Heat map timing and colours

[Rick Walsh]

On 7 Oct 2016 23:26, "Willem Ferguson" <willemferguson at zoology.up.ac.za>
wrote:
>
> On 05/10/2016 03:40, Rick Walsh wrote:
>>
>>
>> The exact points on the colour scale are interpolated between points on
the HSV (hue, saturation, value) colours scale
>>
>> Tissue pressure below ambient pressure points are:
>> tissue pressure negligible relative to ambient pressure (rapid descent
to depth): "bright" cyan (HSV = 180 deg, 1, 1)
>> tissue pressure ~ 53% of (ambient pressure * fraction inert gas in air):
"bright" blue (HSV = 240 deg, 1, 1)
>
> Is 53 the bottom limit of this class or the top limit of the class (i.e.
is the interval 0-53 or 53-79) ??
>
>
>> tissue pressure = 80% of (ambient pressure * fraction inert gas in air):
"bright" purple (HSV = 270 deg, 1, 1)
>> tissue pressure = (ambient pressure * fraction inert gas in air): black
(HSV = 270 deg, 1, 0)    <---- this is special because it is where your
tissues end up if you breath air on the surface
>> tissue pressure = ambient pressure: "medium" green (HSV = 270 deg, 1,
0.68)
>>
>> Tissue pressure above ambient pressure points relative to M value
(tissue "gradient factor") are:
>> 10% of M value = "bright" green (HSV = 120 deg, 1, 1)
>> 55% of M value = "bright" yellow (HSV = 60 deg, 1, 1)
>
> Is 55 the bottom limit or the top limit of this interval? (i.e. is the
above interval 11%-55% or 55%-99%, assuming there are some non-described
intermediate colours included in this interval) ??
>>
>> 100% of M value = "bright" red (HSV = 0 deg, 1, 1)                  (Is
this    -> 100%  or is it 100% ->  ??)
>>
>> 140% of M value = white (HSV = 0 deg, 0, 1)
>>
>> I hope you never see the colours beyond red in an actual dive - but you
can in a test plan if you set GF > 100%, or VPM-B with zero conservatism
and a deco dive with a reasonably long bottom time, which can result in an
equivalent GFhigh >100%.
>>
>>
> Some questions inline in the text above
>
> Also, meaning of black:
> 1) An air dive to 40m will have a tissue pressure of nitrogen of up to 4
bar (equivalent to the pressure at the bottom black line in the pressure
graph in the info box, looking at fast tissues)
> 2) In this case, up to a pressure of 0.53*4 = 2.12 bar the colour in the
heat map should be cyan.
> 3) Breathing air at the surface, tissues end up with a nitrogen pressure
of 0.8 bar.
> This is way within the cyan zone of the heat map.
>
> Please explain in more detail so that willem can start thinking straight?
>

Sorry, I didn't explain well at all what was happening.
Firstly, the points I gave you are the exact colours at the exact ratios of
tissue pressue to ambient pressure (when tissue pressure < ambient
pressure), and gradient (= tissue pressure minus ambient pressure) to M
value (aka gradient factor). Between these points, the colours are
interpolated on a gradual scale.

Using the example of a rapid descent to 40m (5 bar!) on air. By rapid, I
mean too fast for any significant ongassing to occur, which is reasonably
true for slow tissues, but not really for the fastest. Let's pretend 1 bar
= 1 ata, because nearly everyone else does and it's pretty close.
On reaching 40m:
Tissue pressure = tissue pressure at surface = 0.79 * 1 bar = 0.79 bar
Ambient pressure = 5 bar
Tissue pressure /ambient pressure = 0.79 / 5 = 0.158 = 16%

Now, at tissue pressure / ambient pressure = 0 we have cyan (hue = 180
deg), and at tissue pressure / ambient pressure = 53% we have blue (hue =
240 deg).  Interpolating between those points, at 16% we have a colour with
hue of 198, which is a light blue.

After a few tissue half-times, the tissues become saturated, so:

Tissue pressure = 0.79 * 5 bar = 3.95 bar

Ambient pressure = 5 bar

Tissue pressure / ambient pressure = 3.95 / 5 = 0.79 = fraction of inert
gas in air

So the heat map shows black.

You can see this example in the planned dive below.  On descent (2 minutes
to get to 40m), all but the slowest tissue are at light blue.  After 60min
at 40m, the fastest tissues are now saturated (with air), so the heat map
is black for them.  At this point, the slow tissues have still barely
saturated, so they're still light blue.

[image: Inline images 1]

Does this help?
On ascent, the process is similar, but more complicated because you have to
calculate the M value, which is different for each tissue, and varies with
depth.

Cheers,

Rick
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