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K J Van Camp

Publications and source records attributed to K J Van Camp.

At least 19 recordsLinked to original sources
PubMed1986

Simulation of pathological high impedance tympanograms.

The Vanhuyse, Creten, and Van Camp (1975) model for analyzing high frequency tympanograms predicts the shapes of conductance, susceptance, and admittance tympanograms from the relationship between resistance and reactance tympanograms at the tympanic membrane. This model has been applied primarily to low impedance middle-ear pathologies but has not been applied extensively to the more commonly occurring high impedance pathologies. The purpose of this study was to extend the Vanhuyse et al. (1975) model to high impedance pathologies and to identify tympanometric parameters associated with otosclerosis, secretory otitis media, and lateral ossicular fixation. Data from previous experiments on the shape and absolute values of resistance and reactance tympanograms were used to calculate 678-Hz admittance tympanograms that were unique to each of the three high impedance pathologies. Guidelines for differentiating among the middle-ear pathologies on the basis of high frequency tympanometric shapes are presented.

Acoustic Impedance Tests↗
PubMed1986

Normative multifrequency tympanometric data on otosclerosis.

Acoustic resistance, reactance and phase angle were assessed for the two probe tone frequencies (220 and 660 Hz) on 29 otosclerotic middle-ear systems under accurately defined experimental conditions. Only otosclerotics with normal tympanic membranes were accepted in this statistical survey. The main purpose of these measurements was to provide numerical data for middle-ear modelling. If nevertheless a diagnostic parameter is sought from these data, the immittance values can be compared with data obtained on 30 normals under identical experimental conditions. The phase angle at 660 Hz seems the best choice, but the discrimination power is still poor.

Acoustic Impedance Tests↗
PubMed1986

A tympanometric approach to otosclerosis.

A formula has been elaborated to estimate the resonance frequency of the middle ear from non-simultaneously recorded susceptance and conductance tympanograms at 220 and 660 Hz. The formula is tested on 30 normal and 29 otosclerotic ears. From these experimental results one can conclude that the middle-ear model (proposed by Lutman), from which the formula was deduced, is too crude to assess the resonance frequency. Nevertheless a ratio of phase angles functions at 220 and 660 Hz, introduced in that formula, is always qualitatively linked to the resonance frequency. Experimental data proved that this ratio can be used to distinguish tympanograms from otosclerotic ears with normal tympanic membrane from those obtained from normals. A statistical treatment is proposed to estimate the probability of false-positive or false-negative cases as a function of the value of that ratio.

Acoustic Impedance Tests↗
PubMed1985

Multifrequency tympanometry in normal ears.

Susceptance and conductance tympanograms were recorded from 10 normal subjects with probe frequencies ranging from 220 to 910 Hz. Tympanometric shapes progressed through an orderly sequence of patterns, becoming more complex with increasing probe frequency. When the direction of ear-canal air pressure change was from negative to positive values, more complicated tympanometric shapes occurred for all subjects, compared to the positive to negative direction. The results are discussed in relation to the Vanhuyse et al. [Scand. Audiol. 4:45-50, 1975] model of tympanometric shapes. In general, the model is a good first approximation to the distribution of tympanometric patterns from normal ears.

Acoustic Impedance Tests↗
PubMed1985

Immittance audiometry. Normative data at 220 and 660 Hz.

Normative immittance data for normal ears were collected at 220 and 660 Hz probe tone frequencies. The experimental set-up enabled conversion of simultaneously recorded susceptance and conductance data to resistance, reactance, admittance and phase angle tympanograms. Special attention was given to the subtraction of the ear canal admittance and to the pump speed. This paper demonstrates first the frequent occurrence (43.2%) of W-shaped tympanograms at 660 Hz probe tone in healthy ears. This percentage is not influenced by age, sex or pump direction. Normative data of the central extremum of the tympanogram are reported only for those immittance components in which W-notching does not occur. The wide variance of measurements in the population precludes the creation of subcategories. The intra-individual variation is much smaller and the authors advocate to use the value of the contralateral healthy ear as a reference.

Acoustic Impedance Tests↗
PubMed1984

Tympanometric middle-ear pressure determination with two-component admittance meters.

