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PubMed1988

Auscultated fetal heart rate accelerations. III. Use of vibratory acoustic stimulation.

The auscultated acceleration test has been proposed as a simple, inexpensive screening test for fetal health; previous studies of the auscultated acceleration test used external stimulation to elicit fetal movement. This study was conducted to explore the ability of the auscultated acceleration test to predict nonstress test results when vibratory acoustic stimulation is used to elicit fetal reactivity. After antepartum nonstress testing on 100 gravid women between 28 and 43 weeks' gestation, a 6-minute auscultated acceleration test protocol was performed with two vibratory acoustic stimulations to the maternal abdomen if no spontaneous fetal heart rate acceleration occurred. The ability of the auscultated acceleration test to predict nonstress test results after selected variables were controlled for was as follows: sensitivity, 75%; specificity, 97.6%; false-positive results, 14.3%; and false-negative results, 4.7%. Logistic regression analysis indicated that, in addition to the auscultated acceleration test, gestational age and race contributed significantly to the prediction of nonstress test results. Although specificity and the false-positive rate were improved, the use of vibratory acoustic stimulations to elicit fetal movement did not improve the validity of the auscultated acceleration test in terms of sensitivity and false-negative results over previous studies. However, the auscultated acceleration test continues to show potential as an initial screening test for fetal assessment. In addition to recommendations for further research, methodologic issues related to sampling techniques are identified.

Acoustic Stimulation↗
PubMed1988

Binaural acoustic stimulation exercises protective effects at the cochlea that mimic the effects of electrical stimulation of an auditory efferent pathway.

Low-level acoustic stimulation of one (contralateral) ear reduced the neural desensitization caused by a simultaneous loud sound exposure in the other (ipsilateral) ear in a loss-related manner. Greatest reductions in the temporary threshold shifts (TTS) in the exposed ear were obtained when the exposure would have caused large amounts of TTS. Low-level exposures (reduced intensity or duration of exposure) which caused low levels of TTS, from which the cochlea could recover relatively quickly, were not affected by the contralateral stimulus. Intermediate levels of TTS showed intermediate levels of reduction for the same contralateral acoustic stimulus. These effects were similar to effects previously demonstrated with electrical stimulation of an efferent pathway to the cochlea, the crossed olivocochlear bundle (COCB); lesioning the COCB prevented the contralateral stimulus from having any effect on TTS due to an ipsilateral exposure. Like COCB stimulation, the contralateral acoustic stimulus had tonic effects, so that reductions in ipsilateral TTS could be obtained even when the contralateral stimulus was presented 5 min before the ipsilateral exposure. With 10 min delay no effect on TTS occurred. The contralateral stimulus did not appear to cause any changes in responses in the ipsilateral cochlea prior to the loud sound exposure. These results are discussed as indicating an interaction between the two inputs at a central locus, leading to activation of the COCB fibres to the cochlea exposed to the loud sound.

Acoustic Stimulation↗
PubMed1991

An evaluation of antenatal fetal acoustic stimulation.

Fetal heart rate reactivity was evaluated following acoustic stimulation testing (AST). The AST and NST (non-stress test) were compared with regards to certain adverse perinatal outcome criteria, and in a selected sample of cases, to other surveillance tests. These tests were the oxytocin challenge test (OCT) and biophysical profile (BPP). 479 tests were performed on 240 high-risk patients. The AST significantly increased fetal heart rate reactivity. With regards adverse perinatal outcome criteria, there was no significant difference between the AST and NST in relation to sensitivity, specificity or predictive values. In the 38 patients with both non-reactive NSTs and reactive ASTs, 5 (13.5%) had immediate follow-up surveillance tests (OCTs and/or BPPs) that were non-reassuring and necessitated delivery. In four of the five cases, there was evidence of potential fetal compromise. These preliminary observations suggest that the AST may have evoked reactivity in fetuses with early compromise, and raise concerns about replacing the NST with the AST as a primary screening test of fetal well-being.

Acoustic Stimulation↗
PubMed1991

[Study of fetal responses to external vibratory acoustic stimulation].

Effects of a 5-second external vibratory acoustic stimulation (VAS, 500 Hz, 75 db) were studied in 155 healthy pregnant women from 34 to 41 weeks' gestational age on the fetal heart rate and gross fetal body movement. Fetal behavioral states were also studied in 88 out of the 155 patients. The following results and conclusions were obtained. 1) VAS induced significant increases in the fetal heart rate baseline, the mean amplitude, the mean duration, and the mean time spent % of fetal heart rate accelerations and gross fetal body movements. 2) VSA induced significant changes in fetal behavioral states at states 1F and 3F, but no changes in states 2F and 4F. 3) Reaction to VAS was recognized also in the low birth weight (less than 2,500 g) group, but the duration of the reaction was shorter than that in the normal (greater than or equal to 2,500 g) group. 4) By lowering the incidence of false non reactive NST with VAS test, it was possible to predict the fetal prognosis better than NST alone. 5) Inasmuch as VAS changed the fetal behavioral state from resting phase to active phase, the use of VAS in addition to NST was very helpful in more accurate understanding of fetal heart rate monitoring.

