Pneumothorax is a common cause of breathlessness in critical care patients, especially following trauma. Essentially due to a tear in the lung that allows air to escape and collect in the pleural space. They can be termed primary or secondary depending on whether they are related to an underlying lung disease. Depending on the size of the pneumothorax and the state of the patient, the symptoms may be absent to severe: sharp chest pain worse on inspiration, shortness of breath, and wheeze. In patients who are mechanically ventilated, a chest drain is usually required; they are also at much higher risk of tension pneumothorax. There are two techniques commonly used in the insertion of a chest drain and the choice depends on the operator, the patient and the size of the pneumothorax: seldinger chest drain and 'surgical' chest drain.