Biomedical subjects

W P Fifer

Publications and source records attributed to W P Fifer.

At least 19 recordsLinked to original sources

PubMed2005

Sleeping position and electrocortical activity in low birthweight infants.

OBJECTIVE: To evaluate the effects of prone and supine sleeping positions on electrocortical activity during active (AS) and quiet (QS) sleep in low birthweight infants. DESIGN: Randomised/crossover study. SETTING: Infant Physiology Laboratory at Children's Hospital of New York. PATIENTS: Sixty three healthy, growing, low birthweight (birth weight 795-1600 g) infants, 26-37 weeks gestational age. INTERVENTIONS: Six hour continuous two channel electrocortical recordings, together with minute by minute behavioural state assignment, were performed. The infants were randomly assigned to prone or supine position during the first three hours, and positions were reversed during the second three hours. OUTCOME MEASURES AND RESULTS: Fast Fourier transforms of electroencephalograms (EEGs) were performed each minute and the total EEG power (TP), spectral edge frequency (SEF), absolute (AP) and relative (RP) powers in five frequency bands (0.01-1.0 Hz, 1-4 Hz, 4-8 Hz, 8-12 Hz, 12-24 Hz) were computed. Mean values for TP, SEF, AP, and RP in the five frequency bands in the prone and supine positions during AS and QS were then compared. In the prone sleeping position, during AS, infants showed significantly lower TP, decreased AP in frequency bands 0.01-1.0 Hz, 4-8 Hz, 8-12 Hz, 12-24 Hz, increased RP in 1-4 Hz, and a decrease in SEF. Similar trends were observed during QS, although they did not reach statistical significance. CONCLUSIONS: The prone sleeping position promotes a shift in EEG activity towards slower frequencies. These changes in electrocortical activity may be related to mechanisms associated with decreased arousal in the prone position and, in turn, increased risk of sudden infant death syndrome.

Cerebral Cortex↗

PubMed2001

Physiologic responses to cognitive challenge during pregnancy: effects of task and repeat testing.

Physiological responses to stress during pregnancy are believed to influence birth outcomes. Researchers have studied pregnant women in laboratory stressor paradigms to investigate these associations, yet normative data on cardiovascular and respiratory responses to laboratory challenge during pregnancy are not yet established. To begin to establish such normative data, this study examined the effects of task and repeat stressor exposure on reactivity in third-trimester pregnant women. Thirty-one healthy pregnant women (mean age=27 years; range 18-36) between the 33rd and 39th week of pregnancy, were instrumented for continuous electrocardiography, blood pressure (BP), and respiration data. Subjects rested quietly for a 5-min baseline and then performed both a mental arithmetic stressor and a Stroop color-word-matching task, each 5 min in length and each followed by a 5-min recovery period. The order of the tasks was counterbalanced. After each 5-min period, subjects rated the period on a 10-point stress scale. Averaged across task type and challenge period, systolic and diastolic BP and respiration rate increased significantly in response to cognitive challenge, but heart rate (HR) did not. When data were examined for task and period effects, the following results emerged: the Stroop task elicited significantly greater systolic BP and HR reactivity than the arithmetic task, yet subjects rated the arithmetic task as more stressful. Averaged across task type, subjects showed greater systolic BP reactivity during the second challenge period compared to the first. Finally, women's BP tended to drift upward and did not return to baseline during the first recovery period. These findings indicate that averaging data across tasks and periods can obscure the time course of response patterns that may be important in the study of associations between maternal stress and perinatal development, as well as in other research on reactivity to repeat stress exposure.

Adolescent↗

PubMed2000

Maturational changes in heart rate and heart rate variability in low birth weight infants.

