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PubMed1990

Fetal acoustic stimulation in the early intrapartum period as a predictor of subsequent fetal condition.

Fetal acoustic stimulation has recently received much attention in the literature. This study evaluates fetal acoustic stimulation in the early intrapartum period as a predictor of subsequent fetal condition. The study group consisted of 201 patients, approximately 60% of whom had complicated pregnancies. All were in the latent phase of labor with singleton, vertex-presenting fetuses. Gestational age ranged from 37 to 43 weeks. Fourteen of the 201 fetuses (7%) showed a nonreactive response to fetal acoustic stimulation and those fetuses were at significantly greater risk of initial and subsequent abnormal fetal heart rate patterns, meconium staining, and cesarean delivery because of fetal distress and Apgar scores less than 7 at both 1 and 5 minutes. Transient fetal heart rate decelerations after a reactive response occurred in 25% of patients; however, fetal outcome was not worse in this group. A reactive response to fetal acoustic stimulation was associated with high specificity and negative predictive values. Therefore we conclude that fetal acoustic stimulation in the early intraprtum period may discriminate the compromised from the noncompromised fetus.

Acoustic Stimulation↗

PubMed1996

Is intrapartum vibratory acoustic stimulation a valid alternative to fetal scalp pH determination?

OBJECTIVES: To determine the association between fetal heart rate accelerations, whether spontaneous or induced by vibratory acoustic stimulation, and subsequent scalp pH values in presence of a suspicious intrapartum fetal heart rate tracing, and thereby assess the ability of accelerations to predict a concurrent normal fetal scalp blood pH. DESIGN: Prospective observational study of 253 labours involving 421 pH samples. SETTING: Tertiary care university hospital of Genoeva. INTERVENTION: Vibratory acoustic stimulation through the maternal abdominal wall for five seconds prior to fetal blood sampling. MAIN OUTCOME MEASURES: Spontaneous fetal heart rate reactivity (accelerations) in the 10 min preceding vibratory acoustic stimulation, vibratory acoustic-induced reactivity prior to fetal blood sampling, and scalp pH value. RESULTS: The positive predictive value of a reactive fetal heart rate response after vibratory acoustic stimulation was 78% (95% CI 73-84%) and 97% (95% CI 94-99%) for scalp pH values of > 7.25 and > or = 7.20, respectively. Similar observations occurred with spontaneous reactivity. Of concern, 7 out of 31 (23%) occasions where the scalp blood pH was less than 7.20 appeared to be associated with a normal fetal heart rate response to vibratory acoustic stimulation. CONCLUSION: Fetal heart rate acceleration induced by vibratory acoustic stimulation was significantly associated with a normal scalp blood pH higher than 7.25. However, vibratory acoustic stimulation offers no advantage over observation of spontaneous fetal heart rate tracings and cannot safely replace fetal blood sampling during labour.

Acoustic Stimulation↗

PubMed1981

Stimulated acoustic emissions in the ear canal of the gerbil.

Ear-canal sound pressure and cochlear potentials were monitored inthe anesthetized gerbil to study the origins of acoustic emissions produced by transient and continuous stimuli. No evidence was found of any delayed emissions (echoes) originating within the cochlea in the acoustic or cochlear microphonic (CM) waveforms. However, strong acoustic and CM distortion products occurred when two primary tones of moderate levels were presented to the ear; the site of origin of these products was traced to the cochlea. Further, the levels of distortion followed a complex time course after anoxia, often becoming stronger after animal death for up to one hour, then decaying to the noise floor of the system. The disappearance of the distortion products was coincident with elimination of both the negative endocochlear potential and the CM response to a fundamental tone.

Acoustic Stimulation↗

PubMed1992

Computerised cardiotocography following vibro-acoustic stimulation.

To study the effect of vibro-acoustic stimulation (VAS) to the mean fetal heart rate (FHR), period of high and low FHR variation, overall variation (msec and bpm) and short term variation (msec). In a prospective study 17 pregnant women between 34-42 weeks gestation admitted to antenatal ward for obstetric complications two 60 min FHR recording was carried out with an interval of 30 min in between recordings. On a random basis the fetus was stimulated by a vibro-acoustic stimulator for 5 sec at the beginning of one of the two 60 min FHR recordings. Automated analysis of the FHR, tocodynamometry, and maternal perception of fetal movements was done by a commercially available computerized programme (System 8000). It was possible to obtain the two 60 min recordings with signal loss of < 10% in 12 out of 17 patients. No changes were observed when the FHR parameters for 60 min after VAS was compared with the control period. When analyzed in segments of 0 to 10, 11 to 20, 20 to 40 and 41 to 60 min the mean baseline FHR was significantly higher after VAS during the first 10 minutes compared with any 10 or 20 min segment of the control period or any such segments 10 min after VAS. Concomitantly the overall variation and short-term variation was significantly lower during the first 10 minutes following VAS (p < 0.05) compared with the parameters in the corresponding periods during the control period.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗

PubMed1995

Correlation of fetal heart rate decelerations following acoustic stimulation with perinatal outcome.

