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Biomedical subjects

B Håkansson

Publications and source records attributed to B Håkansson.

At least 19 recordsLinked to original sources
PubMed2001

Bone-anchored hearing aids: current status in adults and children.

The BAHA is the only cochlea stimulator in clinical use using bone conduction as the mode of stimulation. Sound transmitted through bone conduction is a natural way of hearing and the fundamentals of bone conduction are presented. The simple but important procedure has been refined and is presented in some detail. As the BAHA is approved by the Food and Drug Administration for children, aspects relevant for this age group will be addressed. The future includes semi-implantable BAHA, percutaneous electrical coupling, and a BAHA for tinnitus suppression.

Adult↗
PubMed2000

A bone-anchored hearing aid for patients with pure sensorineural hearing impairment: a pilot study.

This pilot study assesses the potential benefits of an optimized bone-anchored hearing aid (BAHA) for patients with a mild to moderate pure sensorineural high frequency hearing impairment. The evaluation was conducted with eight first-time hearing aid users by means of psycho-acoustic sound field measurements and a questionnaire on subjective experience; all of the patients benefited from the BAHA. On average, the eight patients showed improvement in PTA threshold of 3.4 dB and in speech intelligibility in noise of 14%. Seven of the subjects, also fitted with present standard air conduction hearing aids (ACHA) found the ACHA thresholds to be improved more than the BAHA ones. In speech tests, the ACHA was only slightly better; these patients chose between their different hearing aids according to the sound environment. Although the BAHA was preferred for wearing and sound comfort, it cannot be used as the sole aid for patients with pure sensorineural impairment.

Acoustic Stimulation↗
PubMed2000

Vibration characteristics of bone conducted sound in vitro.

A dry skull added with damping material was used to investigate the vibratory pattern of bone conducted sound. Three orthogonal vibration responses of the cochleae were measured, by means of miniature accelerometers, in the frequency range 0.1-10 kHz. The exciter was attached to the temporal, parietal, and frontal bones, one at the time. In the transmission response to the ipsilateral cochlea, a profound low frequency antiresonance (attenuation) was found, verified psycho-acoustically, and shown to yield a distinct lateralization effect. It was also shown that, for the ipsilateral side, the direction of excitation coincides with that of maximum response. At the contralateral cochlea, no such dominating response direction was found for frequencies above the first skull resonance. An overall higher response level was achieved, for the total energy transmission in general and specifically for the direction of excitation, at the ipsilateral cochlea when the transducer was attached to the excitation point closest to the cochlea. The transranial attenuation was found to be frequency dependent, with values from -5 to 10 dB for the energy transmission and -30 to 40 dB for measurements in a single direction, with a tendency toward higher attenuation at the higher frequencies.

Acoustic Stimulation↗
PubMed1996

Linearity of sound transmission through the human skull in vivo.

The linearity of sound propagation through the human skull was investigated. One male subject, equipped with bilateral skin-penetrating titanium fixtures for attachment of bone-anchored hearing aids, was studied thoroughly. Three different methods were used: comparison of the frequency response functions estimated at different signal levels (using stepped sine as well as random noise), comparison of the coherence function at different signal levels (using random noise), and the Hilbert transform of the estimated frequency response function. Frequencies from 0.1 to 10 kHz and signal levels up to 77 dB HL at discrete frequencies were used. No indication of any significant nonlinear behavior was found with the three methods used.

Bone Conduction↗
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↗