Severe hypoxemia in children with upper airway obstruction during sleep does not lead to significant changes in heart rate

Life-threatening cardiac arrhythmias, including bradyarrhythmias, are well-known sequelae of obstructive sleep apnea syndrome (OSAS) in adults and are associated with apnea and severe hypoxemia. Since the clinical expression of OSAS in children is different, we questioned whether arrhythmias are a common feature of pediatric OSAS. Therefore, we analyzed R-R interval patterns from 12 subjects (age 8 months to 14 years) with OSAS in detail. The diagnosis of pediatric OSAS is based on clinical signs of loud snoring and paradoxical respiratory efforts, as well as elevated end-tidal carbon dioxide tension (PETCO2) and major phasic decreases of oxyhemoglobin saturation (SaO2). Two hundred and nine episodes of severe hypoxemia, defined as SaO2 values < or = 85% lasting > or = 30 seconds, were identified. Only 29 (14%) of these episodes were associated with obstructive apneas. The R-R intervals were analyzed before and during each desaturation. Compared to baseline, mean and minimum R-R intervals (RRmean, RRmin) decreased during the desaturation episodes (P < 0.05), while maximum R-R interval (RRmax) increased (P < 0.05). Although the absolute changes in all parameters were significantly different from baseline, the magnitude of these changes was small, with a mean of -5.3%, -12.2%, and 10.4% for RRmean, RRmin, and RRmax, respectively. No child had life-threatening arrhythmias. Although severe hypoxemia existed in these children, the magnitude of the R-R interval changes was modest, and profound bradycardia as described in adults, was rare.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of acute hypoxia on metabolism and ventilation in awake piglets

We studied the effect of acute sustained hypoxia on ventilation (VE) and oxygen consumption (VO2) over one hour during quiet wakefulness in young (6 days) and older (6 weeks) piglets in thermoneutral conditions during baseline, moderate hypoxia (PaO2 approximately 45 mmHg), and severe hypoxia (PaO2 approximately 30 mmHg). During severe hypoxia, ventilation and pH increased while PaCO2 decreased in both age groups. Blood gas changes (decreases PACO2, increases pH), but not ventilatory changes, were greater in the older piglets (P < 0.05). VO2 decreased similarly (-30%) while VE/VO2 rose over 160% in both age groups. During moderate hypoxia, changes in blood gas, VE, and VO2 were in a similar direction, but smaller in magnitude. We conclude that: (1) changes in blood gases and VO2 are amplified by maturation and severity of hypoxia and (2) blood gas changes are greater in older vs young piglets despite similar ventilatory responses suggesting maturational differences in CO2 production or dead space ventilation.

Klippel-Feil sequence and sleep-disordered breathing in two children

We report two children with severe sleep-disordered breathing associated with Klippel-Feil sequence. In both patients, minor vertebral anomalies were associated with a major hindbrain anomaly. In one child, the Klippel-Feil sequence had been diagnosed previously, but the hindbrain anomaly was not recognized. Two years later, this child developed fatal obstructive sleep apnea. In the other child, neither the Klippel-Feil sequence nor hindbrain anomaly had been identified before the child's presentation with sleep-disordered breathing characterized by bradypnea and stridor. Because many of the complications of hindbrain anomalies may be amenable to neurosurgical treatment, we recommend that patients with Klippel-Feil sequence be followed for the development of sleep-disordered breathing. Sleep complaints need prompt evaluation with polysomnography, whereas neurologic signs require imaging with attention to the cervicomedullary junction. Unsuspected CNS disorders must be considered in children who present with stridor or serious respiratory disturbances during sleep.

Adult criteria for obstructive sleep apnea do not identify children with serious obstruction

