 Welcome to emergency medicine video. The segment is on pneumothorax. In this part, we will discuss the causes and presentations of pneumothorax. Pneumothorax is defined as air in the pleural cavity. That is the potential space between the parietal, pleura, and the visceral pleura. What are the effects of pneumothorax? Depending on the size, it can first impair oxygenation and ventilation. Second, if there is a one-way valve leaking air into the pneumothorax, it could potentially squeeze the mediastinum over to the unaffected side. As a result of that, there is decreased venous return to the heart. Blood pressure then drops and the patient can go into cardiac arrest. Therefore, a pneumothorax is a must-not-miss diagnosis. How does a pneumothorax occur? It can occur spontaneously or by trauma. We will discuss each of these separately. Spontaneous pneumothorax happens when there are blebs and boli that rupture in the patient's lungs. It can happen in patients with no underlying lung disease, also known as primary spontaneous pneumothorax. It can also happen in patients with underlying lung disease, that's known as secondary spontaneous pneumothorax. Primary pneumothorax usually affects thin and tall patients. Smoking and other genetic factors such as Marfan syndrome also increases the risk. Secondary spontaneous pneumothorax occurs in patients with lung problems. The most common ones are COPD and asthma. They can also occur in the settings of infections, such as TB and PCP. Traumatic pneumothorax happens when there is a puncture in the pleura, and therefore the air rushes into the space. They can be caused nitrogenically by medical procedures. These include biopsy, thorough syntheses, and intercostal nerve blocks. Basically, any procedures that involve puncturing the chest wall. They can also happen in the setting of trauma with penetrating injury, either in the setting of an open wound all the way down to the pleura, or from rib fractures puncturing the pleura. Tension pneumothorax is usually seen in traumatic pneumothorax. Since in those settings it's more likely to see the one-way valve effects pushing air into that space. Let's move on to presentations of pneumothorax. Patients with spontaneous pneumothorax will present with chest pain in the affected side. The pain is usually severe, sudden onset. It might feel like stabbing and sharp. It might radiate to the shoulder. The pain is also worse with inspiration. On examination, depending on the size of the pneumothorax, the patient can have shortness of breath, particularly if they have underlying lung disease. The vital signs on examination will show tachypnea, sometimes even a drop in their oxygen saturation. When you listen to their lung, you might hear that there is decreased breath sounds on the affected side, although this is a challenge to hear in a noisy emergency department. In traumatic pneumothorax on history, you will want to ask about the history of procedures and trauma. On examinations, besides the signs that you see in patients with spontaneous pneumothorax, we should also look for open wounds. What about for tension pneumothorax? What should we look for on examination? Since the mediandostina will be pushed towards the unaffected side, we should look for tracheo deviation to the unaffected side. Since there is also decreased venous return, you would expect the patient's regular venous pressure to be high. The patient's blood pressure will also be low. You may also appreciate further decreased breath sounds on the affected side. This is a patient who would appear to be in significant respiratory distress. This is a diagnosis we have to make clinically without doing x-rays. In summary, in this section, we discuss the causes and presentation of pneumothorax. In the next part, we discuss the investigations and treatment. Thank you for watching.