Sunday, July 1, 2012

Middle Ear and Sinus Problems in Flying


Middle Ear and Sinus Problems in Flying

During climbs and descents, the air in our closed cavities expands or contracts due to a difference between the pressure of the air outside the body and that of the air inside the body. 

If the air expands pressure builds up within the cavity and pain is experienced if it can't escape. Trapped gas expansion accounts for ear and sinus pain, as well as a temporary reduction in the ability to hear.

The physical ear consists of an outer conical shaped structure called external pinna. A middle chamber, that connects to the outside atmosphere, and the inner ear. 

The middle and inner ear are located in a small cavity in the bone of the skull. The tympanic membrane separates the outer ear and middle ear. The Eustachian tube connects the middle ear to the outside atmosphere. Pressure differences between the middle ear and the outside atmosphere are equalized by the Eustachian tube.There is a right and left Eustachian tube. They are normally shut but they open during chewing, yawning or swallowing to equalize the pressure.

A slight difference in external pressure and middle ear pressure can cause discomfort.

During a climb, middle ear air pressure may exceed the pressure of the air in the external ear canal, causing the eardrum to bulge outward. Pilots become aware of this pressure change when they experience alternate sensations of “fullness” and “clearing.”

 During descent, the reverse happens. While the pressure of the air in the external ear canal increases, the middle ear cavity, which equalized with the lower pressure at altitude, is at a lower pressure than the external ear canal. This results in the higher outside pressure, causing the eardrum to bulge inward.

This condition can be more difficult to relieve where the partial vacuum tends to constrict the walls of the Eustachian tube. To remedy this often painful condition, which also causes a temporary reduction in hearing sensitivity, pinch the nostrils shut, close the mouth and lips, and blow slowly and gently in the mouth and nose.

This procedure forces air through the Eustachian tube into the middle ear. It may not be possible to equalize the pressure in the ears if a pilot has a cold, an ear infection, or sore throat. A flight in this condition can be extremely painful, as well as damaging to the eardrums.

If experiencing minor congestion, nose drops or nasal sprays may reduce the risk of a painful ear blockage. Before using any medication, check with an AME to ensure that it will not affect the ability to fly.

In a similar way, air pressure in the sinuses equalizes with the pressure in the flight deck through small openings that connect the sinuses to the nasal passages. An upper respiratory infection, such as a cold or sinusitis, or a nasal allergic condition can produce enough congestion around an opening to slow equalization. As the difference in pressure between the sinuses and the flight deck increases, congestion may plug the opening. This “sinus block” occurs most frequently during descent. Slow descent rates can reduce the associated pain. A sinus block can occur in the frontal sinuses, located above each eyebrow, or in the maxillary sinuses, located in each upper cheek. It will usually produce excruciating pain over the sinus area. A maxillary sinus block can also make the upper teeth ache. Bloody mucus may discharge from the nasal passages.

Sinus block can be avoided by not flying with an upper respiratory infection or nasal allergic condition. Adequate protection is usually not provided by decongestant sprays or drops to reduce congestion around the sinus openings. Oral decongestants have side effects that can impair pilot performance. If a sinus block does not clear shortly after landing, a physician should be consulted.

Travelers on commercial planes, where pressurization is set at 6,000 feet, may experience pain if the passageways are blocked before takeoff.  Techniques described above, if not illegal, can alleviate the expected difficulty before takeoff.