Although obstructive sleep apnea (OSA) occurs in the pediatric population, diagnostic criteria have not been established. Since criteria for adult OSA are well established, we asked whether commonly used adult criteria, such as the apnea index (based on the number of obstructive apnea [OA] events per hour), would identify children with serious sleep-related upper airway obstruction. Polysomnographic data were analyzed from 20 children (ages 8 months to 16 yr) with clinical evidence of upper airway obstruction during sleep (loud snoring and labored breathing) and who had cyclic oscillations of oxyhemoglobin saturation (SaO2) during sleep. The overnight studies included sleep state (EEG, EOG, and EMG), SaO2, ECG, nasal (end-tidal CO2) and oral (thermistor) airflow, chest and abdominal movement (inductance plethysmography), and video camera and behavioral observations. Measurements included the number of obstructive events > or = 10 s, the number of desaturations (> or = 5% decrease lasting > or = 5 s), the number of desaturation episodes to < 90%, < 85%, and < 80% lasting > 5 s, and the percentage of sleep time with SaO2 values < 90%. Gas exchange was impaired as evidenced by cyclic decreases in SaO2 and elevated PETCO2 values (maximum value 58 +/- 6 mm Hg). The children experienced 175 +/- 168 (range 6 to 609) episodes of decreased SaO2 > 5%, with an average minimum SaO2 of 66 +/- 13% (range 30 to 85%). The average number of apnea events was only 1.9 +/- 3.2 events/h (range 0 to 10.4).(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of unique sets of GPI-linked proteins by different primary neurons in vitro

We have surveyed the proteins expressed at the surface of different primary neurons as a first step in elucidating how axons regulate their ensheathment by glial cells. We characterized the surface proteins of dorsal root ganglion neurons, superior cervical ganglion neurons, and cerebellar granule cells which are myelinated, ensheathed but unmyelinated, and unensheathed, respectively. We found that the most abundant proteins are common to all three types of neurons. Reproducible differences in the composition of the integral membrane proteins (enriched by partitioning into a Triton X-114 detergent phase) were detected. These differences were most striking when the expression of glycosylphosphatidyl-inositol (GPI)-anchored membrane proteins by these different neurons was compared. Variations in the relative abundance and degree of glycosylation of several well known GPI- anchored proteins, including Thy-1, F3/F11, and the 120-kD form of the neural cell adhesion molecule (N-CAM), and an abundant 60-kD GPI-linked protein were observed. In addition, we have identified several potentially novel GPI-anchored glycoproteins on each class of neurons. These include a protein that is present only on superior cervical ganglion neurons and is 90 kD; an abundant protein of 69 kD that is essentially restricted in its expression to dorsal root ganglion neurons; and proteins of 38 and 31 kD that are expressed only on granule cell neurons. Finally, the relative abundance of the three major isoforms of N-CAM was found to vary significantly between these different primary neurons. These results are the first demonstration that nerve fibers with diverse ensheathment fates differ significantly in the composition of their surface proteins and suggest an important role for GPI-anchored proteins in generating diversity of the neuronal cell surface.

Myelin formation following transplantation of normal fetal glia into myelin-deficient rat spinal cord

Structurally normal myelin sheaths develop in the spinal cord of juvenile myelin-deficient rats (mdr) 11 days after transplantation of normal fetal spinal cord fragments or cultured cells that do not yet express galactocerebroside. Cultures result in more extensive myelin formation, and in both cases the myelin that forms is located primarily at or near the site of transplantation. Myelin formation also occurs after transplantation of postnatal donor tissue, but the extent diminishes with donor age, and none was seen after transplantation of adult donor tissue over the two-week period studied. Injection of killed tissue, tissue derived from mouse donors or an extract of myelin also did not lead to myelin formation. The results imply that myelin formed in the host following transplantation was generated by oligodendrocytes newly differentiated from donor precursor cells rather than by donor oligodendrocytes that were already mature at the time of transplantation or by host oligodendrocytes that took up components of the injected material. We conclude that exogenous fetal glial cell precursors are able to survive, differentiate and form myelin in the environment of the juvenile mdr spinal cord.

Type 1 astrocytes inhibit myelination by adult rat oligodendrocytes in vitro

We have determined the effect of Type 1 astrocytes on the myelination of dorsal root ganglion cell axons by oligodendrocytes obtained from adult animals. Experiments were initiated by the addition of oligodendrocytes [purified either by density gradient centrifugation and treatment in culture with 5-fluorodeoxyuridine (FdU) or by fluorescence-activated cell sorting after immunostaining with antigalactocerebroside antibody] to cultures of purified neurons. In control conditions, the added oligodendrocytes proliferate and, after 4 weeks, accomplish substantial myelination of the sensory axons. Type 1 astrocytes (purified from cultures of dissociated newborn rat cerebral cortex by vigorous shaking to remove less adherent cells) or fibroblasts (purified from cultures of cranial periosteum by serial replating) were added to some of these cultures after the oligodendrocytes had attached and started to proliferate. We observed that the added Type 1 astrocytes, but not the added fibroblasts, strongly inhibited myelination and caused decreased oligodendrocyte proliferation or survival. These effects of added Type 1 astrocytes were reproduced with Type 1 astrocyte-conditioned medium. We conclude that Type 1 astrocytes can release soluble factors that inhibit oligodendrocyte myelination.

