To me a pass through is when the arrow passes through.

Night Stalker, is it possible that there is a difference between a drainage tube hooked up to suction and a 'solid arrow in terms of the effectiveness in draining blood.

As to the original question, A pass through must, well, pass through.  As stated before, If two holes, but the arrow is still in the animal it is an incomplete pass through.

bm22 has it right that the arrow can cause faster and further flight if still in the animal.  Many of the critters I shoot are in sight till they fall and it's not unusual for them to stop after the arrow falls out.  

The arrow does keep the hole open. Remember, the area near the front leg has many layers.  Skin, rib, various muscles.  All these act to close off the hole for much of the critters flight.  I think blood trails, especially for the first part of the animals flight, are more dependant on how far up the body the holes are than anything else.

Oh, I'm not doubting that an arrow can keep a hole from closing up.  I just doubt that it is normally important, especially for deer.  I see it blocking the flow of blood from the wound almost as much as it keeps it open. I doubt there are any studies to prove it, one way or another.  Since it would be nearly impossible to reliably get the 'incomplete pass through', it seems to me a much better strategy to go for the complete pass through.  Wow!  Cabin fever must have me pretty bad to be responding to these threads.

Pass-thru to me is Arrow completly in and out.in the ground or in a tree!!

I'm with Bjorn

I didnt read the above, so hope I am not repeating, I would consider a pass through to be like you said the broadhead goes through the opposite wall of the rib cage.  And a complete pass through to be when the entire arrow goes through the animal!

Patrick the drain I am talking about is not under suction. It kind of big rubber band.(penrose)
Do not get me wrong guys, I want all the penitration I can get. I do like it  when the arrow goes through and the animal runs off and you can hear the arrow hitting to brush. The opposite hole is important. Whether you hit a big artery makes all the diferance in the world. You can shoot completly through and into the ground and not hit a big artery in the chest. The animal will expire but you will have less blood to follow.
How many have experienced this. Same hit, some good blood trails and some just adequate. I just saying, it's a crap game.

Oh yea, the odds are a little greater when using a 3 bladed head but it still a game of chance when your looking for a big vessel.

If you are looking at your arrow sticking out of the dirt...that's a pass through.  Otherwise you've got an exit hole.

Which ain't a bad thing...

I say it as pass through and total pass through.
I way prefer the latter because most critters I've got a pass through on,have then turned around an fell on my flamin' arrow breaking it,,,,vindictive buggers,,LOL.