Heat lost due to Heliox

[IDNeon357]

The Navy Diving Manual specifies that:

The respiratory heat loss alone increases from 10 percent of the body’s
heat generating capacity at one ata (atmosphere absolute), to 28 percent at 7
ata, to 50 percent at 21 ata when breathing helium-oxygen.

The problem with this statement is it isn't clear. Is 10% at 1atm normal for air? Or much higher than air and representative of Heliox? I just wanted to see if I can find a secondary source that confirms the Navy statement, but haven't found one.

Or rather, haven't found what normal respiratory loss is when breathing normal air at 1 atm.

Any guidance would be appreciated.

 

[tbone1004]

@IDNeon357 taken from this
https://apps.dtic.mil/dtic/tr/fulltext/u2/a094132.pdf

it appears at quick glance that this is during normal respiration which likely is due to a combination of evaporative cooling in the lungs, and the temperature differential between the body core temp and the inspired gas temperature.

 

[IDNeon357]

@IDNeon357 taken from this
https://apps.dtic.mil/dtic/tr/fulltext/u2/a094132.pdf

it appears at quick glance that this is during normal respiration which likely is due to a combination of evaporative cooling in the lungs, and the temperature differential between the body core temp and the inspired gas temperature.

How did you find this document? Just a google search? If so what were your keywords? This document looks both extremely specific but also extremely on-point to what I wanted to follow-up on.

 

[tbone1004]

How did you find this document? Just a google search? If so what were your keywords? This document looks both extremely specific but also extremely on-point to what I wanted to follow-up on.

strong google-fu, but I also knew that it would have come out of some NEDU study if they were quoting very specific numbers like that. The first search was in the rubicon foundation where that study also lives, but Gene must not have OCR'd it yet, so I just put the following terms into google which gave the article as the first result.
terms were-navy respiratory heat loss diving

 

[Akimbo]

Ask any saturation diver, thermal conductivity numbers are deceiving. Helium is about 6x more conductive than Nitrogen but it feels a lot higher. The deceptively large surface area of the lungs is a factor and lower Oxygen (typically 0.3 to 0.5 PPO2 for indefinite exposures) is another, thus higher helium percentages. Of course increasing Helium density through compression is part of the equation.

In addition to requiring higher ambient temperatures to maintain "shirt sleeve comfortable", the allowable temperature range narrows with depth. This post discusses it in more detail: What is Saturation Diving?, Post #9