To provide insight into the maturation of neural mechanisms responsible for variability in heart rate during quiet and active sleep, 6-hour continuous electrocardiographic recordings and simultaneous minute-by-minute behavioral activity state assignments were performed in 61 healthy, growing low birth weight infants. The infants weighed 795-1600 g at birth and ranged between 31-38 weeks in postconceptional age. During this age interval there was a decrease in heart rate during quiet sleep and an increase in both time domain and frequency domain measures of the variability in cardiac interbeat intervals. In quiet sleep, global variability, measured as SD of R-R intervals, increased in relation to age, as did higher frequency variability, measured as the square root of the mean of squared successive differences in R-R intervals. Developmental changes in the 0.5-2.0 Hz spectral power band of RR-interval variability, another measure of high frequency variability, paralleled the changes seen in the time domain measure. Evaluation of patterns of changes in the magnitude and direction of successive interbeat intervals provided evidence that the incidence of sustained accelerations or decelerations increased whereas the incidence of no change in consecutive RR-intervals decreased as infants matured. Among the various measures of heart rate variability, the incidence of sustained change and no change in successive interbeat intervals were most closely related to postconceptional age in both sleep states. The overall decrease in heart rate, increase in heart rate variability, and increase in the pattern of changes in interbeat interval with postconceptional age are consistent with the maturation of the autonomic cardio-regulatory activity from 31-38 weeks age.

Electrocardiography↗

PubMed2000

Evidence of transnatal auditory learning.

There is converging evidence for fetal retention of auditory experience into early postnatal life, but critical tests with appropriate controls are rare due to methodological hurdles. Research has been conducted on newborn response to naturally occurring stimuli such as heartbeats, intrauterine recordings, pre- and postnatal versions of the maternal voice, father's voice, and unfamiliar voices. Postnatal experience cannot be ruled out as a possible explanation for many results. Only one critical prenatal exposure experiment with postnatal testing has been carried out and published in a peer-reviewed scientific journal. Interpretation of acoustic and linguistic information on intrauterine recordings suggests that the prosodic features of speech (pitch contours, rhythm, and stress) are available to the fetus. This is compatible with newborn responses and may contribute to language acquisition during the first year. There is no sound evidence that providing extra prenatal auditory stimulation benefits the developing child, and there are potential risks.

Fetus↗

PubMed2000

Maternal stress responses and anxiety during pregnancy: effects on fetal heart rate.

This study examined the effect of an acute maternal stress response and anxiety on fetal heart rate. Seventeen healthy, 3rd-trimester pregnant women (mean age = 26 +/- 6 years) were instrumented for continuous electrocardiography, blood pressure (BP), respiration, and fetal heart rate (HR). Subjects completed the state anxiety subscale of the State Trait Personality Inventory (STPI), then rested quietly in a semirecumbent position for a 5-min baseline period, followed by either a 5-min arithmetic or Stroop color-word task. Over the entire 5-min stress period and when averaged across all subjects, the stressors led to significant increases in maternal systolic BP and respiratory rate but changes in maternal HR, diastolic BP, and fetal HR were not significant. However, when subjects were dichotomized into groups that had above or below average anxiety scores [ANX(+) and ANX(-)], both groups had similar respiration rate increases to the stressors, but the BP and fetal heart rate (FHR) responses were significantly different. Women in the ANX(-) group had significantly greater BP responses compared to women in the ANX(+) group whereas the fetuses of ANX(+) women showed significant HR increases and the fetuses of ANX(-) women exhibited nonsignificant decreases. These findings suggest that women's acute emotional reactivity during pregnancy can influence fetal HR patterns and that a stress-induced increase in maternal BP is not the primary signal by which a women's stress response is transduced to her fetus. The results are consistent with the hypothesis that maternal psychological variables may shape the neurobehavioral development of the fetus.

Adult↗

PubMed1999

Body position, sleep states, and cardiorespiratory activity in developing low birth weight infants.