Plasma beta-casomorphin-7 immunoreactive peptide increases after milk intake in newborn but not in adult dogs

To determine the relation between milk intake and plasma levels of beta-casomorphins as a function of age, we studied the levels of beta-casomorphin-7 immunoreactive material (BCMIR) in 2- and 4-wk-old beagle neonates and adult dogs following milk intake. We used three kinds of milk: 1) bovine casein-based milk formula; 2) canine bitch's milk, and 3) soy protein-based (noncasein) formula. Using a new extraction technique, BCMIR was isolated from plasma and assayed by radioimmunoassay at 0, 2, 4, and 6 h after feeding. We found that BCMIR increased significantly in both 2- and 4-wk-old puppies post bovine and canine milk feeding, but not after soy protein formula. Base-line values were about 80-120 fmol/ml and increased to 100-120% 2 h after bovine casein intake in the older puppies and by 4 h in the younger group. BCMIR levels were undetectable in adult dogs before or after bovine milk feeding. Beta-casomorphin-7 added to plasma was rapidly degraded whereas BCMIR was stable. Chromatographic profiles demonstrated that the BCMIR moiety is larger than beta-casomorphin-7. Our data suggest that the appearance of BCMIR in the plasma of neonatal dogs is a result of beta-casein degradation along a permeable gastrointestinal mucosa. We speculate that morphiceptin and beta-casomorphins can be cleaved from BCMIR and may have important physiologic effects.

Effect of enkephalins on cardiac output and regional blood flow in conscious dogs

To investigate the effects of enkephalins on cardiac output and regional blood flow, we administered D-Ala-D-Leu-enkephalin (DADLE) intracisternally (ic) to 14 chronically instrumented unanesthetized dogs. Measurements were made at base line, 20, 45, and 75 min after DADLE (25 or 125 micrograms/kg) and 15 min after naloxone (5 micrograms/kg ic). After 125 micrograms/kg DADLE, all animals developed hypoventilation, bradycardia, and decreased O2 consumption without hypotension. Cardiac output decreased (-34%), but brain blood flow increased (+110%). Blood flow decreased to the diaphragm (-38%), heart (-21%), skeletal muscle (-40%), skin (-67%), pancreas (-79%), and gastrointestinal tract (-26%). After 25 micrograms/kg DADLE, there were no consistent changes in cardiac output or regional blood flow. Four additional animals (without DADLE) were exposed to altered inspired gases to reproduce the blood gas changes after DADLE. These animals developed hyperventilation without bradycardia and increased brain (+114%) and diaphragm (+649%) blood flow. We conclude that centrally administered enkephalins produce 1) a parallel decrease in ventilation, heart rate, O2 consumption, and cardiac output and 2) a major blood flow redistribution, primarily dictated by the effects of opioids on ventilation, heart rate, and metabolism.

Home monitor follow-up of persistent apnea and bradycardia in preterm infants

We reviewed our experience with home monitor observations of 83 preterm infants (postconceptional age, 36 to 44 weeks) who had persistent apnea, bradycardia, or cyanosis. Polygraphic recordings before discharge showed that 92% of these infants had cardiorespiratory abnormalities that included prolonged (greater than 20 s) apnea, excessive periodic breathing (greater than 15%), bradycardia (greater than 80 beats per minute), feeding hypoxemia, or elevated carbon dioxide values. At home, 70 infants had either no alarms or alarms that resolved spontaneously, while 13 (16%) had more serious episodes that required parental intervention, including mouth-to-mouth ventilation in one infant. While polygraphic studies were helpful in documenting specific cardiorespiratory abnormalities, neither these abnormalities nor the clinical characteristics of the infants identified those infants experiencing subsequent home monitor alarms requiring parental intervention. Our data suggest that some preterm infants with persistent episodes of apnea, bradycardia, and cyanosis beyond 36 weeks of postconceptional age remain at risk for future serious episodes for several months.

