**7. Pneumothorax and air travel**

Commercial air traffic is on the rise. The number of medical emergencies on-board aircraft is increasing as the age-increasing general population becomes more mobile and adventurous. Travellers with respiratory diseases are at particular risk for in-flight events. Exposure to lower atmospheric pressure in a pressurised cabin at high altitude may result in pneumothorax. Gas expansion within enclosed spaces in the human body could expand by 25–30% at the typical cruising altitude of a commercial airline flight, causing significant hypoxia. Patients at risk are those with bullae, cystic lung disease, lymphangioleiomyomatosis (LAM), pulmonary Langerhans cell histiocytosis, cystic pulmonary adenomatoid malformation (CPAM) and cystic bronchiectasis [80].

The currently available guidelines are admittedly based on sparse data and include recommendations to delay air travel for 1–3 weeks after thoracic surgery or resolution of the pneumothorax [80]. No fatalities have been reported due to pneumothorax on-board aviation generally; however, true incidence of specific illnesses associated with air travel has been difficult to assess.

The diagnosis of pneumothorax can be career limiting in the US Air Force. Once an SP has been diagnosed in an individual, he/she will be grounded from further flight duties until either 9 years have elapsed without a recurrence or there has been a bilateral parietal pleurectomy [81].

Barotrauma during or after scuba diving (also on the rise) can rarely lead to pneumothorax, especially on sudden ascent not allowing time for equilibrium. The data is sparse, and there is no solid recommendation about this sport in the literature. Snorkelling sport up to a depth of 10 m does not seem to increase the risk of pneumothorax.
