Search PubMed⌕ Search

Biomedical subjects

A Ivarsson

Publications and source records attributed to A Ivarsson.

At least 55 records · Page 3Linked to original sources
PubMed1983

The airway resistance of the naso-frontal duct during and after acute frontal sinusitis. A long term follow-up of 49 trephined frontal sinuses.

A new pressure flow method for function tests and calculation of the airway resistance in the naso-frontal duct is presented. With this pressure flow technique the function and airway resistance of the naso-frontal duct was tested in 49 patients who were trephined for acute frontal sinusitis. The tests were performed during the primary healing period (0-16 days) and in a long term study 2, 6 and 12 months after operation. The patients were also checked radiologically and clinically. A prolonged healing period (more than 6 days) corresponded significantly to a high incidence of recurrent disease. With this method it is possible to define groups where recurrences might be expected because of impaired function of the naso-frontal duct.

Adolescent↗
PubMed1983

Hearing deterioration in shipyard workers. Serial audiometry over a four-year period.

The hearing thresholds of a total of 58 workers aged 20 to 65 years were measured annually over a period of 4 years using Békésy sweep-frequency audiometry. Using these data, accurate values of the yearly rate of change of hearing threshold level were calculated. The rate of change of hearing threshold level due to presbyacusis was obtained from several data sets, and the rate of change of hearing threshold level due to noise was calculated. When the average hearing threshold level over the frequency range 2-8 kHz was considered, it was found to be possible to establish a significant rate of threshold shift caused by exposure to noise for yearly changes as small as approximately 2 dB. In the cases investigated about 30% of the ears showed a significant deterioration in hearing ability due to noise. When comparing the permanent threshold shift caused by noise in groups of younger and older workers, it was found that the younger workers exhibited less threshold shift than expected, whereas the older workers showed a greater threshold shift than expected.

Adult↗
PubMed1983

High speed tympanometry and ipsilateral middle ear reflex measurements using a computerized impedance meter. A comparison with the results obtained by a conventional impedance meter.

By means of a new computerized impedance meter, middle ear pressure, tympanograms and ipsilaterally elicited middle ear reflex can be recorded and presented in 3 sec. Owing to the fast rate of air pressure change in the external ear canal it is not necessary to have a completely airtight seal around the ear probe when recording middle ear pressure, which saves time. Results obtained using the new device and those obtained by a conventional impedance bridge are compared.

Acoustic Impedance Tests↗
PubMed1983

Patency of the nasofrontal duct during frontal sinusitis.

In a series of frontal sinuses trephined due to frontal sinusitis the airway resistance of the nasofrontal duct was tested during the healing period as well as in a long-term follow-up study up to one year. The nasofrontal duct was more resistant to passage for air than for saline during the healing period. A high incidence of recurrences was found in cases with high airway resistance of the duct, a prolonged primary healing period and when major nasal pathology was found.

Airway Resistance↗
PubMed1983

Automated rhinomanometry.

In order to facilitate measurements and calculations in rhinomanometry a microprocessor is used. Pressure and flow signals, obtained from microtransducers, are automatically calibrated by drawing known volumes of air through a standardized test-nose, while the signals are read by the computer. When the patient is connected, the pressure-flow curves are displayed on a screen. At adequate breathing, the computer reads the pressure and flow 200 times per second for a few breaths. It performs all calculations and presents data describing the pressure-flow relationship, e.g. in terms of the resistance, where the curve crosses a circle with a certain radius in a polar coordinate system. Automatically calculated data were compared to manually derived ones in six healthy subjects and twenty patients with symptoms of nasal obstruction. There was a close correlation between the two sets of data. It is concluded that the described automated rhinomanometer facilitates the rhinomanometric procedure and gives accurate data on nasal airway resistance.

Airway Resistance↗
PubMed1983

Physiological and behavioral effects of tilt-induced body fluid shifts.

This paper addresses the "fluid shift theory" of space motion sickness. The primary purpose of our research was the development of procedures to assess individual differences in response to rostral body fluid shifts on earth. Experiment I examined inner ear fluid pressure changes during head-down tilt in intact human beings. Tilt produced reliable changes. Differences among subjects and between ears within the same subject were observed. Experiment II examined auditory threshold changes during tilt. Tilt elicited increased auditory thresholds, suggesting that sensory depression may result from increased inner ear fluid pressure. Additional observations on rotation magnitude estimation during head-down tilt, which indicate that rostral fluid shifts may depress semicircular canal activity, are briefly described. The results of this research suggest that the inner ear pressure and auditory threshold shift procedures could be used to assess individual differences among astronauts prior to space flight. Results from the terrestrial observations could be related to reported incidence/severity of motion sickness in space and used to evaluate the fluid shift theory of space motion sickness.

Adolescent↗
PubMed1982

Reliability in tests of the eustachian tube function.

With the aid of a quantitative impedance method and a pressure chamber, the capacity of the Eustachian tube to equilibrate pressure differences across the tympanic membrane was repeatedly determined in 20 otologically healthy men. The test-retest reliability was calculated from five determinations of static pressure equilibration of over- and underpressures of 10 cmH2O and 10 determinations of equilibration of dynamic pressure changes. The pressure opening level of the tube during pressure increase in the middle ear was significantly lowered in the initial determinations. The residual pressure in the middle ear after maximum equilibrating efforts during pressure increase in the chamber was also significantly lowered. For the rest, the test-retest reliability was good. Ears with perfect tubal function had better test-retest reliability for all parameters tested than ears with poorer function. The significance of repeated measurements and the value of reliability determinations are discussed.

