Acoustic Stimulation Test Research Articles

Evaluation of the Contralateral Acoustic Stimulation Test After Audiological Examination of the Central Auditory System in Individuals with Normal Hearing

The aim of our study was to evaluate the contralateral acoustic stimulation tests of central auditory system after audiological examination of individuals with normal hearing. In this context, a number of criteria were considered for the determination of individuals with normal hearing. Normal hearing provides the ability to live independently in the social environment of an individual, and the level of hearing is considered necessary for enabling communication with the environment. A total of 15 individuals were included in our study. In all individuals, five different frequencies were obtained compared to the threshold for both ears. The frequencies were 1000 Hz, 1414 Hz, 2000 Hz, 2828 Hz and 4000 Hz; and the suppression thresholds were also measured. After audiological tests were performed for our study, the same measurements were repeated. Looking at the results of the study, a statistically significant difference was found between the measurement results for right and left ears in individuals with normal hearing (P<0.05). Result: In order to see the suppressive effect, the integrity of the neural structures must be preserved starting from the medial nucleus of the superior olivary complex and reaching the OHCs. According to the results obtained in our study, we can conclude that MOCR is active, and the central nervous system is not impaired after the audiological evaluation. However, it is thought that a further study should be conducted with a larger sample group in order to obtain more specific results. Keywords: Contralateral suppression, normal hearing, otoacoustic emissions DOI: 10.7176/JHMN/87-06 Publication date: March 31 st 2021

Fetal acoustic stimulation test for early intrapartum fetal monitoring

The fetal acoustic stimulation test (FAST) is a simple cost effective screening test for antenatal fetal monitoring. The aim of the study was to evaluate the FAST as a screening test for early intrapartum fetal well being. An initial non stress test (NST) followed by a FAST using corometric model 146 was carried out in 486 participants in early labour with uncomplicated singleton pregnancies and > 32 weeks gestation. A repeat NST was recorded in the participants who had an initial non reactive NST. The results of the NST and FAST were compared with fetal outcome. Maternal perception of fetal movements after FAST, results of NST before and after FAST, and the babies' 5 minute APGAR scores were measured. Of the 486 participants 413 (85%) noticed fetal movements after FAST. Initial NST was non reactive in 203 (42%) but 149 (31%) became reactive after FAST. Compared to the NST, FAST had a better sensitivity (97% vs 62%, p < 0.001), specificity (100% vs 87%, p = 0.017), positive predictive value (100% vs 98%, p = 0.024), negative predictive value (79% vs 17%, p < 0.001) and accuracy (99%vs 64%, p < 0.001) in predicting 5 minute APGAR < 7 in the baby. FAST is a reliable screening test for assessing fetal well being in early labour. It complements the NST and is better than the NST alone.

Comparative Study of Nonstress Test and Fetal Acoustic Stimulation Test in Assessment of Fetal Well-being

ABSTRACT Objectives To compare and evaluate the role of nonstress test and acoustic stimulation test on the perinatal outcome. Materials and methods Around 100 patients above 34 weeks of gestation were selected and subjected to nonstress test (NST) and acoustic stimulation test (AST) on weekly basis to find whether fetus is reactive or nonreactive, and followed till delivery to find out the perinatal outcome. Results When comparison of reactive NST and reactive AST was done, the incidence of meconium staining was 8 (9%) and 9 (9.6%), clinical fetal distress 16 (18.8%) and 18 (19.3%), operative interference for fetal distress 17 (19.3%) and 20 (21.5%), low Apgar score at 5 minutes 1 (1.1%) and 1 (1%), neonatal deaths 3 (3.3%) and 3 (3.2%), low birth weight 27 (30.6%) and 29 (31.1%), and NICU admission 13 (14.7%) and 13 (13.9%) respectively. While the incidence of meconium staining was 4 (33.3%) and 3 (42.8%), clincal fetal distress 8 (66.6%) and 6 (85.7%), operative interference 6 (50%) and 3 (42.8%), low Apgar score at 5 minutes 3 (25%) and 3 (42.8%), neonatal death 4 (33.3%) and 4 (57.1%), low birth weight 7 (58.3%) and 5 (71.4%) respectively in nonreactive NST and nonreactive AST groups.