The objective of this study was to determine the effects of body position (supine vs prone) on cardiorespiratory activity during quiet and active sleep in growing low birth weight (LBW) infants. The effect of postconceptional age on cardiorespiratory activity in the two positions was also evaluated. Fifty-one healthy, growing, appropriate for gestational age LBW infants (795-1600 g), ranging from 26-37 weeks in gestational age, were evaluated. All subjects were enrolled in an ongoing study of the effects of quality of dietary energy on the rate and composition of weight gain. Infants were randomly assigned to the supine or prone position for the first 3 h of the 6-h studies; the position was reversed for the second 3 h. Continuous recordings of cardiorespiratory activity were performed along with simultaneous minute by minute assignment of behavioral sleep state. Measurements of heart rate (HR), heart period variability (RR-SD), respiratory rate (f), and respiratory variability (fSD) were made each minute. Low birth weight infants had higher HR and f and lower RR-SD and fSD in the prone position compared to the supine position, during both quiet and active sleep. With increasing postconceptional age, positional differences in HR increased during quiet sleep and differences in RR-SD increased during both sleep states. These data demonstrate systematic differences in cardiorespiratory control related to body position during sleep. We speculate that such positional differences are due to variations in autonomic control, and may, in turn, contribute to variations in susceptibility to sudden infant death syndrome.

Aging↗

PubMed1999

Cardiorespiratory responses to bidirectional tilts in infants.

Prior research in newborns has shown that head-up and head-down tilting elicits sustained increases and decreases in heart rate, respectively. Other studies in older infants have suggested that the pattern of heart rate responses to head-up tilting varies with risk for sudden infant death syndrome (SIDS). In this study, heart and respiratory rate changes following bidirectional tilting were recorded in sleeping infants on Day 1 or 2 of life, and during the period of maximum risk for SIDS, at 2 and 4 months of age. Newborns show increases in heart rate following 30 degrees head-up tilts and decreases in heart rate to 300 head-down tilting. Respiratory rates decreased to head-up tilting but did not change significantly to head-down tilting. While respiratory rate changes at 2 and 4 months of age are comparable to those of newborns, and decreases in heart rate to head-down tilting are similar across ages, sustained elevations in heart rate following head-up tilting are no longer apparent at the older ages. These results are consistent with the hypothesis that, during the period of maximum risk for SIDS, infants may have reduced ability to compensate for challenges that lead to decreases in blood pressure.

Age Factors↗

PubMed1999

Postural differences in cardiac dynamics during quiet and active sleep in low birthweight infants.

To study the effects of body position (supine versus prone) on changes in cardiac inter-beat interval during quiet and active sleep, 6-h continuous electrocardiographic recordings and simultaneous minute-by-minute behavioural activity state assignments were made in 61 healthy, growing, low birthweight infants. The infants weighed 795-1600 g at birth and ranged between 30-38 wk in postconceptual age. Infants were randomly assigned to the supine or prone position for the first 3 h of each study; the position was reversed for the second 3 h. Higher heart rates and lower time and frequency domain measures of inter-beat interval variability were observed in the prone position as compared to the supine position, during both quiet and active sleep. In addition, an analysis of consecutive increases and decreases in the instantaneous heart rate revealed a lower incidence of sustained accelerations or decelerations in the prone position. Although consistent findings concerning inter-beat interval variability and sleeping position were obtained from all analytic techniques, the differences derived from analysis of consecutive inter-beat changes were the most robust. These differences in multiple measures of cardiac rate and rhythm between prone and supine positions suggest that autonomic control of the heart is altered by body position, the net effect on heart rate being increased sympathetic dominance.

Autonomic Nervous System↗

PubMed1998

Effects of sleeping position and time after feeding on the organization of sleep/wake states in prematurely born infants.

