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For screening congenital and early acquired sensori-neural hearing loss, otoacoustic emissions (OAEs) are widely accepted. Middle ear pathology is highly prevalent among infants and young children. The presence of middle ear pathology has a negative effect on the presence of OAEs and accounts for many of the false-positive rates in neonatal screening for permanent hearing loss [1]. In ears with abnormal (negative) middle ear pressure caused by Eustachian tube dysfunction, the OAEs are attenuated [2]. Other studies showed that artificial higher air pressure in the external ear canal of normal ears also resulted in a reduction of OAEs [3, 4]. The accompanying relative negative pressure in the middle ear results in increased stiffness of the transmission system and a loss of OAEs amplitudes.

In this study we investigated whether measuring OAEs at compensated middle ear pressure (CMEP) in children with middle ear disease resulted in higher pass rates than at ambient pressure.

Fifty-one children with hearing complaints, aged between 1 and 6 years (mean 4 years and 10 months), were seen in the outpatient ward of the University Hospital Maastricht, the Netherlands. They were scheduled for diagnostic audiometry, including OAE measurement with and without pressure compensation (GN Otometrics). In all patients, OAEs were measured first at ambient pressure and secondly at CMEP (Fig. 1). Furthermore, these results were combined in a two-step scenario where a fail at ambient pressure is followed by measurement at CMEP. Fig. 2 presents OAE measurement at ambient pressure, at CMEP, and the two-step scenario for eight pass/fail definitions (definitions presented in Table 1).

In our selected population, pass rates varied between 3.9% and 39.2% at ambient pressure, depending on the pass criteria used. Measuring at CMEP resulted in pass rates varying between 5.8% and 37.3% for the same pass definitions. The two-step scenario resulted in equal pass rates for a few definitions and higher pass rates for most, varying between 5.9% and 41.1% (Fig. 2). However, in some ears, the result at CMEP changes a pass at ambient pressure into a fail.

Our patients were referred for diagnostic audiometry. Consequently, the fail score is rather high. When used in a normal population for screening, we expect higher pass rates at ambient pressure. The gain of a two-step scenario, which includes CMEP, is rather small. But a small increase in the number of passes in itself saves a lot of time and money when further analysis, such as repeated hearing measurements, ENT consulting, BERA, and eventual placement of grommets as part of the diagnostic process, is no longer necessary.

In this population with middle ear pathology, OAEs are more often absent at ambient pressure than at CMEP. However, since measurement at CMEP changed in some cases a pass at ambient pressure into a fail, a single screen at CMEP is not advisable.

The pass definition used has an important influence on pass/fail rate. In the presence of transient middle ear pathology, this aspect deserves further attention.

These preliminary results show that a two-step scenario, where a fail at ambient pressure is followed by a measurement at CMEP, produces a higher pass rate. This pass rate is highly dependent on the chosen pass/fail definition. Further analyses should reveal the relationship between middle ear pathology and the absence or presence of OAEs and the possible application of measuring OAEs at CMEP.