Helium question

[JRod]

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How does helium affect the flow of O2?

 

[mjl1717]

I can tell you what it does to reduce the chance of decompression sickness
when mixed with O2 while diving:
1)Its one half as soluble as N2 so less is dissolved in tissues.
2) It has one seventh the molecular wt. as N2 so (therefore diffuses more
rapidly thru tissue.
3) Both these factors reduce the risk of the bends
4))Another advantage of a helium O2 mixture for divers is its low density
which reduces the work of breathing.
5)Pure O2 mixtures cannot beused at depth because of the risk of O2 toxicity.
Hope this helps

 

[Rom]

I found a question regarding Helium and Caison disease. In deep see divers by replacing helium for nitrogen they usually have less a risk of gas in blood... Otherway is should no make much difference... there's also further info in this article regarding He in anesthesia : http://www.ivis.org/advances/Steffey_Anesthesia/driessen2/chapter_frm.asp?LA=1

 

[Rom]

mjl1717 is right on the point

 

[TommyGunn04]

yeah, we have "heliox" at our hospital. I hear it's used for things like status asthmaticus, in attempts to avoid/delay intubation.

 

[starayamoskva]

I can tell you what it does to reduce the chance of decompression sickness
when mixed with O2 while diving:
1)Its one half as soluble as N2 so less is dissolved in tissues.
2) It has one seventh the molecular wt. as N2 so (therefore diffuses more
rapidly thru tissue.
3) Both these factors reduce the risk of the bends
4))Another advantage of a helium O2 mixture for divers is its low density
which reduces the work of breathing.
5)Pure O2 mixtures cannot be used at depth because of the risk of O2 toxicity.
Hope this helps

Risk of nitrogen bends is less with helium, but you can get the bends from Helium as well. Helium off gasses from tissues much faster than nitrogen does and requires precise decompression stops. The risk varies dependent upon exposure times. While the solubility of helium is less, the diffusivity is significantly higher resulting in the evolution of bubbles.

The purpose of helium in diving is not for a decrease in risk of bends. Nitrogen is narcotic at depth and replacing nitrogen with helium allows a diver to go to deeper depth without having the narcotic effects of large amounts of nitrogen. The helium acts a diluent and generally will be used as a Trimix with oxygen and nitrogen. The oxygen portion is routinely as low as 10% of the total gas with as much as 50% helium and the balance being made of nitrogen for normal recreational "technical" diving. The diver generally chooses the amount of nitrogen in the mix based on how "narced" he/she tolerates well (equivilent narcotic depth). Many divers like to keep their END at around 120-130 feet depending on the type of dive they are doing. The ratio of helium and nitrogen is often determined by the divers desire to avoid both nitrogen narcosis and CNS oxygen toxicity. Current recommended guidelines for CNS oxygen exposure preclude oxygen pressures greater than 1.6 bar.

Probably more information than you were interested in but it is a pet peeve of mine to have incorrect info concerning diving perpetuated. 😉

You are correct that heliox is used for asthma patients to decrease the work of breathing because it is less dense than pure oxygen or oxygen enriched air.

 

[bigfrank]

I wonder how those divers sound when they come back up -- like chipmunks!!

 

[starayamoskva]

I wonder how those divers sound when they come back up -- like chipmunks!!

yeah we can in fact sound like chipmunks but usually use a decompression mix that doesn't contain helium so it's out of the system by the time we surface. 😀