Formulae

                            VO2 = (Qs (FsO2 - FiO2 )) /  1 - FiO2

                           FiO2 = ((FsO2 * Qs) - VO2) /  Qs - VO2

 

VO2 = Oxygen metabolic rate

FiO2 = Inspired oxygen

Qs = Flow rate in lpm

FsO2 = supply oxygen percentage

Equivalent Air Depth

 

                     EAD = ((FN2 / .79) * D / 33) - 33

 

FN2 - Fraction of Nitrogen

D - Depth

Memory Aid for;                                    Pg = P * Fg         P = Pg / Fg         Fg = Pg / P

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Pg - Partial Pressure of the gas i.e. PO2

P - Pressure in ata

Fg - Fraction of the gas i.e. FO2

 Ambient pressure                                                           

                                                  ( P / 33 ) + 1

P - Pressure in ata

Flow through a sonic orifice    

Flow  (lpm) = 11Pbar * D2

P = pressure in bars

D = diameter in mm