This was a retrospective study of acoustic stimulation response and perinatal outcome of 688 fetuses undergoing nonstress testing. Acoustic stimulation was performed within 7 days of delivery, and responses were classified based on the presence of an acceleration, deceleration, or both. Responses were correlated with perinatal outcome. Abnormal outcome was defined as: cesarean section for nonreassuring fetal heart rate patterns with an acidotic umbilical artery cord gas; delivery at less than 32 weeks for nonreassuring antenatal fetal testing; meconium aspiration syndrome or mechanical ventilation at 36 weeks or greater; neonatal seizures; 5-minute Apgar score less than 7; and stillbirth. Fetuses who demonstrated deceleration responses were significantly more likely to have abnormal perinatal outcomes when compared with those with acceleration responses (p < 0.001). Although combination acceleration-deceleration responses were more often associated with abnormal perinatal outcome when compared with pure acceleration responses, differences were not significant. A deceleration response following acoustic stimulation is associated with increased risk for adverse perinatal outcome and may merit further evaluation.

Acoustic Stimulation↗

PubMed1989

The acoustic stimulation test in the anencephalus: preliminary results.

It is not yet clear whether the acoustic stimulus influences the fetus by auditory or vibrational pathways. The anencephalic fetus is an interesting model for the study of the pathway for receipt of acoustic stimulation because of the near absence of cerebral hemispheres. After the traditional nonstress test (NST), the response to acoustic stimulation was assessed in eight fetal heart rate (FHR) recordings of six anencephalic fetuses of gestational age between 18 and 39 weeks. Although four preterm fetuses demonstrated nonreactive results in the NST, two term fetuses revealed reactive NSTs. However, none of these six anencephalic fetuses responded to acoustic stimulation. These data suggest that the cerebral cortex is the origin or transmission route of the FHR response to acoustic stimulation. We hypothesize that the normal fetus might receive externally applied sounds via auditory pathways rather than vibratory pathways, at least in term pregnancy.

Acoustic Stimulation↗

PubMed1988

A critical appraisal of fetal acoustic stimulation as an antenatal test for fetal well-being.

Fetal acoustic stimulation is becoming a common modality for antepartum testing. The purpose of this study was to review the available literature on the subject to establish whether safety and efficacy have been determined. Safety could not be substantiated. The frequency, intensity, duration, and number of stimuli varied greatly among publications. There is no uniform nomenclature to score test results, and even the definition of the fetal acoustic stimulation test is not uniform. Data on the efficacy of the test are limited. Before fetal acoustic stimulation becomes part of standard obstetric care, rigorous clinical testing is required.

Acoustic Stimulation↗

PubMed2026

Transient acoustic stimulation induces time-dependent synaptic remodeling and enhancement of auditory nerve output after threshold recovery.

BACKGROUND: Acoustic stress can alter cochlear function even in the absence of permanent threshold elevation; however, synaptic consequences of transient acoustic stimulation remain incompletely understood. OBJECTIVE: This study aimed to investigate whether transient acoustic stimulation induces changes in the auditory nerve output and cochlear ribbon synapse morphology following hearing threshold recovery. METHODS: Young adult CBA/CaJ mice were exposed to band-limited acoustic stimulation (45-2,000 Hz, 95 dB SPL, 2 h). Auditory brainstem responses (ABRs), hair cell and spiral ganglion neuron survival, and synaptic morphology were evaluated before exposure and up to 2 weeks post-exposure. RESULTS: ABR thresholds were transiently elevated immediately after exposure but largely recovered by 1 day post-exposure. In contrast, ABR wave I amplitudes significantly increased after threshold recovery across multiple test frequencies. Ribbon-associated puncta in both inner and outer hair cell regions exhibited biphasic temporal changes, with an initial decrease immediately after exposure followed by an increase at 1 day post-exposure. The ribbon-associated punctal area also increased after exposure and remained elevated at later post-exposure time points. No significant loss of hair cells or spiral ganglion neurons was observed. Exploratory genomic analysis suggested enrichment of pathways related to metabolic defense and cellular stress responses. CONCLUSIONS: Transient acoustic stimulation induces time-dependent synaptic remodeling and enhancement of peripheral auditory nerve output without overt cellular degeneration. These findings support a model in which early cochlear responses to acoustic perturbation include adaptive synaptic plasticity and gain regulation, extending current concepts of noise-induced cochlear change beyond irreversible synaptic loss.

