(The following forum post and consequent PM responses to queries comes via the edersbow forums. It was posted to provide information on the ever-popular belief that there is a 'void' above the lungs - an area, which hit with a 'perfect' broadhead shot, supposedly results in the animal not being killed/recovered.)
The date of this renewed post is Oct 2009.
From: LTG Date: 19-Oct-05
OK. Enough. I normally am strictly a lurker, but I can't take anymore. I am a Pulmonologist (Lung Dr) and avid archer. As a disclaimer, I am not privy to what others have seen or witnessed. I am only trained in normal mammalian anatomy. As such, I offer the following:
1) The lungs are not "glued" to the chest wall. That said, they are mechanically linked by fluid forces between the chest wall pleural surface and the lung pleural surface. The example I use for my students is to take a zip lock bag, put in a very small amount of fluid to "wet" the surfaces and close the bad squeezing out all the air. Then try to separate one bag surface from the other. Can't be done without ripping the bag or putting air into the system. During normal respiration, the chest wall expands a small amount and the lung expand to remain constantly in contact no matter how fast or sharply you breath in. The diaphragm moves up and down a good deal as well, but again, the lungs are in continual contact with the diaphragm. The lungs never separate from chest wall - pleural space is a "potential space" until disease causes fluid to accumulate (effusion), bleeding (hemothorax), or chest wall puncture or lung rupture (pneumothorax). There is no anatomic or physiologic void.
2) the lungs of all large mammals have recesses that reach above the horizontal lowermost reach of the spinal column. I will gladly attach computer tomographic images (CT scan) from man, pig, sheep to demonstrate that you can not design a path that goes under the spine that will not puncture at least one lung (assuming we are talking about the chest cavity).
3) Not all pneumothoraces are lethal. Even bilateral lung puncture can be survived if there is not a large "sucking chest wound" and/or the lung slices quickly seal up with blood clot. Most of these animals will die, but a few can travel a long way even with "double lung" hits if only the tops of the lungs are sliced.
So, there is no void except in the beliefs of some; you can hit an animal below the spine and not recover it.
From: LTG Date: 19-Oct-05
Knife2sharp
No, the "void" is a mythical location. The term is a poor choice of words for it implies a lack of vital tissue. Not all double lung hits at the top of the lungs will be lethal. Most still will be, but will give poor blood trails just due to geometry. Used to see this a lot more when I hunted more from the ground. I think it is relatively rare because most arrows are going to deflect off bone creating more damage. In addition, many of our animals who go down fast do so from large vessel violation (aorta, pulmonary artery, vena cava) with bleeding causing collapse long before asphyxiation.
From: LTG Date: 19-Oct-05 Private Reply
Knife2sharp
one common misconception is that a pneumothorax (collapsed lung) is an all or nothing phenomena. This is not true. Now certainly with a big open chest wound, most certainly the lung will collapse completely, but this still happens on a breath by breath basis (breath in creates negative pressure drawing air through open wound) and can take many minutes (= many yards if running). Also, if chest wound seals up (narrow slit, fat, clot, etc), lung may only leak a little air during expiration (positive pressure in lung to get breath out) and only partially collapse. Humans and deer have two separate pleural cavities (one for each lung), so dropping one lung leaves the other relatively unscathed. The bison has a single pleural space and was relatively "easy" to kill with even a one lung shot. That said, I have heard that an arrow to the chest of a bison may still take large fractions of any hour to put it down.
From: LTG Date: 19-Oct-05 Private Reply
Matt - exactly.
In addition, remember your fluid dynamics and air flow resistance factors. A deer trachea (windpipe) provides a much bigger cross sectional area than most any broad head wound (area of circle vs intersecting slits). Thus, air will still follow path of least resistance and animal will be able to inspire until pressure in pleural space impedes air entry through normal channels. This scenario also presumes a "sucking" chest wound whereby entrained air through wound on inspiration does not escape on expiration (think ball valve). Very deadly. However, a true open pneumothorax (air in and out wound during respiratory cycle) can be tolerated for a very long time (ask many of our young men getting shrapnel wounds overseas or any trauma center doc)
From: LTG Date: 20-Oct-05 Private Reply
I am amazed how many folks have shown an interest in this topic. Nice to see people genuinely interested in the physiology of archery hunting. The bottom line on one lung hits is that they are very survivable if no major pulmonary artery is cut. Think of the lung arteries as roots of a tree. They start out pretty big as the main artery comes out of the heart, then branch repeatedly until down to the size of capillaries ((10 microns diameter). If you center punch the root (hilum) of the lung, you have cut an artery only a bit smaller than the aorta. Although at considerably lower pressure than the aorta, the pulmonary artery to each lung receives 50% of the cardiac output. No other organ can boast this fraction of total blood flow. This is the major reason a double lung hit is so deadly. Combine the blood loss with large volume pneumothorax and the animal may just fall over after a couple of steps. However,most times I suspect they bleed to death before they asphyxiate. Now if you do not cut a big artery, the bleeding may stop, the lung may only partially collapse, and the animal will be able to travel a long way (or may survive). Much more similar to a gut shot, yet in my experience these guys do not lay down. I suspect many are lost at great distance. Those that live must not get infected and must endure the pain and athlectic disadvantage of a pneumothorax. For those of you who have had a spontaneous pneumo, you know about the pain and shortness of breath. This would be fascinating, albeit ethically difficult research. I shoot Thunderheads - I like big holes and close shots.
Tom Gross from Iowa Goes by the handle "LTG"
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Basic knowledge of animal anatomy is of prime importance to the hunter, especially when bow hunting. Since the killing of game with a broadhead relies solely on hemorrhaging, the arrow must be placed in the most effective location. In general, this is the heart/lung area of the animal.
The pictures above illustrate the location of the heart and lungs, and the corresponding concentrations of blood vessels. An arrow which passes through both lungs will generally result in the animal being subdued very quickly.
Another important factor to note is the location of leg bones. When a deer or other 4-legged mammal is standing at rest, it's leg bones are clear of the heart/lung area and a good shot is offered. But when the near leg is lifted (see bottom picture), part of the target area is covered. A shot with archery equipment should be taken only when the near fore foot is on the ground, preferably with that leg slightly ahead of the other.