Acoustic Stimulation↗
PubMed2003

Vestibular evoked myogenic potentials using simultaneous binaural acoustic stimulation.

The aim of this study is to investigate the feasibility of recording vestibular evoked myogenic potential (VEMP) using simultaneous binaural acoustic stimulation (B-VEMP), and compare it with that using monaural acoustic stimulation (M-VEMP). Seven healthy volunteers were evoked by initial B-VEMP test and subsequent M-VEMP test, whereas vice versa in another 7 volunteers. All 14 subjects demonstrated both B-VEMPs and M-VEMPs, without significant difference in the latencies of p13 and n23. When using interaural amplitude difference (IAD) ratio for interpreting amplitude, B-VEMPs did not differ significantly from that of M-VEMPs. Hence, B-VEMPs can produce information equivalent to M-VEMPs in terms of response rate, latencies, and IAD ratio in healthy subjects. Likewise, similar results were also shown in the patients with unilateral Meniere's disease. In conclusion, B-VEMPs provide neither different information nor less variability, as compared with M-VEMPs. In addition, B-VEMPs can offer information on unilateral inner ear (saccular) pathology similar to that by M-VEMPs. Furthermore, recording from binaural stimulation can be used as a possibly more convenient mode compared with two monaural recordings, especially when testing young or old or disabled patients, since a continuous muscular effort is required during recording.

Acoustic Stimulation↗
PubMedDate not supplied

Different behavioral and electrographic effects of acoustic stimulation and dibutyryl cyclic AMP injection into the inferior colliculus in normal and in genetically epilepsy-prone rats.

The behavioral and electrographic effects of acoustic stimulation (100 dB) and injection of dibutyryl cyclic AMP (cAMP, 10 nmol) into the inferior colliculus were studied in normal and genetically epilepsy-prone (GEPR-9) rats. Acoustic stimulations induced behavioral seizures only in GEPR-9 rats; the seizures were associated with electrographic epileptiform discharges recorded from the inferior colliculus. Injections of dibutyryl cAMP into the inferior colliculus caused wild running episodes resembling the initial phase of audiogenic seizures in both groups. However, in GEPR-9 rats these episodes progressed to significantly more severe seizures than in normal rats and the convulsions culminated into status epilepticus. During drug-induced seizures, epileptiform activity was present in the inferior colliculus in both groups. The seizure generalization latency was markedly shorter in GEPR-9 rats than in normals. Furthermore, in GEPR-9 rats, the seizure generalization latency was in the same range with either acoustic stimulation-induced or dibutyryl cAMP-induced seizures. The data suggest that the increased susceptibility of genetically epilepsy-prone rats to acoustic stimuli may be related to a malfunction of the cyclic AMP system within the inferior colliculus.

Acoustic Stimulation↗
PubMed2004

Low-frequency loud acoustic stimulation and goal-directed arm movements.

OBJECTIVE: To analyse the effects of low-frequency loud acoustic stimulation on goal-directed movements involving the arm. Low-frequency sound stimulation impairs eye stability, evokes a subjective tilt of the visual surround in subjects presenting Tullio's phenomenon and induces, in normal subjects, short-latency evoked potentials in the neck and limb muscles. MATERIAL AND METHODS: Healthy subjects performed goal-directed movements in the horizontal plane with the right (dominant) arm to a fixed 3 degree-wide target positioned at an angle of 30 degrees, with the instruction to perform fast and accurate movements to the target and to hold the final position. This fast-pointing task was performed in association with sound-induced vestibular-otolithic stimulation (110 dB SPL, 500 Hz) in the absence of visual guidance (i.e. pointing at a memorized target in the absence of target or pointer cues). Pointing errors were analysed by computing the constant errors made by the subjects (mean error). Pointing errors were also correlated with movement kinematics (movement duration, peak velocity, time to peak velocity) and with the reaction time of movement. RESULTS: The low-frequency loud acoustic stimulation modified the final position of the arm-pointing task at the memorized target in the absence of vision. CONCLUSION: Goal-directed movements are achieved by means of sensory interactions between visual, somatosensory and vestibular information and the vestibular-otolithic signals contribute to the accuracy of voluntary arm movements.

Acoustic Stimulation↗
PubMed1999

The predictive value of fetal acoustic stimulation.

