Dense air and Respiratory efficiency

[LoCz]

Dr Deco (not sure if this is your field) i wondered if you could shed some light on this subject i was thinking about recently.

What is the relationship between breathing (respiratory efficiency) dense air at depth and breathing normal air on land. Does lung volume play a factor in 02 consumption at depth even though the 02 is more dense. Is 02 wasted as a result of it being more dense?

Also another point. Is it possible to train at altitude as a diver in order to increase red blood cell count and therefore decrease 02 consumption when diving? Or will this cause consequences regarding DCS.

 

[Dr Deco]

The major factor that plays a role in oxygen consumption is work load [activity level]. Lung volume does not play a role in consumption and oxygen is not wasted. When air is very dense, the work of breathing with the regulator increases; but this is not so appreciable at rec diver depths.

One could train at altitude and increase red cell counts but this does not reduce oxygen consumption. It is creases the availability of blood oxygen to the tissues.

It is possible that the risk of DCS might increase if blood was made more viscous and gas exchange was rendered less efficient.

 

[LoCz]

Heh i was in a rush when writing the Q. Work rate can be increased in the presence of higher concentrations of 02, due to an increase in red blood cell count...doh.

:goofy:

Dr deco ...what about higher pressure tanks. Would this be possible so we could cram more 02 in there. New and stronger materials perhaps which will allow us to compress air more etc etc.

 

[danreind]

Gas Density is probably more important in terms of CO2 removal than for O2 transfer. It seems that as gas density increases there is a tendency to not breath sufficiently for CO2 exchange (but there is plenty of oxygen being exchanged). My understanding is that this is either a conscious or subconscious trade-off, the body permits a higher CO2 level in exchange for less energy being expended breathing. But I'm more of a bubble guy so don't quote me on the CO2 retention thing. Since CO2 aggravates both oxygen toxicity and narcosis, this is a concern for deep diving.

An interesting thing about rebreathers is that it doesn't matter how fast you breath, your oxygen consumption only depends on the workload. Typically only a couple cubic feet of oxygen are actually required on a dive, the other 78 cubic feet in a typical air tank is essentially just filler to allow you to get rid of CO2. Open circuit is pretty inefficient, but it's simple and economical and the best choice for recreational diving.

One common item of confusion is the role of physical fitness in O2 consumption. Fit people actually have a higher resting O2 usage than out of shape people because they have more muscle mass and a higher minimum metabolism. However the maximum rate of oxygen consumption is much higher for fit people - so fitness IS important for emergencies.

Just a few thoughts,

Dan

 

[LoCz]

Thanks danreind , nice to meet you btw


:goofy: