Biomedical subjects

K Laitakari

Publications and source records attributed to K Laitakari.

At least 19 recordsLinked to original sources

PubMed2001

Computerized in-situ test for bone conduction hearing aids.

Conventionally, bone-conduction (BC) hearing aids are tested with skull simulator devices and the individual adjustments are reliant on psychoacoustic free-field audiometry. Here we present a novel PC-based system for in situ measurements of BC hearing aids. With the presented system, we are able to measure the hearing aid induced skull vibrations in relation to the individual BC hearing threshold at given frequencies. According to the preliminary measurements, the vibration levels are relatively low but the system is sensitive enough for relevant measurements.

Acoustic Stimulation↗

PubMed2001

The Finnish speech-in-noise test in MELAS mutation and other sensorineural hearing impairments.

A computerized adaptive Finnish speech-in-noise test has recently been developed. The purpose of the present study was to measure speech recognition thresholds in noise (SRTN) in patients with sensorineural hearing impairment (SNHI) caused by mitochondrial mutation [mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS)] and in patients with SNHI from other causes and to compare them with those in normal hearing controls. SRTN differed significantly between controls and the patients with SNHI from other causes and between controls and the MELAS group, but not between SNHI patients and the MELAS group. Hearing in a noisy environment seems to be as impaired in MELAS patients as in patients with SNHI from other causes, in spite of the possible coexisting defects in the central nervous system.

Adult↗

PubMed2001

Carhart notch effect in otosclerotic ears measured by electric bone-conduction audiometry.

The Carhart notch is an elevation in the middle-frequency bone-conduction threshold of an ear with clinical otosclerosis. The study population consisted of 138 patients with clinical otosclerosis. Conventional air-conduction (AC) and bone-conduction (BC) and electric bone-conduction (EBC, with Audimax 500 audiometer) thresholds were measured 2 weeks before and 7 months after stapes surgery. The EBC thresholds were converted from mA values to dB SPL to compare the results obtained with the different methods. The mean differences in the BC thresholds before and after the operation were 3.2 dB (95% CI 1.9-4.6) at 1 kHz and 7.6 dB (95% CI 6.1-9.1) at 2 kHz. The mean differences in the EBC thresholds were 5.4 dB (95% CI 3.8-6.9) at 1 kHz and 5.3 dB (95% CI 3.4-7.1) at 2 kHz. Thus, both methods showed a distinct Carhart notch effect.

Audiometry, Pure-Tone↗

PubMed2001

Finnish speech in noise test: long-term reproducibility.

A computerized adaptive Finnish speech in noise test was developed recently. As part of the test's evaluation process the long-term stability of speech recognition threshold in noise (SRTN) was determined. The non-operated ears of 164 stapes surgery patients were assessed preoperatively and at 1, 7 and 19 months postoperatively. Short-term and long-term repeatability were equal. The absolute intraindividual differences were 1.5 dB on average.

Audiometry, Pure-Tone↗

PubMed2001

The Finnish speech in noise test for assessing sensorineural hearing loss.

A computerized adaptive Finnish speech in noise test was developed recently. As part of the test's evaluation process 172 patients with sensorineural hearing loss including 20 normally hearing subjects were measured using pure-tone audiometry, speech recognition threshold in noise (SRTN) test and conventional speech audiometry without background noise. As anticipated, sensorineural hearing loss yielded an elevation of SRTN although individual differences were considerable. The SRTN test was accurate as the absolute difference between individual repeated SRTNs was, on average, 1.5 dB (SD 1.5 dB) when the range of possible test values is from approximately -12 to +20 dB. On average, the learning effect was 0.5 dB.

Audiometry, Pure-Tone↗

PubMed2000

Otoacoustic emissions and tympanometry in children with otitis media.

