A patient has been admitted with a penetrating injury to the chest that has gone through the pleural membranes. Explain how this injury will disrupt pulmonary ventilation and the pressure changes that occur.


Quick answer:

An injury that has punctured the pleural cavity will result in the pleural cavity being filled with blood. The patient's lung will collapse, and the patient will be unable to breathe. The patient will have to undergo surgery in order to close the injury and have a chest drain inserted.

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The pleural cavity is located between two membranes (visceral membrane and parietal membrane) that are between the lungs and chest wall. The pleural cavity is filled with pleural fluid, which holds the two membranes together through pressure and tension. The pleural cavity is held in a constant state of negative...

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pressure allowing the pressure within the lungs to increase and decrease as we exhale and inhale, respectively.

A patient that has a chest injury that has penetrated the pleural cavity will have a mixture of blood and air enter the pleural cavity. This equalizes the pressure of the pleural cavity with that of the surrounding atmosphere instead of allowing the pleural cavity to remain in a state of negative pressure. This also causes the visceral membrane and parietal membrane to separate. Furthermore, when the rib cage moves out, the lungs do not expand with the rib cage.

Due to the injury, the lungs cannot expand, and the pressure within the lungs drops and remains low. This also means that respiration is suspended, and air cannot be pulled into the bronchi. The lung affected by the injury will shrivel up and become known as a "collapsed" lung. The patient will likely need to undergo surgery to close the penetration and possibly insert a chest drain to drain the blood from the pleural cavity.

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Explain how a penetrating injury will disrupt pulmonary ventilation and the pressure changes that occur.

The pleural membrane is a thin, moist structure with two layers. The outer layer lines the inside of the rub cage and diaphragm, and the inner layer covers the lungs. The intrapleural space is located between the two layers. The intrapleural space contains fluid secreted by the two membrane layers, which allows the layers to slide over each other as the lungs expand and deflate during breathing. The seal of the pleural membranes keeps the lungs connected to the rig cage. This results in a negative pressure within the intrapleural space. During inhalation, the pressure within the intrapleural space becomes even more negative. If the pleural membrane or intrapleural space is ruptured (e.g. due to a stab wound or spontaneous rupture), air enters into the intrapleural space and results in an air-containing space between the lungs and chest wall. This causes the intrapleural space to fill with blood and additional fluids and cancels the negative pressure atmosphere necessary for breathing. The seal of the pleural membranes will be broken, and the movement of the chest wall will no longer expand the lung for breathing. The lung in the injured area will collapse. Pleural membrane and intrapleural space injuries can be repaired with surgery and usually require a chest drain device to remove the fluid.

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