OBJECTIVE: To compare the predictive abilities, test duration times, and incidence of nonreactive results in the acoustic stimulation test (AST) and the nonstress test (NST). METHOD: Four-hundred randomly selected patients, delivering within 7 days of a preceding test, were divided into two groups (group I: NST; group II: AST). In the AST group, fetal heart rate tracing were recorded for the first 5 minutes as a baseline recording. If the reactivity criterion was not met, transabdominal acoustic stimulation to the fetal head was performed. In the NST group, nonreactive tests were followed by a repeat NST. In both groups, nonreactive tests were followed by oxytocin challenge test (OCT) on the same day. Depressed 5-minute Apgar scores (< 7) and an umbilical arterial blood pH of < 7.2 were taken as indicators of fetal distress. Sensitivity, specificity, and predictive values of NST and AST were calculated and compared. RESULTS: The incidence of nonreactive tests was lower in the AST group. AST decreased the test duration time by 10.1 minutes. The sensitivity values were 87.5% in the NST group and 85.7 in the AST group; specificities of were found to be 94% for AST and 88% for NST. The negative predictive value was found to be 98% in each group, but the positive predictive value was 54.5% in the AST group and 38.8% in the NST group. CONCLUSION: AST offers benefits, by decreasing the incidence of nonreactive tests and reducing the test time. AST lowers the rate of false positives without changing the negative reliability of NST. It is a safe test and allows more efficient use of perinatal services.

Acoustic Stimulation↗
PubMed1996

Respiratory and electrocortical responses to acoustic stimulation.

Although sleep-related obstructive apnea is most often associated with transient arousal, the impact of this arousal on respiratory control remains unclear. We employed binaural tone bursts (.5 second duration) to elicit repetitive transient arousals from sleep during polygraphic recordings in 5 adult volunteers. By this method, we elicited repetitive transient arousals with a mean duration of approximately 10 seconds from all stages of sleep. With respect to the 3 pre-stimulus breaths, acoustic stimulation was associated with increased tidal volume and decreased inspiratory duration for at least 4 breaths. These respiratory responses to acoustic stimulation were not significantly influenced by either presence of transient arousal from sleep or the sleep state from which arousal occurred. We conclude that transient electro-cortical state changes may be repeatedly evoked from all sleep stages by transient acoustic stimulation in normal sleepers. This sensory stimulation represents a significant respiratory stimulus even when generalized arousal from sleep does not occur.

Acoustic Stimulation↗
PubMed1986

Fetal response to vibratory acoustic stimulation in periods of low heart rate reactivity and low activity.

The fetal response to vibratory acoustic stimulation during periods of low fetal activity and low fetal heart rate reactivity was studied in 10 healthy pregnant women at term. In each case, two periods of low reactivity were studied. Consecutive cases alternated: The vibratory acoustic stimulus was applied 10 minutes after the first nonreactive period in half of the cases; the remainder were stimulated during the second nonreactive period. The unstimulated period served as a control. After vibratory acoustic stimulation the baseline fetal heart rate, the mean number of fetal heart rate accelerations, and, the number of fetal movements were significantly increased with values in the control nonstimulated periods (p less than 0.0001). This consistent response to vibratory acoustic stimulation may prove to be clinically useful in altering periods of low reactivity observed during nonstress testing of normal fetuses.

Acoustic Stimulation↗
PubMed1986

Intrapartum assessment of fetal well-being: a comparison of fetal acoustic stimulation with acid-base determinations.

Many authorities advocate the use of fetal blood sampling as the final arbiter of abnormal intrapartum fetal heart rate patterns. Alternatively, the presence of an acceleratory fetal heart rate response to scalp stimulation during fetal scalp blood sampling led to the observation that, if present, the likelihood of acidosis was remote. Consequently a prospective intrapartum analysis of evoked accelerations and fetal acid-base status was undertaken. Patients who, on the basis of abnormal fetal heart rate patterns, were judged candidates for acid-base assessment underwent transabdominal acoustic stimulation. The presence or absence of an acceleration was then determined. Sixty-four patients with abnormal intrapartum fetal heart rate patterns underwent intrapartum acoustic stimulation. Thirty fetuses were reactive and all had a pH of greater than or equal to 7.25. Of the 34 fetuses who were nonreactive, 18 were acidotic. This preliminary observation suggests that acoustic stimulation may be a reasonable clinical alternative to fetal blood sampling when a reactive pattern is observed. In the nonreactive fetuses additional evaluation would appear warranted.

Acid-Base Equilibrium↗
PubMed1998

Fetal vibro-acoustic stimulation with a can--a clinical study.

