NOISESCAN- AN EXPERT SYSTEM FOR INDIVIDUAL HEARING PRESERVATIONJukka Starck, Esko ToppilaFinnish Institute of Occupational Health, Helsinki, Finland

Ilmari Pyykk Karolinska Hospital, Stockholm, Sweden

LARGE VARIATION IN NIHL PRESENT MODELS?ISO 1999-1990AGEA-WEIGHTED EQUIVALENT LEVELGENDER

The variation in NIHL according to ISO1999

RISK FACTORS CAUSING EFFECTS TO HEARING

PURPOSE OF THE STUDYTO EVALUATE THE ROLE OF VARIOUS RISK FACTORS IN THE DEVELOPMENT OF NIHLTO UTILIZE THE RESULTS IN ESTABLISHING THE HEARING CONSERVATION PROGRAM, NOISESCAN

STUDY POPULATION N=552PAPER MILL WORKERSN=285SHIPYARD WORKERSN=168FOREST WORKERSN=99MEANSTDSYSTOLIC BP (mmHg)13617DIASTOLIC BP(mmHg)8612CHOLESTEROL6.01.3LANIIN(dB)999LANIOUT (dB)1076SMOKINGY/NPAIN KILLERSY/NVWFY/N

1 risk factor=Significant difference at 95 % level

Chart3

7.59.58333333339.2307692308

7.58.33333333339.8076923077

4.16666666676.259.4230769231

7.512.516.7307692308

8.333333333315.833333333327.1153846154

1.666666666718.333333333323.0769230769

12.516.458333333326.3461538462

Lani

At least 3 risk factorsNo significant changes

Chart6

10.41666666679.573170731710.9926470588

7.58.414634146311.5073529412

8.33333333339.75609756112.9411764706

15.416666666716.280487804920.1838235294

27.522.621951219528.3088235294

16.666666666721.463414634126.6176470588

32.524.451219512231.9117647059

Lani

This is the main page of NoiseScan. By pressing the different icons or menu items the submodules can be activated. From the left side the icons are:- identification of the subject- medical history- risk analyses;smoking, solvents, pain killers- objective findings; BP, Chol- exposure to work noise- exposure to military noise- exposure to free time noise- ear status- audiograms- high frequency audiograms- tinnitus- otoacoustic emissions- ISO model- NoiseScan model

As example the window for other exposure is shown. Information about smoking, use of painkiller and exposure to solvent is asked in a user friendly simple way.

So far our model smoking and usage of painkillers are included to the model. Exposure to organic is used as an explaining factor for NIHL with no quantitative estimate.

RESULTSNOISESCANUSED AT SELECTED WORKPLACES IN THE MINE INDUSTRY, CAR MANUFACTURING, THE PAPER AND PULP INDUSTRIES, AND MILITARY OCCUPATIONS

PRELIMINARY RESULTS SHOW THAT THE SYSTEM IS VERY APPLICABLE AND HELPS OHC IN ESTABLISHING HCP

NOISESCAN HELPSIT PREDICTS INDIVIDUAL NIHLIT INCREASES ACCURACY OF EXPOSURE ESTIMATIONSIT SHOWS THE PROTECTION EFFICIENCY OF HPDsIT CAN BE USED TO COMPARE THE EFFICIENCY OF HCP ACTIONSIT CAN BE USED TO DEVELOP INDIVIDUAL HCPIT UNIFORMS CLINICAL PRACTICESIT SHOWS THE ROLE OF CONFOUNDING FACTORS IN NIHL

HOW TO GET IT?DEMO VERSION IN WWW.EISOSH.ORGVERSION 2 IN EXPERIMENTAL USE, AVAILABLE ON CD NEW VERSION AVAILABLE AUTUMN 2000 APPLICABLE BOTH FOR CLINICAL WORK AND RESEARCH PURPOSES

PUBLICATIONSStarck, Toppila, Pyykk. Management of Sophisticated Hearing Conservation Program. AJIM suppl 00:1-4(1999)Starck, Toppila, Pyykk. Smoking as a Risk Factor in Sensory Neural Hearing Loss among Workers Exposed to Occupational Noise. Acta Otolarlyngol 119:302-305 (1999)Pyykk, Toppila, Starck, Juhola, Auramo. Database for a Hearing Conservation Program. Scand Audiol 29:52-58 (2000)Toppila, Pyykk, Starck. Individual Risk Factors in the development of Noise- Induced hearing Loss. Noise and Health. Accepted for publication 2000.Toppila, Pyykk, Starck. Age and Noise- induced Hearing Loss. Occ Env Health. Accepted for publication 2000.

The development of the data base and the expert program, NoiseScan, begun approximately 10 years ago. The system is designed to utilize our earlier, as well on-going study results on risk factors that are known to increase individual susceptibility to the development of noise-induced hearing loss (NIHL).One basic concept for NoiseScan is the ISO 1999-1990 model that is based on age, total noise exposure, and gender.Risk assessment of NIHL based on ISO 1999, 1990The distribution of NIHL can be calculated based on the parameters. The percentile curves above show that the variation is large; the difference between 10th and 90th percentile is 60 dB when the subjects are exposed to a noise of 100 dB(A) for 30 years. The percentiles have been calculated for 4 the kHz audimetric frequency.Risk factors that are known to contribute to the development of NIHL can be divided into exposure and individual susceptibility factors. In exposure to work noise we should consider also the impulse content of noise, and the protection efficiency of hearing protectors (HPD). Other noise exposure, such as free time and military noise, have to be included into the calculations in order to estimate life time exposure to noise up-to-date. Organic solvents are very ototoxic and should be included to the exposure pattern. The same concerns can be attributed to the usage of pain killers and to smoking habits.

