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Biomedical subjects

R E Lasky

Publications and source records attributed to R E Lasky.

At least 37 records · Page 2Linked to original sources
PubMed1993

Binaural maximum length sequence auditory-evoked brain-stem responses in human adults.

This study compared monaural and binaural maximum length sequence auditory-evoked brain-stem responses (MLS ABRs) in normal hearing adults. The first experiment demonstrated that reliable binaural MLS ABRs could be recorded which were essentially the same as those recorded monaurally. The second experiment generalized this finding by assessing a range of intensities including threshold stimuli. ABR thresholds, wave V latency x intensity and amplitude x intensity functions, wave V latency and amplitude reproducibility, and waveform reproducibility were comparable for the monaural and binaural MLS ABRs with some minor qualifications. In the third experiment, comparability of monaural and binaural MLS ABRs was generalized to a range of rates from those used conventionally to rates far faster than possible with signal averaging. Again, there was little difference between the binaural and monaural MLS ABRs over the range of rates assessed.

Acoustic Stimulation↗
PubMed1992

Maximum length sequence auditory evoked brainstem responses in human newborns and adults.

Experiment 1 investigated developmental differences at high stimulus rates by using maximum length sequences (MLSs) and cross-correlation techniques to recover auditory evoked brainstem responses (ABRs). Reliable MLS ABRs were recorded in all of the newborns tested at the highest rate presented (minimum interpulse interval = 1.1 msec). Interpreting developmental rate effects from latency and amplitude shifts is problematic. Identification of higher order kernals offers new information concerning developmental rate effects. Kernel slices were measured at lower rates in more adults than newborns, suggesting that the newborn auditory system is less sensitive to temporal nonlinearities than the mature auditory system. This runs counter to developmental rate studies using conventional stimuli. Experiment 2 investigated developmental differences at high rates due to varying stimulus intensities. MLS wave V intensity functions were less steep than conventional wave V intensity functions. MLS thresholds were also higher than conventional thresholds (primarily due to the newborn data). Without equating for signal-to-noise ratio, it is difficult to make unambiguous conclusions concerning the observed developmental differences.

Acoustic Stimulation↗
PubMed1991

The effects of rate and forward masking on human adult and newborn auditory evoked brainstem response thresholds.

Several investigators have reported that human newborn auditory brainstem evoked response (ABR) thresholds to clicks are about 10-20 dB higher than human adult thresholds to the same stimuli (Galambos & Hecox, 1978; Shulman-Galambos & Galambos, 1979; Lasky, Rupert, & Waller, 1987). The present study replicated these results, but, in addition, addressed developmental differences in ABR thresholds due to forward masking and changes in stimulus repetition rate. Eight human newborns and seven human adults served as subjects. Newborn ABR thresholds to a 100 microseconds click which followed a 82 db(A) SPL 50 ms broadband forward masker by 10 ms were significantly more elevated relative to their unmasked ABR thresholds than were those of the adults. Relatively loud sounds seem to have a greater effect on the newborn's ability to process subsequently presented soft sounds than they do on adult processing. In contrast, changes in repetition rate of 100 microseconds clicks from 10/s to 50/s had no greater effect on newborn than adult ABR thresholds. At near threshold stimulus levels, rate effects on the ABR are not apparent in newborns nor adults.

Adult↗
PubMed1990

Neonatal intracranial hemorrhage: I. Changing pattern in inborn low-birth-weight infants.

Many reports of the occurrence of periventricular-intraventricular hemorrhage (PVH-IVH) are biased by the inclusion of both inborn and outborn infants. To obviate this selection bias we examined a large inborn population of low-birth-weight infants to determine if the incidence of PVH-IVH changed over a 3-year interval from March, 1982 through February, 1985. Serial cranial ultrasonography was performed in 463 consecutive infants of birth weight less than or equal to 1500 g who survived for more than 8 h. The incidence of PVH-IVH decreased from 31.5% and 29.3% in years 1 and 2, respectively, to 23.7% in year 3 (P less than 0.05). The latter reflected a fall in the incidence of grades III and IV PVH-IVH, but no change in the incidence of grades I and II. This observation was not attributable to changes in mortality, the distribution of infants by birth weight and estimated gestational age in each year of the study, or infants excluded from the analysis. Contrary to most reports, 21.9% of all PVH-IVH during the 3 years were first diagnosed after 14 days postnatal age and were predominantly grade I. These results document not only a change in the epidemiology of PVH-IVH in an inborn population, but also the importance of serial cranial ultrasonography beyond the first week of life.

