Dense air - breathe less?

[keralucu]

Hey Tomcat

phew.... and I thought it was just me who didn't get the laws of Physics!

I have no idea if the way you explained it is correct, but it does make me understand it a lot better!

Cheers

 

[turnerjd]

Originally posted by tomcat
keralucu,

in short, it doesn't matter how dense the gas gets, we need about the same volume of air in our lungs for co2 to be expelled because of various gas laws and equilibria of pressure of gases between our blood stream and our lungs.

docs, pls correct me if the summary is wrong.

tomcat

Basically yes.

Two things cause us to breath

1. too much CO2 - this is what happens normally, and under water - sensors in the body tell us that there is too much CO2 and its time to get rid of it. - CO2 is generated by the cells in our bodies at a pretty much constant rate - and is going to be independent of pressure etc.. BUT it is dependent upon physical activity level (to do more, the cells require more energy, and they give out more waste products)

2. Not enough O2 - this is what happens at altitude - the body is still producing the same ammount of CO2 at the same rate, but the O2 isn't arriving quickly enough, in this case the body is yelling for more 02 as it can't meet its demand - a bit like being hungry.

When we are under water we are still producing CO2 at the same rate, so, irrespective of air density etc.. our body sais 'too much CO2 in the blood NOW - breath!' so our rate of breathing stays the same.

The only effect that being under pressure will have is that the process of getting O2 to the haemoglobin, which is already pretty efficient will become a little bit (a very little bit) more so.

You were nearly right, it is the rate at which we breath rather than the volume in the lungs that doesn't really change.

Jon T

 

[keralucu]

Thanks Dr Jon, tomcat, Scubadoc et al... I understand a little better now, but will still be reading this thread again several more times!

Cheers