Understanding the tympanogram

A tympanogram is the result of conducting tympanometry, presented as a graphical representation of middle ear compliance relative to air pressure. It is typically produced using a tympanometer, a specialized instrument designed to evaluate the condition of the middle ear.

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They are helpful in the fields of audiology and otolaryngology as they can verify middle ear function and aid in the diagnosis of issues like ear infections or problems arising with the eustachian tube.

Interpreting a tympanogram requires expertise and is best performed by audiologists, ear, nose and throat specialists, otolaryngologists, or other qualified healthcare professionals. These experts analyze tympanogram results in conjunction with other diagnostic tests to determine the most appropriate course of treatment for the patient.

How to interpret a tympanogram

Understanding a tympanogram involves interpretation of the graph produced by a tympanometry test.

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Tympanogram types

There are several types of tympanograms, each reflecting different conditions of the middle ear. According to Jerger's classification (1970), the most common types are Type A, Type B, and Type C.¹

In recent years, additional variations have been introduced to better describe and differentiate specific middle ear disorders, reflecting advancements in diagnostic approaches.

The frequency used during the test significantly influences the interpretation of the results. Tympanometry curves plot eardrum compliance as a function of the pressure applied to the ear canal, providing valuable insights into middle ear health.

Source: Amplivox

Graph	Type
	Type A This is the most common and represents normal middle ear function. It shows a sharp peak in compliance (the Y-axis) at or around 0 daPa, which means that the middle ear system is most compliant at atmospheric pressure. This suggests that the middle ear is functioning correctly.
	Type As This is similar to a Type A tympanogram but has a reduced peak compliance. It indicates reduced compliance of the middle ear system, which can be seen in conditions like otosclerosis.
	Type Ad This type of tympanogram has high peak compliance. It can indicate that the middle ear system is too flexible. This flexibility can be due to problems such as a disconnected ossicular chain or a hypermobile section of the eardrum.
	Type B This is a flat tympanogram with no peak. It suggests that there is little to no movement of the eardrum and middle ear system in response to changes in air pressure. This is often seen in cases of middle ear fluid (effusion) or when the ear canal is blocked.
	Type C This tympanogram shows a peak compliance but shifted to the negative pressure side of the X-axis. It suggests negative pressure in the middle ear and can be indicative of eustachian tube dysfunction.

Other parameters should also be assessed alongside the test compliance curve. Examples of these include the maximum compliance curve values (air pressure in daPa and compliance value in ml), the curve’s width, also known as the gradient (in daPa) and the volume of the ear canal (measured in ml).

The ear canal volume (ECV) is especially important, as it can be utilized to distinguish between a perforated eardrum (high volume) and an otitis media (regular volume).

Evaluate the characteristics

Alongside the type, other tympanogram properties can deliver valuable data in terms of interpreting results:

• Peak height: The compliance peak’s height suggests the degree of middle ear compliance.
• Peak pressure: Peak compliance pressure is key for identifying diseases, including eustachian tube dysfunction.

Normative data

Tympanograms often include a normative area on the graph, typically represented as a rectangle. For a tympanogram to be classified as "normal" (Type A), its peak should fall within this area. This visual cue simplifies interpretation, as it allows practitioners to quickly assess whether the peak is within the acceptable range.

It’s important to refer to practice guidelines and recommendations from your local or national authority to ensure you are using the appropriate normative values when evaluating tympanometry results.

Correlate with clinical data

Tympanograms are just one piece of the puzzle in assessing middle ear function. To diagnose or understand the tympanogram, it is important to consider the patient's medical history, audiometry, and symptoms.

Industry-leading tympanometers

Amplivox offers industry-leading handheld and desktop tympanometers designed to deliver fast and accurate middle ear measurements for all age groups, including neonates.

With large LCD displays, users can view test progress and diagnostic results in real-time during and after the automatic test, making interpretation straightforward. The data can also be processed efficiently to support high-quality customer care.

These tympanometers also feature single-click integration with third-party Electronic Medical Record (EMR) systems, including Noah, Auditbase, and OtoAccess^®. This seamless connectivity ensures efficient data transfer, streamlining workflows and enhancing overall productivity.

References and further reading

1. American Speech-Language-Hearing Association. ASHA Practice Policy. [online] Available at: https://www.asha.org/policy.

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