After pulling the trigger, many hunters have eagerly tracked a frothy pink blood trail, eventually coming upon the harvested animal. A closer look at the animal reveals the bullet has punctured the ribcage and blood has bubbled at the entry site, streaked down the animal’s side, ending in a puddle on the tundra. This might be considered a good shot, as it resulted in minimal meat being wasted. However, an animal can live for a time with a punctured lung, so unless you had nice broadside shot that passed through both lungs, you might be in for an even longer pack out.
In the above scenario, the targeted animal was downed by the bullet or broad head that punctured the lung, a condition known in medical terms as an “Open Pneumothorax” or a “Sucking Chest Wound.” Although an optimal result to have on your harvested animal, in a human it would be life threatening to have a puncture wound to your chest.
In brief, the physiological effect of the puncture wound is quite simple. The brain of a healthy person is triggered to breathe by a rise in carbon dioxide levels. As a healthy person inhales, the diaphragm drops and the chest cavity expands, creating a vacuum. This expansion of the lungs decreases pressure in the lungs and creates a vacuum resulting in fresh air entering the body. The chest soon contracts, the diaphragm comes up, increasing air pressure inside the lungs, forcing air from the airway. It is a simple involuntary exchange of air that occurs 12-20 times per minute in most adults. The respiratory system in general is very inefficient, each breath inhales 21% oxygen and exhales about 16% oxygen. The body only retains 5% oxygen with each breath.
If the body suffers a traumatic event that results in an injury from the outside that penetrates through the lung, a new airway is created. In this case, when the diaphragm drops, the chest expands and air enters the chest cavity through the new hole. As air enters the new hole in the chest cavity it may not end up in the lungs, but rather in the space between the lungs and the rib cage (pleural space). At the same time, when exhaling, air is expelled via the new hole outside the body.
If the chest is punctured due to trauma it will begin to collapse, resulting in a pneumothorax (“air in the chest”). In this case, when the chest expands, air will enter the pleural space (between the chest wall and lungs) through the new hole. This air prevents the lung from expanding, and the internal pressure in the pleural space eventually collapses the lung. At the wound site, air is visible bubbling through the blood.
What may cause an open chest wound?
Possible causes of an open chest wound include the obvious, such as a gunshot or arrow puncture to the chest, back or sides. Falling on a tent stake, sharp willow branches could have the same effect. Likewise, trauma injuries such as falling on a rock, or rolling the ATV could result in a broken rib that punctures the lung.
Next time you are following a frothy pink blood trail you can remember to take note of how the blood bubbles at the wound site. You will be witnessing a sucking chest wound.