Introduction

•  The examination should be directed to the presence of any condition which would impair respiratory functions or pressure equalization during flight.

• Ear drums should be examined for any pathology, perforations and for the adequacy of pressure equalization. Pressure equalization should be assessed by observation of the drum during a Valsalva maneuver.

• Vestibular function should be normal.

• Auricle and mastoid region should be carefully examined for scars and deformities due to past operations.

External Auditory Meatus

• This is inspected by pulling the auricle upwards, backwards and outwards to straighten the external canal. 

• Presence of wax, foreign body, exostosis or discharge is noted.  Wax is removed by a blunt hook probe or syringing.  While syringing, the stream of water is directed against the posterior-superior wall of the meatus and not against the wax, foreign body or the drum. 

• Syringing is contraindicated in the presence of perforation of tympanic membrane due to danger of activating middle ear infection and primary infection of canal itself. Syringing should be done carefully if thinned out / scared / tympanic membrane is suspected by candidate’s history, and if tympanic membrane is not visible.

Tympanic Membrane

• must be inspected quadrant-wise.  Carefully look for scars, tympano-sclerotic plaques or retraction of membrane as also evidence of tympanoplasty.

• Eustachian tube patency is of paramount importance for the candidate’s ability to ventilate the middle ear voluntarily for adjustment of pressure variations during flight through ascent or descent. 

• To test the patency of the tube, Toynbee, Frenzel’s or Valsalva method is recommended. 

• Toynbee’s manoevre involves closing the mouth and nose and swallowing &clicking of the eardrums must be evident.

•  Frenzel’s manoevre is carried out by voluntarily closing the glottis, mouth and nose and increasing nasopharyngeal pressure by contracting the muscles of the floor of the mouth and superior constrictors of the pharynx.  The advantage of Frenzel’s manoevre is that it can be performed during any phase of respiration and is independent of intra-thoracic pressure.  Outward bulging of the drum can be seen through the otoscope. In doubtful cases of eustachian tube function, impedence audiometry should be carried out.

Tuning Fork Tests

• This should be employed to ascertain the type of hearing loss present.

Rinne’s Test

• This test compares the duration of bone conduction of sound with that of air conduction.

• A 512 Hz tuning fork is activated and the stem is placed firmly over the upper part of mastoid process.

• When the sound is no longer heard, the vibrating tuning fork is transferred to a position, which places its prongs at a distance of about 1 cm from the external auditory meatus. 

• Normally the fork is heard twice as long by air conduction than by bone conduction (Negative Rinne’s).

• If both AC and BC are relatively diminished it indicates perceptive type of hearing loss; BC is longer than AC it indicates conductive hearing loss.

Weber’s Test.  

• In performing this test, an activated 512 Hz tuning fork is placed on the vertex of the skull or forehead.

• The sound originating in the vibrating fork is conducted by bone to both ears. A normal individual hears the sound equally in both the ears. 

• If the sound is lateralized and better heard in the affected ear it points to conductive deafness of that ear.

• If it is heard better on the normal side, it points to perceptive deafness in the affected ear.

• In considerable bilateral perceptive deafness, the sound may not be heard at all. In bilateral conductive deafness it will be heard clearly in both the ears or in the ear with better cochlear function.

Absolute Bone Conduction Test (ABC). 

• This test is done as above except that the meatus is occluded to exclude any ambient noise.

• In this way prolonged bone conduction is rarely noted but shortening of bone conduction is regarded as a sign of impaired cochlear function. 

• It offers better and accurate assessment of cochlear function.

Hearing Acuity

• Each ear must be tested separately. 

• It is necessary to standardize the technique so as to make findings reproducible and comparable. 

• The candidate stands in a quiet anechoic room at a distance of 600 cm from the examiner with his back turned towards the latter. 

• This prevents lip reading. An assistant will mask the ear not under test. 

• Masking is done by placing a stiff 4” x 4” piece of paper over the auricle and using the pulp of finger tip to make a gentle circular rubbing motion producing a continuous rustling sound. T

• he examiner should whisper with the residual air, at the end of an ordinary expiration.

• The candidate is asked to repeat the words, phrases and numbers spoken by the examiner. 

• The distance at which the candidate clearly hears conversational and whispered voice by each ear is recorded as CV and FW.

Voice Test (Free Field Hearing)

• For Conversational Voice (CV), sound level should be 60 dB at 1 meter;

• For Forced Whisper (FW) it should be 45 dB at 1 meter

Pure Tone Audiometry

• Candidates for Class 2 medical certification will require a pure tone audiogram at the initial examination.