OBJECTIVE: To examine otoacoustic emission and tympanometric findings in children with surgically confirmed middle ear effusion (MEE). DESIGN: A total of 102 children aged 0.7 to 11.4 yr undergoing surgery because of otitis media were included in the study. A tympanometric examination and transient evoked otoacoustic emission (TEOAE) measurement were performed on each ear before myringotomy. MEE was aspirated, weighed and classified as mucoid or nonmucoid. TEOAE measurements were compared with the quantity and quality of MEE and to the tympanometric findings. RESULTS: Fifty (72%) ears out of the 65 ears containing effusion showed reduced TEOAE. The quantity of effusion was associated significantly (p < 0.001) with the TEOAE responses, and mucoid effusion reduced the emissions more than nonmucoid. The sensitivity of tympanometry in identifying the ears without recordable TEOAE was 73% and the specificity 81%. CONCLUSION: MEE results in a significant reduction in TEOAEs even when the effusion is nonmucoid. This suggests that transmission of acoustic energy to and from the middle ear is altered in children experiencing any form of otitis media with effusion.

Acoustic Impedance Tests↗

PubMed1997

Chronic suppurative otitis media and cholesteatoma. Vanishing diseases among Western populations?

A population-based survey of patients who had undergone surgery for chronic ear disease over the past 30 years in northern Finland revealed that the number of new surgical cases of both chronic suppurative otitis media and cholesteatoma has declined sharply after a peak in 1971-1974 and is now almost non-existent in contrast to the number of patients being operated on for chronic dry perforations, which has remained more or less the same. Most of the patients with chronic suppurative otitis media and cholesteatoma had had chronic ear trouble as early as the 1940s or 1950s. Moreover, if an active chronic otitis media developed in these cases, it started at a younger age than in cases with an onset after the 1950s. These facts may indicate that the decrease seen in this population is in close connection with the introduction of antimicrobials in the treatment of acute otitis media in the mid-1950s in the area.

Adult↗

PubMed1997

From posterior crus stapedectomy to 0.6 mm stapedotomy--towards reliability in otosclerosis surgery.

In the 1980s, in Oulu, clinical otosclerosis was primarily managed with posterior crus stapedectomy and in the 1990s, the method was changed to stapedotomy. This retrospective study was carried out to assess the results of different methods of stapes surgery in the hands of one surgeon. Subsequent primary stapes operations in 1989-1990 (91 operations including 74 posterior crus stapedectomies and 1 Causse stapedotomy) and in 1993-1994 (117 operations including 1 posterior crus stapedectomy, 95 Causse pistons) were analysed. Changes in air and bone conduction thresholds were compared 5 weeks, 7 months and 19 or more months postoperatively. There was a significant difference in hearing (air-conduction-AC and bone-conduction-BC) in favor of Causse 0.6 mm teflon piston prostheses as compared to posterior crus stapedotomies at 7 months and 19 or more months. Likewise, the 4 kHz gain at the same time was also significantly better with Causse 0.6 mm all teflon piston. At 5 weeks, 81% of posterior crus stapedectomies and 78% of Causse stapedotomies had air conduction thresholds within 10 dB of preoperative bone conduction. However, at 7 months, the corresponding figures were 68% and 89%. Re-operations were performed in 26.7% posterior crus stapedectomies but only in 1% Causse 0.6 mm teflon piston stapedotomies. In the hands of the senior author (KL), the change from posterior crus stapedectomy technique to stapedotomy with 0.6 mm Causse teflon piston in primary stapes surgery proved to be successful. Surprisingly, the AC and BC hearing in the Causse stapedotomy group kept on improving during the follow-up.

Follow-Up Studies↗

PubMed1997

New speech-in-noise test in different types of hearing impairment.

A new test was developed to assess speech recognition in noise. The test was designed to be run in a personal computer supplied with a sound card. One thousand disyllabic test words and noise were stored in digitized form on the hard disk of the computer. The measure given by this test is speech recognition threshold in noise (SRTN) corresponding to 50% recognition. The present series of 180 cases with various hearing impairments and 39 controls were examined with speech-in-noise test and conventional audiometry. In keeping with earlier studies, the SRTN turned out to be significantly elevated in cases with sensorineural hearing impairment; this elevation was related to the grade of hearing impairment. On the other hand, no essential difference was seen between the SRTN values of subjects with mixed hearing impairment and persons with normal hearing.