Epidemiologic studies provide strong evidence for the conclusion that sleeping in the prone position places infants at greater risk for sudden infant death syndrome (SIDS). Prior studies in newborn infants found that in the prone sleeping position there is less time awake and more quiet sleep, but little change in the amount of active sleep. To determine whether the effects of sleeping position on state distribution vary with time after feeding, we studied prematurely born infants in both the prone and supine sleeping positions. Sleep states were recorded each minute during interfeed intervals. Results demonstrate expected effects of sleep position on state distribution: prone sleeping is associated with a 79% increase in quiet sleep and a 71% decrease in time awake. While the decreases in time awake are seen throughout the interfeed interval, increases in quiet sleep in the prone position are found only within the first hour and again near the end of the interfeed interval. These results are consistent with the hypothesis that prone sleeping could increase risk for SIDS by altering the organization of sleep, and that time after feeding may play an important role in the expression of these effects.

Analysis of Variance↗

PubMed1997

A novel quantitative measure of Tracé-alternant EEG activity and its association with sleep states of preterm infants.

This study describes the application of a novel quantitative method for classifying patterns of EEG activity that are associated with the predominant sleep-states of newborn infants. Periods in which there are bursts of high-voltage slow wave activity in the EEG that alternate with periods of low-voltage activity are termed Tracé-alternant. During active or REM sleep. Tracé-alternant is absent and EEG activity is characterized by a variable mixture of frequencies including intermittent high frequency (10-20 Hz) activity superimposed on slower frequencies. Results show that an analytic method previously developed in fetal baboons for identifying EEG segments with and without Tracé-alternant successfully distinguishes homologous patterns of EEG activity in preterm infants. This method provides an excellent objective approach for monitoring changes in EEG patterns that are coincident with behaviorally defined sleep states.

Animals↗

PubMed1997

Patterns of fetal perinasal fluid flow in cases of congenital diaphragmatic hernia.

OBJECTIVE(S): Our purpose was to expand the previous reported series of observations of fetal perinasal fluid flow in cases of antenatally diagnosed congenital diaphragmatic hernia, characterize the timing parameters of the fetal breath cycle, and define the relationship of fetal perinasal fluid flow and the diaphragmatic component of fetal breathing movements. Our hypothesis was that characteristics of diaphragm-related and nondiaphragm-related perinasal fluid flow and other breath cycle characteristics differ in cases of congenital diaphragmatic hernia compared with controls. STUDY DESIGN: Fetal perinasal fluid flow velocity and fetal chest wall movements were studied in 24 cases of uncomplicated pregnancy, and flow was studied in 24 cases of antenatally diagnosed congenital diaphragmatic hernia at gestational ages ranging from 30 to 41 weeks. The examination of fetal perinasal fluid flow velocity was performed with use of an ultrasonography system applying color flow and spectral Doppler analysis. Breath-to-breath interval, time of inspiration, time of expiration, and peak inspiratory and expiratory velocities were determined for each type of perinasal flow. RESULTS: The study revealed that the time of expiration in cases of congenital diaphragmatic hernia at 30 to 36 and 37 to 41 weeks of gestation was significantly shorter than in cases of uncomplicated pregnancy. The ratio of time of inspiration and breath-to-breath interval in cases of diaphragmatic hernia was approximately 30% higher (p = 0.001) at 30 to 36 weeks of gestation than in cases of uncomplicated pregnancy. The study also showed that in cases of congenital diaphragmatic hernia the expiratory peak velocity ratio at 30 to 36 weeks of gestation was significantly lower than in cases of uncomplicated pregnancy. CONCLUSIONS: We conclude that by Doppler ultrasonography measurements of fetal perinasal fluid flow, in cases of congenital diaphragmatic hernia, we can evaluate the timing parameters of fetal diaphragm-related breath cycles, the relationship of intraalveolar and intraamniotic pressures, and fetal upper respiratory tract resistance. Fetuses with diaphragmatic hernia spent significantly more time with diaphragm-nonrelated perinasal flow than did fetuses in cases of uncomplicated pregnancy, which can cause the increased loss of lung liquid and consequently be associated with pulmonary insufficiency in the early neonatal period.

Body Fluids↗

PubMed1996

Patterns of perinasal fluid flow and contractions of the diaphragm in the human fetus.