Animals↗

PubMed2004

Differentiation between benign and malignant hepatic lesions: utility of color stimulated acoustic emission with the microbubble contrast agent Levovist.

OBJECTIVE: This study was undertaken to determine whether the examination of color stimulated acoustic emission in the late phase of Levovist (SH U 508A; Schering AG, Berlin, Germany) enhancement is helpful in the discrimination between benign and malignant liver lesions. METHODS: Fifty-six patients with focal hepatic lesions were examined. Diagnosis of the lesions was confirmed by liver biopsy, computed tomography, or scintigraphy. Thirty-one patients had malignant liver lesions: hepatocellular carcinoma (n = 14), cholangiocellular carcinoma (n = 1), metastasis (n = 14), and lymphoma (n = 2). Twenty-five patients had benign lesions: focal nodular hyperplasia (n = 8), hepatic adenoma (n = 1), focal hyposteatosis or hypersteatosis (n = 6), hemangioma (n = 7), and regenerative cirrhotic nodules (n = 3). After a delay of 5 to 10 minutes without scanning, the liver was examined by color stimulated acoustic emission with a fast sweep of 1 to 3 seconds. RESULTS: All patients with homogeneous color stimulated acoustic emission in the late phase of Levovist enhancement had benign liver lesions (P < .001; specificity, 100%; sensitivity, 68%; positive predictive value, 100%; and negative predictive value, 79%). Eighty-one percent of the patients with nonenhancing lesions in the late phase surrounded by enhanced liver parenchyma had malignant liver lesions (P < .001; specificity, 72%; sensitivity, 94%; positive predictive value, 81%; and negative predictive value, 90%). Interobserver agreement (weighted kappa value) improved from 0.570 +/- 0.038 for baseline sonography to 0.918 +/- 0.028 for color stimulated acoustic emission sonography. The area under the receiver operating characteristic curves for color stimulated acoustic emission sonography (0.927) was significantly higher than for baseline sonography (0.739; P < .05). CONCLUSIONS: Color stimulated acoustic emission in the late phase of Levovist enhancement has a high specificity and sensitivity for differentiation between benign and malignant focal liver lesions.

Analysis of Variance↗

PubMed2003

Effects of acoustic stimulation on cardiovascular regulation during sleep.

The interaction of wake-sleep states and acoustic stimulation on cardiovascular regulation was studied on rats implanted with electroencephalogram and electromyogram electrodes and an arterial catheter. Mild acoustic stimuli (1000 Hz, 90 dB, 50-ms beeps) were administered during Wakefulness (W), non-rapid eye movement (NREM) sleep and REM sleep and the changes induced in heart period (HP, ms) and mean arterial pressure (MAP, mmHg) were analyzed. Two 30-s sequences of beat-to-beat HP and MAP values were considered before (I) and after (II) acoustic stimulation, respectively. By the effect of stimulation, state-dependent stimulus-locked HP and MAP oscillations were observed, HP oscillations being grossly parallel to the MAP ones but delayed with respect to MAP in the ascending part only; HP and MAP spontaneous fluctuations (HP and MAP variability) increased in NREM and REM sleep (but not in W); HP vs MAP correlation coefficient increased in an algebraic sense. These results show that 1) acoustic stimulation primarily affects the peripheral resistance, and secondarily, through the baroreceptor reflex, HP, thereby increasing the impact of peripheral versus centrally driven autonomic influences on the heart; 2) in NREM sleep, heart excitability is higher than requested by the baroreflex function; 3) cardiac variability is increased by acoustic stimulation during sleep (but not in W); this, in addition to the effects of point 2, may favor cardiac arrhythmias in NREM sleep. Thus, mild acoustic stimuli not perturbing cardiovascular regulation during W may create a specific risk factor during sleep in pathophysiologic conditions.

Acoustic Stimulation↗

PubMedDate not supplied

Fetal acoustic stimulation in early labor and pathological fetal acidemia: a preliminary report.

