Why use tympanometry in general practice: A review

Table 2 Key messages about practical use of tympanometry

Airtight sealing between the tip of the tympanometer and the ear canal is important. If there are problems with sealing use a little water or cream on the tip, and more pressure towards the ear canal and at the same time pull the external ear up and backwards to stretch the ear canal. Alternatively use a bigger and more solid tip

In order to perform valid tympanometry the sound signal and air pressure have to pass through the ear canal. That means there must be no earwax blockade and the probe has to point in the direction of the ear canal. Partly ear wax occlusion does not disturb the measurement

The result of the tympanometry is a curve, called a tympanogram. The curve is characterized by the height of the curve (compliance), the flatness of the curve (gradient), and location of the peak on the x-axis (pressure). These three characteristics will be given as figures on the screen of the tympanometer, together with the curve (Figure 1)

The fourth value measured by the tympanometer is the ear canal volume. It is important to compare the volumes of left and right ear canal. Normally they will be nearly the same, if the same size of tip is used in both ears. A very small ear canal volume measurement can occur because of ear wax blockade or because the tip is pointing towards the wall of the ear canal. A high ear canal volume is seen in ears with perforation of the tympanic membrane or ventilation tube (grommet) in function. A blocked grommet gives a normal ear canal volume

The appearance of the curve and the figures has to fit (quality assurance)

Any not-normal curve should be repeated to exclude any artefacts

The curves are often classified according to Jerger/Fiellau-Nikolajsen in Type A = normal peaked curve with pressure between +50 and -99 daPa (decaPascal), Type B is a flat curve without peak, and Type C1 peak curve with negative pressure (-100 to -199), and Type C2 a peaked curve with negative pressure of -200 daPa or less (Figure 1)

Other curve types are also described. Type D is a very high curve (high compliance), meaning a very flexible tympanic membrane, often because of atrophy. Type P is a peaked tympanogram with positive pressure above +50 daPa, often because of acute otitis media with a bulging tympanic membrane

The tympanogram has to be compared with the history and objective findings

A flat tympanogram (Type B) means a stiff tympanic membrane and predicts fluid in the middle ear (a positive predictive value of more than 90%)

A normal tympanogram (Type A) means a middle ear without fluid and an intact tympanic membrane (a negative predictive value of more than 95%)

Types C1 and C2 tympanograms are often seen in children with a runny nose. These types are a stage “in between”, i.e., they can develop into a Type B or A tympanogram. In daily clinical practice C1 is often classified as normal. Some of the ears with Type C2 tympanograms have a mixture of air and effusion in the middle ear