• Required to be done in a quiet room with intensity of background noise < 35 dB. Pure Tone Audiometer (PTA) with reference zero for calibration of audiometer is as per ISO.

• There shall be no hearing loss in either ear, when tested separately, of more than 35dB at any of the frequencies 500, 1 000, and 2 000 Hz, or of more than 50 dB at 3 000 Hz.

• Applicants for Class II Medical Assessment should be tested by Pure Tone Audiometry at first issue of    the assessment and after the age of 50 yrs, not less than once every 2 years.

Applicants for Class I Medical Assessment

•  Require a PTA at first issue, once every 5 years till 40 years of age,  once every 2 years till 60 years &  every time after 60.

• An applicant with hearing loss greater may be declared fit provided he has normal hearing performance against a background noise that reproduces or simulates the masking properties of flight deck noise upon speech and beacon signals.

• The minimum qualifying limit for the Speech Discrimination Score (SDS) is 50%.

In addition, the following pathological conditions need to be excluded.

                         (i)     There shall be no acute/chronic active pathological process of middle / inner ear e.g. congestion, retraction or perforation of the tympanic membrane, Eustachian Tube  dysfunction, otosclerosis etc.

                       (ii)     No permanent disturbances of vestibular apparatus e.g. Labyrinthitis, Acoustic neuroma Meniere’s Disease etc.

                     (iii)     No serious malformation or serious, acute / chronic affection of upper aero digestive tract, e.g. cleft palate, severe adenoids, nasal polyps or deviated nasal septum causing nasal obstruction  etc.

                     (iv)     Stuttering / other speech defects sufficiently severe to cause impairment of speech communications shall be assessed as being unfit.

Pure Tone Audiogram

• An audiogram provides accurate measurement of both air and bone conduction thresholds. 

• In air conduction, the test tone travels along the normal route i.e., reaches ear as an air borne pressure wave conducted mechanically by middle ear to cochlea to auditory nerve and higher auditory pathways. 

• In bone conduction the test tone applied to mastoid process of temporal bone goes directly to cochlea bypassing the external and middle ears. 

• This, therefore, depicts the acuity of only sensori-neural elements of hearing mechanism and is relatively unaffected by changes in the outer and middle ears. 

• Limitation of bone conduction is that thresholds beyond 80 db are not measurable.

Procedure for Pure Tone Audiometry

• Requirements for Audiometry are a reasonably noiseless test environment (an acoustically treated chamber with ambient noise of 25-30 db) & well positioned headphones exactly over the opening of external auditory meatus.

• The test must be thoroughly explained to the subject & it must be made clear to him that this being a subjective test, his co-operation is of utmost importance.

Technique of Air Conduction Test:

• The better ear is tested first.  The test is begun with a 1000 Hz sound and then the other frequencies are tested in the following order 2000 – 4000 – 8000 – 1000 repeated – 500 – 250 Hz. 

• In each frequency the threshold is ascertained as follows:  The examiner first introduces the sound at an arbitrarily presumed supra-threshold level. 

• If the subject hears the tone, then the tone is reduced in steps of 10 db till the subject stops hearing. 

• Once this stage is reached, the tone is raised by 5 db till the subject hears again.  This is the threshold at this particular frequency.

• In case of doubt / suspected malingering, it is retested and the results compared for consistency. 

Tympanometry

• It is a non-invasive procedure, which measures the impedance matching system of the middle ear.

• External auditory canal is examined for wax, debris and tympanic membrane for any scar or disease.

• External auditory canal is sealed hermetically with probe and readings are taken in the form of tympanogram.

• It shows various types of graphs, as under.

•                                                             (i)     Type A:     It is further sub divided into:

•   Type Ad: Peak is open e.g. ossicular dissociation.

•   Type As: Peak is low flat e.g. otosclerosis.

•                                                           (ii)     Type B:      Peak is flat e.g. otitis media with effusion

•                                                         (iii)     Type C:     Graph shows a negative pressure in the middle ear.

Speech Intelligibility Test

• The aim of the test is to ascertain whether an individual has a hearing performance (in each ear separately) equivalent to that of a normal person against background noise. 

• This will represent the masking properties of flight deck noise upon speech and beacon signals. 

• Noise levels in the cockpit are normally 70 db and rarely exceed 80 db.

• During this test, performed in soundproof room, a list of 20 Phonetically Balanced words is used with speech at 80 or 90 db against a background noise of 70 or 80 db respectively. 

• Aviation types of message or digits are not used. Intelligibility reduces when the level of both speech and noise are raised.

• A score of 50% and above is considered satisfactory.

• This test is valid for trained pilots only, whose experience helps them overcome a disability