External Vibratory Acoustic Stimulation Research Articles

A simplified fetal biophysical profile

Objective: To modify the classic fetal biophysical profile (FBP) with the aim of obtaining rapid and accurate information about actual fetal condition in non-compromised fetuses with a subsequent favorable outcome and to be suitable for a number of outclinic patients. Methods: Four-hundred and ninety-four fetuses from singleton pregnancies in two randomized groups were monitored by the modified FBP (mFBP) and 168 of them after the external vibratory acoustic stimulation (VAS/mFBP). The mFBP was characterized by two main characteristics: non-stress test was excluded and the testing was finished at the moment when all of the three fetal biophysical activities became normal. The external VAS was applied only in cases with no evidence of fetal activity at the start of the FBP. Results: Of the examined fetuses, 326 fetuses in the control group were monitored by the mFBP and there were 316 (96.9%) favorable outcomes and 10 (3.1%) adverse perinatal outcomes. The sensitivity, specificity and positive and negative predictive values of the mFBP score in predicting adverse perinatal outcome were 60, 99, 66.7 and 98.7%, respectively. In the study group of 168 fetuses there were 165 (98.2%) favorable outcomes and three (1.8%) adverse perinatal outcomes. The sensitivity, specificity and positive and negative predictive values of the VAS/mFBP were 66.7, 100, 100 and 99.4%, respectively. The efficiency of the VAS/mFBP in predicting perinatal mortality alone was even higher. After the external VAS and the first 5 min of the modified testing approximately two-fifths (41.8%) of healthy fetuses with a subsequent good outcome exhibited normal in all of the three biophysical activities and approximately two-thirds (65.5%) of them after 10 min. In the VAS/mFBP group of healthy fetuses, during the same time periods, normal breathing movements were observed in 72% and 87% of fetuses, respectively. Conclusions: According to our results the mFBP and particularly the VAS/mFBP antenatal protocol as a new and rational variant of the FBP could improve fetal assessment allowing in cases of non-compromised fetuses rapid and accurate information about actual fetal well-being. Because of its high accuracy and a reduced testing time the antepartal method with observation of fetal breathing movements after VAS is becoming acceptable as a screening of fetal well-being evaluation in outclinic conditions.

Fetal biophysical profile and vibratory acoustic stimulation in high-risk pregnancies

To determine the influence of the non-stress test (NST) on the efficiency of the fetal biophysical profile (FBP) and to test the clinical usefulness of the FBP and its combination with vibratory acoustic stimulation (VAS) in managing high-risk pregnancies. One hundred twenty fetuses of preeclamptic patients were included in a prospective study. Five standard variables of the FBP were observed ultrasonically following NST. In cases of non-reactive NST, external VAS was applied and the FBP score calculated and compared with the FBP score before VAS. Of 120 calculated FBPs, 102 (85%) had normal profile scores before VAS and 104 (86.7%) after VAS. No statistically significant difference was found. The sensitivity, specificity, and positive and negative predictive values of the FBP score in predicting poor perinatal outcome were 94.7%, 94.4%, 75% and 99%, respectively. VAS produced a high conversion (58.8%) of non-reactive NST to reactive fetal heart rate pattern. The false-negative rate of the FBP score was 9.8 per 1000, which did not increase after VAS. The efficiency of the FBP score was not significantly improved by VAS, although a high conversion of non-reactive to reactive NST was produced. The FBP with its three 'acute biophysical variables' was found to be an accurate method of antepartum assessment even without an NST. The low incidence of perinatal complications among patients with normal FBP scores, permits the conservative management of preterm high-risk pregnancies.

Effect of the vibratory acoustic stimulation on fetal heart rate patterns of premature fetuses

The purpose of this study was to examine the heart rate patterns before and after a standardized external vibratory acoustic stimulation in a group of 24 healthy premature fetuses at 32–35 weeks gestational age. FHR was analysed on line by Sonicaid Computer System 8000. A significant increase in the number of accelerations and an increase of variation after stimulus were observed. All other FHR patterns such as baseline, high and low episodes did not change significantly.

Sonographic Verification of a Nuchal Cord Following a Vibratory Acoustic Stimulation-Induced Severe Variable Fetal Heart Rate Deceleration with Expedient Abdominal Delivery

A case is presented in which external vibratory acoustic stimulation performed following a nonreactive nonstress test produced a severe variable deceleration of the fetal heart rate. A clinically suspected nuchal cord was confirmed by ultrasound. This rapid precise antepartum diagnosis of cord compression prevented untimely delay and led to immediate abdominal delivery of a nonacidotic, yet hypoxic, infant. This report suggests care be taken when fetal vibratory acoustic stimulation is applied in cases of oligohydramnios and a known existing nuchal cord.

