Mailing List Archive

Mailing List: techdiver

Message Display

>
>
>
>On Mon, 4 Jul 1994, A.APPLEYARD wrote:
>
>>   On Fri 1 Jul 1994 09:54:28 +22305714 (HST) Richard Pyle wrote (Subject: Re:
>> O2 Rebreathers for hang):-
>>
>>   > [The advantage of using an oxygen rebreather for decompressing, begins to
>> be lost if nitrogen etc outgassed by the diver accumulate in the rebeather's
>> closed circuit] ...
>>
>>   How much bulk of nitrogen is absorbed by a diver?, even if he is (say)
>> saturated with nitrogen at 200 feet. Would it make much of an effective
>> concentration when outgassed and mixed with a breathing-bag-ful of oxygen?
>
>I've been trying to get a handle on this one for a long time.  Bill
>Hamilton told me it was on the order of one liter per atmosphere at
>saturation.  So, at saturation at 200 feet (say, about 7 ATA), there
>should be 7 liters of nitorgen (i.e., a LOT).  Of course it all depends on
>how saturated you really are, and how big, err, um.... voluminous your
>body is.
>
Richard,

this figure of 1 litre nitrogen/bar at saturation seems about right, 
presuming it means 1 bar air saturation.  You can get a rough feel 
for this by multiplying bogy weight in kilograms by nitrogen solubility.
Lets say the the body is 80% water and 20% fat (actually more like 
72% water, 18% fat, 10% puppy dog tails in males) and the respective 
solubilities for nitrogen are 0.012ml/ml/bar and 0.052ml/ml/bar.  This 
gives a combined "body solubility of 0.02ml/ml/bar.  Assume a 70kg body 
weight and this being mostly water is approximately 70 litres.
0.02ml/ml/bar X 70,000ml X 0.8bar = 1.12 litres nitrogen at saturation.
This also seems to be roughly equal to the amount of nitrogen offgassed 
with isobaric inert gas change after saturation in the paper I mentioned
in my previous post.  Of course you would need to know how saturated you
are and this would require working out a whole body half-time for gas
uptake and elimination, how about 30 minutes-just a guess!!!

David Doolette
ddoolett@me*.ad*.ed*.au*

Navigate by Author: [Previous] [Next] [Author Search Index]
Navigate by Subject: [Previous] [Next] [Subject Search Index]

[Send Reply] [Send Message with New Topic]

[Search Selection] [Mailing List Home] [Home]