Session 2: Objective testing Flashcards
1
Q
What is tympanometry?
A
Objective measure of the compliance or mobility of the tympanic membrane
- it works as It assesses eardrum mobility as a function of changing air pressures in the ear canal.
2
Q
What is the standard probe tone for adults in tympanometry?
A
A 226 Hz probe tone is used for adults.
3
Q
What is the standard probe tone for infants under 6 months in tympanometry?
A
A 1000 Hz probe tone is used for infants younger than 6 months.
4
Q
define admittance
A
- Amount of
acoustic energy
that flows into
ME system - Denoted as Y
and is
measured in
acoustic mmhos
5
Q
define impedance
A
- Total opposition
of the middle
ear system to
the flow of
acoustic energy - It is denoted as
Z and measured
in acoustic
ohms
6
Q
define susceptance
A
- System is
susceptible to
allowing sound to
enter - Therefore is the
compliment of
admittance - Units are in mhos
(in electrical terms
these are now
measured in
Siemens)
7
Q
define reactance
A
- Opposition to
allowing sound
entry - Therefore the
compliment of
impedance - Units are in
ohms
8
Q
How is the middle ear (ME) system like a compliant spring?
A
The ME system behaves like a spring, transferring energy between the mass of the eardrum and the stiffness of the ME system, similar to a bungee jump where energy oscillates between the spring and mass.
9
Q
How does the bungee jump analogy explain energy transfer in the ME system?
A
Mass (e.g., the jumper or eardrum): Moves due to external energy (acoustic energy for the eardrum).
Spring (e.g., stiffness of ME system): Absorbs and stores energy as the mass moves forward, then releases it to move the mass back.
This oscillation continues, transferring energy between the mass and spring.
10
Q
What determines the opposing factor in the ME system?
A
- If the system moves slower: The spring (stiffness) is the opposing factor.
- If the system moves faster: The mass (inertia) is the opposing factor.
10
Q
What happens if no other force is applied to the ME system?
A
The system will oscillate back and forth at its resonant frequency, where energy transfer between mass and stiffness is most efficient.
11
Q
What contributes to the stiffness in the ME system?
A
- ME ligaments and
tendons - Tympanic membrane
- The air enclosed in the
ear canal and middle
ear space
11
Q
How does the eardrum behave in this model?
A
- The eardrum acts as the mass, moving due to acoustic energy.
- It transfers this energy to the stiffness of the ME system, and the process reverses, sending energy back to the eardrum mass.
12
Q
What contributes to the mass in the middle ear (ME) system?
A
- Pars flacida of the TM
- Ossicles
- Perilymph in the
cochlea - Mesenchyme clinging
to the ossicles in
infants
13
Q
What contributes to the friction in the ME system?
A
- Tympanic membrane
- ME tendons and
ligaments - Narrow passages
between the ME cavity
and the mastoid - Viscosity of the
perilymph and the
mucous lining of the
ME cavity
14
Q
Why is 226 Hz used in tympanometry for adults?
A
The 226 Hz probe tone is used because it is below the average adult resonance frequency of 900 Hz, making the system stiffness-controlled at this frequency.
15
Q
Why are mass and friction effects minimal at 226 Hz?
A
At this frequency, the stiffness dominates, and mass and friction effects are very small, allowing for more accurate measurement of tympanic membrane compliance.
16
Q
What term is commonly used for tympanometric measurements at 226 Hz?
A
Tympanometric instruments often use the term ‘compliance’ instead of ‘admittance’ at this frequency.
16
Q
What does calibration at 226 Hz represent?
A:
A
At 226 Hz, the true compliance value is equivalent to the volume of air in the ear canal, measured in milliliters (ml) or cubic centimeters (cc).
17
Q
What is the relationship between admittance and cavity size at 226 Hz?
A
Admittance is 1 mmho when measured in a 1 ml (cc) cavity, providing a standardized reference for compliance measurements.
17
Q
How is equivalent ear canal volume obtained?
