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Chris,
In reply to:
On Tue, 11 Jun 1996, Chris Hellas wrote:
> >The manual (Joe Odom, 1995, rev 1, 3/96) used by TDI in training/
> >certifying divers for the Atlantis I indicates that the currently
> >available 7.6 L/min constant mass flow valve using (recommended) EAN50 on
> >the unit delivers an FiO2 of 32% at a VO2 of 2.0 L/min and an FiO2 of 35%
> >at a VO2 of 1.75 L/min, using the standard equation.
>
> Interesting! - I have the Draeger manual, which quotes 7.2 L/min.
The latest edition page 23 (Joe Odom, Revsion 1, March 1996) says 7.5, but
my TDI instructor, Mike Pratt (who by the way is an engineer) says that it
is 7.6 L/min.
> Drager quote an FiO2 of 34.7% for a VO2 of 1.5 litre/min. Some
> discrepancies I suggest!!!!!!. Perhaps the equation TDI are using is not
> so 'standard'.?
Again Joe Odom's book p40 gives the following equation for calculating
fiO2:
fiO2 = ((fsO2 X Qs) - VO2) / (Qs - VO2)
where Qs = gas flow rate
fsO2 = source gas oxygen
VO2 = oxygen metabolized
Is this not an appropriate formula?
> Draeger state that : - 'The equipment was designed for maximal use of
> 2.5 L/min of oxygen.If the diver consistently uses 2.5 L/min of oxygen
> then the oxygen level being circulated will be at a minimum of 17% by
> volume.'
This is very interesting. Using Odom's formula above, I get an fiO2 of
25.5% not 17%. What am I doing wrong? I *mean* about the math :-)
Let me know,
Peter Heseltine
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