OBJECTIVE: To determine if a nonreactive response to fetal acoustic stimulation in early labor can predict a significantly higher risk of umbilical arterial pH <7.10 or <7.00. METHODS: Fetal acoustic stimulation was applied to the fetuses of term parturients (gestational age > or =37 weeks) with cervical dilation of < or =5 cm. The responses to stimulation were correlated with cesarean delivery for fetal distress and umbilical arterial pH. Student's t-test, Chi-square, and Fisher exact test were used; P < 0.05 was considered significant. Relative risks (RR) and 95% confidence intervals (CI) were calculated. RESULTS: The study population contained 271 subjects, of which 90% (244) had a reactive response following acoustic stimulation and 10% (27) a nonreactive response. The maternal demographics, time interval from stimulation to delivery (8.3 +/- 8.7 vs. 8.3 +/- 8.4 h; P = 1.00) were similar in the two groups. Compared to those with a reactive response, patients with a nonreactive response had a significantly greater risk for: 1) cesarean delivery for fetal distress (2.0% vs. 11.1%; P = 0.03, RR 4.1, 95% Cl 1.5, 60.5), 2) umbilical arterial pH <7.10 (2.0% vs. 14.8%; P = 0.007, RR 5.0, 95% CI 2.2, 11.6), and 3) umbilical arterial pH <7.00 (0.8% vs. 7%; P = 0.05, RR 5.0, 95% CI 1.8, 15.2). CONCLUSION: A nonreactive response to fetal acoustic stimulation in early labor is associated with a significantly increased risk for cesarean delivery for fetal distress and neonatal acidosis. This finding extends the potential value of acoustic stimulation as an intrapartum admission screening test.

Acidosis↗

PubMed2004

Acoustic stimulation promotes the expression of inducible nitric oxide synthase in the vestibule of guinea pigs.

Loud acoustic stimulation is known to cause inner ear disturbance. We examined immunohistochemically the vestibule of 12 guinea pigs after acoustic stimulation. The animals were divided into two equal groups: a control group and an acoustic stimulation group. The temporal bones were fixed by means of a cardiac infusion of fixative and immunohistochemically stained for inducible nitric oxide synthase (iNOS). The temporal bones in the control group did not show any iNOS. In the acoustic stimulation group, immunoreactivity for iNOS was detected in the supporting cells and sensory cells of the sensory epithelium, in the dark cell areas and in the vestibular ganglion cells. These findings suggest that free radicals are involved in the pathogenesis of noise-induced inner ear damage. Furthermore, free radicals may cause vestibular damage, as is seen in noise-induced inner ear damage.

Acoustic Stimulation↗

PubMedDate not supplied

[Smooth pursuit eye movements evoked by head-phone acoustic stimulation].

Smooth pursuit eye movement evoked by binaural acoustic stimulation is examined in the present work. The effect of lateralization was achieved by modulating the interaural difference in intensity, within the headphone, following a pendular pattern. The test was performed on 10 healthy subjects; oscillation frequencies of the acoustic target being 0.15, 0.5 and 0.83 Hz, stimulus intensity 65 and 92 dB SPL. The acoustic signal consisted of white noise. Each trial was performed with eyes closed and then with eyes open. The results demonstrate that sinusoidal eye movement can only be obtained in a few subjects when the acoustic target has the lowest velocity and especially at the higher intensity. In all other cases eye movement was characterized by multiple saccades. The variability in eye movement amplitude is reduced and the value of this parameter decreases significantly under open-eye conditions. The data obtained are in agreement with other reports obtained with free field acoustic stimulation and demonstrate that smooth pursuit eye movement is principally an ocular reflex. In conclusion, acoustic smooth pursuit eye movement appears normally to be characterized by multiple saccades whose pattern can be modulated by intensity and oscillation frequency of the acoustic target as well as by the presence of visual inputs and attentional factors.

Acoustic Stimulation↗

PubMed1985

Non-opiate analgesia following stressful acoustic stimulation.

The change in the nociceptive reactions of rats was characterized after stressful acoustic (115 dB) stimulation. Acoustic loading for five minutes resulted in considerable analgesia in the hot-plate test, whereas a significant analgesic response was not observed in the tail-flick test. The analgesic reaction after acoustic stimulation was resistant to naloxone pretreatment and was also found in morphine-tolerant rats, but the acute thermoregulatory and analgesic effects of morphine were greatly potentiated by simultaneous acoustic loading. Substance P or cholecystokinin treatment likewise failed to prevent the analgesic effect of auditory stimulation. No tolerance developed to the analgesic effect on repeated stressing. Diltiazem, a slow calcium channel blocker, facilitated the analgesia. The data suggest a stress-induced analgesia with obviously non-opiate properties, although an indirect involvement of opiate effects could not be excluded.

