Pure tone audiometry and tympanometry Flashcards
What is pure tone audiometry?
This is a hearing test that measures a persons ability to register different sounds, pitches or frequencies
Where is pure tone audiometry carried out?
This is carried out in a soundproof room that meets nationally recognised criteria
How are audiometers calibrated?
Audiometers are calibrated to measure air conduction thresholds between 125 and 8,000 Hz and bone conduction thresholds between 250-6000Hz
And are calibrated to measure maximum air conduction thresholds of 120dB and bone conduction of around 50dB lower than this value
What is meant by a pure tone?
Pure tones are the simplest of all sounds
They have a specific, single frequency, amplitude, phase and duration
What is the unit for pure tone amplitude?
decibels
What are the 3 main transducers used to present pure tones to patients?
- Headphones
- Insert earphones
- Bone conduction
How will adults usually register a response to a sound in pure tone audiometry?
Pressing buttons
How will children usually register a sound in pure tone audiometry?
Play items such as dropping coins into a piggy bank
How is air conduction tested in pure tone audiometry?
- Assessed using headphones or insert earphones
- Assesses the entire auditory pathway
How is bone conduction tested in pure tone audiometry?
- Assessed using a bone conductor
- Bypasses the external and middle ear and stimulates the inner ear
What decibel level of hearing loss is classified as mild?
20 - 40 dB
What decibel level of hearing loss is classified as moderate?
41 - 70dB
What decibel level of hearing loss is classified as severe?
71 - 95 dB
What decibel level of hearing loss is classified as profound?
> 95 dB
How are results of pure tone audiometry presented?
Audiogram
Describe the layout of an audiogram axis
What does O on an audiogram mean?
Air conduction right ear
What does an X on audiogram mean?
Air conduction left ear
What does a ∆ on audiogram mean?
Bone conduction
What is meant by masking in pure tone audiometry?
Sometimes, if there is a vast difference between the hearing ability of the ears, the good ear can pick up sounds and the brain thinks that the bad ear can hear them
Narrow band masking can be used by playing a masking noise to the good ear
This should be added after an initial test with the test being repeated
The masking sound should then be increased by 10dB and retested to find a new masking threshold 3 more times
What are the masking symbols used in pure tone audiometry?
What are the features of sensorineural hearing loss on audiogram?
- No significant bone gap
- High pitched sounds affected first
What causes permanent sensorineural hearing loss?
Damage to the hair cells within the cochlear, or damage to the cochlear nerves
What type of hearing loss is shown?
Sensorineural - Affects air conduction and bone conduction so both follow same pathway. Higher pitched sounds heard first, so hairs affected more by sound
What are the features of conductive hearing loss on audiometry?
- Significant air-bone gap
What is shown?
Conductive hearing loss
What are the features of mixed hearing loss on audiogram?
- Significant air-bone gap in parts
- No air-bone gap in others
What are some causes of mixed hearing loss?
- Genetic factors
- Birth defects
- Infections
- Tumours or masses
- Head injuries
What is shown?
Mixed hearing loss
What is shown?
Mixed hearing loss
What is tympanometry?
This is an examination used to test the condition of the middle ear, mobility of the eardrum and the conduction of the ossicular chain by creating variations of pressure in the ear canal
What is shown on a type A tympanogram?
Normal eustachian tube function. Eardrum is moving normally with a pressure change.
What is shown on a type B tympanogram?
This shows that something is restricting ear drum movement, most likely fluid in glue ear (Ossification would show type As, not B)
What is shown on a type C tympanogram?
The drum is moving but something is retracting it (Negative pressure from the eustachian tube) - This is reversed by the Valsalva move
What is shown by a type As tympanogram?
Ossification of the tympanic membrane
What is shown by a type Ad tympanogram?
When a patient has a perforated eardrum, the measured canal volume may be quite large, as the measurement is going beyond the area between probe and drum and now into the middle ear via the perforation. If the ossicular chain is disarticulated, the drum may become flaccid (Type Ad-deep tymp).
