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Biomedical subjects

P Osterhammel

Publications and source records attributed to P Osterhammel.

At least 19 recordsLinked to original sources
PubMed1987

Cumulative and acute toxicity of repeated high-dose tobramycin treatment in cystic fibrosis.

Forty-six patients with cystic fibrosis and chronic bronchopulmonary Pseudomonas aeruginosa infection entered a study of tobramycin-related chronic and acute nephro- and acousticovestibular toxicity. The patients (mean age, 15.7 years) had previously received 2-week courses of tobramycin therapy, for a mean cumulative total of 279 days each. The cumulative tobramycin dose ranged from 632 to 7,644 mg/kg. The patients were studied before and at the end of a 2-week course of treatment with tobramycin (10 to 20 mg/kg per day) to discriminate between acute and chronic toxicity. In patients studied at the beginning of the present course of treatment, the glomerular filtration rate, measured as 24-h creatinine clearance, did not correlate with the cumulative dose of tobramycin received during previous courses. Eighteen patients (39%) had a reduced glomerular filtration rate compared with normal values (mean, 12.5% reduction) but normal serum creatinine values. Two patients (5%) had a high-frequency hearing deficit (above 8 kHz), but only one deficit was possibly related to tobramycin. No chronic vestibular toxicity was observed. During the course of treatment, no patients developed acute nephrotoxicity. After 2 weeks of treatment 32% had a slightly reduced hearing threshold (15 to 30 dB) in two or more high frequencies, and 28% had a fall in vestibular response greater than 25% of the initial value but remained within normal limits. Thus, the acute and chronic toxicity of repeated high-dose tobramycin treatment in cystic fibrosis patients seems to be very mild.

Adolescent↗
PubMed1982

Significance of H1 and H2 receptors in the human nose: rationale for topical use of combined antihistamine preparations.

The aim of this experiment was to study the importance of histamine H1 and H2 receptors in the human nose. We therefore provoked 25 healthy human subjects with histamine after local pretreatment with the H1 receptor antagonist, chlorpheniramine maleate, the H2 receptor antagonist, ranitidine hydrochloride, and a combination of these two antihistamines. The histamine-induced increase in nasal airway resistance was 52% inhibited by combined use of the two antihistamine sprays (p less than 0.05), 22% by chlorpheniramine alone (p less than 0.05), and 29% by ranitidine. The two sprays together were significantly better than the H1 antagonists alone (p less than 0.05). These results suggest an equal importance of H1 and H2 receptors in nasal blood vessels, and an additive effect of H1 and H2 antihistamines. Although chlorpheniramine effectively blocked tickling and the reflex-mediated symptoms, sneezing and hypersecretion, ranitidine had no effect, which suggests an H1 and not an H2 effect on sensory nerve endings in the airway epithelium.

Administration, Topical↗
PubMed1979

High-frequency audiometry. Age and sex variations.

286 normal subject representing both sexes and seven age groups from 10 to greater than or equal to 70 years were tested with both conventional pure tone audiometry and high frequency audiometry (4--20 kHz) using a previously described free field system. The subjects were selected according to very strict criteria. Results from conventional audiometry are similar to other findings in presbycusis studies, though sex difference was seen for the oldest age groups, but only at the frequencies 4 and 5 kHz where the male population showed a significantly poorer hearing. The same sex difference was observed by high frequency audiometry at 4 and 8 kHz. From 10--20 kHz no sex difference was present. At the high frequencies there is an abrupt decrease in hearing sensitivity already from youth. Hitherto, no international standard for zero dB hearing level exists for frequencies above 8 kHz. It is questioned whether a general standard is meaningful at all and that normative data for various age groups should instead be used as a reference level.

Adolescent↗
PubMed1978

Auditory brain stem responses in patients with acoustic neuromas.