The fetal acoustic stimulation test: a reliable and cost effective method of antepartum fetal monitoring

A healthy foetus, if exposed to external sound stimulation, often responds with vigorous movements which can be felt by the mother. A hypoxic foetus usually does not show this response. To evaluate the fetal acoustic stimulation test (FAST) in antepartum fetal monitoring. Prospective interventional study carried out at the Teaching Hospital, Galle. An initial non-stress test (NST) followed by a FAST using the Corometric model 146 was carried out in 423 high risk pregnant women. The response to FAST was assessed and compared with the NST. A repeat NST was recorded in women who had an initial non-reactive NST. The results of the NST and FAST were compared with the fetal outcome if the woman delivered within 24 hours. Maternal perception of fetal movements after FAST, results of NST before and after FAST, and the babies' 5 minute Apgar scores if delivered within 24 hours of the FAST. Of the women, 349 (82.5%) noticed fetal movements after FAST. Of the 167 women who complained of absent or reduced fetal movements, 67% felt fetal movements after FAST. Ninety one had a nonreactive NST and 43 (47%) became reactive after FAST. Compared to the NST, the FAST had less sensitivity (93% vs 100%, p = 0.01), better specificity (79% vs 45%, p = 0.001), better positive predictive value (67% vs 50%, p = 0.02), similar negative predictive values (96% vs 100%, p > 0.05) and better accuracy (83% vs 69%, p = 0.03) in predicting neonatal asphyxia (5 minute Apgar score < 7) if the baby was delivered within 24 hours after the test. The FAST is a reliable, cost effective screening test for antepartum fetal monitoring. It significantly reduces the false positive (non-reactive) NST and has a good negative predictive value.

Fetal acoustic stimulation for early intrapartum assessment of fetal well-being

Fetal heart rate monitoring is widely used to assess fetal well-being during labor. A 20-min recording of the fetal heart rate immediately after Ž . the admission of patients in labor admission test may be of value as a screening procedure for fetal w x distress 1 . In a busy labor ward without a sufficiency of monitors and personnel, the obstetrician may be greatly aided by an evaluation performed early in the course of labor that can differentiate the fetus likely to tolerate the stress of labor from one that cannot. The usefulness of fetal acoustic stimulation in the early intrapartum period was considered to be the clinical application of a w x screening technique 2]4 . The aim of this study is to evaluate the usefulness of fetal acoustic stimulation test in the early intrapartum period as a screening test to predict perinatal outcome. This prospective study was performed in the labor room of Ramathibodi Hospital, Mahidol University, Bangkok, Thailand. Inclusion criteria

A randomized controlled trial of a new fetal acoustic stimulation test for fetal well-being

OBJECTIVES: Our purpose was to determine (1) whether a fetal acoustic stimulation test results in more palpable fetal movement compared with a mock test (control) and (2) whether palpated fetal movements after a fetal acoustic stimulation test are accompanied by a reactive nonstress test. STUDY DESIGN: In a randomized controlled trial we studied women seen in the labor and delivery suite for various indications. Women were excluded for multiple gestation, <31 weeks' gestational age, treatment with magnesium sulfate or narcotics, or ruptured membranes. Informed consent was obtained from eligible women, who were then randomized to a test or control group. We placed an acoustic stimulator on the abdomen of each woman, but only the test group was stimulated. We assessed fetal movement by a grading system: 0 = no fetal movement felt by patient or tester, 1 = fetal movement felt by patient only, 2 = fetal movement felt by tester, 3 = visual movement seen by tester. A positive fetal acoustic stimulation test result was defined as one with any fetal movement felt or seen by the tester (grades 2 or 3). We then performed a nonstress test. We compared rates of a positive fetal acoustic stimulation test in the test and control groups with the χ 2 test. A p value <0.05 was considered significant. RESULTS: We randomized 297 women to the test group and 280 women to the control (mock test) group. Of women tested with the fetal acoustic stimulation test, 81% had fetal movement by palpation or visualization (grades 2 or 3) compared with 19% of the control group ( p < 0.0001, odds ratio 19.29, 95% confidence interval 12.42 to 30.07). Of the test group, 283 (95%) had a reactive nonstress test and 14 (5%) had nonreactive tests; the control group had 267 (95%) reactive and 13 (5%) nonreactive nonstress tests. Of 242 patients in the test group with a positive fetal acoustic stimulation test, 236 (98%) had a reactive nonstress test. Of those in the test group with fewer than three contractions per 10 minutes, 164 (89%) had a positive fetal acoustic stimulation test. Of these, 162 (99%) had a reactive nonstress test. CONCLUSION: The fetal acoustic stimulation test evokes significantly more palpated or visualized fetal movement than in controls. Palpated or visualized fetal movement after acoustic stimulation was almost always accompanied by a reactive nonstress test. (Am J Obstet Gynecol 1997;176:1386-8.)

