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DivePal Gradient Factors and M values

Discussion in 'DiveNav' started by CandiveOz, May 27, 2019.

  1. CandiveOz

    CandiveOz Barracuda

    So DivePal allows you to specify your own gradient factors for dive planning/playing. But it takes it one step further where you can specify the M values for each compartment of the Buhlmann ZH-L16 model (see screen shot below; GF 100/100). To validate this functionality I tried to replicate a GF 85/85 by adjusting the Nitrogen PM0) to 85%.

    (PM0)-1bar)*0.85+1bar =

    Expecting a shift in the M line with no change in slope ie 85/85, I actually get something like 100/85! I'm not sure if I am missing a step. One thing I did notice is that for the 1st compartment, the PM0 defaults to 3.224 when it should be 3.24 or if using 1b; 2.96 but this number can be easily corrected by the user. Any help would be appreciated.

    divepal Gradient table.PNG
  2. loosenit2

    loosenit2 Solo Diver

    Great read on understanding M-Values by Erik Baker. Have not found any literature that contradicts or disproves his writings.

    "A misconception among some divers is that M-values represent a hard line between "getting the bends" and "not getting the bends." This might explain why some divers routinely push the limits of their tables or dive computer. The experience of diving medicine has shown that the established limits (M-values) are sometimes inadequate. The degree of inadequacy is seen to vary with the individual and the situation. Accordingly, it may be more appropriate to describe an M-value as "a solid line drawn through a fuzzy, gray rea" (see
    Figure 2). The reasons for this lack of definitude involve complex human physiology, variations among individuals, and predisposing factors for decompression sickness." (Baker, Erik C.: Understanding M-values)

  3. CandiveOz

    CandiveOz Barracuda

    Hi @loosenit2
    Thanks for responding. I am familiar with Baker's paper on M-values. It was from one of his tables that I was able to spot the error of the first compartment in the Selective Gradient Editor of Divepal above. Hopefully someone who has used this functionality of the program can provide some guidance. Thanks for your recommendation. I completely agree. :)

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