Birth Weight↗
PubMed1990

Neonatal intracranial hemorrhage: II. Risk factor analysis in an inborn population.

The ability to predict the occurrence of neonatal periventricular-intraventricular hemorrhage (PVH-IVH) would be useful in the design of clinical trials to prevent its occurrence. Therefore, data were collected from 463 consecutive infants less than or equal to 1500 g birth weight delivered between March 1, 1982 and February 28, 1985. This large population made it feasible to divide the infants into two groups, using one group to develop a model predictive of ICH and the second group to test the validity of the model. Infants were randomly grouped by sex, race, gestational age, birth weight, month of birth, mortality, and incidence and grade of worst PVH-IVH. In Group A (n = 232), respiratory distress syndrome, ventilator therapy, PaCO2 greater than or equal to 60 mmHg, PO2 less than or equal to 40 mmHg greater than or equal to 2 h, lower 1- and 5-min Apgar scores, lower pediatric estimation of gestational age, and pneumothorax were significantly associated with PVH-IVH by univariant analyses (chi 2, P less than 0.03). Multivariant discriminant analysis performed on Group A revealed that pneumothorax, cesarean section, PaCO2, and ventilator therapy were most predictive of PVH-IVH, but sensitivity was 55% and specificity 78%. Applying the model to Group B, sensitivity decreased to 21% while specificity rose to 93%. Logistic regression, which takes into account non-normally distributed variables, did not improve predictability.(ABSTRACT TRUNCATED AT 250 WORDS)

Apgar Score↗
PubMed1988

An analysis of potential biases in the loss of indigent infants to follow-up.

Loss to follow-up is a major problem in indigent inner-city populations. We evaluated a large, well-described, inborn indigent population of high-risk infants (HRI) and control infants (CI) to assess possible selection biases in loss to follow-up at one year adjusted age. Serial clinic visits, phone calls, and letters and payment of $20.00 for attending at 1 year was used to minimize patient loss. Yet, the 1 year loss rate was high, and among HRI, greater for ventilator-treated infants greater than 1500 g birthweight (71/114; 62%) than for ventilator-treated very-low-birthweight (VLBW; less than 1500 g) infants (39/108; 36%) or non-ventilated VLBW infants (62/145; 43%) (P less than 0.05). Multivariate analyses indicated that those lost to follow-up were at no greater risk of a poor outcome on the basis of prenatal and perinatal medical and socioeconomic findings than were those in the same risk group (HRI or CI) or subgroup of HRI who were examined at 1 year. In a review of hospital records, similar rates of hospitalization and neurologic problems during infancy were identified for HRI examined and HRI lost to follow-up. The identification of such morbidity during infancy may be less complete for HRI lost to follow-up than for those examined. Thus, the high frequency of deficits observed in follow-up evaluation of indigent HRI is unlikely to result from loss of unaffected infants.

Child Health Services↗
PubMed1987

Disappointing follow-up findings for indigent high-risk newborns.

Indigent populations have received little attention in neonatal follow-up studies. We conducted "blinded" evaluations one year past term for 204 indigent high-risk infants who were ventilator treated or had a very low birth weight (VLBW) (less than or equal to 1500 g) and 85 healthy term controls from families similar to those of the high-risk infants. Marked developmental delay (Bayley Mental Developmental Index, less than 70) or gross motor abnormality occurred in 2% of controls, 27% of VLBW infants, 33% of ventilator-treated infants, and 39% of ventilator-treated VLBW infants. Despite considerable effort to prevent attrition, 43% of high-risk survivors were unavailable for follow-up at the one-year visit. Even if all of these infants were assumed to be normal, the incidence of developmental delay exceeded that in 11 of 12 recent studies. Indigent high-risk infants deserve considerable follow-up attention because of their high rate of attrition and developmental delay.

Anthropometry↗
PubMed1987

Reproducibility of auditory brain-stem evoked responses as a function of the stimulus, scorer and subject.