Search for the most predictive tests of fetal well-being in early labor

The aim of the study was to evaluate the admission CTG alone and in combination with the following tests: fetal acoustic stimulation test (FAST), maternal perception of sound provoked fetal movement (mpSPFM), amniotic fluid index (AFI), and umbilical artery doppler studies in early labor. 1092 singleton pregnancies in cephalic presentation, and with intact amniotic membranes at 37 weeks gestation or more, were admitted in early labor to the labor ward at the National University Hospital, Singapore. Admission tests were performed, and labor managed according to established labor ward protocol. Of all the tests performed, only the results of the admission CTG and color of the amniotic fluid were known to the obstetrician. If the admission CTG is normal, AFI is > 5 cm and there is an acceleratory responses to FAST the incidence of fetal distress is low. In the presence of a reactive admission CTG and in the absence of thick meconium, fetal heart rate response to FAST and the AFI provided a better selection of the high risk fetus that would require closer monitoring or early delivery. When the admission CTG was suspicious, FAST, AFI, and blood flow velocity waveform studies may allow more confident prediction of the ability of the fetus to withstand the stresses of labor.

Fetal acoustic stimulation test: Stimulus features of three artificial larynges recorded in sheep

OBJECTIVE: The purpose of the current study was to evaluate the characteristics of vibroacoustic devices used for fetal stimulation. STUDY DESIGN: Intrauterine sound pressure levels over a frequency range of 40 to 5000 Hz were measured with hydrophones in anesthetized sheep. Stimulators included the AT&T (Martinsburg, W.V.) and Servox (Hearing Instruments, Piscataway, N.J.) artificial larynges, the Corometrics fetal acoustic stimulator (Wallingford, Conn.) and an electric toothbrush. RESULTS: Intrauterine spectral patterns resulting from stimulation with the AT&T, Servox, and Corometrics devices were characterized by numerous high-level overtones above a fundamental frequency between 97 and 163 Hz. Fundamental frequencies recorded during toothbrush stimulation were 22 to 24 Hz with reduced but identifiable overtones up to 250 Hz. CONCLUSIONS: Fetal vibroacoustic stimulators that operate on the principle of the electronic artificial larynx produce very similar intrauterine sound pressure levels.

The acoustic stimulation test and antenatal cardiotocography as diagnostic tools in high risk pregnancies

SummaryA prospective random allocation clinical trial was undertaken to compare standard antenatal cardiotocography with the fetal acoustic stimulation test. Two hundred and twenty-five patients with high risk pregnancies at term had either standard cardiotocography (group I) or an acoustic stimulation test (group II). The incidences of non-reactive tests was 10 per cent in group I and 15 per cent in group II did not differ statistically. Fetal distress occurred during labour in 13 per cent in patients with reactive cardiotocograms and 75 per cent if the record was unreactive (P < 0˙001); and in 12 per cent with reactive and 81 per cent with non-reactive acoustic stimulation tests (P < 0 ˙001). Standard antenatal cardiotocography and the acoustic stimulation test are equally valuable in detecting fetal distress in high risk term pregnancies. The acoustic stimulation test offers the advantage of reducing testing time and can be used to confirm a non-reactive standard test.

