Maico Ero Scan Pro Operating Instructions Manual

Contents

Maico Ero Scan Pro Operating Instructions Manual Manual pdf 7 page image

Operating Instructions4outside pressure by the ear tip. A manometer and a pump, which can produce both positive andnegative pressure, are connected with tube C. Less sound is reflected to the microphone when theeardrum is stiff and the eardrum transmits the majority of the sound via the middle ear to the inner ear.The highest compliance is normally reached with an air pressure corresponding to the outside pressure.While performing tympanometry measurements,a continuous change of positive and negativepressure is produced by the pump of theinstrument in the outer auditory canal. Thecompliance is measured simultaneously andshown in a diagram (the tympanogram) whichillustrates the compliance in ml or mmho over thepressure in daPa. The area for normaltympanogram curves is hatched. Here you cansee that the highest compliance is reached withnormal pressure. When you create positive andnegative pressure the eardrum stiffens - thecompliance decreases. So you can drawconclusions on the condition of the middle earfrom the form and the values of thetympanogram.NOTE: 1.02 mm H2O = 1.0 daPa.1.4 Acoustic ReflexAcoustic reflex refers to the reflexive contraction of the stapedius muscle in response to soundstimulation (typically 70-100dB). This contraction causes reduced mobility of the ossicular chain andreduces the compliance of the tympanic membrane which is measured by the probe as a change inadmittance. The Stapedial (acoustic) reflex is always bilateral in response to loud sound presented toeither ear, and the lowest level that causes a change in admittance is called the reflex threshold.Typically the average threshold is around 85dB HL with normal limits falling between 70 and 95dB HL.