To date, there are objective techniques of hearing study, allow the detection of hearing loss and to determine the degree of hearing loss in children of all ages, including newborns. The most complete coverage of the newborns in order to detect hearing disorders can be achieved by performing hearing screening and the formation of groups at risk of hearing loss and deafness [6].
The most effective system for early identification of children with hearing impairment involves on the first phase registration of otoacoustic emissions (OAE), which is held on the stage of newborn maternity hospital. The advantage of the method is that the OAE can be to register on 3-th days of life the newborn. The method can also be used in premature infants [2;4].
Material and Methods
Audiological newborn screening was conducted on the basis of maternity complex in the 2-nd clinic of Tashkent medical academy. In total 446 newborns were examined. From them 388-full-term (the term of a gestation of 37 weeks and more) and 58-prematurely born (gestation term less than 37 weeks) the child. According to research problems two groups of the surveyed were allocated.
A group of 388 full-term (1-st group) newborn babies made with a gestational age of at least 37 weeks and birth weight of at least 2500 g. Gestational age in this group of infants ranged from 37 to 42 weeks, the average was 39,1 weeks; birth weight was from 2500 to 4800 g, medium — 3320, the minimum Apgar score 4 and the maximum 9. Group of 58 preterm infants (2-nd group) gestational age ranged from 26 to 36 weeks, the average stood at 28,8 weeks ; birth weight was from 1400 to 2230 g, the average was 1540. Minimum Apgar score was 2 points, maximum 8 points. Average age premature infants at the time of the inspection was 36.4 ± 2.7 weeks; full-term infants: 40.2 ± 1.3 weeks.
TEOAE (Transient-evoked OAE) and DPOAE (Distortion product OAE) conducted using standard audiological equipment «Neuro-Audio Screen» (manufacturer — Russia). To register into the ear canal is placed miniature probe, in the case of TEOAE one phone and microphone, and for registration DPOAE — two phones and a microphone.
Results of the study
Initial evaluation using TEOAE have been 446 children. In 399 (89.5%) was recorded TEOAE within normal limits.
An analysis of the characteristics of TEOAE was conducted on the basis of registration of 58 preterm and 341 full term infants. A total of 116 registrations made in preterm infants: 58 to the left ear and 58 from the right, and 682 registrations in term neonates: 341 left and 341 right.
As TEOAE characteristics were measured: TEOAE amplitude at frequencies of 1.0 kHz, 1.4 kHz, 2.0 kHz, 2.8 kHz and 4 kHz, the number frequency bands in which TEOAE been registered, the total power response.
The number of frequency bands in which the present TEOAE reflects the width of the frequency spectrum of the recorded TEOAE. Possible values: on (no TEOAE) to 5 bands (TEOAE recorded throughout the frequency spectrum). Since the results showed that the average number of frequency bands for term infants is greater than 4 and less than 4 in preterm and left and right. A significant difference in the amount semi-active frequency bands between groups of full-term and preterm infants as a right and left.
From the comparison of TEOAE in the abduction left and right shows that in full-term infants more than the total capacity of response and the number of frequency bands semi-active right. However, statistical analysis revealed no significant difference in the amplitude of the TEOAE, the total power response, the amount of any premature or full-term children.
The difference in age between term and preterm infants at the time of the inspection was 6 weeks (the age of preterm infants at the time of examination was 35.4 weeks, full-term infants 41.2 per week).
For all measured values scatter in the data (average statistical deviation) in premature infants was higher than that of full-term.
Record DPOAE was performed in 388 full-term and 58 premature infants. In total 116 registrations at prematurely born babies were made: 58 from the left ear and 58 from the right; and 776 registrations at the full-term newborns: 388 at the left and 388 on the right. Total DPOAE with one or two ear was present in 407 (91.3%) of the 446 children surveyed.
Statistical processing undergone DPOAE following characteristics: frequency band, which is registered DPOAE, the number of recorded peak amplitude response (average power DPOAE). For the analysis of frequency range at measurement of DPOAE the minimum and maximum frequencies at which there was DPOAE peak were noted.
Premature infant’s frequency range in which the recorded DPOAE proved narrower than in term: average width of the frequency range is in preterm abduction 1.3 kHz and 1.7 kHz on the left to the right, while the left term of 1.5 KHz and 1.9 kHz right. Significant differences between the width of the frequency bands in term and preterm infants had been received.
The maximum number of peaks DPOAE term infants exceeded the number of peaks in premature infants. Term infants were up to 17 peaks DPOAE abduction at the left and right side 19, while preterm children maximum number of peaks DPOAE was respectively 11 and 12, left and right. The average value of the number of peaks at the left abduction was similar in term and preterm infants. On the right the average number of peaks in term infants was significantly higher than the number of peaks in premature babies.
Average amplitude of DPOAE at the full-term babies exceeds amplitude at prematurely born children on 0.5 at assignment at the left and 2.7 dB on the right. For the right ear received significant differences between the amplitudes DPOAE preterm and full-term infants.
There was no difference between the values of the characteristics DPOAE for left and right ears, for girls and boys.