The role of intrapartum vibroacoustic stimulation in the prediction of neonatal myasthenia gravis

Background — The exact mechanism for the development of neonatal myasthenia gravis is unclear, and the occurrence of neonatal myasthenia gravis cannot be predicted. Case — A case of normal duration of fetal forearm extention with return to flexion in response to vibroacoustic stimulation, and the pertinent details concerning neonatal myasthenia gravis and vibroacoustic stimulation test are described. Conclusion — Inasmuch as fetal acoustic stimulation test results in a fetal reaction resembling the startle response of the newborn, we think that it will be worthwhile to perform this test antenatally in the next encountered fetuses of myasthenic mothers in order to assess its role in the prediction of neonatal myasthenia gravis.

Should assessment of amniotic fluid volume form an integral part of antenatal fetal surveillance of high risk pregnancy?

This study was conducted to evaluate the role of the Amniotic Fluid Index (AFI), used along with nonstress cardiotocography (NST) and fetal acoustic stimulation test (FAST), when required, in prediction of adverse pregnancy outcome. Over a 3-year period 565 pregnant women had antepartum fetal surveillance due to various high risk pregnancy factors and delivered within 7 days of the test. Antepartum fetal surveillance included nonstress cardiotocography together with estimation of AFI. Need for induction of labour, presence of meconium at rupture of membranes, Caesarean section for fetal distress, Apgar score at 5 minutes, need for neonatal endotracheal intubation, admission to neonatal special care unit and perinatal death were the main outcome measures. Nonreactive nonstress tests and Caesarean sections for fetal distress were more common and neonatal outcome was significantly poorer in patients with AFI < 5 cm than in those with higher AFI values. Of the 4 perinatal deaths in the group with AFI < 5 cm, 3 had a reactive NST within 7 days of fetal death. It is concluded that pregnancy outcome is often poor in the presence of very low AFI and in these cases a reactive NST loses its usual reassuring value. It is suggested that AFI estimation should be included as an integral part of antepartum fetal surveillance of high risk pregnancies.

No evidence of hearing loss due to fetal acoustic stimulation test : Arulkumaran S.; Skurr B.; Tong H.; Kek L.P.; Yeoh K.H.; Ratnam S.S.OBSTET. GYNECOL. (1991) 78/2 (283–285)

The fetal acoustic stimulation test is used increasingly for fetal assessment. To evaluate the possibility of acoustic trauma, 465 children who had been exposed to vibroacoustic stimulation in utero were screened at 4 years of age for high-frequency hearing loss. A hand-held audiometer with test tones at 25 dB for 1000 and 4000 Hz was used because responses at this level indicate hearing within normal limits for middle and high frequencies. Thirty-one children failed the test. Failure to respond was followed by inspection of the ear canal for wax, tympanometry, and reflex measurement to assess the tympanic membrane, middle ear, and eustachian tube. Hearing was retested across the full frequency range using conventional audiometric technique, and referral for otolaryngologic examination and treatment was made if necessary. The causes of hearing loss were impacted wax in 12, current or recent upper respiratory tract infection with eustachian tube dysfunction and middle ear effusion in 15, and unresolved middle ear effusion after treatment with antibiotics for otitis media in two. Profound bilateral sensorineural hearing loss of unknown origin was found in one and slight bilateral gently sloping hearing loss in another. Retesting of all children with conductive hearing loss indicated that hearing had returned to normal after treatment. None of the children showed evidence of hearing loss.

Fetal panting: Yet another response to the external vibratory acoustic stimulation test

Fetal panting at a rate of 119 respiratory movements per minute, persisting for 40 minutes after external vibratory acoustic stimulation, was noted in a fetus at 33 weeks' gestation. Subsequent fetal outcome was good. The possible underlying pathophysiologic mechanism is discussed.

653 The acoustic stimulation test (AST) as a predictor of fetal outcome

653 The acoustic stimulation test (AST) as a predictor of fetal outcome

Fetal acoustic stimulation in early labor in patients screened with the admission test

Fetal heart rate reactions to the fetal acoustic stimulation test were investigated in 952 women in early labor. All had cephalic presentations (>33 weeks of gestation) and were screened with a 15-minute fetal heart rate recording (admission test) before the sound stimulation was applied. Three different types of responses were observed: type I, an accelerative response; type II, a biphasic response with acceleration(s) followed by a deceleration; type III, no response or a prolonged deceleration (>60 beats/min and >60 seconds). A type I response was recorded in 98.0% of the women after a reactive admission test result, in 90.2% after an equivocal admission test result, and in 42.9% after an ominous admission test result. Fetal distress in labor occurred in these three groups in 2.0%, 22.2%, and 35.7% of cases, respectively. The risk for fetal distress was high after an ominous admission test and a type III response on the fetal acoustic stimulation test (75.0%). The fetal acoustic stimulation test might be of value in labor and give additional information about fetal well-being in patients previously screened by the admission test. Testing time can be shortened after an equivocal admission test.