Adult↗

PubMed1997

New computerized Finnish speech in noise test and binaural hearing.

Aided and unaided binaural versus monaural recognition of speech has been studied with more or less laborious methods when speech and noise sources are spatially separated. The efficacy of the new Finnish speech in noise test to show binaural advantage was evaluated in free field conditions. Thirteen subjects with normal hearing were tested measuring speech recognition thresholds in noise (SRTN) in anechoic chambre with different situations of spatial separation of speech and noise sources monaurally and binaurally. The noise source was fixed above the head (treating both ears similarly) and equidistant speech was delivered at different azimuths. SRTNs with mixed speech and noise without spatial separation served as normalizing reference. Differencies in SRTNs consistently followed the changing head and pinna shadow effects on the speech-to-noise ratio with a smaller binaural advantage. This new test seems to give quite economically the same results as those of previous more sophisticated investigations on speech recognition in free field situations.

Hearing↗

PubMed1996

A comparison of three vibrators in static posturography: the effect of vibration amplitude on body sway.

In static posturography, proprioception is often disturbed using vibrators applied bilaterally to the calf muscles. The effect of vibrator amplitude on body sway was compared in static posturography using bilateral vibrators on the calf muscles of 30 healthy male military conscripts at frequencies of 50 and 90 Hz. Postural stability was measured in terms of BSV (body sway velocity), and maximal displacements of the centre of force (MAXY, MAXX) in the anterio-posterior and lateral directions. In comparing the effects of vibration to base stance without vibration, BSV seemed to be the most sensitive parameter. A vibration of 50 and 90 Hz significantly influenced BSV values with the two most eccentric loads, an effect which could not be confirmed using any other parameter. This result could be obtained even with a small amplitude (around 0.7 mm free/0.3 mm fixed) in our healthy subjects. The BSV effects may be even more pronounced in clinical work with patients and postural disorders. Thus, when proprioceptive stimulations is used in posturographic measurements, differences in the tested magnitude of the stimulation amplitude with a constant frequency will significantly affect postural stability, even in healthy subjects.

Acceleration↗

PubMed1996

Speech recognition in noise. Development of a computerized test and preparation of test material.

In adaptable, Finnish language, "speech in noise" test was developed using a personal computer equipped with a sound card. each of the 1000 test items stored as a separate digitized wave form file on the hard disk of a personal computer consisted of disyllabic words on one stereo track and synchronized speech noise on the other. Because only a few randomly selected words are presented in this test for SRTN (speech recognition threshold in noise or S/N ratio corresponding to 50% recognition) the selection and equalization of test material is considered to be crucial to the achievement of reproducible results in short time. Equalization of the test items (word + noise) in accordance with degree of difficulty, by adapting the noise signal to the properties of the corresponding word, and selection of 510 of the initial 1,000 recordings with the smallest SDs are described. The effect of this procedure on the test-retest reliability of testing SRTN is evaluated. Despite contrary expectations, the procedure appears to have no effect on the reliability of the speech recognition threshold in noise (SD from 1.5 to 1.7 dB).

Audiometry, Speech↗

PubMed1995

Objective real ear measurements of bone-conduction hearing aid performance.

Conventional bone-conduction and bone-anchored hearing aids are tested with skull simulator devices; individual adjustments are reliant on psychoacoustic free-field audiometry, which can be quite demanding for the patient. A method is presented in which the induced skull vibrations are measured with an accelerometer and then analysed with Fast Fourier Transformation (FFT). With this method, frequency characteristics, harmonic distortion and dynamic response can be analysed.

Bone Conduction↗

PubMed1995

Assessment of bone conduction prosthesis in situ.

Conventional and bone anchored bone conduction hearing aids can be tested with skull simulating devices and the individual adjustment rely on time consuming psychoacoustic audiometry in free-field which can be quite demanding for the patient. A method is presented in which the hearing aid induced skull vibrations are collected with an acceleromotor and recorded on a digital audio tape. The recordings are analysed with Fast Fourier 'Transformation (FFT) by using a signal processor. The free-field test signal can be either narrow-band or white noise. Changes in frequency characteristics can be easily monitored with white noise as signal, harmonic distortion and dynamic response can be analysed reliably by using pure tones. The inter-individual comparisons can be made when calibration is based on skull vibrations at the individual bone-conduction hearing thresholds. Two case reports are presented and discussed.

