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Biomedical subjects

V Chernick

Publications and source records attributed to V Chernick.

At least 55 records · Page 3Linked to original sources
PubMed1985

Interference of cardiovascular sounds with phonopneumography in children.

We have used fast Fourier transform and power spectra analysis to determine possible interference of cardiovascular sounds with the analysis of breath sounds in children. Ten normal children, 8 to 13 yr of age, were studied with sound transducer over midprecordium, right upper lobe, and right lower lobe along with simultaneously recorded ECG and air flow. Detection of R-waves facilitated sampling of sound segments at defined flow rates, with inclusion or exclusion of heart sounds. Measurements during breath-holding and without heart sounds served as baseline values. Heart sounds were only slightly attenuated over the right upper lobe. There was a considerable overlap in the power spectra of heart and breath sounds, mainly in frequencies below 100 Hz. Analysis of low-frequency components of normal breath sounds requires sampling during parts of the cardiac cycle that are free of cardiovascular sounds.

Adolescent↗
PubMed1985

The effect of anticholinergic treatment on postexertional wheezing in asthma studied by phonopneumography and spirometry.

Postexertional wheezing is an important clinical sign of nonspecific airway hyperreactivity. We have studied wheezing after exercise in 6 asthmatic subjects, 13 to 20 yr of age, using spectral analysis of recorded tracheal sounds. Automated spectral characterization was used to measure wheezing as a proportion of respiratory time. Anticholinergic treatment with ipratropium bromide (Atrovent) was compared with placebo to investigate effects on postexertional wheezing, and pulmonary function was compared with the result of respiratory sound analysis. Atrovent did not abolish exercise-induced bronchospasm but improved preexercise lung function and thereby caused a parallel upward shift in the response curves. Wheezing after Atrovent was significantly less, later in onset, and mainly expiratory at 20 min after exercise. Wheezing as a percentage of total respiratory time correlated well with FEV1, Vmax50, and SGaw. Analysis of respiratory sounds and automated quantification of wheezing may be a useful complementary test of bronchial obstruction in asthma.

Adolescent↗
PubMed1984

Response to cold air hyperventilation in normal and in asthmatic children.

To assess the sensitivity of isocapnic hyperventilation with cold air in detecting airway hyperreactivity in asthmatic children, we studied 13 asthmatic patients (mean age 11.1 years) and 10 normal children. Cold air challenge consisted of 4 minutes of moderate hyperventilation plus another 4 minutes of maximal hyperventilation, both with subfreezing air (-16 degrees to -18 degrees C). Exercise and IHCA tests were done within 5 days and in random sequence. Mean (+/- SE) maximal % delta FEV1 after IHCA was 27 +/- 5.1% in the asthmatic children vs 4.5 +/- 1.2% in the normal subjects (P less than 0.01), even though there were no significant differences in the maximal minute ventilation equivalent between the two groups. Mean maximal % delta FEV1 after exercise was 31.7 +/- 5.6 in the asthmatic group. There was no difference in the sensitivity of the exercise and IHCA tests to detect bronchospasm in asthmatic children. Airway obstruction after IHCA was sharp and brief: maximal at 3 minutes after challenge, and back to 10% of baseline after 11 minutes. In seven asthmatic children the refractoriness to cold air and exercise was studied by repeating each test within 30 minutes; all seven showed significant refractoriness to exercise, and six showed no refractoriness to IHCA. We conclude that exercise and cold air-induced bronchospasm have different physiologic mechanisms, and that cold air testing can be used as a routine challenge to identify airway hyperreactivity in children.

Adolescent↗
PubMed1984

Hypercapnia alters sleep state pattern.

Mild hypercapnia in the adult animal does not affect sleep pattern but more severe hypercapnia in the fetus increases the duration of REM sleep. Adult male rats were exposed daily for 2-3 h sessions at random to 6, 7, and 8% CO2 or room air. Breathing CO2 caused a 60% increase in sleep onset latency, a 28% decrease in sleep duration, but no change in percent time spent in REM. However, the duration of REM sleep episodes increased by 30%. Thus, in both fetal and adult animals severe hypercapnia appears to have a similar effect on sleep pattern.

