry, or not to laugh hysterically at an inappropriate moment, I sometimes hold my breath.  And when I'm concentrating such as threading a needle, or taking a splinter out, or using a glue gun, then I hold my breath too. I do not breath hold when using scissors, but I always count how many actual cuts I make in the item.  How interesting, I shall now need to keep a holding breath diary.  I may well post again in several hours time with the relevant results. Curiouser and Curiouser.

[jimess]

Thanks everyone. Not entirely confident my question was answered but very informative stuff all the same.

Thank you Space for your 'home made' abbreviations - gave me a sly, underhand chortle.

[Peter Pedant]

Of course I was making it up.

eleven litres is lll isnt it in this font ?

and I can't do the -1 bit as an exponent.

but its not unclear and quite near SI.