A
By using air pressure at an impedance mismatch setting, the tympanometer can calculate the equivalent ear canal volume in ml (cc).
18
Q
What does a Type A tympanogram indicate?
A
- Characteristics: Peaks at 0 daPa.
- Indication: Normal middle ear function.
19
Q
What does a Type Ad tympanogram indicate?
A
- Characteristics: Unusually high peak.
- Indication: Suggests ossicular discontinuity (e.g., dislocation of middle ear bones).
20
Q
What does a Type As tympanogram indicate?
A
- Characteristics: Reduced peak.
- Indication: Suggests ossicular fixation (e.g., stapes is stiffened).
21
What does a Type B tympanogram indicate?
- Characteristics: Flat, no peak.
- Indication: Suggests reduced movement due to middle ear fluid, space-occupying tumor, or other obstruction.
21
What does a Type B tympanogram with an abnormally large volume indicate?
Indication: Indicates perforation of the tympanic membrane or a patent grommet.
22
What does a Type B tympanogram with a small volume indicate?
Indication: Suggests the probe is against the ear canal wall or the ear canal is blocked with cerumen (earwax).
23
What does a Type C tympanogram indicate?
Characteristics: Negative pressure.
Indication: Indicates Eustachian tube dysfunction.
24
What does it mean that the neonatal ear is a mass-dominated system?
- A mass-dominated system is one where the mass of the components primarily influences the system's behavior rather than stiffness or compliance.
*Ossicles: Small bones in the middle ear.
*Residual mesenchyme: Tissue around the ossicles.
*Perilymph: Fluid in the cochlea.
*Pars flaccida: A more compliant section of the tympanic membrane.
24
what are some changes that happen in a neonates Eustachian tube Middle ear?
* Initially osseous portion of the canal is underdeveloped and it becomes distensible when pressure is
applied
* Bony portion of the EC forms over time
* Decrease in the mass of the middle ear due to mesenchyme loss
* Change in bone density
* Ossicular joints show a tightening
* Tympanic ring fuses
* Increases in the size of the ear canal, middle ear cavity and mastoid
* Change in tympanic membrane orientation and flexibility
25
What frequency to use for neonates tympanometry?
* Suggested to use a probe tone of 1000Hz for neonates
26
What is neonatal middle ear (ME) resonance, and how does it differ from adult ME resonance?
- Neonatal ME resonance is lower than adult ME resonance, meaning neonates amplify and transmit low-frequency sounds more effectively.
- This occurs because neonatal middle ear structures are softer, smaller, and less stiff, including:
*Underdeveloped ossicles.
*Residual mesenchyme tissue.
*Increased compliance of the tympanic membrane and ear canal walls.
- By approximately 4 months of age, ME resonance reaches adult levels as the structures mature.
- Implications:
*Neonates hear low frequencies better than high frequencies.
*Hearing tests and diagnostics must account for this developmental difference.
*Speech perception and sound localization improve as ME resonance matures.
- Does not attain adult values until roughly 4 months of age
27
what are the findings about ear canal motion and tympanogram shapes in neonatal ears?
*Ear Canal Motion:
- Neonatal ear canals are compliant and exhibit motion in response to low-frequency probe tones (220–660 Hz).
This motion leads to resonant amplification of sound within the ear canal.
*Tympanogram Shape:
- Despite the motion of the ear canal walls, the shape of the tympanogram remains unaffected, as it reflects the function of the middle ear rather than the ear canal dynamics.
*Key Implication:
- Tympanometry is a reliable tool for assessing neonatal middle ear function, as ear canal wall motion does not distort tympanometric results.
28
why do we use 100Hz probe instead of 226 graphwise?
- 1000 Hz tympanograms: Provide clearer and more distinct peaks, indicating better detection of middle ear function and any abnormalities.
- 226 Hz tympanograms- Show flatter or less distinct tympanogram shapes, which are less reliable in neonates because the ear canal compliance interferes with accurate
The 226 Hz tone is more suitable for older children and adults as their ear structures are stiffer and less compliant.
