Effect of hyperbaric oxygen therapy in comparison to conventional or placebo therapy or no treatment in idiopathic sudden hearing loss, acoustic trauma, noise-induced hearing loss and tinnitus. A literature survey.

With the published clinical data to hand on the therapeutic results of patients with idiopathic sudden hearing loss, acoustic trauma or noise-induced hearing loss, it may be confirmed that 65% of those polypragmatically treated patients demonstrated a hearing improvement of 19 +/- 4 dB. In 35% of the cases, no hearing improvement was detected independent of the drugs administered. This corresponds to the results obtained from placebo-treated patients who demonstrated a hearing improvement of 20 +/- 2 dB in 61% of cases and no hearing gain in 39% of cases (fig. 1). A different set of results was obtained from patients with a hearing loss who were treated either with prednisolone or placebo. The percentage of patients who achieved normal hearing again in the placebo-treated group amounted to 31% and 38% and in the verum-treated group 50% and 78%. It may be concluded that a placebo therapy is equally effective to that of all nonsteroidal drugs. Problems arise when comparing non-treated patients since information on spontaneous remission rates differs greatly in the references, i.e. between 25-68% for spontaneous full remissions and 47-89% for spontaneous partial remissions. From a statistical view, 35% and 39% of patients experienced no success with nonsteroidal drugs or placebo, respectively. These patients can still be helped with HBO therapy. 18 patients only underwent primary HBO therapy. In all other 50 studies evaluated here with a total of 4, 109 patients suffering from idiopathic sudden hearing loss, acoustic trauma or noise-induced hearing loss and/or tinnitus, HBO therapy was administered as a secondary therapy, i.e. following unsuccessful conventional therapy. If the onset of affliction was more than 2 weeks but no longer than 6 weeks, one half of the cases showed a marked hearing gain (in at least 3 frequencies of more than 20 dB), one-third showed a moderate improvement (10-20 dB) and 13% showed no hearing improvement at all (fig. 2). 4% no longer experienced tinnitus, 81.3% observed an intensity decrease and 1.2% an intensity increase of their tinnitus condition. 13.5% remained unchanged (fig. 2). If HBO therapy was administered at a later stage, but still within 3 months following onset of affliction, 13% showed a definite improvement in hearing, 25% a moderate improvement and 62% no improvement at all. 7% no longer suffered from tinnitus, 44% reported an intensity decrease, a similar percentage noticed no change and 5% a temporary deterioration of their tinnitus condition. If the onset of affliction was longer than 3 months up to several years, no hearing improvement can be expected in the majority of patients (fig. 3); however, one third of the cases reported an intensity decrease of tinnitus, 60-62% reported no change and 4-7% noticed a temporary intensity increase (fig. 4). In conclusion, it may be deduced that HBO therapy is recommended and warranted in those patients with idiopathic sudden deafness, acoustic trauma or noise-induced hearing loss within 3 months after onset of disorder.

[Simultaneous determination of oxygen partial pressure in the scala tympani, electrocochleography and blood pressure values in the guinea pig]. / Simultane Sauerstoffpartialdruck-Bestimmungen in der Scala tympani, Elektrokochleographie und Blutdruck-Messungen nach Knalltraumata bei Meerschweinchen.

Nineteen guinea pigs were exposed to impulse noise from gunfire (G3 of the Federal German Army, 156 dB peak SPL), 6+6 shots or 12+6 shots, with a 3-s pulse interval. For simultaneous measurements of pO2, cochlea microphonics (CM) and compound action potentials of the auditory nerve (CAP), we used the thin 0.5 microns microcoaxial needle electrode described by Baumgaertl and Luebbers, which was placed through the roundwindow membrane into the scala tympani to a depth of 1000 microns. After exposure to the first 6 or 12 gunshots, the pO2 increased by about 20% of the original values in 12 guinea pigs (63%). In the following 30 min of recovery time the pO2 decreased, stabilized or showed a further decline. There were only 3 animals with a pO2 loss of 70% of the original values. Most animals showed a decline of 25% at the end of the recovery period. In all animals after 6 additional shots, the pO2 only decreased by another 5% of the original values. Amplitudes of CM and CAP were reduced by about 40% of the original values after 6 or 12 shots and by another 20%-24% (CM) and 5%-15% (CAP) after 6 additional shots. The intra-arterial blood pressure in the common carotid artery remained constant. The results are discussed with respect to the well-known morphological damage, subsequent ion imbalance and hypoxia within the cortilymph after exposure to gunfire. These changes are reflected in the loss of CMs and CAPs.