Acoustic Impedance Tests↗
PubMed1982

Effect of flight on the Eustachian tube function and the tympanic membrane system--a follow-up study.

The Eustachian tube function in 32 aviation trainees was comprehensively tested in simulated flights in a pressure chamber on three occasions during their training. Their mean flight experience between tests comprised 150 h in jet training planes and 260 h in jet fighters. Their capacity to clear the ears in descent did not improve convincingly between tests, but the pressure opening level in ascent was significantly lowered. The elasticity of the eardrum system was significantly increased. The results suggest that the first test, before the flight training, is reliable for selection purposes. Reasons for difficulties in finding good agreement between test results and results of actual flight training are discussed.

Aerospace Medicine↗
PubMed1982

Patency tests of the maxillary ostium in health and disease.

Three different maxillary ostial function tests (simultaneous pressure recording in nose and sinus; simultaneous differential pressure and flow recording across the ostium; pressure recording at a constant artificial air-flow into the sinus) have been evaluated on healthy subjects and used in clinical materials. No quantitative evaluation of the ostial function was possible when using the simultaneous nasosinusal pressure recording method. The ostial function can be expressed as ostial resistance or as corresponding equivalent ostial diameter with the pressure-flow and the constant artificial air-flow methods. An isolated determination of the ostial function in both sinu-nasal and naso-sinusal directions during nasal breathing was only possible with the pressure-flow method. No impaired ostial function was found in cases with maxillary pain and intrasinusal cysts, but in chronic sinusitis the ostial function was considerably deteriorated. In cases with impaired ostial function the constant artificial air-flow method does not mirror the true functional state due to the non-physiological air-flow level used. Thus, the pressure-flow method seems to be the most physiological one.

Airway Resistance↗
PubMed1981

Comparison of Eustachian tube function measured by the microflow method and a new quantitative impedance method.

Eustachian tube function in 25 applicants for flight training was tested during simulated flights using two methods alternately; the integrating microflow method with a stationary pressure chamber, and a new quantitative impedance method in combination with a new mobile pressure chamber. All ears were tested by both methods. The results of the various tests did not differ significantly between methods. The reliability of the measurements was good and almost equal in both methods. Several practical advantages with the new impedance method in combination with the mobile pressure chamber make it preferable.

Acoustic Impedance Tests↗
PubMed1980

Calculation of noise dose from time distribution of sound levels.

The noise from ten different sites in a machine factory was measured and cumulative time distributions of the sound pressure were constructed. From these distributions it is possible to calculate the energy mean level, the equivalent sound level as well as the average sound pressure level. Calculations based on knowledge of the times during which only a few sound pressure levels are exceeded give values deviating systematically from the exact value. Because of the systematic nature of the deviations corrections can be made for them. The accuracy of this method is relatively high.

Acoustics↗
PubMed1980

Noise dose measurements with stationary and ear-borne microphones.

Precision measurement of noise doses with stationary and mobile, ear-borne, microphones were made on ten workers (emery-grinders, welders and platers). The workers selected in each group differed from one another in the amount they moved about during their working day. The differences in the reverberant field at their working places were also taken into account. Very large noise dose differences, up to 20 dB, between stationary and mobile dose measurements were found and it was not possible to find any correction factors for these differences.

Acoustics↗
PubMed1980

The reliability of Békésy sweep audiometry recording and effects of the earphone position.

The hearing thresholds of subjects with hearing impairment of different severity were tested several times. The reliability of the hearing threshold measurements were analysed and compared to the inter-aural variations, the learning effects, the degree of noise-induced hearing impairment and the application of the earphones. The main factor determining the reliability of the hearing threshold is the application of the conventional earphone. A preliminary test-retest with the earphone adapted to an ear speculum for sound transmission to the external ear canal suggests that the precision of the Békésy sweep hearing threshold measurement can obviously be increased in the frequency range of 2 to 8 kHz.

Adult↗
PubMed1980

Hair cell damage in the guinea pig due to different kinds of noise.

Guinea pigs were exposed in groups of five animals to intense pure-tones or impulse noise, where either the intensity or the exposure duration was varied. The damage to the inner ear was analysed histologically and the loss of outer hair cells was used as damage parameter. The intensity in the pure-tone experimets was varied from 102 to 120 dB sound pressure level. The hair cell damage was not increasing proportionally over the entire intensity range. Above a certain critical level of intensity the damages started to increase more rapidly. This could be explained by theories stating that different mechanisms are responsible for the damage below and above the critical level. When the animals were exposed to impulse noise and the duration of the exposure was doubled the hair cell damage was also doubled up to an exposure time of 24 hours. At longer durations the increase of the damage seemed to level off. Animals exposed to impulse noise for 6 hours and with an equivalent sound level of 102 dB showed slightly higher mean damages than animals exposed to a corresponding continuous pure-tone. The results indicate that the total energy concept is a too simplified hypothesis concerning inner ear damage.

Age Factors↗
PubMed1980

The difference in protection efficiency between earplugs and earmuffs. An investigation performed at a workplace.

The hearing thresholds of shipyard workers have been measured with a Békésy sweep audiometer. The number of employees at different workplaces is so large that it is possible to select groups of workers of specified ages who have been employed by the shipyard for many years. These workers have used either earplugs of earmuffs for 5--10 years and have also been working all the time in almost the same noise environment. Three ways of investigation have been used to observe differences in the hearing levels between 'plug-men' and 'muff-men'. All three show a greater hearing impairment for 'muff-men' than for 'plug-men'. Under certain conditions earplugs provide the most effective protection although the attenuation is higher for earmuffs than for earplugs.

Adult↗