29
What is the occurrence of middle ear effusion (MEE)in neonates?
- High Initial Prevalence: Studies show that 80%-90% of neonates have MEE within the first few days of birth.
- Decline Over Time: Prevalence decreases steadily to around 10-20% by 30–35 days after birth.
- Possible Cause: High early prevalence is likely due to residual fluid from the birthing process.
- Clinical Implications:
*Most cases resolve naturally over time.
*Careful follow-up assessments are essential to distinguish transient MEE from persistent cases that may impact hearing and development.
30
what are the steps for the high frequency tympanometry procedure?
1- Calibrate Equipment: Ensure the tympanometer is calibrated and (check in an ear or cavity).
2- Perform Otoscopy: Inspect the ear canal to check for any obstructions or abnormalities.
3- Select Ear Tip: Use either conical or flanged ear canal tips based on the best fit.
4- Set Tympanometer: Configure the tympanometer to a 1000Hz probe tone with admittance measurement.
5- Pressure Sweep: Use a sweep direction from +200 to -400 daPa (or extend to -600 daPa if needed).
6- Pressure Change Rate: Set a fast rate of 600 daPa/sec for efficient results.
Repeat Trace:
7- Repeat the measurement if necessary, especially for abnormal or unclear results, to ensure accuracy.
30
How are results classified in 1000Hz tympanometry based on peak identification?
- Scenario 1:
- Baseline drawn from +200 to -400 daPa.
One positive peak identified.
Classification: Normal.
- Scenario 2:
- Baseline drawn from +200 to -400 daPa.
Two peaks identified (one positive, one negative).
Classification: Normal (positive peak takes precedence).
31
Why is obtaining normative data for 1000Hz tympanometry in neonates challenging?
- No established pass/fail criteria for standardizing results.
- Variability in test parameters, such as pump speed, can affect results.
- Published normative values exist but are difficult to generalize across the neonatal population.
*Key Issue: Lack of a universally accepted standard measure complicates the application of normative data.
31
Normal Tympanometry in Paediatrics
*For Neonates (Under 6 Months):
- Probe Tone: 1000 Hz (high-frequency probe tone is recommended for infants due to mass-dominated ear systems).
- Key Parameters:
- Positive peak above the baseline is classified as normal.
- Traces with a "flat" or "trough-shaped" peak are classified as abnormal.
- Ear canal volume is typically disregarded with 1000 Hz probe tones as it is not precise.
*For Infants and Young Children (6 Months–7 Years):
- Probe Tone: 226 Hz (standard for older children).
- Key Normative Ranges:
- Middle Ear Pressure (MEP): -100 to +50 daPa (values below -100 daPa may indicate Eustachian tube dysfunction).
- Compliance /Admittance: 0.2 to 0.9 cm³ for children.
- Ear Canal Volume (ECV): 0.4 to 1.0 cm³.
*For Older Children and Adults:
- Probe Tone: 226 Hz.
- Key Normative Ranges:
- Middle Ear Pressure (MEP): -50 to +50 daPa.
- Compliance /Admittance: 0.3 to 1.6 cm³.
- Ear Canal Volume (ECV): 0.6 to 2.5 cm³.
32
What are the key characteristics and considerations for OAE testing in neonates?
*Characteristics:
- OAEs are large in neonates with good high-frequency response.
- Present from birth, even in pre-term babies.
*Considerations for Testing:
- Reduced success rate in the first 2 days of life due to amniotic fluid in the ear.
- OAEs are usually absent when middle ear fluid is present.
- Testing is quick to perform.
- The baby must be settled and quiet (not necessarily asleep).
- Results can be affected by noise from the child or the environment.
- A good probe fit is essential for accurate results.
33
what are the uses of OAEs?
*Newborn Screening:
- Used in the NHSP as the initial screening test for well babies.
- Well babies can be discharged if OAEs are clear, provided no risk factors are present and there are no parental concerns.