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.

振動音刺激に対する胎児応答に関する研究

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.

Severe Fetal Bradycardia Caused by External Vibratory Acoustic Stimulation

A case is presented in which external vibratory acoustic stimulation performed on a term fetus produced severe prolonged bradycardia, necessitating emergency cesarean section delivery. The possible pathogenesis is discussed.

Fetal heart rate and activity patterns in growth-retarded fetuses: Changes after vibratory acoustic stimulation

Seventeen pregnant women who subsequently were delivered of infants with birth weights less than the third percentile were studied for examination of fetal heart rate and fetal activity patterns before and after a 5-second external vibratory acoustic stimulation. None of the fetuses was acidotic at birth. A reduced time was noted during which accelerations in heart rate occurred (50% less) and long-term fetal heart rate variability (25% less) in small for gestational age fetuses compared with age-matched, normally grown fetuses. The incidence of gross fetal body movements was significantly lower (40% less) in small for gestational age fetuses than in those who were appropriate for gestational age. Fetal heart rate and fetal activity patterns after stimulation with the electronic artificial larynx in small for gestational age fetuses were similar to those of appropriate for gestational age fetuses.

Fetal responses to vibratory acoustic stimulation: Influence of basal heart rate

Forty-three healthy pregnant women between 26 and 40 weeks' gestation were studied to determine the influence of prestimulation basal heart rate on the maximum amplitude of the first fetal heart rate acceleration after external vibratory acoustic stimulation. A significant negative correlation was found between the maximum amplitude of the first fetal heart rate acceleration and the prestimulation basal fetal heart rate from 30 weeks to term. In the presence of fetal tachycardia (basal fetal heart rate greater than 160 beats/min), more than 50% of fetal heart rate accelerations after stimulus were less than 15 beats/min amplitude. There was also a significant maturational process in the immediate fetal heart rate response to vibratory acoustic stimulation that occurred between 26 to 28 and 30 to 32 weeks characterized by a prolonged increase in basal fetal heart rate and an increase in the maximum amplitude of the first acceleration after stimulation.

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.

Severe fetal bradycardia caused by external vibratory acoustic stimulation

A case is presented in which external vibratory acoustic stimulation performed on a term fetus produced severe prolonged bradycardia, necessitating emergency cesarean section delivery. The possible pathogenesis is discussed.

Ultrasonic Imaging of Normal Fetal Response to External Vibratory Acoustic Stimulation

Ultrasonic Imaging of Normal Fetal Response to External Vibratory Acoustic Stimulation

Ultrasonic imaging of normal fetal response to external vibratory acoustic stimulation

Fetal facial reactions and response decrement patterns to external noise stimulation were studied to characterize normal fetal neurobehavior in the third trimester. Response decrement, or habituation, is thought to reflect higher central nervous system function. Two hundred women with uncomplicated pregnancies, who were subsequently delivered of healthy infants at term, were studied between 26 and 41 weeks' gestation. After ultrasound views of the fetal face were obtained, a vibratory acoustic stimulus was applied repetitively to the maternal abdomen near the fetal head. Response decrement was defined as cessation of all components of the facial reaction, except eye blinking, over two sequential stimuli. Three response patterns were scored: (1) no startle, (2) startle without response decrement, and (3) response decrement by 12 stimuli. Whereas only 53% of fetuses between 26 and 27 weeks displayed startle reaction, all fetuses displayed startle responses by 28 weeks. As gestational age advances, an increasing number of fetuses exhibit response decrement, from no decrement at 26 to 27 weeks to 100% decrement at 40 to 41 weeks. A maturation of neurobehavioral response patterns takes place in normal third-trimester pregnancies. Response decrement testing may be a useful tool for in utero neurologic evaluation.

External vibratory acoustic stimulation near term: Fetal heart rate and heart rate variability responses

Twenty-five pregnant women between 36 and 40 weeks' gestational age were studied to examine effects of a 5-second external vibratory acoustic stimulus on the fetal heart rate and fetal heart rate variability. Where was an immediate significant increase in the basal heart rate, which persisted for 1 hour after the stimulus, compared to that of the control subjects. There was also a significant increase in the total time during which accelerations occurred for the first 20 minutes after the stimulus. There were no changes in computer-derived indices of fetal heart rate variability. Maternal blood pressure and heart rate were not altered following vibratory acoustic stimulus. We hypothesize that external vibratory acoustic stimulus causes a change from a state of sleep to a state of wakefulness in near term healthy fetuses.