Analysis of Variance↗
PubMed1984

Naloxone reduces decrease in ventilation induced by hypoxia in newborn infants.

The mechanism responsible for the decrease in ventilation during breathing of low fractional concentration of inspired O2 in the newborn infant is poorly understood. The present study tested the hypothesis that endogenous opiates account for this ventilatory decrease. Eleven healthy newborn infants breathed 15% O2, balance N2 for 5 min following an injection of saline and following an injection of naloxone. Neither injection caused a change in minute ventilation (VE) or ventilatory pattern when the infants were breathing room air. However, the decreased ventilation during hypoxia following naloxone was significantly less than that following saline. VE dropped about 14% following saline but only about 4% following naloxone. However, the adult ventilatory response to hypoxemia, i.e., a relatively sustained increase in VE, was not attained. Naloxone had no influence on the occurrence of periodic breathing during hypoxemia. Thus in the healthy full-term newborn infant, endogenous opiates account only for a part of the decreased ventilation during hypoxemia.

Humans↗
PubMed1984

Indomethacin-induced fetal breathing: mechanism and site of action.

The mechanism and site of action of indomethacin-induced fetal breathing (FB) was investigated in 26 chronically prepared fetal lambs. Indomethacin, which preferentially blocks prostaglandin production, was infused into the fetal circulation in two stages, 60 mg in 10 min and 60 mg over 7 h. Indomethacin stimulated sleep-state independent FB that was greatly reduced or abolished by infusions of prostaglandin E2 (PGE2). Infusions of nordihydroguaiaretic acid, which preferentially blocks the synthesis of leukotrienes, had no consistent effect on either fetal sleep or breathing activity when administered alone or after indomethacin. This suggests that the characteristic FB induced by indomethacin is due to inhibition of prostaglandin synthesis (PGE2) and not due to an overproduction of leukotrienes. The indomethacin effect on FB was observed in all fetuses tested including those deprived of peripheral chemoreceptor function, vagotomy, decortication, or spinal cord section at the T1 level. Complete constriction of the ductus arteriosus for many hours had no effect on FB. We conclude that inhibition of PGE2 synthesis stimulates FB by a central mechanism other than the cortex.

Animals↗
PubMed1984

ECoG and breathing activity in fetal lambs after undercut of cerebral cortex.

Reduction of cortical inhibition has been suggested as a possible mechanism for the transition from episodic fetal to continuous postnatal breathing. Twelve fetal lambs were chronically decorticated at 112-115 days gestation. Lateral rectus, neck, and diaphragmatic electromyogram (EMG), electrocorticogram (ECoG), and tracheal and arterial blood pressure were monitored after allowing 3 days for recovery. The fetal lambs were studied for 4-28 days in 2- to 4-h sessions/day. There were no episodes of low-voltage high-frequency ECoG activity. The mean duration (+/- SD) of rapid eye movements (REM) measured by lateral rectus EMG [11 +/- 7.9 min and periods of tonic activity or silence [non-REM (NREM)], 14 +/- 7.4 min] in decorticated fetuses were not statistically different from REM (12 +/- 5.1 min) and NREM (15 +/- 6.8 min) sleep periods in intact fetuses. After decortication, the percentage of time (+/- SD) occupied by different states were phasic diaphragmatic EMG activity 36 +/- 7.8%, tonic diaphragmatic EMG 21 +/- 8.6%, and diaphragmatic silence 43 +/- 14.2%. Phasic diaphragmatic EMG activity occurred together with REM, the latter being present 45 +/- 3.7% of the time. Despite decortication, between 115 and 125 days gestation ECoG changed from a trace alternans to a high-voltage low-frequency pattern. We conclude that the cerebral cortex is not responsible for apnea during fetal life. In addition, these data suggest that the cerebral cortex may normally be the source of ECoG synchrony.

Animals↗
PubMed1984

Human pancreatic growth hormone releasing factor (hpGRF-1-40) stimulates GH release in the ovine fetus.

