Vibratory Acoustic Stimulation Research Articles

Evaluation of non-reassuring fetal heart rate patterns with fetal pulse oximetry combined with vibratory acoustic stimulation

Evaluation of non-reassuring fetal heart rate patterns with fetal pulse oximetry combined with vibratory acoustic stimulation

Evaluation of non-reassuring fetal heart rate patterns with fetal pulse oximetry combined with vibratory acoustic stimulation

Objective: To determine the value of fetal pulse oximetry and vibratory acoustic stimulation in the presence of non-reassuring fetal heart rate patterns during labor.Design: Prospectivestudy in women monitored by cardiotocography and fetal pulse oximetry during labor.Materials and methods: During a period of 18 months, 907 consecutive parturients in labor were monitored bycardiotocography. Out of these women, 63 were selected on the basis of a non-reassuring fetal heart rate tracing during the first stage of labor. In these cases, fetal pulse oximetry was applied. Vibratoryacoustic stimulation was applied in fetuses without spontaneous reactivity in order to evaluate the fetal status.Results: Our cases were classified into three groups, according to the lowerfetal oxygen saturation levels, from the time of oximetry application until delivery. Group A consisted of 29 cases where fetal oxygen saturation levels were ≥41%, group B (20 cases) with fetal oxygensaturation of 31-40% and group C (14 cases) with levels of <30%. Spontaneous reactivity was observed in 15 fetuses of group A and seven of group B, while no case of reactivity was noted in group C. Vibratoryacoustic-induced reactivity was associated with low fetal oxygen saturation levels. The mean umbilical artery pH levels were 7.29 ± 0.051 in group A, 7.21 ± 0.057 in group B and 7.04 ±0.05 in group C.Conclusion: Fetal pulse oximetry should be indicated not only in fetuses without any reactivity but also in those with induced reactivity, after the application of vibratoryacoustic stimulation.

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.

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

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. Prospective observational study of 253 labours involving 421 pH samples. Tertiary care university hospital of Genoeva. Vibratory acoustic stimulation through the maternal abdominal wall for five seconds prior to fetal blood sampling. 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. 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. 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.

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.

The effect of vibratory acoustic stimulation on fetal middle cerebral artery resistance and instantaneous fetal heart rate from 20 to 42 weeks gestational age: [formula omitted], M. Cabbad and G Kofinas. Dept. Ob/Gyn, The Brooklyn Hosp. Ctr., Brooklyn, NY

The effect of vibratory acoustic stimulation on fetal middle cerebral artery resistance and instantaneous fetal heart rate from 20 to 42 weeks gestational age: [formula omitted], M. Cabbad and G Kofinas. Dept. Ob/Gyn, The Brooklyn Hosp. Ctr., Brooklyn, NY

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.

Prenatal Sonographic Diagnosis, Assessment, and Management of a Fetus with a Quadruple Nuchal Cord at 39 Weeks' Gestation

A case of prenatal sonographic diagnosis of a quadruple nuchal cord is presented. Perinatal assessment included nonstress, oxytocin challenge testing, and Doppler velocimetry studies of the umbilical artery and fetal vibratory acoustic stimulation. Obstetric management of this case is discussed.

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.

446 Does vibratory acoustic stimulation cause in utero gasping?

446 Does vibratory acoustic stimulation cause in utero gasping?

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.

Human fetal behavioral states after vibratory stimulation

A total of 14 healthy pregnant women between 37 and 41 weeks' gestational age were studied to determine the effects of a 5-second external vibratory stimulus (100 Hz, square wave) on human fetal behavioral states. Fetal behavioral state observations were made with simultaneous recordings of fetal heart rate, gross fetal body movements, and fetal eye movement between 8:30 am and 4:00 pm . During the first episode of behavioral state 1 F (quiet sleep state) ≥ 10 minutes duration on two consecutive half days, the vibratory stimulus was placed on the surface of the maternal abdomen over the fetal head. Each fetus received one 5-second vibratory stimulus during either the first or second half day of observation. The time at which the instrument was applied but no vibratory stimulus was administered was considered as the control period. All women were then observed for 2 hours after the control period and after stimulation. A transition period from a quiet sleep state to a stable active sleep state (state 2F, rapid eye movement sleep) averaged ≤ 53 minutes after stimulation, as compared with 23 minutes after the control period. These changes in fetal behavioral states persisted for 20 minutes after vibratory stimulation. There also was an immediate and sustained increase in long-term fetal heart rate variability, the number of fetal heart rate accelerations and gross fetal body movement during the first 20 minutes after stimulus, without changes in basal fetal heart rate. We hypothesize that changes in fetal behavior seen after application of low frequency vibratory stimulus are more physiologic than the profound changes in fetal heart rate and gross fetal body movement previously described after vibratory acoustic stimulation with an electronic artificial larynx.

The intrauterine sound environment of the human fetus during labor

Ten pregnant women near term with medical indications for internal monitoring during labor were studied to quantify the intrauterine sound environment. The intrauterine background noise was measured with a miniaturized hydrophone placed transcervically at the level of the fetal neck under ultrasonographic guidance. In eight women no cardiovascular noise was audible and the intrauterine noise consisted predominantly of low-frequency noise (<100 Hz) from 60 to 85 dB. Above 100 Hz, the sound pressure level was <60 dB, decreasing to 40 dB above 500 Hz. In only two women maternal cardiovascular sounds were audible during uterine relaxation and disappeared during uterine contraction. Maternal bowel sounds and maternal vocalization were well above the intrauterine background noise. Because of this relative quietness, we hypothesized that the fetal acoustic environment could be altered significantly during antenatal vibratory acoustic stimulation.