Our aim was to identify patterns of fetal perinasal fluid flow, and to determine the relationship of pattern of flow to the diaphragmatic component of fetal breathing movements. Twenty-four fetuses were studied with the use of two ultrasound systems simultaneously. Continuous video-tape records of the color and spectral Doppler imaging of fluid flow velocity in the nose and of the movements of the fetal diaphragm were made on two video recorders during 30-min study sessions. Two different patterns of fetal perinasal flow were recognized. One type had a rapid rate and low amplitude, and was independent of ultrasonographically observed movements of the fetal diaphragm. The other type had a lower rate and higher amplitude, and was uniformly related to diaphragmatic contractions. The breath-to-breath interval, time of inspiration, time of expiration and peak inspiratory and expiratory velocities were determined for each type of perinasal flow. Two ratios were used to quantify the change of peak flow velocity. There were significant differences in the values of all timing parameters between diaphragm-related perinasal flow velocities and those not related to the diaphragm, at both 30-36 and 37-41 weeks of gestation. The rate of perinasal flow related to diaphragmatic contraction cycles was one-third that of the flow cycles not related to diaphragmatic contraction (approximately 50 vs. 148 cycles/min). For both patterns of perinasal flow velocity, the expiratory peak velocity ratio was about 1.6 times higher than the inspiratory peak velocity ratio. We conclude that, in uncomplicated pregnancy, one pattern of fetal perinasal fluid flow reflects activity of the diaphragm. We speculate that the contractions of the fetal airway smooth muscle or oropharyngeal-laryngeal muscle groups are the origin of the second pattern of perinasal flow.

Blood Flow Velocity↗

PubMed1995

Methodological issues in coding sleep states in immature infants.

Thirty-five healthy, premature infants, ranging from 30-39 weeks postconceptional age, were observed continuously for 6 to 24 hr. Behavioral state and electroencephalographic patterns were coded for each minute. Using these data, three questions regarding coding of states of sleep were addressed: What is the concordance between behavioral codes and specific EEG patterns? Does the concordance between behavioral codes and EEG patterns change with postconceptional age? What range of error can be expected when observation periods shorter than 24-hr are used to estimate the daily distribution of quiet sleep (QS) and active sleep (AS)? With behavioral codes as the standard, concordances of EEG patterns for QS and AS were 72.5 and 92.1% respectively. With EEG patterns as the standard, behavioral codes for QS and AS agreed 83.0 and 88.9%. Agreement between behavioral codes and EEG patterns for QS increased with age. Finally, variation in estimates of the daily distribution of QS and AS decreased dramatically as the length of observation increased from 3 to 24 hr.

Arousal↗

PubMed1994

The role of mother's voice in the organization of brain function in the newborn.

Newborn infants prefer the sound of the maternal voice within the first two days after birth. This early preference may be based on prenatal experience. The mother's voice is reported to be the most intense acoustical signal measured in the amniotic environment. Data showing the ability of the newborn to demonstrate voice preferences are presented. We have also investigated the response of the perinatal autonomic nervous system to speech sound stimulation. Both the newborn and fetus show heart rate decelerations in response to speech sounds. This cardiorespiratory attentional response occurs during sleep when sensory stimulation is probably influencing perinatal brain development. Early experience with voice has both acute and enduring effects on the developing brain. These effects have ramifications for the development of the auditory system, as well as for later social and emotional development. Further speculation and discussion on the form, function and assessment of newborn responsiveness to voice will be offered.

Brain↗

PubMed1993

Response of the premature fetus to stimulation by speech sounds.