The effects of growth hormone-releasing factor, hpGRF (1-40), on plasma GH levels were studied in chronically catheterized ovine fetuses between 71 to 134 days of gestation. The basal ovine (o) GH levels in the fetus ranged between 41 - 144 ng/ml, while values in the ewe were often less than 6 ng/ml. hpGRF (1-40), 5 micrograms/kg infused into a fetal vein, markedly stimulated GH release in all nine fetuses. The maximum increase above pretreatment levels (net increases) ranged from 65 ng/ml to 498 ng/ml, with a mean net increase of 229 ng/ml. The responses of oGH in fetuses at younger gestational age appeared to be greater than in older fetuses. Mean plasma oPRL did not change after hpGRF infusion. These results indicate that somatotrophs in fetal sheep in mid- and late gestation have receptors for GRF, and GH secretion may be modulated by GRF at this stage of gestation.

Animals↗
PubMed1984

Prolonged effects of maternal alcohol ingestion on the neonatal electroencephalogram.

Newborn infants of mothers who drink heavily (greater than 2 oz alcohol per day) during pregnancy have been shown to have hypersynchrony of the EEG. The possibility that hypersynchrony is related to acute alcohol withdrawal was tested. Eleven preterm infants of mothers who drank heavily ("alcoholic") were studied at a postnatal age of 4 to 6 weeks using power spectral analysis of EEG signals. This group was compared with a control group with similar racial and socioeconomic status. In addition, a group of ten "healthy" preterm infants was compared with a carefully matched control group. Total power of the EEG during quiet, indeterminate and rapid eye movement (REM) sleep was 162%, 183%, and 188%, respectively, in the infants whose mothers were alcoholic when compared with their control infants or with the healthy preterm infants and their control infants. It is concluded that ingestion of alcohol during pregnancy may result in potentially serious prolonged effects on brain function of the offspring, even in the absence of dysmorphology.

Adolescent↗
PubMed1983

Effects of maternal alcohol intake and smoking on neonatal electroencephalogram and anthropometric measurements.

Anthropometric data and computerized electroencaphalogram analysis during quiet, indeterminate, and active sleep were obtained from infants of mothers of four groups: (1) heavy drinking mothers (greater than 2 ounces of alcohol per day); (2) nondrinking mothers; (3) smoking, nondrinking mothers; (4) nonsmoking, nondrinking mothers. Infants in groups 1 and 2 were matched as closely as possible for postconceptional age, sex, race, and socioeconomic status. Infants in groups 3 and 4 were matched similarly. Infants of alcoholic mothers had a significantly lower birth weight, length, and head circumference than those from the matched control group. Infants of smoking mothers had lower birth weights and lengths than infants of nonsmoking mothers, but head circumference was identical. Hypersynchrony of the electroencephalogram was seen only in "alcoholic" infants, and power spectral density analysis revealed that the average integrated power was significantly increased in quiet, active, and indeterminate sleep. The greatest increase in electroencephalogram power (212%) was seen in active sleep, and this analysis clearly separated 15 of 17 alcohol-exposed infants from the control infants. These data suggest that alcohol has a specific toxic effect on the fetal brain that is not linked with smoking habits. The neonatal electroencephalogram is affected even in the absence of dysmorphology and thus may be the most sensitive indicator of fetal alcohol toxicity.

Adolescent↗
PubMed1983

Drug-induced changes in fetal breathing activity and sleep state.

Drugs reported to stimulate fetal breathing (FB) were injected into a femoral vein of near-term fetal lambs during rapid eye movement (REM) and non-REM (NREM) sleep. The primary response to NaCN, 0.25-0.5 mg, a dose which did not flatten the electrocorticogram, was a brief burst of gasping in any sleep state. When injected during REM sleep, NaCN caused the cessation of spontaneous FB and the onset of gasping. Stimulation of FB was observed infrequently. Caffeine (10 mg) and doxapram (3 mg) frequently caused an immediate change in sleep state or arousal. The incidence of FB increased concomitantly with a change to REM sleep or wakefulness (W), but FB still ceased with the onset of NREM sleep. When administered during an episode of spontaneous FB during REM sleep, both caffeine and doxapram caused stimulation of the frequency and depth of breathing. Pilocarpine (4 mg) caused arousal and gasping followed by prolonged vigorous breathing that was dependent on intact carotid sinus nerves. Indomethacin (120 mg over several hours) did not affect sleep states but induced FB in both NREM and REM sleep. In summary, in the fetus the primary effect of NaCN is to suppress spontaneous FB and induce gasping and the effects of pilocarpine, caffeine, and doxapram are intimately related to sleep states or arousal. Indomethacin causes the conversion from episodic fetal to continuous postnatal-type breathing. These data indicate the importance of assessing fetal state of consciousness in interpreting the respiratory response to drugs.