*Follow-Up Testing:
- OAEs are quicker than ABR and do not require the baby to sleep.
- Should be used alongside ABR for babies in SCBU (Special Care Baby Unit).
- Useful indication of normal cochlear function in difficult-to-test children, those with additional needs or
suspected non-organic hearing losses
- OAEs helpful to confirm good OHC function and reassure parents
33
Limitations of OAEs:
- Only indicate outer hair cell function, not normal hearing.
Babies who pass
- OAEs may still have Auditory Neuropathy Spectrum Disorder (ANSD), though this is unlikely in well babies.
33
How does speech testing contribute to hearing assessments and ruling out ANSD?
- True Hearing Ability: Speech testing provides a better indication of the individual’s actual hearing capability compared to physiological tests like OAEs or ABR.
- ANSD Detection: Helps distinguish between normal hearing function and Auditory Neuropathy Spectrum Disorder (ANSD), which may not be apparent in other tests.
34
what is the BSA guidelines criteria for diagnostic OAE interpretation?
*Pass Criteria:
- Signal-to-Noise Ratio (SNR) ≥ 6 dB for the majority of frequency bands (e.g., 1 kHz, 1.5 kHz, 2 kHz, 3 kHz, and 4 kHz).
- good equal spread of frequencies should be present and not ringing at the stimulus
- the stimulus should be finished b 4ms to into interfere with the recording.
- The OAE response is clearly above the noise floor.
- Reproducibility and stimulus stability should be within acceptable limits (≥ 70%).
*Fail Criteria:
- SNR < 6 dB for most frequency bands.
- OAE response is below or close to the noise floor.
- Low reproducibility or poor stimulus stability (< 70%)the key measurement parameters and interpretations to assess the presence and quality of diagnostic OAEs. If the SNR is below the threshold, or the OAE response is not above the noise floor, it generally indicates a failed test.
35
Why is ABR (Auditory Brainstem Response) important in the diagnosis of hearing loss?
*Quick Assessment:
- ABR allows for a rapid evaluation of auditory function, particularly useful in newborns and difficult-to-test populations.
*No Delay in Diagnosis and Intervention:
- ABR provides immediate results, enabling timely diagnosis and early intervention for hearing loss, which is crucial for speech and language development.
*Diagnosing All Types of Hearing Loss:
- ABR can diagnose a wide range of hearing loss types, including sensorineural, conductive, and retrocochlear hearing losses.
36
what equipment is needed for ABR equipment?
* Calibrated equipment
* Tone pop for AC and BC
* Using chirp as a stimulus?
37
what are suitable room conditions for ABRs?
– sound treated/sound proofed room with extra room for baby feeding and changing
38
when are the parents given the ABR results?
* Communication with the parents/guardians before, during and after the appointment is very important
* Families should be provided with results and information at the end of the baby’s assessment
* Do not keep families waiting for results
39
Why are correction factors necessary when applying ABR equipment readings to neonatal results?
- Calibration of the ABR equipment is performed on adults such that correction factors are necessary
when applying equipment readings to neonatal results
40
When should assessments for babies with hearing concerns be performed, and what factors should be considered?
- Assessments should generally be performed by 4 weeks corrected age.
- It becomes more difficult to get babies to settle for testing after 8 weeks, and even more so by 12 weeks.
- Multiple appointment visits may be needed to complete testing.
- For SCBU babies, assessments can start at 35 weeks gestational age.
- If there are neural maturational effects, an extra test around the expected birth date is good practice.
- Assessments should be completed by 3 months of age.
- Sedation should not be required for babies under three months and only in exceptional circumstances for babies under 1 year.
41
When might masking be necessary during hearing tests?
- Masking is necessary when there is a risk of sound from the test ear being heard by the non-test ear, especially during tests like ABR (Auditory Brainstem Response).
- Masking ensures that the test results are accurate by preventing cross-hearing, where sound from the test ear could be picked up by the non-test ear, leading to false results.
