Hi Mr Rawles,
I would like to make a comment on the letter by Walker In The Woods: Sucking Chest Wounds and Exsanguination. Air is sucked through the wound during exhalation and then is trapped, causing pressure. This pressure slowly builds and will eventually cause the pressure to be applied to the heart. This pressure will eventually cause hypoxia and cardiac arrest as the lungs cannot draw in enough oxygen to keep the body going or the heart will be pressed to the point that it cannot function.
The physiology is that the resistance to air ingress is much less through the wound in the chest than through the pharynx and trachea. Normally, when the diaphragm contracts, it creates a negative pressure inside the chest which causes air to move from the outside into the nasopharynx and down the trachea and bronchial tree into the lungs. With an opening in the chest wall, the air moves through the wound into the pleural space because it offers less resistance than the long nasopharynx-oropharynx-trachea-bronchial tree-lung pathway. As the air accumulates in the pleural space, it exerts pressure on the lung and the lung and chest contents ( heart, great vessels, lymph nodes, etc.) then shift away from the side that has the wound. This moves the contents of the mediastinum (chest contents) toward the unaffected side and creates what is know as a tension pneumothorax. The increased pressure in the chest causes pressure on the heart and great vessels, and one can envision the heart and vessels being collapsed because of the increasing pressure surrounding it, much like one of those squeeze balls gets smooshed by the pressure of a hand. Unable to fill completely (with the blood that is returning from the body to be sent to the lungs to pick up oxygen and then back to the heart to be distributed to the body), the heart loses it’s ability to propel all of it’s blood forward and the plumbing to the heart (vessels) cannot fill completely because they are collapsing too. Less blood being pushed around means less oxygen to the tissue, including the brain..
If there is an exit wound, that wound must be covered with thick gauze padding and then an occlusive dressing (occlusive means that air cannot pass through.) this means using a piece of plastic to cover the gauze then tapping the whole thing down making sure to seal all four sides. Once this is accomplished the next step is to cover the entrance wound with an occlusive dressing, again sealing it on all four sides .
Although the author details an occlusive dressing taped on 4 sides on the entrance and again on the exit wound, if the air has entered the chest cavity each time the patient inhales, you need to leave one of those dressings taped only on 3 sides to allow air trapped in the chest cavity to escape upon exhalation so the chest contents do not start to shift to one side…The 3-sided occlusive dressing acts like a one way valve. The patient inhales and the flap is pulled down against the chest wall preventing air ingress through the wound. The patient exhales and increases intrathoracic pressure and air is expelled out of the pleural space, through the wound opening, under the non-taped edge to decrease the pneumothorax on that side and hopefully, prevent the tension pneumothorax.
Realize, the angiocath is used only for a tension pneumothorax, not a simple pneumothorax. If you put an angiocath into the 2-3rd rib space (between the second and 3rd ribs), you create an open pneumothorax and the patient will need a chest tube placed until the air leak stops. That is Hard, if not impossible to do unless you have a prepper doctor around, so make friends with a prepper doctor!
Disclaimer: This letter does not constitute professional advice. It is intended for general informational use only. No doctor-patient relationship is implied nor otherwise established between the author and blog readers.
I would also like to thank the author for his service to our country. Thanks! – Lonestar Doc