Establishment Of Real-ear-to-coupler-difference Average Values Of 0-3-year Old Childrenand Its Application In Hearing Aid Fitting

With the progress of newborn hearing screening and hearing diagnosis technology,people pay more and more attention to the early intervention of hearing-impaired children.For the children diagnosedwith permanent hearing impairment,hearing aid fitting is internationally recognized as the effective means of intervention.For children with severe or profound hearing loss who belong to the candidates of cochlear implant,they also need to wear hearing aids before and after the implantation.So the number of children who needs hearing aidsare enormous.Due to the low adaptability of young hearing-impaired children,the difficulty of subjective evaluation method and the scarce of objective verification method,how to provide accurate amplification foryoung hearing-impaired children,to ensure the safety,comfort and audibilityof hearing aids is the problem in pediatric amplification field.This is an urgent problem to solve.The aim of this study is to develop a objective and valid method of hearing aid fitting for young hearing-impaired children.Insertion gain will come out when outside sound go to external ear canal through hearing aids.Besids the hearing aids,the sound pressure level is related to the volumn of external canals.So it is necessary to focus on the feature of the individual's external ear canal.Real-ear-to-coupler difference(RECD)is a method in which people's external ear canal features are considered and the sound pressure level of the external ear canal is measured objectively and accuratly.RECD is recognized as an effective method for hearing-impaired children's hearing aid fitting.Now there are the average RECD values based onforeigners in European and American area.Because of the operation complex,time-consuming and low cooperation of children in traditional RECD measurement,RECD is not widely used in clinical practice even in foreigh countries.Researches and application of RECD is few in China.There are still not the average RECD valuesbased on Chinese children.Although a few experts tried to use RECD values in hearing aid fitting for hearing-impaired children,they only can use the average RECD valuesbased on foreigners.Therefore,through RECD empirical research of 244children of 0-3 years old,we want to develop a new and quick RECD measurement method and establish a set of average RECD values base on Chinese children.Then we will check out the vadility of the averge RECD valuesin hearing aids fitting through a follow-up study.This researchaims to explore anobjective and effective hearing aid fitting method suitable for young children with hearing impairment.We hope to improve the efficiency of fitting and enhance the quality of rehabilitation of the children with hearing impairment.Based on an overall review of related researches,the main body of this study is divided into four parts.Part I is the development and validation of a new RECD measuring method.Part II is the establishment of a set of RECD reference standard of 0-3-year-old Chinese children and comparison between Chinese RECD average values and those ones from foreign countries.Part III is the comparison of the goodness of fit between real gain and goal gain of hearing aids under two RECD conditions:Chinese RECD average values and foreign average values.Part IV is the verification of RECD method during hearing aid fitting for young hearing-impaired children.The specific methods and results of the four parts are as follows:Part I:A new RECD measuring method,Tube Fixation and Synchronous Insertion Method(TFSI),was developed after manytrials.The method was convenient,effective,and easy to cooperate for children.Twenty subjects(40 ears)were measured with the conventional RECD measuring method and TFSImethodrespectively.The two sets of RECD values were shown no significant difference(P>0.05).The operation time of using TFSI method(2.15 min)was significantly less than that of using the conventional method(6.03 min)(P<0.05).Thirteen subjects(26 ears)were tested twice with TFSI method.The twice RECD values were compared and proved to have no significant difference(P>0.05).The new RECD measuring method was proved to be effective,time-saving and repeatable.Part?:RECD reference standard of Chinese children below 36 months were established.188 hearing normal children below 3 years received RECD measurement.Almost each child received RECD tests for both left and right ears,so 338 RECD values were collected.The data were divided into 5 groups.Group 1 were 153 values from children at the age of 0-11 months,Group 2 were 96 values from children at the age of 12-23 months and Group 3 were 89 values from children at the age of 24-35 months.Logarithmic regression equations were set up on the base of regression analysis.RECD reference standard(average values)of each month for Chinese children below 36 months were established.It was showed that there were significant difference between Chinese RECD average values and those ones from other countries.The results prompted that it was not appropriate to apply RECD average values from other countries into hearing aid fitting for Chinese children with hearing loss.There were no significant differences between left-ear and right-ear RECD values(P>0.05).There were no significant differences between RECD values of boys and girls(P>0.05).The RECD values of different frequencies(125-8000 Hz)were different significantly(P<0.05).The higher the frequency was,the bigger the RECD values were.Part ?:Twenty hearing-impaired children(32 ears)below 3 years old received hearing aids fitting with application of Chinese RECD reference standard and foreign RECD average values respectively.The goodness of fit between real gain and goal gain were compared between the two RECD conditions.The results showed that the goodness of fit under Chinese RECD reference standard condition was better than that under the the foreign RECD average value condition(P<0.01).It is suggested that it is not appropriate to apply RECD average values from other countries into hearing aid fitting for Chinese children with hearing loss.Part ?:Thirty-six hearing-impaired children below 3 years received hearing aids fitting with the Chinese RECD reference standard.Common evaluations such as aided hearing thresholds,Ling's Six-sound detection test,three auditory questionnaires(IT-MAIS,LEAQ,CAP)and speech audiometry(vowal recognition and consnant recognition)were used before and 1 month,3 months,6 months after the fitting.All the scores of the tests were higher than those ones in the beginning.The results indicated that the children made continuous progress in atuditory development.Three children below 3 years,with moderate,severe,profound hearing loss respectively,were examined as typical cases.They also achieved continuous improvement in auditory skills.So the Chinese RECD reference standard was proved to be effective during hearing aid fitting for young hearing-impaired children.The main innovations of this study are the following:(1)The RECD reference standard(average values)of 0-3-year-old children in China was established.The average values are useful for hearing aid fitting of young children with hearing loss.For those hearing aid dispencers who have no real ear systems or cannot measure RECD for children,they can use the RECD reference standard easily in the process of hearing aid fitting for young children with hearing loss.(2)A new RECD measuring method,Tube Fixation and Synchronous Insertion Method(TFSI),was developed and proved to be quick,valid and suitable for children.It is expected to enlarge the application of RECD method.(3)It is proved that the Chinese RECD reference standard were different from the RECD average values from foreign countries.It is credible to use the Chinese RECD reference standard during the fitting of hearing aids for Chinese children.(4)Chinese RECD reference standard was confirmed to be efficient for hearing aid fitting through practical studies.It provided anew approach of fitting for young children with hearing impairment.(5)A set of hearing aid fitting procedure with RECD method is put forward.It is helpful for improving hearing-impaired children's rehabilitation.