The reproducibility of auditory brain-stem evoked response (ABR) measurements was determined in a series of studies. ABRs were recorded from pre-term (32 and 36 weeks) newborns, term newborns, and adults to 3 different stimuli. Records were scored blindly with no knowledge of the subject, stimulus eliciting the response, or other records by that subject. Two scorers (inter-scorer reliability) and a single scorer over time (intra-scorer reliability) could score records using explicit criteria with a high degree of agreement. In contrast variability between replicate records to the same stimulus from the same subject was considerable. Intra-subject variability was not strongly affected by the age of the subject but was a function of the eliciting stimulus (the low intensity and fast repetition rate stimuli elicited more variable responses than loud, slow stimuli) and the wave measured (wave I latency was significantly more variable than the other measurements). Healthy, term newborns were studied to investigate the reproducibility of ABRs in the first few days after birth. There was a rapid reduction in ABR latency in the first 6-12 h after birth and a more gradual reduction thereafter. The prolonged latencies observed immediately after birth were associated with an elevation in ABR threshold. The reduction in latency was observed in vaginal and cesarean deliveries. These same effects were observed for amplitude of the ABR, but the trends were generally not significant. Despite the large changes in ABR latency within the first few days after birth, ABR latencies in response to some stimuli were significantly correlated between sessions separated by all intervals tested, ranging from 2 h to 2 days.

Adult↗
PubMed1986

Methods for determining auditory evoked brain-stem response thresholds in human newborns.

Previous investigators have reported that newborn auditory evoked brain-stem responses (ABRs) are 20-30 dB higher than adult psychophysical thresholds to the same stimuli. These investigators reduced the intensity of the stimulus until they no longer reported an ABR to the stimulus. We adapted 2 widely used psychophysical methods, the up-down-transformed response (UDTR) method and the method of constant stimuli, for ABR threshold determination of human newborns. Response judgments were made blindly. ABR thresholds of healthy normal newborns by both procedures were no more than 10-15 dB higher than adult psychophysical thresholds. The differences between the newborn ABR thresholds we reported and those in the literature were probably explained by different procedures including the method used to estimate adult psychophysical thresholds. The correlations between ABR thresholds and suprathreshold ABR latencies and amplitudes and latency and amplitude/intensity functions were modest at best. In normal newborns suprathreshold ABR measurements are of little value in predicting ABR thresholds.

Brain Stem↗
PubMed1986

Brainstem auditory evoked potentials in very-low-birth-weight neonates with intracranial hemorrhage.

A study was conducted in very-low-birth-weight (VLBW) neonates to correlate structural damage to the central nervous system due to intracranial hemorrhage (ICH) with electrophysiological function of the lower auditory system as measured by brainstem auditory evoked potentials (BAEP). BAEP testing of 61 VLBW neonates was completed at 36 weeks conceptional age. BAEP Wave III and V latencies significantly increased with increasing severity of ICH. Although significant at conventional levels (P less than 0.05), these correlations were of modest size. Furthermore, after adjusting for the effects of birthweight, hypoxia, lowest pH and associated pCO2 the correlation between ICH and BAEP was reduced in magnitude and no longer significant. Thus, there is little evidence that ICH shortly after birth affected functioning of the auditory brainstem pathways in VLBW neonates at 36 weeks conceptional age.

Brain Stem↗
PubMed1984

A developmental study on the effect of stimulus rate on the auditory evoked brain-stem response.

Four groups of subjects were presented auditory stimuli differing only in repetition rate. One group was adults, another term newborns, and the other 2 groups were preterm newborns tested at respectively, 32 and 36 weeks postconceptional age. All 4 groups were judged to be audiologically and neurologically normal at the time of testing. Six stimulus repetition rates were presented to each subject, 10, 20, 40, 50, 66 2/3, and 80/sec. Auditory evoked brain-stem responses (ABRs) were recorded to each stimulus. Increasing repetition rate increased ABR wave form latencies and decreased ABR wave form amplitudes at all ages tested. For the most reliable measurement, wave V latency, a linear function effectively described the latency-rate function for individual subjects at all ages. The slope of the wave V latency-rate function increased with decreasing age. It was 300 microseconds decade change in rate at 32 weeks, 227 microseconds/decade at 36 weeks, 162 microseconds/decade at term, and 86 microseconds/decade in adults. Wave V latencies were more prolonged by rate than waves I and III and the differences in the rate effects between waves V and I and III increased with decreasing age. Amplitude was a less reliable measurement and amplitude-rate effects were less consistent than latency-rate effects.

Acoustic Stimulation↗
PubMed1984

Maternal-infant interactions at one-year adjusted age in infants at low- and high-risk as newborns.