Individual risk factors include elevated blood pressure and cholesterol level. If a person has vibration induced white finger symptom, he also has a clearly higher risk for NIHL. Hereditary factors may play a remarkable role, too. However, the lack of research results has not been included in the NoisScan model. Effects can be evaluated by several methods as shown above. There are additional early detectors for NIHL than the audiometry. For example, the otoacoustic emission method can be used to localize the injured area in the cohlea.

The conclusion rules used in NoiseScan are mainly based on the studies on paper mill, forest, and shipyard workers. For each individual worker, the parameters shown above have been measured. The mean value for each parameter has been used as a criteria value in order to assign the study population into low and high risk groups. LANIIN is the total noise exposure level inside the hearing protector and LAINOUT is the corresponding level outside the hearing protector.The effect of zero or one contributing risk factor in the three exposure groups shows that the hearing level follows the different noise exposure levels. The higher the noise exposure level, the higher the hearing loss.The vertical axes is for hearing loss and the horizontal axes for audiometric frequency.In subjects with more than two contributing factors, no significant differences were found between the exposure groups. This result indicates the importance of risk factors other than noise to the development of hearing loss. The effect of noise is going to be masked by the other risk factors which can be any of those shown in figure 4.

When the data-base program is opened, several buttons are provided on the computer screen This is the main page of NoiseScan. By pressing the different icons or menu items the submodules can be activated. From the left the icons are:- identification of the subject- medical history- risk analyses: smoking, solvents, pain killers- objective findings: BP, Cholesterol- exposure to work noise- exposure to military noise- exposure to free time noise- ear status- audiograms- high frequency audiograms- tinnitus- otoacoustic emissions- ISO model- NoiseScan model

The user can either add a new case or look at existing ones. After the initial selection, other buttons are activated. The name of the subject is displayed at the top of the screen.

Reasons for hearing loss originating from reasons other than noise can be evaluated by completing the medical history screen. Ear diseases and ear operations are asked about separately on the same screen. If the answer to either of these questions is yes, a new screen is opened. Then the type of disease, operation, or ear pathology is asked about in detail. Neurological diseases and possible central nervous system infections are inquired about, and if the history is positive a screen with detailed questions follows. Explosions or head trauma are asked about, as well.

Vertigo is an indicator of inner ear disease that causes sensory neural hearing loss, mostly independent from NIHL. Tinnitus may or may not be present, and thus may increase the handicap of NIHL. A significant part of the unexplained hearing loss seems to be linked to genetic inheritance. The data base, therefore, includes a question on a possible family history of hearing difficulties. Finally, exposure to aminoglycosides and the presence of vibration, including white finger, is asked.

From the main screen, a button Risk anamnesis opens the screen which contains information on smoking habits, painkiller usage, and exposure to solvents, i.e.. factors which can increase noise effects on hearing.As an example, the window for other exposures is shown. Information about smoking, painkiller usage, and exposure to solvents is asked in a user friendly, simple way.

So far, smoking and painkiller usage are included in the model. Exposure to organic (?) is used as an explaining factor for NIHL with no quantitative estimate.Under Noise exposure button there are three buttons; work noise, free time noise and military noise buttons.Work noise

A data sheet is provided for each work task, noise exposure period, and occupation. A subject may have an unlimited number of noise exposure data sheets included to the total noise exposure calculations. Each data sheet begins with a statement of the work period duration. The time of noise exposure is asked with an accuracy of hours per day and days per week. The noise frequency content is divided into a low-medium or high-medium frequency content. If the noise level is not measured or known, the program provides hints for the noise level based on occupation, work task, environment, and machine type. All certified protectors used in Western Europe are included in the data base with their attenuation specifications. Thus, the attenuation is automatically given on the screen both for low and high frequency noise for the given HPD. In the final calculations, the protection efficiency is considered by taking into account the usage rate of HPDs also by utilizing the HML - check method, and the energy principle (EN 458 - 1993, ISO 1999-1990).

There is a separate data base file for military noise exposure. It collects data on weapon quality, the number of shots both for hand held and large caliber weapons. Also, the type and usage rate of hearing protectors is included in the evaluation of exposure to military noise.

The exposure to free-time noise is collected by using two screens. Attention is paid to shooting sound, music noise, and to work with loud power tools. The usage rate of hearing protectors is queried. In an urban society, noise from vehicles and from rock music is common. They represent a different kind of free-time noise exposure.

The audiometry screen is for feeding in the audiograms. The number of audiograms can be unlimited. When the push button is selected an empty audiogram sheet is displayed. The left mouse button is for the audiogram of the left ear, and the right button for the right ear. In the right corner of the screen, the examination year, quality of the soundproof room, calibration of the audiometry, and type of audiometry are queried. Also, the speech audiometry result can be entered.

After all factors have been entered, and provided that the noise exposure remains the same, the program calculates an estimation for hearing loss progression. The model is based on the ISO-1999-1990 model.

The right side gives a summary of the exposure both outside and inside the hearing protector. The military and free-time noise are also shown.

Pattern recognition evaluates whether the audiograms have correct a shape for noise induced hearing loss.