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Biomedical subjects

W L Creten

Publications and source records attributed to W L Creten.

16 recordsLinked to original sources
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

A search for the most suitable imminent components and probe tone frequency in tympanometry.

The relative occurrence of bell-shaped and various types of W-shaped susceptance-conductance and admittance-phase tympanograms at a probe-tone frequency of 660 Hz was determined from registrations on normal ears. The diagnostic value of the susceptance-conductance versus the admittance-phase representation of tympanograms was studied on pathological middle-ear systems. Using probe-tone frequencies from 510 Hz up to 910 Hz, tympanograms for all four imminent components were recorded on 10 pathological ears and the diagnostic value compared. From the combination of these studies we conclude that the admittance-phase approach at a probe tone frequency between 500 and 700 Hz is a good choice.

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↗
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↗
PubMedDate not supplied

Some physical considerations in the choice of techniques for ossiculoplasty.

A comparative study between the monobloc tympano-ossicular implant and the classical columellar technique is made. Although both give satisfactory audiometric results, the follow-up of the columellar restoration showed some post-operative disadvantages, namely: invagination and perforation of the tympanic membrane, slipping of the columella, and fixation of the columella to the tympanic ring (bony annulus) or to the promontory. In view of the normal tympano-malleal fixation, the normal static pressure accomodation in the incudo-malleal joint and the normal topological situation, monobloc implant obviates the disadvantages inherent in the columellar technique. Two aspects of the monobloc implant need further examination; these are the restoration of the correct rotation axes and the incudo-stapedial connection.

Animals↗
PubMedDate not supplied

Impedance and admittance tympanometry. I. Experimental approach.

In this experimental study a procedure is developed which enables the conversion of susceptance and conductane tympanograms to reactance and resistance tympanograms. Special attention was given to the subtraction of the ear canal admittance. The procedure was applied to bell-shaped and W-notched susceptance and conductance tympanograms. Computed reactance curves showed always an inverted-V shape, computed resistance curves were always flat.

Acoustic Impedance Tests↗
PubMedDate not supplied

Impedance and admittance tympanometry. II. Mathematical approach.

The W-notching of susceptance, conductance and admittance tympanograms, as well as inverted-V shapes, found at high probe tone frequencies are explained, starting from realistic assumptions on the shape of resistance and reactance tympanograms. Necessary conditions for obtaining the different types of tympanograms are given. The theory shows that no pathology is necessary to explain W-notching or inverted-V shapes at higher-frequency probe tones.

Acoustic Impedance Tests↗
PubMedDate not supplied

Hypertension in obese and non-obese non-insulin dependent diabetics a matter of regional adiposity?

There is growing evidence that differences in fat distribution can be predictive for differences in the prevalence of metabolic disturbances, cardio-vascular disease, stroke and death, independent of commonly used indices of obesity. This study evaluates regional body fat distribution as a possible main reason for hypertension in obese and non-obese type II diabetics. 42% of normal weight diabetics with abdominal obesity are hypertensive versus 47% of obese diabetics; only 5% hypertension could be found when a lower body segment fat distribution is present. A significant (p less than 0.001) correlation exists between fat mass topography and both systolic (r = 0.49) and diastolic (r = 0.49) blood pressure. This correlation remains true after correction for body mass index and percent glycosylated hemoglobin. These results suggest that localization of fat in the upper body segment should be considered as a additive risk for hypertension.

Adipose Tissue↗