Exact tympanometric determination of the middle-ear pressure based on the location of the (central) extremum of susceptance, conductance, admittance, impedance, reactance or phase-angle tympanograms is not possible. None of these immittance components reaches its extremum exactly at middle-ear pressure neither at 220 nor at 660 Hz, due to the hysteresis caused by the viscoelastic behaviour of the soft biological tissue of the middle-ear structures. These effects cannot be avoided by lowering the rate of the pressure change during the recordings. The error on the middle-ear pressure determinations using a tympanometric method can be estimated to be of the order of 15 daPa.

Acoustic Impedance Tests↗
PubMed1983

Optimizing tympanometric variables for detecting middle ear traumas.

The combination of the results of different studies lead to the conclusion that the susceptance-conductance immittance audiometer at 660 Hz is not the only useful instrument for the detection of middle-ear traumas. Measurements at probe-tone frequencies from 510 up to 910 Hz prove that the admittance tympanogram combined with the electrical phase angle tympanogram recorded in the 500-700 Hz frequency range have definite advantages.

Acoustic Impedance Tests↗
PubMed1982

A technique for detecting the ipsilateral acoustic reflex.

A technique was explored for detecting the ipsilateral acoustic reflex using one acoustic signal (226-HZ tone) both to elicit the reflex and to measure the impedance of the ear. By eliminating the presentation of two acoustic signals to the same ear, artifactual responses that result from interactions between two signals are avoided. The method provided reflex threshold estimates for five normal subjects that averaged 99.8 dB SPL, in close agreement with previously reported data. A sixth subject, with otosclerosis, showed no evidence of a reflex. With some refinement, the method could become a quick, reliable measurement procedure that avoids some of the problems of conventional methods.

Acoustic Impedance Tests↗
PubMed1981

The diagnostic value of phase-angle tympanograms.

The diagnostic value of susceptance, conductance, resistance, reactance, admittance and phase-angle tympanograms is compared. Phase-angle tympanograms seem to be best suited for the discrimination between normal W patterns and broad irregular curves obtained from ossicular disruptions, luxations and necroses. Several possibilities are proposed: phase-angle tympanograms at the drum, phase-angle tympanograms at the tip of the measuring probe and corresponding phasor curves. The best choice will depend on the kind of data processing and/or measuring equipment available.

Acoustic Impedance Tests↗
PubMed1980

Tympanometry-detection of middle ear pathologies.

Two component susceptance-conductance tympanometry at a probe tone frequency of 660 Hz is superior to admittance tympanometry at 220 Hz for the detection of an ossicular discontinuity, a luxation or a necrosis. It is, however, essential to understand well the difference between non-pathological W-patterns and pathological broad multi-extrema tympanograms. The systematics of normal W-patterns is reviewed and the influence of the sign and magnitude of the pumpspeed on the shape of both types of tympanograms is discussed.

Acoustic Impedance Tests↗
PubMed1979

On the asymmetry of susceptance tympanograms.

The origin of the tail asymmetry of susceptance tympanograms was investigated. A flow-measuring device enabled an accurate determination of ear-canal volume changes produced during tympanometry. From these measurements one finds that not only is the asymmetry due to the earcanal volume change but that finite drum susceptances exist at high transtympanic pressures. This residual susceptance was found to differ in the two tails of the tympanogram. Although no absolute values of those drum susceptances can be computed, it is possible to indicate which pressure side has the greater residual susceptance.

Acoustic Impedance Tests↗
PubMed1976

Two-component versus admittance tympanometry.

The probe tone frequency of electro-acoustic bridges has a direct effect on the shape of the tympanograms obtained. At higher frequencies (800 Hz) typical patterns are generated for eardrum abnormalities and ossicular discontinuities. The 625- and 660-Hz frequencies sometimes prove to be not quite high enough to obtain the expected 'W' or undulating admittance tympanograms. Our investigation proves that much more certainty is given even at 660-Hz probe tone when components B and G are both recorded. The same information for ossicular disruption is found in an admittance (Y) together with a new kind of tympanogram, namely the phase tympanogram.

Audiometry↗