Acoustic Stimulation↗

PubMed1992

A four-year follow-up of hearing and development in children exposed in utero to vibro-acoustic stimulation.

OBJECTIVE: To obtain information of hearing and neuro-development in children exposed to vibro-acoustic stimulation in utero. DESIGN: Information collected from Swedish child care programmes. SETTING: Department of Obstetrics and Gynaecology, Karolinska Institutet, Danderyd University Hospital, Sweden. SUBJECTS: Children of 460 mothers exposed to vibro-acoustic stimulation for the assessment of fetal well-being during high- and low-risk pregnancies during 1985-1987. MAIN OUTCOME MEASURES: Auditory test (20-25 dB at eight frequencies between 500 and 8000 Hz) and general neurological examination at four years of age. RESULTS: No hearing damage or neuro-developmental abnormalities that could be connected to the vibro-acoustic stimulation were found. CONCLUSIONS: Vibro-acoustic stimulation, as applied in clinical practice, did not endanger either neurological development or hearing in children exposed in utero.

Acoustic Stimulation↗

PubMed1997

Suppression of otoacoustic emission is unchanged after several minutes of contralateral acoustic stimulation.

The influence of variable durations of contralateral acoustic stimulation on the suppression of click-evoked otoacoustic emissions was investigated in order to determine whether olivocochlear efferent fibers are equally effective whatever the acoustical stimulation duration or if they show fatigue. The suppression effect was measured for contralateral stimulus durations ranging from 10 to 180 s prior to the onset of otoacoustic emission recording, and continuing throughout the recording time (60 s). No significant stimulus duration effect was found.

Acoustic Impedance Tests↗

PubMed1990

[Behavioral characteristics associated with acoustic stimulation and the neurochemical alterations of monoaminergic systems in rat brain at the steady state of repeated methamphetamine administration].

Behavioral characteristics associated with acoustic stimulation and the neurochemical alterations of monoaminergic systems in rat brain at the steady state of repeated methamphetamine administration were investigated. We confirmed that reverse tolerance in stereotyped behavior was constructed up to the 28th day after repeated intermittent pretreatment with increasing doses of MAP (2.5, 5, and 7.5 mg/kg x 3 and 10 mg/kg x 2, every other day). During acoustic stimulation, locomotor activity in the saline group was significantly increased, but the activity after the stimulation was completely suppressed. In contrast to the saline group, locomotor activity was not influenced by the acoustic stimulation in the MAP group, suggesting that behavioral hyporesponsiveness to acoustic stimulation was induced by MAP treatment. Two days after the last injection, the contents of 5-hydroxytryptamine (5-HT) and 5-hydroxyphenylacetic acid (5-HIAA) in the cerebral cortex, midbrain + thalamus, hypothalamus and striatum were significantly decreased. These changes were maintained up to the 28th day after the drug withdrawal in the cerebral cortex and the midbrain + thalamus. From these results, the persistence of behavioral hyporesponsiveness to acoustic stimulation might be associated with long-lasting reduction of 5-HT synthesis.

Acoustic Stimulation↗

PubMed1998

Intrapartum vibratory acoustic stimulation after maternal meperidine administration.

OBJECTIVE: To examine the effectiveness of the acoustic stimulation test in the interpretation of suspicious cardiotocograms obtained after meperidine administration to the mother during the first stage of labor. SUBJECTS AND METHODS: We studied 45 unselected parturients who received 50 mg meperidine i.m. when cervical dilatation was 5 cm. In all cases a decreased beat-to-beat variability of the fetal heart rate and fetal movements was noted after the injection of meperidine. A vibratory acoustic stimulation was performed in 25 patients (group A) while the remaining 20 (group B) had no stimulation. RESULTS: After the meperidine injection, the acoustic-induced reactivity returned immediately in group A, while the spontaneous reactivity returned 30 minutes later. The mean number of fetal movements in all parturients was 8.71 +/- 2.18 before meperidine administration. Sixty minutes after the meperidine injection the mean number was 8.52 +/- 2.48 in group A and 1.65 +/- 1.81 in group B (p < 0.0001). CONCLUSION: The acoustic stimulation test is an effective method of interpreting suspicions CTG's obtained after meperidine administration to the mother during the first stage of labour.

Acoustic Stimulation↗