The sortie was aborted on the ground that the pilot’s nose was no longer serviceable. The author can recall one aviation incident report in which a pilot had failed to set the controls properly to ensure cabin pressure maintenance, and when he took corrective action, the sudden pressure change gave rise to epistaxis. In the author’s experience, sinus barotrauma is rare: it appears to be more common amongst aircrew than divers, and in all probability, many of the latter cases go unreported. When diving, the ambient pressure doubles in the first 10 metres it takes a further 20 metres to double the pressure again, and then 40 metres for a further doubling, and so on. The pressure changes in flight are relatively modest: 0.5 atmospheres of pressure (atm) is reached at about 6000 metres (commercial airliners are pressurised to 2500 metres or less), but 2 atm is reached at only 10 metres below the surface. Travelling in both directions at a steady rate gives rise to the biggest pressure changes closest to the surface. No such easy option exists for aircrew who have to return to ground eventually. The general advice is to clear early and often, but when diving, if all else fails, the dive should be aborted. The solution to locking is to ascend a short distance, clear the ears or sinuses, and then continue but if the situation has persisted, oedema may make it impossible to unlock. The same considerations apply to the Eustachian tube. On the other hand, on ascent, the uncinate process is pushed away from the ostium and the air escapes readily - Figure 1. If the space around the uncinate process is narrow and it comes into contact with the maxillary sinus ostium, any further attempt to descend will force the two structures together all the more: this phenomenon is known as ‘locking’. The air passages to the middle ears and sinuses have no valves, but the anatomy tends to block the ingress of air. Central to the health and safety of personnel is selection: they are passed fit for flying and diving duties only if they can demonstrate the ability to clear the ears, usually by seeing movement on Valsalva’s manoeuvre. In order to assure the health and well-being of personnel, the Services have specialist occupational medicine departments: under water medicine, at the Institute of Naval Medicine, and aviation at the RAF Centre for Aviation Medicine. At one time, submariners were required to undertake escape training, which required them to be able to dive to 30 metres and Special Forces’ duties may involve diving. Divers may repair defects in ships, ensure security for ships alongside, and engage in bomb disposal. It follows that individuals whose middle ears and sinuses are perfectly healthy under normal circumstances, may nonetheless experience barotrauma.Īll three Armed Services have aviators (because of the rate at which their aircraft may descend, fast jet aircrew are particularly vulnerable) and the Royal Navy and Army have divers. At rest, this movement of air is practically negligible, but it is considerably greater when flying or diving. Gaseous exchange between the cavities and the circulation tends to reduce the pressure, because the partial pressures of gasses within the venous circulation is slightly lower than inspired air. Healthy middle ear cavities and paranasal sinuses are normally in equilibrium with the atmospheric pressure, but if an individual moves away from the surface, either by flying or diving, that equilibrium is maintained only by the movement of air out of, or into the cavities. Barotrauma is an injury which is due to the effects of pressure upon an air-containing space.
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