To compare maternal-infant interactions in high- and low-risk groups, we observed infants who had required neonatal intensive care and otherwise similar infants with normal perinatal histories in a follow-up clinic at one year adjusted age. The developmental level as assessed by the Bayley Scales of Infant Development was significantly lower for the high-risk infants than for the control infants at one year of age. Principal component analyses were used to define interaction patterns in each of five situations. Principal component analyses allow a more meaningful analysis of interrelated maternal and infant behaviors than do standard statistical analyses and minimize the likelihood of misleading 'significant' findings resulting from multiple comparisons. Prior to being examined, mothers of control infants were more likely to adopt an 'en face' position, play with, comfort, talk to, and smile at their infants than were mothers of high-risk infants. Control infants were more likely to smile in return. These differences between control and high-risk mother-infant dyads disappeared when the infants' developmental level was statistically controlled. Group differences in maternal-infant interactions independent of the infants' developmental level were observed in only one situation (collection of blood). Specific medical risk factors had little relation to findings at one year. Maternal-infant interaction should be interpreted in relation to the postconceptional and developmental age as well as the postnatal age of the infant.

Child Behavior↗
PubMed1983

Measurement of bone mineral content of preterm neonates.

Although photon absorptiometry is increasingly used to evaluate bone mineral content of neonates, its reliability in this age group is unclear. The midradius or middistal radius of 12 growing preterm infants was scanned, using a Norland 278 Densitometer. Proper examiner technique and densitometer calibration were first verified. In three infants, the bone edges were not consistently discernible from soft tissue. In the remaining nine infants, apparatus variability (the percent change in bone mineral content of scans repeated without repositioning the infant) was comparable to intraexaminer and interexaminer variability (determined after the same or a different examiner repositioned the infant and repeated the scan). The variability for successive scans ranged from -73% to +60% (SD, 5% to 36%). Adequate reliability for preterm infants remains to be documented for commercially available photon absorptiometers by in vivo studies.

Bone and Bones↗
PubMed1983

Growth, metabolic response, and development in very-low-birth-weight infants fed banked human milk or enriched formula. I. Neonatal findings.

Banked human milk has been widely used, although its composition and nutritional adequacy for preterm infants are uncertain. We randomized 76 healthy infants of less than or equal to 1500 gm birth weight to ad lib feedings of frozen BHM or a protein-mineral-calorie-enriched formula (Similac Special Care) designed to sustain intrauterine accretion rates; BHM contained 2.2 gm fat/100 ml and 60 kcal/100 ml (gross energy). Infants fed BHM ingested more milk (197 vs 165 ml/kg/day) but less gross energy (118 vs 143 kcal/kg/day); grew less rapidly in weight (15 vs 30 gm/day), length (0.7 vs 1.1 cm/wk), and head circumference (0.8 vs 1.2 cm/wk); and were discharged at a lower weight (2200 vs 2348 gm) and older age (61 vs 47 day) than infants fed formula (P less than 0.02). At 37 weeks' postmenstrual age, infants fed BHM were less responsive to Brazelton inanimate stimuli (mean total score 5.0 vs 7.5; P less than 0.02). With few exceptions, blood amino acids, pH, and serum electrolyte values were similar in both groups. The different caloric intake of our feeding groups may explain only part of the large difference in growth rate. Donor milk should not be fed to preterm infants unless it has been analyzed and the feedings shown to provide a nutrient intake considered appropriate to the needs of these infants.

Body Weight↗
PubMed1983

Differences on Bayley's infant behavior record for a sample of high-risk infants and their controls.

3 groups of high-risk newborns and their controls were assessed at 92 weeks post-conceptional age using Bayley's Infant Behavioral Record (IBR). The 3 groups of high-risk infants were those who weighed 1,500 grams or less at birth and required no ventilator therapy, those weighing 1,500 grams or less at birth who required ventilator therapy, and newborns weighing more than 1,500 grams at birth who required ventilator therapy. Controls were healthy term infants matched for 7 socioeconomic and demographic variables. The first principal component of the IBR ratings for the 3 groups of high-risk infants and the controls were similar. All 3 groups of high-risk infants received less desirable IBR ratings on most items than their controls. In addition, there were some differences among high-risk groups; ventilated infants regardless of birth weight received the lowest ratings reflecting overall performance on the IBR, very low birthweight, ventilated newborns were more likely to receive ratings characterizing an overly active infant with a short attention span, and very low birth-weight, never-ventilated infants were most likely to be rated as happy but passive and delayed. The differences between the high-risk infants and controls in large part resulted from infants who were also delayed in terms of their mental and motor development.

Female↗