42
What do high-frequency tympanometry, OAEs, and ABR test for in hearing assessments?
- high frequency= check for middle ear problems, such as fluid or pressure issues, that could affect hearing.
- OAEs (Otoacoustic Emissions): assess the function of the inner ear, specifically the cochlea, by measuring sound waves produced by the cochlea in response to stimuli.
- ABR (Auditory Brainstem Response): evaluates the auditory pathways in the brainstem, measures the brains response to sound to assess hearing and identify any issues with the auditory nerve or brainstem.
43
how is ABR testing done?
Start at 40dBeHL at 4kHz to establish threshold, if there is a response go quieter and vice versa
- If clear response is seen at 30dBeHL at 4kHz they may be discharged ( if no risk factors are
present)
- ABR tested in dBnHL so when converted to dBeHL its 5dB less etc. 35dBnHL= 30dBeHL=Pass
44
what should you do if a HL is present after ABRs?
* If a HL is present then either perform:
– bone conduction testing at the
same frequency
– 4kHz AC on the other ear
45
what should you do if a you get no response for tpABR?
click ABR instead
46
what is the electrode placement for ABRs?
3 electrodes, 1 on forehead high up other 2 on mastoid of each ear.
- * Common electrode: contralateral mastoid or if nape is being used you can use another forehead
electrode (at least 4cm from the positive electrode)
Impedance needs to be below 5000 ohms
46
how do you know what the amount of artefact from electrical inference for ABRs are?
* The amount of artefact from electrical interference is proportional to the difference in impedances
47
What are the key considerations for ABR stimulus?
- Click stimulus: Use an electrical pulse of 100 microseconds.
- Alternating polarity: This helps reduce stimulus artefacts.
- Tone pips: Use a 2-1-2 cycle with Blackman gating preferred.
- NB chirps: Can also be used as a stimulus option.
- Stimulus rate: Must allow enough time for collection before the next stimulus is presented and enable a reasonably quick recording procedure.
- Nerve refractory periods: The stimulus rate should take these into account to avoid interfering with the nerve's response.
- Bone conduction: A slower stimulus rate is suggested when looking for wave 1.
48
Why are supra-aural headphones generally suggested for ABR testing?
Supra-aural headphones are generally suggested due to uncertainties with insert phones, particularly when testing babies, as insert phones may not provide consistent results in this population.
49
Why might stimulus levels be higher in babies when using insert phones?
Babies have a smaller ear canal, so when using insert phones, the stimulus can be 10-20dB higher in babies than in adults due to the differences in ear canal size.
50
What should be ensured when using headphones for ABR testing in babies?
When using headphones, it is important to ensure that the ear canal is not collapsed, as this can affect the accuracy of the results.
50
What are the advantages of using insert phones in ABR testing?
Insert phones help reduce the need for masking and eliminate background noise more effectively than other transducers, providing a cleaner test environment.
51
What is the required specification for a bone vibrator in ABR testing?
The bone vibrator should be able to deliver up to 60dBnHL without distortion (and 50dBnHL at 500Hz). This ensures adequate stimulation without affecting the clarity of the results.
52
Where should the bone vibrator be placed in ABR testing?
The bone vibrator should be placed on the mastoid bone, away from the electrode to prevent interference with the signal.
53
How should the bone vibrator be held in place?
The bone vibrator should be held in place by a headband, soft band, or finger pressure to ensure stable contact during the test.
54
What is the benefit of bone conduction testing in young babies?
Young babies tend to have better inter-aural attenuation, which improves the effectiveness of bone conduction testing in this age group.
55
What if the mastoid is difficult to access for bone vibrator placement?
If the mastoid is difficult to access due to electrode placement, the bone vibrator can be placed on the temporal bone, slightly behind the upper part of the pinna, as an alternative location.
56
Why are correction values necessary for bone conduction testing in babies?
Correction values based on the baby's age are necessary to account for anatomical and physiological differences from adults, ensuring accurate results during testin
57
why do we set amplifier and rejection levels and what are they?