The response of the premature fetus to speech stimuli was studied in 41 healthy pregnant patients at 26-34 weeks gestation. Speech stimuli consisted of repeated syllables ('ee' and 'ah') presented externally over the maternal abdomen at either 100, 105, or 110 decibels (dB). Sound stimuli were delivered during periods of both high and low fetal heart rate variability. During periods of low FHR variability, a decrease in fetal heart rate and an increase in the standard deviation of heart rate were found. During periods of high FHR variability, no significant change in either of these measures was observed. This is the first clear demonstration of heart rate responses to speech stimuli in the premature fetus. As is the case in the term fetus, this response is dependent on baseline heart rate variability which is the primary determinant of fetal state. The clinical usefulness of this finding may be limited by the magnitude of the response.

Acoustic Stimulation↗

PubMed1993

A quantitative method for classification of EEG in the fetal baboon.

Electroencephalographic (EEG) activity is used as a primary indicator of sleep states in adults and infants of many species and in the ovine fetus. We recently reported that the baboon fetus exhibits visually discernable patterns of EEG activity. One pattern of activity, characterized by the intermittent presence of repetitive bursts of high-voltage EEG, is indistinguishable from trace alternant (TA). TA is a distinctive pattern of EEG activity found only during early stages of development in primates. TA is the predominant pattern of EEG activity during quiet sleep in human infants < 2 mo of age. The focus of this study was to derive quantitative parameters that would discriminate TA from other activity and then to develop a method for automated categorization of EEG patterns. Results demonstrate that several parameters derived from frequency-domain analyses are related to visually coded EEG states. Among these parameters, high-frequency power (12-24 Hz) and spectral-edge frequency are good discriminators of EEG patterns. This paper describes a new parameter, EEG ratio, computed as spectral power in the rectified EEG within a band that corresponds to the frequency of bursts of activity during TA (0.03-0.20 Hz) divided by power in the 12- to 24-Hz band. This new composite parameter of EEG activity provides a markedly better correlate of visually coded EEG than any of the individual parameters tested. Using cluster analysis, we devised a method for objective minute-by-minute dichotomization of EEG ratio. The method produces results that agree with visual coding of EEG activity 87.1% of the time.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Vibroacoustic stimulation evokes human fetal micturition.

OBJECTIVE: To examine the effect of vibroacoustic stimulation on fetal voiding as a measure of stress. METHODS: Fetal bladder volumes were examined serially by ultrasound 5 and 1 minutes before and 1 and 5 minutes after vibroacoustic stimulation (21 cases) or sham stimulation (20 cases). RESULTS: In the stimulated group, the mean (+/- SD) bladder volume decreased from 21.7 +/- 11.3 mL 1 minute before stimulation to 12.8 +/- 9.4 mL 1 minute after vibroacoustic stimulation, a statistically significant difference (P < .001). There was no significant decrease in bladder volume in the sham-stimulated fetuses. The correlations between bladder volume 1 minute before and 1 and 5 minutes after vibroacoustic stimulation were statistically significant (P < .01 and P < .001, respectively). CONCLUSION: Vibroacoustic stimulation induces fetal voiding, which may reflect a response to stress.

Acoustic Stimulation↗

PubMed1992

Canonical and non-canonical syllable discrimination by two-day-old infants.

Canonical syllables may be important units in early speech perception as well as production. Twenty infants (mean age 51 hours) (and twenty controls) were tested for their ability to discriminate between members of syllable pairs which were either canonical (paet and taep) or non-canonical (pst and tsp). A discrimination learning method was used in which syllables signalled the availability of either a recording of the mother's voice or silence--one of which was presented if the infant began a sucking burst. Infants in the canonical condition changed sucking patterns during signals over an 18-minute experimental session and activated their mother's voice more than silence, consistent with previous experiments using mother's voice as a reinforcer. In the non-canonical condition, infants also changed sucking patterns but sucked more during the signal for quiet than mother's voice, contrary to previous findings. Differential sucking during the syllables indicated discrimination in both conditions, but infants responded differently depending upon whether the syllables were canonical or non-canonical. The activation of silence in the non-canonical condition may be the result of a preference for quiet, but it is better explained as a failure to progress to a level of differential responding that was reached by the canonical group.

Age Factors↗