Discussion
Comparison of TEOAE between preterm and full-term infants have shown that the amplitude of the TEOAE in term infants over the entire frequency range (except f = l kHz abduction left) is greater than the amplitude of TEOAE premature. The frequency spectrum of TEOAE in full-term infants was significantly wider than in preterm with both ears.
According to [3] differences in the amplitude, frequency spectrum TEOAE between different groups of subjects are absent. However, in later works investigated the dependence of the amplitude of the TEOAE of age [1]. The results showed that the maximum amplitude of the TEOAE recorded in newborns, and gradually decreases with age, measurements were carried out in full-term newborns.
Reducing the TEOAE amplitude and the offset of the frequency spectrum to lower frequencies continues until about 2 years of life, then for about 10 years, the characteristics of TEOAE remain unchanged. Changing the characteristics of TEOAE up to two years mainly due to the changes occurring at the level of the outer and middle ear [5].
Statistical analysis showed that the presence of DPOAE not related to the degree of prematurity of the child (there is no significant correlation with gestational age or with birth weight). Premature babies DPOAE there is not only less than that of full-term, but on the contrary, according to the data obtained, recorded more frequently (tab. 1)
Table 1
TEOAE and DPOAE the examined newborns
| TEOAE | DPOAE | |||||
| Right side | Left side | Both side | Right side | Left side | Both side | |
| Number of newborns | 397 | 392 | 399 | 409 | 405 | 407 |
| 89,4% | 88,3% | 89,5% | 92,1% | 91,2% | 91,3% | |
In this paper for comparing DPOAE between term and preterm infants was found that the amplitude and the number of detected peaks DPOAE were higher in the group of full-term infants, in the abduction right obtained significant difference. Frequency range DPOAE already proved for premature infants, although significant difference was not obtained. The results obtained in this work, significant differences in the amplitude and the frequency spectrum and the TEOAE amplitude and the number of detected peaks DPOAE between preterm and term children can be explained by the difference in age between these groups of children. In this case, the difference in the characteristics of TEOAE and DPOAE between term and preterm infants is determined by the immaturity of the auditory system in preterm infants at the time of the survey, mainly its receptor department, although we cannot exclude the influence of the outer and middle ear. Effect of hypoxic state, which is experiencing almost all premature babies at birth, could hardly affect the PA results, since registration of OAE was held at oxygen independent children not in the intensive care unit or intensive care unit, blood oxygen saturation in preterm infants was within standards at the time of inspection.
CONCLUSIONS
- At prematurely born newborns in comparison with the full-term defined significantly more narrow frequency range and smaller amplitude of TEOAE.
- When registering DPOAE in preterm infants compared with term less than the amplitude of DPOAE, recorded lower peaks DPOAE, obtained significant difference for the right ear. Also, preterm infants observed a narrower frequency spectrum PIOAE.
LITERATURE
- Zhang H., Guo M., Li Y. «Characteristic of distortion product otoacoustic emissions for preterm newborn» Lin-Chuang-Er-Bi-Yan-Hou-Ke-Za- Zhi. 2004 -Jan. — 18(1): 23-6
- Finitzo T., Albright K., O’Neal J. «The newborn with hearing loss: detection in the nursery» Pediatr. 1998 Vol. 102 №6 p.1452-1460.
- Kemp D.T. Stimulated acoustic emissions from within the human auditory system. J Acoust Soc Am. 1978; 64:1386-1391.
- Korres S., Nikolopoulos T.P., Komkotou V., Balatsouras D., Kandiloros D., Constantinou D., Ferekidis E. «Newborn hearing screening: effectiveness, importance of high-risk factors, and characteristics of infants in the neonatal intensive care unit and well-baby nursery» — Otol-Neurotol. — 2005 Nov. — №26 (6)-1186-90
- Tognola G., Parazzini M., de-Jager P., Brienesse P., Ravazzani P., Grandori F., «Cochlear maturation and otoacoustic emissions in preterm infants: a time-frequency approach» — Hear-Res. — 2005 — Jan. — 199(1-2): 71-80
- White K.R., Vohr B.R., Behrens T.R. «Universal newborn hearing using transient evoked otoacoustic emission: results of the Rhode Island Hearing Assessment Project» Semin. Hearing 1993 Vol.14 p. 18-29[schema type=»book» name=»THE COMPARATIVE CHARACTERISTIC OF OTOACOUSTIC ISSUE AT NEWBORNS DEPENDING ON GESTATIONAL AGE» description=»The article presents data audiological examination of 446 newborns with registration otoacoustis issue. It was provide comparative analysis of the performance of otoacoustic emissions in term and preterm infants. In paper present the characteristic features of performance of otoacoustic emissions in premature infants.» author=»Khaydarova Gavkhar Saidahmatovna, Ahundjanov Nozim Obidovich, Nasirillaeva Oydin» publisher=»БАСАРАНОВИЧ ЕКАТЕРИНА» pubdate=»2017-01-09″ edition=»euroasia-science.ru_29-30.12.2015_12(21)» ebook=»yes» ]