Describe the issue:

• Bug
• Change request
• New feature request
• Discussion request

Issue long description:

Today you can only edit the "pSCR metabolic rate O2" (O2met) in the tech setup menu. To actually calculate anything meaningful for pSCR dives you will also need the respiratory minute volume (RMV) of the diver(sac rate essentially).

If you get stressed and have a higher RMV your body use more O2 than normal so you also have a higher metabolic rate. So you end up with a constant RMV/O2met. This is often referred to as the oxygen extraction ratio Ke. (or some times referred to as ventilatory equivalent for oxygen VeqO2)

Today the default O2met is 0.720l and the default MV is 20l. This gives an unusually high Ke of 20/0.72= 27.78

This is easy to miss as you cant adjust the MV (SAC) in the Tech setup menu. You need to go to the Plan dives menu and adjust it there. 0.720l becomes a more reasonable default if the default RMV is 17l 17/0.72=23.61. Closer to the value 22.5 you find in EN 14143:2013, or 20 (range 17-25) Larson 2002. (http://www.teknosofen.com/dcsc_tech.htm)

Choosing a O2met value 0.889 that gives us a Ke of 22.5 with the default RMV 20l seems to be a more sane default.

On the other hand most pSCR divers are fairly experienced divers so a RMV of 20l is probably on the high end of the scale. But since RMV is used in other parts of the software this number is probably more difficult to change to something more realistic for a pSCR diver as 15l.

My suggestion is therefore to display the Ke value in the PSCR section on Tech setup and let the diver control this as a function of RMV/O2met where you can adjust both values or let the diver control the Ke value directly. The ratio between the numbers is what matters from a decompression point of view and this is not clearly expressed in todays view.

Operating system:

Subsurface version:

Steps to reproduce:

Current behavior:

Ke value of 27.78

Expected behavior:

A Ke value that is in the lower twenties. (20-25)

Additional information:

Mentions: