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Biomedical subjects

B Håkansson

Publications and source records attributed to B Håkansson.

At least 19 recordsLinked to original sources
PubMed1995

Force threshold for hearing by direct bone conduction.

The bone-anchored hearing aid is connected, by means of a skin-penetrating bayonet coupling, to an implanted titanium fixture. Hence, direct bone conduction (dbc) excitation is used. Since no international standard of audiometric zero for dbc force threshold exists, it is of general interest to determine the dbc force threshold for normal hearing subjects. Two different methods have previously been applied to estimate the relation between bone conduction (bc) and dbc thresholds. One preliminary problem was to make a measurement of the output-force level of dbc transducers, which is equivalent to the situation in situ. A skull simulator, TU-1000, has been designed for measuring the output-force level of dbc transducers. The skull simulator does, in an adequate way, reflect the mechanical point impedance of the human skull. This opportunity to determine equivalent dbc force thresholds has motivated the present study in which a linear relation between the dbc force threshold and the bc force threshold was estimated. The estimate found in the present study conforms fairly well with the two previously found estimates. It is suggested that the estimate found in the present study be used as the reference equivalent threshold force level for dbc.

Adolescent↗
PubMed1995

The bone-anchored hearing aid. Design principles, indications, and long-term clinical results.

This article presents a summary of design principles, indications, and clinical results obtained with the bone-anchored hearing aid (BAHA). Hearing through bone conduction and mechanical stimulation of the skull with percutaneous versus transcutaneous excitation and the functional capability of the ear level BAHA sound processor is presented. Moreover, the surgical procedure is described and the success rate to establish and maintain osseointegration is presented together with the frequency of skin reactions at the implant site. The audiologic and questionnaire results achieved with the BAHA is also presented and discussed.

Adult↗
PubMed1994

Resonance frequencies of the human skull in vivo.

Patients with skin penetrating titanium implants in the temporal bone, for attachment of bone-anchored hearing aids, have made it possible to investigate the free-damped natural frequencies (resonance frequencies) of the human skull in vivo. The resonance frequencies of the skull of six subjects were investigated. Teh resonance frequencies were extracted from two frequency response functions (acceleration/force) measured on each subject: One point measurement where the force and acceleration were both measured at the same point, and one transcranial measurement where the acceleration was measured contralaterally. Between 14 and 19 resonance frequencies were identified for each subject in the frequency range 500 Hz to 7.5 kHz. The two lowest resonance frequencies were found to be on the average 972 (range 828-1164) and 1230 (range 981-1417) Hz. The relative damping coefficients of all resonances were found to be between 2.6 and 8.9%. Due to the relatively high damping coefficients, it is assumed that the resonance frequencies do not significantly affect bone conducted sound. In the transcranial measurements, however, a few large antiresonances were found which may affect bone-conducted sound. Intersubject variations were large, probably due to individual variations in skull geometry and in mechanical parameters. The results were shown to be consistent with previous results obtained on dry skulls. No obvious correlation between lowest resonance frequency and skull size was found.

Adult↗
PubMed1990

Ten years of experience with the Swedish bone-anchored hearing system.

In 1977, a new phase began in hearing rehabilitation of patients with chronic middle and external diseases and atresias. Thus far, these patients have had to rely on conventional bone conduction and air conduction devices that for various reasons give poor rehabilitation. The principle of the new treatment, made possible by the Swedish bone-anchored hearing system, is simple: sound vibrations are directly transmitted to the skull bone via a skin-penetrating titanium implant and then are further transmitted to the cochlea, bypassing the middle ear. The present paper summarizes our results in 147 patients over 10 years, including a total of 6,334 follow-up months. No significant rate of skin infections was observed. In over 93% of the observations, no sign of adverse skin reaction was seen. When herein-suggested indications for treatment with the bone-anchored sound processor HC-200 are followed, the success rate is over 90%. The improved quality of life reported by the patients is a combination of improved quality of sound, improved comfort, and relief from middle ear and ear canal disease occasioned by conventional hearing aids.

Adolescent↗
PubMed1990

Percutaneous vs. transcutaneous transducers for hearing by direct bone conduction.

There is a substantial need for improvement of the hearing situation for patients, with chronic middle ear or ear canal disorders. To improve hearing for these patients, two different bone conduction hearing systems have been developed. The Nobelpharma Auditory System HC 200-the bone-anchored hearing aid we present here-uses a percutaneous transducer; whereas the Audiant device, developed by Dr. Jack Hough, uses a transcutaneous transducer. In percutaneous transmission, the transducer is directly coupled to the bone by means of a permanent skin penetration, whereas in transcutaneous transmission one part of the transducer is implanted and the other part is kept outside the intact skin and soft tissue. Comprehensive audiologic assessments indicate great differences in performance between the two systems. These differences probably originate in differences in length of gap and in different suspension properties of the two transducer systems. This article will demonstrate that large gaps, such as in the transcutaneous transducer, can be devastating for power consumption, maximum output capability, and second harmonic distortion. Since the properties of the suspension in the transcutaneous transducer are not under adequate control and the complication risk of permanent skin penetration is low, we continue to concentrate our efforts on percutaneous transducer systems.

Bone Conduction↗
PubMed1989

Inhibitory effects of nasal drops components on granulocyte chemotaxis.

A possible toxic effect of components in nasal drops on chemotaxis by human granulocytes was studied. The vasoactive substances oxymetazoline chloride and xylometazoline chloride gave a successive reduction of chemotaxis down to zero for a concentration of 500 mg/l which is around that used in commercial preparations. The preservative benzalkonium chloride which is used in nasal drops in a concentration of 200 mg/l was deleterious for chemotaxis at a concentration of 0.8 mg/l. Thiomersal was deleterious for chemotaxis at a concentration of 1 mg/l which should be compared with a concentration of 24 mg/l used as preservative in nasal drops. Together with previous studies the present results indicate that the addition of preservatives in nasal drops should be questioned especially as they can be safely distributed without any risk of bacterial contaminations nowadays.

Administration, Intranasal↗
PubMed1989

The inhibition of granulocyte phagocytosis by various components of nasal drops.

The effect of two decongestive substances and two preservatives used in nasal drops on phagocytosis by human granulocytes was studied. The vasoactive substances oxymetazoline chloride and zylometazoline chloride incubated with human granulocytes during 20 min. gave a reduction of phagocytosis to almost zero when using concentrations found in commercially used nasal drops (500 mg/l respectively 1000 mg/l). However, a dilution of 1:100 was consistent with an almost normal phagocytic function. The preservatives benzalkonium chloride and thiomersal gave a dose related reduction of phagocytosis down to zero. A dilution of 1:100 of the benzalkonium chloride solution used commercially (200 mg/l) and a dilution of 1:10 of the thiomersal solution used commercially (24 mg/l) were needed to get an almost normal phagocytic function. These results together with previous studies indicate that the addition of preservatives in nasal drops should be questioned, excluded or replaced with other less harmful substances.

Administration, Intranasal↗
PubMed1989

Skull simulator for direct bone conduction hearing devices.

The Bone-Anchored Hearing Aid (BAHA) is a direct bone conduction hearing device which has given patients with various middle ear disorders a significantly improved quality of life. As the BAHA has gained acceptance as a valuable contribution to the Swedish hearing aid rehabilitation program, the need for equipment which can perform objective frequency response measurements has grown. Such equipment is indispensable for carrying out quality assurance, service, and fitting evaluation. To meet the above-mentioned demands, the skull simulator TU-1000 has been developed. The dynamic behaviour of the skull simulator TU-1000 can be characterized as that of a rigid mass body with a weight significantly exceeding the weight corresponding to the dynamic mass of the transducer incorporated in the BAHA. The motions of the mass body are measured by an accelerometer the output signal of which is amplified by a precalibrated amplifier. The output signal is proportional to the output force level from the BAHA. The skull simulator TU-1000 is capable of measuring the output force level from the BAHA with high reliability for frequencies ranging from 100 Hz to 10 kHz.

Biomechanical Phenomena↗
PubMed1986

An examination of the surface corrosion state of dental fillings and constructions. I. A laboratory investigation of the corrosion behaviour of dental alloys in natural saliva and saline solutions.

Electrochemical measurements on amalgams and gold alloys in natural saliva and saline solutions have been performed. The results show strong inhibiting effects of some components in natural saliva on the surface corrosion behaviour of amalgams. For the gold alloys the cathodic reduction of oxygen was notably lower in natural saliva than in saline solutions. For galvanic combinations of gold and amalgams substantially lower currents than those calculated from thermodynamic data can be expected in natural saliva.

Corrosion↗
PubMed1986

An examination of the surface corrosion state of dental fillings and constructions. II. A clinical study on patients with orofacial complaints.

A group of 115 patients with orofacial complaints has been examined. A new method for intraoral measurement of electrode potentials on the surface of the amalgam fillings and prosthetic constructions has been developed and applied. The possible connections between the measured electrode potentials and patients' saliva properties and their complaints have been discussed. No correlations between measured electrode potentials of the metallic fillings and constructions and important saliva properties could be found. No connections between the measured electrode potentials and the patients' complaints could be proved.

Adult↗
PubMed1986

The mechanical point impedance of the human head, with and without skin penetration.

The fact that a titanium screw can be implanted into the mastoid portion of the human skull, at the same time establishing a permanent, reaction-free skin penetration, has made it possible to attach a new bone conduction hearing aid directly to the skull. To understand and improve this new method of bone stimulation, the mechanical point impedance of the titanium screw-skull system was measured. The conventional point impedance of the skin-covered mastoid portion of the temporal bone was also measured and the difference in magnitude between the two impedances was calculated. An impedance head (Brüel & Kjaer 8001) and an FFT analyzer (Hewlett-Packard 5423) were used for mechanical point impedance measurements. Seven patients have been investigated. The magnitude of the impedance for the screw-skull system was found to be generally between 10 and 30 dB higher than that for the conventional skin-covered mastoid bone. One conclusion is that the conventional point impedance of the skin-covered mastoid portion of the human skull is essentially due to the properties of the skin and subcutaneous soft tissue. Another conclusion is that a much lower stimulation velocity is needed, with skin penetration, to produce a given hearing sensation.