In the continuing search for methods to diagnose acoustic neuromas at an early stage, we have applied the auditory brain stem response examination to 27 patients with surgically verified acoustic neuromas. It is confirmed that the main indicator of retrocochlear versus cochlear disease is the interaural latency difference of the Jewett5 wave, the IT5. Women exhibit significantly lower latency values to J5 than men, approximately 0.25 msec. Age also has some influence, so that the J5 latency tends to increase with age, but in this investigation the trend did not reach statistical significance. We were unable to find a correlation between tumour size and IT5. Even if the audiogram shows a considerable hearing impairment at 2 kHz this technique can be used without any correction factors, when the stimulus is a 2 kHz filtered tone-pip. In the presence of an acoustic neuroma there will often be adaptation of the response and it is preferable to arrange the mode of stimulus presentation so that this phenomenon eventually becomes prominent. One patient came out with a false-negative result. We believe this to have been due to our lack of experience at that time and that today we would have recognized the presence of a tumour. If this correction is accepted, the series contains no false-negatives. Regardless of this it can be concluded that for the time being, out of the functional audiological tests, the auditory brain stem response examination is the most reliable indicator for the presence of retrocochlear lesions.

Adolescent↗
PubMed1977

Frequency following auditory brain stem responses in man.

The most interesting electrode positions for recording the FFR are the Vertex and the mastoid. The response is greatest at the Vertex. At the mastoid it comes earlier and probably in a different phase. As a combined result of these relations the responses are in opposite phase with a 500 Hz stimulus, and at 400 Hz they are in-phase. The Vertex-derived response is contaminated by the Jewett waves and at the mastoid there is in addition a CM-like activity. In order to simplify the interpretation we recommend use of the Vertex only as active electrode position, with reference electrodes on the neck, which is largely neutral. A very effective stimulus is a 500 Hz tone-burst with rise-fall times of 2 msec and a plateau of 6 msec. Shorter stimuli yield a smaller response, and with longer stimulus duration, adaption becomes a problem. The Jewett wave contamination can be eliminated by means of recording the response twice with opposite stimulus polarity and subtracting the two from each other.

Acoustic Stimulation↗
PubMed1977

The frequency selectivity of the 500 HZ frequency following response.

In order to evaluate the frequency selectivity of the 500 Hz FFR we applied narrow-band masking at closely spaced center frequencies in the range 0.25 to 4 kHZ. The results show clearly that it is the apical part of the cochlea that generates the 500 Hz FFR, but the area of the basilar membrane that contributes is rather broad. It was evident that some of the masking effect that was observed in the Vertex-derived response stemmed from as yet obsure brain stem mechanisms. Examination of 3 patients with selected types of hearing impairment confirmed the masking results. When there is a low frequency loss there will still be a 500 Hz FFR and the same is true when the loss is in the medium to high frequencies. It is possible that precise determination of the latency to single waves in the response may allow a more exact prediction with regard to which location on the basilar membrane generates the response in the individual patient.

Acoustic Stimulation↗
PubMed1977

Auditory brain stem responses in the diagnosis of cerebellopontine angle tumours.

There is a constant search for more reliable methods of diagnosing cerebellopontine angle tumours at an early stage. The auditory brain stem responses promise to be of use as such a method. In two patients with extracanalicular neurinomas we found a definitely abnormal brain stem response even though conventional tests produced a cochlear type of test pattern. In a third patient with a meningeoma we obtained a similar type of response. Here the conventional tests clearly pointed to the presence of retrocochlear disease. Characteristic findings are a broadening of the whole nerve action potential and a delay in the appearance of the Jewettv-FFP7 complex.

Adult↗
PubMed1977

A quasi-free-field transducer system for high-frequency audiometry.

Previous attempts to measure human hearing capacity in the high frequencies (8 to 20 kHz) have only been met with rather limited success. Based on the results of Shaw and co-workers we have developed a free-field transducer system where the stimuli are delivered from a point source and meet the ear as plane progressive waves at a carefully chosen angle of incidence. The system can be calibrated in a precise manner by means of a specially designed coupler. Preliminary results indicate that the procedure is easily applicable also in a group of inexperienced test subjects and the test-retest variability was within such limits that are acceptable for subjective audiometric testing. These results require validation in a large group of subjects and we hope it will be possible to establish normative values for various age groups.

Audiometry↗