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In the 1930s the vacuum-tube aid came into usage. There was still much doubt concerning the efficiency of a
hearing aid for the person with sensorineural hearing loss. The development of the transistor and the transistor
hearing aids opened up a new era in design and fitting. No longer was it necessary to have a bulky, inefficient
instrument. Significant advances and refinements in hearing aids can be expected to continue.
If an applicant requires an aid, counselling in the selection of an aid to meet individual needs is necessary.
Weight, size and concealment of the aid are secondary. By testing appropriately powered aids with frequency
response characteristics deemed suitable for the particular hearing loss involved, it is often possible to
demonstrate clear-cut and significant improvements in performance.
The degree of hearing loss and the discrimination scores, as well as the ear that is habitually used on the
ICAO Preliminary Unedited Version — October 2008 III-12-22
earphones, are factors to consider in the initial selection. In many instances, it may be necessary to test
hearing-aid use in each ear separately and binaurally to determine the most appropriate fitting.
The use of personal hearing aids is usually not accepted during flight performance of professional flight crews.
Arguments against the use of hearing aids for licensing purposes centre around their delicate nature, their
relatively low reliability, and their suboptimal acoustic performance. However, personal hearing aids are not
normally required in flight because of the mandatory aircraft intercom and radio equipment. The best aids
presently available provide a maximum of approximately 70 per cent of normal speech perception in
environments of even relatively low ambient noise. This results from the frequency-response characteristic of
aids, which is not "flat" in the 500-3 000 Hz range (as in the normal ear's response) and which above 3 000 Hz
shows deep "valleys" in which ambient noise intrudes, masking adjoining frequencies. The point is made that
the use of hearing aids is by no means functionally analogous to the use of correcting lenses for a refractive
error.
Consideration of the technical characteristics of hearing aids for other than professional pilots leads to the
recommendation that they should not be used in flight unless approved following a full investigation and
assessment taking into account all of the operational implications under Annex 1, 1.2.4.8.
NOSE AND PARANASAL SINUSES
Nose
It is important for a pilot to have a normal-functioning nose. Impairment of the sense of smell may cause the
first faint odour of gas, oil or smoke to go unnoticed. A malfunctioning nose can cause serious problems in
regard to aeration of the sinuses and the Eustachian tube with resultant middle ear pathology.
A careful examination of the nose can and should be done. In some cases, where the mucosa of the septum and
the turbinates are swollen, it is impossible to examine it carefully unless a shrinking agent, such as
neosynephrine or xylometazolin solution is used. Most examinees do not object to a flat pledget of cotton
(soaked) placed in each nostril.
Paranasal sinuses
The sinuses are somewhat difficult to examine, but there are definite procedures that are useful. Deep
palpation (pressure) over the maxillary sinus may elicit discomfort or pain. The same is true with pressure over
the anterior surface of the frontal or deep digital pressure over the floor of the frontal. This can be done by
placing the finger under the superior bony rim of the orbit and having the examinee flex the head. If this
produces pain, the examinee will tilt the head away from the pressure.
If there is a purulent exudate in the nose, examine carefully and determine where the maximum accumulation
is. A useful tool in the sinus examination is transillumination. It should be pointed out, however, that this
technique may be misleading on account of the numbers of false positives and negatives found. This
investigation can be done easily and requires only a dark room and any type of bright light. To examine the
frontal sinuses place the light under the superior bony orbital rim and shield the light from your eyes. If the
frontals are both clear, one can assume that they are essentially normal. If one is clear and one fails to transmit
light (remains dark) then the condition should be examined further. The maxillary sinuses are transilluminated
in a similar manner, placing the light in the mouth, near the hard palate, with lips tightly closed. If any
abnormality or gross difference is noted or if any clinical doubt arises, additional diagnostic procedures, such
as X-ray or better CT-scan is required. If the frontal and maxillary sinuses are all transilluminated clearly, do
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Manual of Civil Aviation Medicine 2(85)
