Air travel and the ear-Aeromedical Examiners lecture 2011

14 December 2018 Written by Training 4367
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Malta Aeromedical Examiner Seminar

St James Hospital Sliema Boardroom-8 November 2011

-Presentation commentary: Barotrauma of the middle ear-clinical features and investigation

 

Air passengers and crew frequently present to their general physician or otolaryngologist with the effects of barotraumas on the middle ear, due to the effects of change in ambient pressure in individuals unable to equalize their Eustachian tube. This occurs usually due to obstruction associated with upper respiratory tract infections or allergy.

During cabin pressurization (aircraft ascent), the air in the middle ear cavity expands and is passively discharged down the Eustachian tube. During repressurization (descent), however, the oedematous Eustachian tube frequently locks shut and air cannot ascend from the nasopharynx to the middle ear cavity. In this case, rise in ambient pressure tenses the tympanic membrane inwards causing hemorrhage from capillary trauma in the middle fibrous layer of the tympanic membrane.

Unless equalisation occurs, further pressurization causes a serous fluid effusion from the capillaries of the middle ear cavity mucosa. Further mismatch in pressure may cause frank bleeding into the middle ear with formation of haemotympanum (clotted blood in the middle ear).

Clinically patients feel pain in the ear during aircraft descent, together with a ‘blocked’ ear.

All these changes are identified on otoscopy. Middle ear effusion and intra-tympanic haematoma are further confirmed by audiometry and Impedance testing.

Clinicatl Features

Intra-tympanic membrane haemorrhages give the patient a feeling of temporary blockage and are self limiting with the eventual absorption of blood. Fluid in the middle ear may on its own take several weeks to resolve while haemotympanum may take up to three months.

Tuning fork tests demonstrate the presence of a conductive hearing loss on the affected side, that is, Rinne test is negative and Weber lateralizes to the affected ear.

Investigation

Audiometry is carried out which confirms an air-bone gap between sound perceived through the headphones (which is reduced) and sound perceived through the bone-conduction probe (normal level which is the sensorineural function on that side).

Impedance testing, by which middle ear pressure is measured, is carried out by means of a probe that seals the ear canal. A sound is directed at the tympanic membrane and its reflection is picked up, while altering the pressure in the ear canal. As pressure varies from positive to negative and the tympanic membrane moves in and out, the recorded sound reflection varies. A peak is reached when external pressure in the ear canal is equal to the pressure in the middle ear. This is the normal case, known as type A, where a gaussian curve peaks at around atmospheric pressure.

The impendance test or tympanogram shows an abnormal trace in the case of serous effusion or haemotympanum, where the peak is recorded at a negative pressure (type C). There may be no peak at all (type B).

 

Treatment

Unless there are any contraindications (such as hypertension), decongestants and antihistamines do help resolution of serous effusion or haemotympanum. A short course of oral steroids, in my experience, gives the fastest resolution but attention should be paid to contraindications in patients who may be diabetic or hypertensive. Patients are asked not to ‘pop’ their ears as this may make the situation worse, and should be patient while the condition resolves. Flying is contraindicated until the middle ear is full aerated once more. Prophylactic non-sedating antihistamines may help ease discomfort and allow safer travel in the future for patients with nasal allergy who have to travel on unavoidable business trips.