OBJECTIVE: To assess the usefulness of the can as a fetal vibro-acoustic stimulator in the clinical environment. PATIENTS AND SETTING: 112 high-risk obstetric patients at Coronation Hospital, Johannesburg. METHOD: 161 vibro-acoustic stimulation tests with a can and 159 non-stress tests (NSTs) were performed. The results of the can test were compared with those of the NSTs and with fetal outcome at delivery. RESULTS: The can test showed poor sensitivity (5/9). Three of the 4 false-negative results were due to placental abruption that occurred subsequent to the can test. The ability of the can test to predict a reactive NST and good fetal outcome was 94% (negative predictive value). CONCLUSIONS: In view of the reasonable negative predictive value, the test should be evaluated further as a screening test at primary care level, where there are few or no cardiotocographic facilities.

Acoustic Stimulation↗
PubMed1988

Umbilical and uterine artery blood flow velocities after vibratory acoustic stimulation.

Twelve healthy pregnant women between 37 and 41 weeks' gestational age were studied to determine the effects of external vibratory acoustic stimulation on the blood flow velocity waveform in the umbilical and uterine arteries. There was a significant decrease in umbilical peak-systolic/end-diastolic ratio during the first 5 minutes after stimulus after comparison with control ratios. Analysis of the frequency distribution of instantaneous fetal heart rate values during Doppler measurements suggested that the decrease in umbilical peak-systolic/end-diastolic ratio was due to fetal tachycardia rather than a change in the placental vascular resistance. The uterine artery peak-systolic/end-diastolic ratio was not altered after vibratory acoustic stimulation.

Acoustic Stimulation↗
PubMed1991

[Clinical evaluation of antepartum vibratory acoustic stimulation test].

A prospective comparative study between antepartum vibratory acoustic stimulation test (VAS-T) and nonstress test (NST) was done in 103 pregnant women. Of the 103 cases, 101 of VAS-Ts were positive and 2 negative, with no false negative result. 76 of NSTs were positive and 27 NSTs were negative, with 26 false negative result. The mean duration of VAS-T was 56 seconds. It showed that VAS-T as an effective antepartum monitoring test was safe and much less time consuming. As compared with NST, the false negative rate of VAS-T was reduced, thus the predictive value of negative VAS-T increased. A positive VAS-T predicts with high precision that the fetal well-being is satisfactory, while a negative VAS-T prognostic that the fetal outcome is poor.

Acoustic Stimulation↗
PubMed2000

Effect of ethanol on BOLD response to acoustic stimulation: implications for neuropharmacological fMRI.

The effects of ethanol on acoustically stimulated blood oxygenation level-dependent (BOLD) signal response in healthy humans was examined with echo planar functional magnetic resonance imaging (fMRI). An acquisition mode minimizing neuronal activation by scanner noise in combination with acoustic excitation by a pulsed 1000-Hz sine tone was used. Paradigms were repeated three times before and after the ingestion of 0.7 g of ethanol/kg(body weight). Linear correlation analyses (r>/=0.40) revealed bilateral BOLD responses in the auditory cortex. Significant voxels covered a cortical volume of approximately 3 ml that was reduced by approximately 40% after ethanol. The BOLD signal change initially reaching approximately 3% was reduced by 12-27%, depending on the definition of the region of interest for signal quantitation. Because ethanol produces vasodilation, the hemodynamic contribution to the BOLD signal change was estimated by modeling the relationship between regional cerebral blood flow (rCBF) and BOLD signal changes. Assuming a baseline flow increase by 10% after ethanol intake, the resulting 'Flow-BOLD-Dependence' (FBD) curve suggested that the ethanol-related BOLD signal reduction was approximately 7-12% greater than the reduction contributed purely by vasodilation. However, simultaneous determination of rCBF and regional cerebral blood volume would be required for an exact quantitation of the neuronally induced BOLD response. Although the FBD model needs empirical validation, its cautious implementation appears to be helpful if fMRI is used in combination with vasoactive drugs.

Acoustic Stimulation↗
PubMedDate not supplied

[The relationship between the parameters of the early and late oscillations of human cortical evoked potentials and the rhythm of acoustic stimulation].

The amplitudes of all deflections of the slow auditory evoked potential (AEP) regularly decrease in alert subjects with the increase of stimulation rate. As compared with the late deflections (P2N2), the decrease of the amplitude of comparatively early deflections (N1P2) is more pronounced. It is a rather logarithmic, than a linear function of the interstimulus interval. The degree of amplitude diminution of slow AEPs due to a greater stimulation rate depends on the intensity of acoustic stimul: at greater sound intensities the decrease is more pronounced. The higher rates of stimulation produce, along with a decreased amplitude, a shorter peak latencies of all slow AEP deflections (except the peak of deflection P1). In narcotic (chloralhydrate) sleep higher rates of stimulation are not attended with any regular changes in the amplitude and peak latencies of the slow AEP.

Acoustic Stimulation↗