Animals↗
PubMed1983

Chronic extracellular recording of fetal medullary neuronal activity.

A technique for chronic extracellular recording of neuronal activity in the medullary region of fetal sheep during different sleep states is described. Of 51 recorded neurones, 54% were associated with respiration, blood pressure changes, or muscle electromyograms, and 46% were nonspecific. During apnea (nonrapid-eye-movement sleep) both inspiratory and expiratory neurons had random intermittent activity. Thus apnea is not associated with tonic expiratory neuronal activity.

Animals↗
PubMed1983

Bacterial tracheitis--an old disease rediscovered.

During a 3-year period, seven children with bacterial tracheitis were admitted to the intensive care unit of the Winnipeg Children's Hospital. The illness was characterized by fever, toxicity, and stridor. Respiratory difficulty was secondary to copious thick purulent tracheal secretions. In the majority of patients the illness was caused by Staphylococcus aureus, and the rest had Hemophilus influenzae infection. Viral studies in five patients were negative. Most patients required endotracheal intubation and frequent tracheal toilet to prevent serious airway obstruction. In our ICU, bacterial tracheitis accounted for about 14 per cent of admissions with infectious upper airway obstructive illness, while epiglottis and croup accounted for 55 per cent and 31 per cent, respectively. Only 5 per cent of children with croup admitted to the hospital were admitted to the ICU. Bacterial tracheitis has reappeared, at least in North America, as an important and serious cause of obstructive upper airway disease in children and must be recognized early in order to prevent catastrophic airway obstruction.

Airway Obstruction↗
PubMed1982

Naloxone reverses neonatal depression caused by fetal asphyxia.

Pregnant near-term rabbits were given an intravenous dose of saline or the opiate antagonist naloxone and then asphyxiated. The fetuses were delivered by cesarean section and evaluated for respiration, color, muscle tone, response to stimulation, and general activity at 1, 3, 5, 10, 15, and 30 minutes of age. The naloxone-treated pups had significantly better scores during the first 15 minutes after birth than the saline-treated pups. Naloxone did not adversely affect the scores of nonasphyxiated pups. These data suggest that endogenous opiates worsen the neonatal depression caused by intrauterine asphyxia and that this effect can be reversed by naloxone.

Animals↗
PubMed1982

Influence of sleep state on the response to hypercapnia in fetal lambs.

The effect of sleep state on the respiratory response to hypercapnia was studied in 14 chronic fetal sheep, 125-140 days gestation. Fetal PaCO2 was raised by 11 to 34 Torr by gradually increasing the maternal FICO2 to 0.09. Fetal sleep state was monitored. Fetal breathing (FB) was analysed in terms of frequency (f), tracheal pressure (TP) and ventilation equivalent (VEq) = sigma TP /min. In 16 out of 17 experiments on apneic fetuses in NREM sleep, the fetuses switched to REM sleep and in 14 instances began to breathe within 2 1/2 min thereafter. The PaCO2 at which apneic fetuses started breathing was 54.8 +/- 8.4 Torr (mean +/- SD). In 4 out of 10 trials on breathing fetuses in REM sleep the fetuses switched to NREM sleep and stopped breathing before removal of the CO2 stimulus. During REM sleep hypercapnia stimulated FB by an increase in TP and by a reduction in the number and duration of apneic pauses. It is concluded that in the fetal lamb CO2 stimulates breathing only during REM sleep and that this stimulus is superimposed on the basic mechanism that stimulated spontaneous FB during this sleep state.

Animals↗