[Simultaneous determinations of oxygen partial pressure in the scala tympani, electrocochleography and blood pressure measurements in noise stress in guinea pigs]. / Simultane Sauerstoffpartialdruck-Bestimmungen in der Scala tympani, Elektrokochleographie und Blutdruck-Messungen unter Lärmbelastungen bei Meerschweinchen.

In 14 guinea pigs the pO2 in the perilymph of the scala tympani fell to 50%-80% of the original value during exposure to noise consisting of 4,000 Hz clicks with a repetition rate of 20/s, 100 dB CHL = 120 dB SPL p.e., repeated twice over a period of 24 minutes each time. For the measurements of the pO2 we used the thin 0.5 micron micro-coaxial needle electrode described by Baumgärtl and Luebbers, which was placed through the round-window membrane in the scala tympani to a depth of 600 micron. The simultaneously recorded CAP latency times were prolonged by 0.8 ms at a test loudness of 60 and 80 dB CHL. The amplitudes of the CM had declined by 60%-70% of the original values at a test loudness of 80 dB SPL p.e. The intra-arterial blood pressure in the common carotid artery of all animals remained constant. As the cortilymph spaces communicate with the perilymph of the scala tympani, our measured decline of pO2 in the perilymph could indicate a cortilymph hypoxia. During exposure to noise the oxygen-dependent Na+ and K+ pumps, which maintain the ion balance and function of the organ of Corti, can decompensate due to lack of oxygen. That would lead to a K+ contamination of the cortilymph and to an intracellular Na+ accumulation, which can cause microstructural damage (hair cell-cilia fusion, hair cell, synaptic and dendritic swelling, hair cell contraction and sustained depolarization), which would be reflected in the CMs and CAPs.

[Microperforation and removal of the round window membrane. Short- and long-term study in animal experiments using electrocochleography and evoked response audiometry]. / Mikroperforation und Entfernung der Rundfenstermembran. Tierexperimentelle Kurz- und Langzeitstudie mittels Elektrokochleographie und ERA.

Our earlier animal experiments on guinea pigs showed that instrumental perforation of the round window membrane by a 0.2 mm platinum wire leads to an instant loss of the inner ear functions. The membrane defect healed in a few days, the cochlear structures remained intact, and the compound action potential of the auditory nerve and the brain-stem responses could be evoked again with normal latency times within 2 weeks. 1. In the studies reported here we first carried out microperforations with a 1 micron needle electrode, which caused no changes of the hearing potentials (cochlear microphonics, compound action potential of the auditory nerve, brain-stem responses), and no visible defect of the round window membrane and no perilymph outflow. 2. The removal of the round window membrane and the withdrawal of the perilymph led to a loss of the cochlear microphonics and to a considerable increase of the latency times of wave I (Jewett). The hearing potential regained their original values after 2 weeks without closure of the round window niche. The round window membrane had regenerated spontaneously and the scala tympani was again filled with perilymph. After covering the round window niche with a connective tissue graft, the hearing potentials regained their original values after 2 weeks, as they had done without cover of the round window niche. The round window membrane regenerated below the tissue graft and the scala tympani was also filled again with perilymph.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term study after perforation of the round window. Animal experiments using electric response audiometry.

The round-window membrane of the inner ear of the guinea pig was perforated with a platinum wire under ketamine-xylazine anaesthesia. The latency times of waves I and V (Jewett) increased to 0.6 ms at 100 dB click HL stimulus loudness. The interpeak latencies did not change (4.0-4.2 ms). At 60 dB CHL stimulus loudness, no responses were discernible. Closure of the membrane damage by adhesive fibrin tissue had no effect on the auditory nerve potentials or the brain-stem responses. Normal latency times of waves I-V were seen 7 days after perforation. There was no difference between the animals with repaired and unrepaired membrane damage. We observed spontaneous healing of the round-window membrane 7 days after perforation, and a normal organ of Corti.

[Hyperbaric oxygen therapy in sudden deafness]. / Zur hyperbaren Sauerstofftherapie beim Hörsturz.

Based on two independent studies, an attempt is made in this paper to demonstrate the effect of hyperbaric oxygen therapy used as a supportive measure to accompany standard treatment in recent acute loss of hearing and in acute loss of hearing where preoperative treatment has proved unsatisfactory. Whereas hyperbaric oxygen therapy is superior to the standard treatment alone as far as the cochlear perception dysacousis and tinnitus in recent acute loss of hearing are concerned, these results could not be reproduced in existing, preoperatively treated acute loss of hearing. As such, hyperbaric oxygen therapy under the strict supervision of a specialist physician has proved an effective supportive measure in the treatment of recent acute loss of hearing.

Instrumental perforation of the round window. Animal experiments using cochleography and ERA.

