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A Engelhorn

Publications and source records attributed to A Engelhorn.

9 recordsLinked to original sources
PubMed1998

Unilateral testing of utricular function.

A modified rotatory chair test is reported in which radial acceleration, generated by eccentric displacement of the subject during constant angular velocity, is exploited as a unilateral stimulation to the otolith organs. During constant angular rate rotation, the test subject is displaced laterally on the rotating turntable by 3.5 cm, so that one labyrinth becomes aligned with the rotatory axis while the second - eccentric - labyrinth is solely exposed to the altered gravito-inertial acceleration (GIA). Previously reported results showed that the direction of the response is independent of the direction of turntable rotation, ruling out any canal influence, and indicated that in a normal population the response, measured in one eye, was symmetrical for displacement of the left and right labyrinths. This mode of stimulus thus appears to elicit a unilateral otolith-ocular response (OOR). Examination of this unilateral OOR was extended in the present study; comparative testing with head-tilt to gravity, i.e. involving bilateral stimulation to the otolith organs, was carried out. Movements of both eyes were recorded (by three-dimensional video-oculography), in order to examine response conjugacy. To verify the specificity of the unilateral stimulus, tests were performed with patients who had previously undergone unilateral section of the vestibular nerve as treatment for acoustic neuroma. The eccentric displacement profile (EDP) and head-tilt stimulus each included ten cycles of left-right oscillation in order to permit signal averaging. In the normal subjects (n=12) the torsional component of the OOR proved to be both labyrinth-symmetrical and conjugate, during both bilateral and unilateral otolith stimulation. OOR gain (ocular torsion/GIA tilt) was higher for bilateral than unilateral stimulation. Bilateral OORs, obtained from three of the five unilaterally deafferented patients, proved less symmetrical and conjugate than in the normals. Unilateral OORs in all five patients were characteristically asymmetrical, with little or no response during stimulation of the diseased labyrinth.

Acceleration↗
PubMed1996

Ocular counterrolling in response to asymmetric radial acceleration.

The fact that the labyrinths are positioned at approx. 3.5 cm from the head-centric axis leads to the generation of systematic radial acceleratory, or centrifugal, forces during physiological head rotations. Under physiological conditions, the forces exerted on the right and left maculae are generally assumed to be equal and opposite. In the present test, however, the subject was displaced eccentrically during constant angular velocity so that one labyrinth was aligned concentrically with the rotatory axis, whilst the other was exposed to the radial acceleration component generated by the chair rotation. In comparison with previous testing based on subjective setting of the visual vertical, three-dimensional eye movements were recorded in order to obtain an objective measure of the otolith-ocular response mechanisms in the brainstem. The results obtained from normal subjects demonstrate a predominant ocular counterroll (OCR) response to this asymmetric, or unilateral application of linear acceleration. The direction of the OCR response proved to be independent of direction of rotation. The findings demonstrate a symmetrical response magnitude for stimulation of the left and right maculae. In comparison with the OCR response to head-tilt, which can be described as critically damped, the time course of the present response appeared to be underdamped.

Acceleration↗
PubMed1977

[Enflurane and fluorconcentrations in maternal and fetal blood during anaesthesia for for caesarean Section (authors transl)].

During anaesthesia for caesarean sections, the placental transfer and metabolism of Enflurane were investigated in 14 cases. In 3 cases, the administered concentration of 0.4 vol.% Enflurane showed too slight anaesthesia. In 11 cases, 0.6 vol.% Enflurane were delivered to the maternal respiratory mixture. A gaschromatographic method was used to measure the maternal and fetal blood concentrations of Enflurane. The calculated maternal mean value of Enflurane showed a concentration of 330 mumol/l which corresponds to 6.07 mg/100ml; the fetal mean value was 148 mumol/l or 2.72 mg/100 ml. This means that during operating time about 44.8% from the maternal Enflurane concentration has crossed to the fetus. The metabolic break down of Enflurane could be demonstrated by the measurement of inorganic fluorides in the maternal and fetal blood. The fluor concentration in the maternal blood increased during the operation and reached a mean value of 15.5 mumol/l at the time of birth; the mean value in the cord vein was at the same time 9.28 mumol/l which corresponds to 61% of the maternal concentration.

Anesthesia, Obstetrical↗