* Amplifier and rejection levels:
– There to reject unwanted electrical activity
– Recommendation: set at ±3 and ±10μV
– Logical to set them at ±5μV to start and then adjust as necessary
– The lower the achieved levels, the better the signal to noise ratio in the averaged trace
– The higher the reject level the more noise is allowed into the trace
58
What is the purpose of setting a high pass filter to 30Hz and a low pass filter to 1500Hz in ABR testing?
- High Pass (30Hz): The high pass filter at 30Hz filters out low-frequency noise, such as muscle activity, while preserving the energy of wave V, especially near threshold levels.
- Low Pass (1500Hz): The low pass filter at 1500Hz filters out high-frequency noise, ensuring that only the relevant frequencies for the ABR response are recorded, and reducing unnecessary noise that doesn’t contribute to the response.
59
What are the typical settings for averaging and window length in ABR testing, and why is the SN10 component important?
*Averaging:
- Typically set at 2000 sweeps, but 1500 sweeps may also be used in some cases.
- For tone pip testing, 3000 sweeps may be necessary due to the smaller size of the response.
- In exceptional circumstances, lower sweep counts of 1000 for click and 1500 for tone pip can be used when the response is very clear.
*Window Length:
- A sufficiently long window is necessary to ensure that no component of the recording is missed, particularly the SN10 component.
60
Why is it important to establish a clear first set of traces in AC tone pip ABR testing?
- Helps determine presence or absence of a response.
- Essential for identifying responses near threshold levels.
60
what s SN10 component n ABRs?
- SN10 component is crucial to capture because it provides information about the integrity of the auditory pathway in the brainstem.
- typically appears around 10 milliseconds
61
What are the possible outcomes after testing with 4kHz AC at 40dBeHL in AC tone pip ABR?
- Clear response: Proceed to 4kHz AC at 30dBeHL bilaterally.
- No further testing required: Discharge if clear response is obtained.
61
Why are earphones preferred over inserts in AC tone pip ABR testing?
- Calibration is simpler with earphones.
- Insert depth can alter sound levels, especially in neonates.
- Earphones are less likely to wake the baby.
62
What steps should be taken if the 4kHz AC threshold is raised during ABR testing?
- Investigate the nature of the hearing loss (HL).
- Perform BC tpABR at 4kHz to identify if there is a conductive component.
- If BC tpABR is normal and AC tpABR is raised, it suggests a conductive hearing loss (CHL).
- If BC tpABR suggests sensorineural hearing loss (SNHL), further ABR testing should be done to develop a fuller picture of the neonate’s hearing.
- After 4kHz testing, the next frequency to test is 1kHz AC tpABR.
63
What is the decision-making process for determining an ABR response?
- is there a clear 'ABR like' response?-> yes>clear response (CR)
- is there a clear 'ABR like' response?-no? is the average gap between the optimally superimposed replications <25nV? - if no inconclusive (INC)
- is there a clear 'ABR like' response?-no? is the average gap between the optimally superimposed replications <25nV? if yes> are the waveforms appropriately flat and without evidence of a response?> if yes?> response absent (RA)
64
What is the advantage of performing BC ABRs on neonates?
- Neonates have an interaural attenuation of between 20-30dB due to their skulls still fusing.
- This natural attenuation helps improve the accuracy of bone conduction ABR (BC ABR) testing, as it reduces the likelihood of sound crossing over to the opposite ear, leading to more reliable results.
65
What is the concern regarding ABR peer review?
Concern: There is wide variation in the interpretation of ABR traces, which could lead to mismanagement of children. Some may not be aided or prematurely discharged, even though amplification is recommended for them.
66
What does a profound loss look like for ABRs?
No pass response at 30dBeHL, jumbled line even at louder freq, no peak at 5
67
What does a moderate loss look like for ABRs?
Pass response not at 30dBeHL, peak at 5 visible. Lower freq jumbled up but higher freq start to show a clearer ABR