Acoustics↗
PubMed1986

A speech-to-noise ratio test with the bone-anchored hearing aid: a comparative study.

Hitherto, for persons with impaired hearing who cannot use an air conduction hearing aid, the only alternative has been a conventional spring-loaded bone conduction hearing aid. Now, with minor surgery, a titanium screw can be implanted in the bone behind the ear and a coupling, which penetrates the skin, can be attached, giving a new kind of hearing aid--the "bone-anchored hearing aid." Improved quality of sound is one of the patients' subjective assessments. Improvement was not confirmed by a standard speech-discrimination test. With new speech material consisting of sentences in noise, the speech-to-noise ration (SN) has been determined for 24 patients. Patients who previously used a conventional bone conduction hearing aid improved their SN on the average by 3.3 dB. The most important difference between the two aids related to improved SN is probably the increased audibility between 600 and 6000 Hz.

Adolescent↗
PubMed1984

Hearing thresholds with direct bone conduction versus conventional bone conduction.

Some patients who need hearing aids are unable to use an aid which transmits the sound via the external ear canal but have to use a bone-conduction hearing aid. The pressure needed to apply the transducer often gives the patient discomfort, and the attenuating effect of the skin gives poor electroacoustical function of the aid. A permanent skin penetration has made it possible to develop a bone-anchored hearing aid with all components in one housing. Ten patients have been equipped with such an aid. This paper deals with a comparative hearing threshold measurement on 10 patients. Békésy audiometry was performed and a conventional Oticon (A-type) transducer was used. In the frequency range 600 to 6 000 Hz, there was a lowering of 10-20 dB in thresholds when skin penetration was performed. This lowering in thresholds means lower transducer distortion, lower electrical gain, and lower power consumption to produce a given sensation level.

Acoustic Impedance Tests↗
PubMed1978

A cold box for the transport and storage of vaccines.

A cold box capable of maintaining a temperature below +4 degrees C for 1 week was constructed and tested in the laboratory and under field conditions. Cooling is produced by commercial cold packs precooled in a deep-freeze or the freezing compartment of a refrigerator. The box can take approximately 3000 doses of vaccine and is simple, cheap and strong. It is primarily intended for storage of vaccines during field trips by vaccination teams, as an alternative to the refrigerator in regional and peripheral stores in the case of an electrical power failure, and for the delivery of vaccines from regional store to the district.

Cold Temperature↗
PubMedDate not supplied

Analysis of the mechanical impedance of bone-anchored hearing aids.

Some patients who need hearing aids are unable to use an apparatus which transmits the sound via the external ear canal and have to use a bone conduction hearing aid. The bone vibration transducer of this aid is applied to the skin over the mastoid process and the sound is transmitted via the soft tissue and bone to the cochlea. The pressure needed to apply the transducer often gives the patient discomfort and the damping effect of the soft tissue gives poor quality of the sound transmitted. Advances in the ability to permanently implant foreign material in the body and perform permanent skin penetration has made it possible to develop a bone-anchored hearing aid. Fourteen patients have been equipped with such hearing aids. To be able to give these patients the best hearing aid, a new transducer has to be constructed to match the new situation. The impedance of the bone-anchored titaniumscrew/skull has been studied and the resistance and reactance of the mechanical impedance have been measured. The influence of a damping soft tissue layer over the bone has been analyzed. The difference between the impedance of the skull and the impedance of the soft tissue + skull was in the order of 10 to 25 dB depending on the frequency.

Acoustic Impedance Tests↗
PubMedDate not supplied

The bone-anchored hearing aid. Principal design and a psychoacoustical evaluation.

Hearing aids can be divided into two groups, distinguished by the principle of how sound is transmitted to the cochlea. The greatest and most important group is that consisting of air conduction (AC) hearing aids, whereas the other group consisting of bone conduction (BC) hearing aids is relatively small but nevertheless important for patients with particular types of hearing disorder. Conventional bone conduction hearing aids are not in common use, mainly because of several drawbacks. The implantation of a titanium screw into the mastoid portion of the temporal bone has made it possible to obtain a permanent and reaction-free rigid penetration of the skin. A newly developed bone conduction hearing aid was connected to such a screw. This new hearing aid is named 'the bone-anchored hearing aid' (BAHA) and it is characterized by a single housing construction. The transducer piston of the BAHA is directly connected to the titanium screw by a low-profile coupling arrangement. Ten patients were equipped with this new hearing system. In a comprehensive questionnaire, all patients reported that they preferred the BAHA to their old hearing aid. The major reasons were improvements in practical arrangements, wearing comfort, aesthetic appearance, and sound quality. Improvements in speech reception were not verified by the discrimination tests, but 6 out of 10 patients subjectively reported clearly improved sound quality. The group of patients who may benefit from the BAHA of present standard includes patients with a sensorineural hearing loss of at most 50-60 dB HL.

Adolescent↗