Fetal acoustic stimulation testing

Abstract Antepartum fetal heart rate testing, specifically the nonstress test, is of accepted value in the antenatal surveillance of high-risk pregnancies. Fetal rest-activity cycles coupled with arbitrary test intervals appear to lead to falsely nonreactive tests. Methods to alter fetal behavioral states have not been uniformly successful. A retrospective analysis of the adjunctive use of acoustic stimulation at our institution demonstrated a 50% reduction in the number of nonreactive tests. Consequently a prospective randomized clinical trial was undertaken to compare the standard nonstress test with the fetal acoustic stimulation test. Those patients randomized to the fetal acoustic stimulation test underwent transabdominal acoustic stimulation with a Model 5C electronic artificial larynx. The incidence of nonreactive tests was 14% in the control group and 9% in the study group ( K 2 = 11.09, p=0.004). A significant reduction in testing time was also observed. The fetal acoustic stimulation test offers advantages over the traditional nonstress test by lowering the incidence of nonreactive tests and reducing testing time.

Fetal acoustic stimulation testing: II. A randomized clinical comparison with the nonstress test

Antepartum fetal heart rate testing, specifically the nonstress test, is of accepted value in the antenatal surveillance of high-risk pregnancies. Fetal rest-activity cycles coupled with arbitrary test intervals appear to lead to falsely nonreactive tests. Methods to alter fetal behavioral states have not been uniformly successful. A retrospective analysis of the adjunctive use of acoustic stimulation at our institution demonstrated a 50% reduction in the number of nonreactive tests. Consequently a prospective randomized clinical trial was undertaken to compare the standard nonstress test with the fetal acoustic stimulation test. Those patients randomized to the fetal acoustic stimulation test underwent transabdominal acoustic stimulation with a Model 5C electronic artificial larynx. The incidence of nonreactive tests was 14% in the control group and 9% in the study group (K2 = 11.09, p = 0.004). A significant reduction in testing time was also observed. The fetal acoustic stimulation test offers advantages over the traditional nonstress test by lowering the incidence of nonreactive tests and reducing testing time.

Fetal acoustic stimulation testing: A retrospective experience with the fetal acoustic stimulation test

The nonstress test is of accepted value in the surveillance of high-risk pregnancies. In order to improve the efficiency of testing, the authors retrospectively evaluated the adjunctive use of acoustic stimulation testing (FAS-TEST) in 1241 patients who underwent 3464 antepartum fetal heart rate tests. The results were compared to those in the previous 6 months during which time 1307 patients underwent 3573 nonstress tosts. The frequency of nonreactive tests was 12.6% in the nonstress test group and 6.1% in those patients who underwent the FAS-TEST. The antepartum fetal death rates were not significantly different when the two groups were compared. The FAS-TEST decreases the percentage of nonreactive tests in a high-risk population and, as a consequence, may reduce the testing time.

Antepartum fetal heart rate response to sound stimulation: The acoustic stimulation test

The fetal heart rate acceleration response to an acoustic stimulation was compared to the traditional nonstress test in regard to pregnancy outcome, as reflected by the incidence of intrapartum fetal distress, meconium staining of the amniotic fluid, 1- and 5-minute Apgar scores, and perinatal mortality. Fetuses with spontaneous or sound-generated reactivity had comparably good outcomes with respect to all outcome measures investigated. Fetuses who lacked spontaneous or sound-stimulated reactivity had an increased risk for intrapartum fetal distress. The acoustic stimulation test is a safe and rapid test of fetoplacental sufficiency that appears to perform comparably to the nonstress test. The acoustic stimulation test significantly shortens total antepartum testing time and expense.