Adult↗

PubMed1994

Carhart notch and electric bone-conduction audiometry.

The Carhart notch is a depression in the bone-conduction audiogram of patients with clinical otosclerosis. The middle frequencies from 0.5 to 2 kHz, which correspond to the resonance frequency of the middle ear, can be substantially improved following successful stapes surgery. Twenty-nine consecutive patients with clinical otosclerosis were tested 2 weeks before and 7 months after stapes surgery with conventional air-conduction (AC) and bone-conduction (BC) audiometry and electric bone-conduction (EBC) audiometry using an Audimax 500 audiometer. The BC thresholds improved at 0.5-2.0 kHz corresponding to the Carhart notch. On average, the EBC thresholds remained more stable, showing no Carhart phenomenon, which supports the concept that EBC stimulation is not entirely equivalent to conventional BC audiometry, but has a different mode of action on the inner ear.

Adult↗

PubMed1994

The repeatability of posturographic measurements and the effects of sleep deprivation.

The repeatability of posturographic measurements and the effects of sleep deprivation on them were investigated in 23 volunteers over a period of four months. Postural stability was studied by evaluating body sway velocity and the maximal and average vibration-induced shifts of the centre of pressure in the anterio-posterior and lateral directions. The posturographic test was performed with and without exposure of the calf muscles to vibration. Subjects were tested both with their eyes open and closed, and the measurements were performed weekly during the first month and once every month thereafter. The interindividual results differed more than the intraindividual ones, indicating that posturographic measurements are most suitable for functional monitoring in one person's tests. The dispersion of the results did not diminish with time, nor did the body sway decrease. The findings suggest that no learning takes place in nontrained persons. In the second part of the research, measurements were performed twice after the subjects had been awake the previous night or 24 hours. Postural stability did not deteriorate in this situation.

Adult↗

PubMed1993

Microcomputer with a sound card. Low-cost flexibility for audiometry.

An ordinary Personal Computer equipped with a sound card for entertainment electronics can significantly improve the flexibility of speech and pediatric audiometry. New programming tools have made it possible for the layman to construct his own user-interface.

Audiometry, Speech↗

PubMed1992

EMLA in local anaesthesia of the tympanic membrane.

An ideal agent for local anaesthesia of the tympanic membrane has been missing so far. Recently, however, a eutectic mixture of lignocaine and prilocaine (EMLA, Astra, Södertälje, Sweden) has proved promising. We compared the anaesthetizing efficacy of EMLA, Bonain's solution (cocain, menthol, phenol ana partes) and Xylocain-spray (Astra, Södertälje, Sweden) in 42 voluntary subjects. EMLA was applied on one tympanic membrane and either one of the other two agents in the other ear of each subject. Small cotton pledgets were used for application. Sensitivity of the ear drum was tested under otomicroscope with a cotton tipped wire before and after each local anaesthesia. Full anaesthesia could be reached with EMLA very significantly (p less than 0.001) more often than with Xylocain and almost significantly (p = 0.057) more often than with Bonain's solution. Most of the test subjects preferred EMLA to Bonain's solution of Xylocain. Undesired side effects, including two tympanic membrane perforations, appeared in most of the ears anaesthetized with Bonain's solution. In the clinical part of the study, EMLA topical anaesthesia was used in 127 minor policlinical tympanic membrane procedures like myringotomy and tympanostomy tube assembling. Eighty-three of the procedures were assessed as painless, 36 unpleasant and 8 painful. A 30-min action time of EMLA was considered sufficient in most cases. No EMLA related side effects appeared. In conclusion, Bonain's solution is recommended to be replaced by EMLA or a corresponding agent for local anaesthesia of the tympanic membrane.

Administration, Topical↗