Effect of Vibratory Acoustic Stimulation on the Duration of Fetal Heart Rate Monitoring Tests

The ability of vibratory acoustic stimulation to shorten the duration of antepartum fetal heart rate monitoring was investigated by a randomized controlled trial. Vibratory acoustic stimulation did not shorten the overall duration of testing. This failure to improve the performance of antepartum monitoring appeared to result from prolonged accelerations, which complicated one third of the tests in which vibratory acoustic stimulation was employed. Further investigation is warranted using less profound methods of fetal stimulation.

Umbilical and uterine artery body flow velocities after vibratory acoustic stimulation : R. Gagnon, R. Morrow, K. Ritchie, C. Hunse and J. Patrick 1988 American Journal of Obstetrics and Gynaecology159, 574–578

Umbilical and uterine artery body flow velocities after vibratory acoustic stimulation : R. Gagnon, R. Morrow, K. Ritchie, C. Hunse and J. Patrick 1988 American Journal of Obstetrics and Gynaecology159, 574–578

Human fetal behavioral states after vibratory stimulation

A total of 14 healthy pregnant women between 37 and 41 weeks' gestational age were studied to determine the effects of a 5-second external vibratory stimulus (100 Hz, square wave) on human fetal behavioral states. Fetal behavioral state observations were made with simultaneous recordings of fetal heart rate, gross fetal body movements, and fetal eye movement between 8:30 AM and 4:00 PM. During the first episode of behavioral state 1F (quiet sleep state) greater than or equal to 10 minutes duration on two consecutive half days, the vibratory stimulus was placed on the surface of the maternal abdomen over the fetal head. Each fetus received one 5-second vibratory stimulus during either the first or second half day of observation. The time at which the instrument was applied but no vibratory stimulus was administered was considered as the control period. All women were then observed for 2 hours after the control period and after stimulation. A transition period from a quiet sleep state to a stable active sleep state (state 2F, rapid eye movement sleep) averaged less than or equal to 3 minutes after stimulation, as compared with 23 minutes after the control period. These changes in fetal behavioral states persisted for 20 minutes after vibratory stimulation. There also was an immediate and sustained increase in long-term fetal heart rate variability, the number of fetal heart rate accelerations and gross fetal body movement during the first 20 minutes after stimulus, without changes in basal fetal heart rate. We hypothesize that changes in fetal behavior seen after application of low frequency vibratory stimulus are more physiologic than the profound changes in fetal heart rate and gross fetal body movement previously described after vibratory acoustic stimulation with an electronic artificial larynx.

Vibratory acoustic stimulation and the flow velocity waveform in the fetal internal carotid artery

Eleven healthy fetuses between 36 and 39 weeks of gestation were studied during the active sleep state to examine effects of a 5-s vibratory acoustic stimulus on the baseline fetal heart rate and flow velocity waveform in the fetal internal carotid artery. There was an immediate marked rise in baseline fetal heart rate with concomitant drop in pulsatility index in the flow velocity waveform of the fetal internal carotid artery, which persisted for at least 15 min after the stimulus. However, when the pulsatility index was standardized for a fetal heart rate of 140 beats/min this index remained virtually unaltered. These data suggest that in the healthy term fetus during active sleep state, a vibratory acoustic stimulus has no measurable effect on cerebral vascular resistance. Since virtually all reported studies on vibratory acoustic stimulation of the fetus were carried-out during the quiet sleep state, the data from the present study do not provide any information on the safety of this device when employed as a means of assessing of fetal well-being.

Preterm and term fetal cardiac and movement responses to vibratory acoustic stimulation

To assess fetal response to vibratory acoustic stimulation, 24 preterm (group A; less than 36 weeks' gestation) and 30 term (group B; greater than or equal to 36 weeks' gestation) pregnancies were studied. Study variables were perceived fetal movement, fetal heart rate, and fetal heart rate pattern. Observer- and patient-perceived fetal movement responses were noted in most cases but were slightly more common in term patients (group A: + fetal movement, patient 87.5%/observer 87.5%) group B: + fetal movement, patient 96.7%/observer 90%). Baseline changes in fetal heart rate (greater than or equal to 10 beats/min) were observed in 46% of preterm fetuses and 70% of term fetuses. Tachycardia (fetal heart rate greater than 160 beats/min) was a common finding in both groups. In group A, tachycardia after vibratory acoustic stimulation persisted more than 1 minute in 29.2% and more than 5 minutes in 12.5% of patients. In group B tachycardia beyond 1 and 5 minutes was noted in 73.3% and 50% of patients, respectively. A significant shift to "awake" fetal heart rate patterns occurred in both groups; 29% to 79% was noted in group A (p less than 0.001) and 46.7% to 90% in group B (p less than 0.001). When vibratory acoustic stimulation was used, the high occurrence of increased baseline, tachycardia, and emergence of unusual fetal heart rate patterns must be recognized to adequately interpret fetal heart rate tracings.

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.