Right chaps.
Firstly, I started this thread because as Peter said, points need raising.
It's no good carrying a field dressing if you don't know how to you it. A "large wound" first aid course and knowledge is better than any field dressing on your harness.
A field dressing only covers the wound, it's no good covering up the wound while it's still peeing blood out underneath.
The first thing I would do is get myself out the tree, you only have seconds to make choices and I wouldn't waste them putting on a field dressing to an arterial bleed.
A turnoquet, if only applied for a minuite even, gives you time to investigate the wound, gather yourself, appraise the situation and find pressure points
Shock is a killer, I wouldn't look at the wound either, I would just concentrate on getting down. If you pass out up the tree through blood loss or shock your hard to treat and valuable time is wasted getting you down.
Once you are down, you stem the blood loss which ever way you can, forget about tornoquets are a last resort. Wrap a cloth around the arm and twist until theres enough pressure to stop the bleed and you can fish around in the and have a look.
If you can see the artery apply pressure, either just outside the wound, on a pressure point nearby (if you know what pressure point are) or stick your fingers in the wound and grab the sucker!
Once you have pressure on or a tournoquet, release the pressure every now and again to allow blood to flow to the damaged limb to stop it dying
THEN, when you have stopped the bleeding apply the field dressing and pressure, if you have laserated arterial bleed as in Petes case, there's no way he could have self treated and got pressure on up the tree, he could have used a pressure point but would have passed out through shock and we'd of lost the poor soul
The best treatment for PeteMc's wound was get the frig down the tree and fast, tournoque while you find a pressure point (a few seconds) if you can't find one whack a field dressing on and apply pressure with the heel of your hand.
The best thing you can take up a tree and this is only MY opinion, is first aid knowledge, your hands and a tape sling