The round window membrane of the inner ear of the guinea pig was perforated under Ketanest anaesthesia. A very rapid and almost total loss of cochlear microphonics, auditory nerve action potential and brain-stem response developed. Replacement of the perilymph with Ringer's solution and surgical closure of the membrane damage had no effect on auditory nerve action potential or brain-stem response. Further decline in the amplitude of cochlear microphonics was halted, however. When perfusion of the round window membrane was carried out whilst the bulla was full with Ringer's solution, no essential decline was seen in the amplitudes of microphonics and auditory nerve action. Only brain-stem response was reduced--temporarily by 40% of the original amplitudinal level--but this showed subsequent recovery. Preservation of cochlear microphonics and auditory nerve action after perforation in Ringer's solution, i.e. excluding air, indicates that air entering the scala tympani is the cause of the sudden hearing loss after round window perforation. Using a simple physical model, an attempt is made to demonstrate this process. The anatomic connections between the round window, cochlear aqueduct and scala tympani are discussed, as are the different ways in which the round window membrane can be perforated.

The effects of hyperbaric oxygen on experimental noise damage to the ears.

The effect of hyperbaric oxygen on cochlear microphonics, action potential of the auditory nerve, and brain stem response damaged by short exposure to noise is varied. Of 26 guinea pigs 14 showed a positive influence as measured by amplitudes. In 12 animals oxygen had little or no effect. The reason for this could lie in the individual reaction to the anesthetic of the section of the auditory nerve tested. The reaction of postmortem cochlear microphonics after hyperbaric oxygen treatment indicates oxygen diffusion through the round window.

[The influences of hyperbaric oxygen (OHP) on the normal inner ear of guinea pigs. Simultaneous registrations of cochlea microphonics (CM) and nerve potentials (AP) (author's transl)]. / Die Wirkung von hyperbarem Sauerstoff (OHP) auf das normale Innenohr des Meerschweinchens. Simultane Ableitungen von Cochleamikrophonpotentialen (CM) und Nervenaktionspotentialen (AP).

Guinea pigs were treated with 3 bar oxygen pressure in a hyperbaric chamber and CMs and APs were simultaneously registrated. The results depended on the kind of the usual anesthesy. If nembutal i.p. was used, the CMs and APs had been increased significant shortly after oxygen pressure reached 3 bar (CMs increased more than APs). If urethane i.p. was used, the CMs and APs increases not so significantly. These results are traced back to the different effect of the both anesthetic drugs on the blood flow in the brain. Oxygen toxicity in the inner ear was observed after OHP of 3 bar more than 30 min but only by APs. The CMs didn't show any signs of oxygen toxicity under the same conditions during 60 min and more.

A longitudinal study of adolescents' future orientation (time perspective).

This longitudinal study was designed to test hypotheses concerning the influence of environmental changes in different groups (educational status; sex) of adolescents on their future orientation (FO). FO was measured through a free-response questionnaire on which the subjects indicated their hopes and fears (which were later categorized into various domains of life by independent judges). On a second questionnaire the subjects adjudged their present and future life in various given domains of life. The sample consisted of 24 male and 24 female adolescents, aged between 14-16 years at the time of the first measurement; the second measurement took place two years later. Half of the subjects of each sex were students at a Gymnasium (preparing for university study) at both times of measurement ("high social status"). The other half of the subjects of each sex were in their last year at the Hauptschule (continuation of elementary education) at the first time of measurement, and had taken up employment (e.g., an apprenticeship) by the time of the second measurement ("low social status"). At the time of the second measurement relatively more hopes and fears were voiced in the domains of personal development and occupation than at the first measurement. Independent of time of measurement, low-status subjects voiced relatively more hopes and fears related to the occupational domain, and boys had a more extended FO than girls. Low-status subjects - as compared to high-status subjects as well as to their own judgments at the first measurement - believed to a greater extent that the materialization of their hopes and fears depended on themselves rather than on external forces. These results support the assumption that FO cannot be dealt with as a global concept and that FO can be modified by change in the external environments, such as entry into an occupation.

[On the effect of hyperbaric oxygen (OHP) at the guinea pig's cochlea insulted by hypoxia (author's transl)]. / Die Wirkung von hyperbarem Sauerstoff (OHP) auf die hypoxisch geschädigte Cochlea des Meerschweinchens.

The effect of OHP (oxygen under high pressure) by examining 17 CO-intoxicated guinea pigs. The following effects have been observed: The microphonics recovered significantly faster after hypoxia caused by CO than under air. Hyperbaric oxygen has a protecting effect on the inner ear. If OHP is applicated before CO, the microphonics decrease less than under normal breathing. The postmortal microphonics increased to a level above the known postmortal slope, suggesting a diffusion of oxygen through the round window.