Home negative pressure ventilation: report of 20 years of experience in patients with neuromuscular disease

Twenty years of experience using negative pressure devices (NPD) at home to ventilate 40 patients with neuromuscular disease is presented. The purpose of the study was to determine the costs, complications, and clinical outcome of this form of respiratory support, and to ascertain the reasons for failure to institute effective negative pressure ventilation (NPV) in nine patients. Emerson tank respirators, used mainly to rest respiratory muscles at night, and intermittent positive pressure breathing machines were used by 98% of patients at an average equipment cost of +2,700 annually. Patients in whom NPV was initiated on an elective rather than emergent basis saved an average of +12,000 during their initial hospitalization. Life table analysis shows a five-year survival of 76%, and a 10-year survival of 61%. Complications were minor and occurred at an average rate of less than one per year per patient at home on NPV. Failure to achieve satisfactory NPV in nine patients was associated with age (six patients were younger than 3 years of age), or severe thoracocervical scoliosis, which prevented proper fitting of the NPD. For reasons of safety, economy, and quality of life, NPV at home is the preferred treatment for patients having neuromuscular disease who need respiratory assistance.

Hypoxemia associated with feeding in the preterm infant and full-term neonate

Polygraphic monitoring studies were performed on more than 150 older preterm infants (postconceptional ages of 36 weeks or more) and full-term neonates to evaluate unexplained or persistent apnea. During polygraphic monitoring, 16 infants were observed to have hypoxemia associated with feedings. The feeding hypoxemia was accompanied by irregular respiratory effort and preceded any associated bradycardia. A comparison group of eight infants with similar gestational and postconceptional ages, but without feeding hypoxemia, was selected retrospectively from other infants referred for evaluation of persistent or unexplained apnea. The group with feeding hypoxemia showed evidence of CNS compromise as manifested by significant elevations of the maximum end-tidal carbon dioxide pressure during sleep and abnormal computed tomograms (7/11 v 0/5 in the comparison group). There was no relationship between feeding hypoxemia and sleep apnea or gastroesophageal reflux. Clinical follow-up showed that the feeding hypoxemia resolved with maturation.

Two siblings with recurrent cardiorespiratory arrest: Munchausen syndrome by proxy or child abuse?

The terms "Munchausen syndrome by proxy" or "Polle syndrome" have been used to describe children who are victims of parentally induced or fabricated illness. This report gives case histories of two siblings (a 7-month-old girl and a 4-year-old boy) with recurrent episodes of cardiorespiratory arrest that were induced by a mother who skillfully resuscitated the children and who demonstrated model parental behavior. Polygraphic monitoring with hidden camera was used to determine that the episodes of cardiorespiratory arrest were parentally induced in the infant. The 4-year-old sibling had previously undergone multiple diagnostic and surgical procedures. After the diagnosis was made in the infant, and the mother was no longer permitted to be alone with the children, neither child had further episodes. A psychologic profile of the mother is presented, and special features of these two and other cases in the literature are reviewed. These cases represent a form of child abuse. A parentally induced illness should be considered in the differential diagnosis of unusual illnesses with bizarre features, even when the parent's behavior appears exemplary.

Infant apnea: polygraphic studies and follow-up monitoring

Twenty-six infants with unexplained and apparently life-threatening apnea were evaluated clinically, underwent eight- or 12-hour polygraphic recordings during sleep, and were then observed on home monitors. The one exception was an infant who was treated with theophylline and not monitored at home. Clinical evaluation revealed a history of vomiting in 19 infants, gastroesophageal reflux (GER) on esophagram in 19, and subtle neurologic abnormalities in ten. Polygraphic studies revealed questionable EEG abnormalities in nine infants, abnormal rapid eye movement (REM) time in four, prolonged apnea in one, and increased frequency of brief mixed (central and obstructive) and obstructive apneas in five. Of the 11 infants who underwent pH monitoring during their polygraphic sleep studies, seven had at least one recorded episode of GER, but the episodes were not accompanied by apnea or bradycardia. Thirteen infants had a subsequent episode of apnea that required stimulation, and in eight infants, cardiopulmonary resuscitation was given. There was two deaths. Two infants subsequently developed seizure disorders. Three of the five infants who underwent surgical fundoplication had recurrent apneic episodes. GER commonly occurred in these infant apnea patients but did not correlate with the clinical outcome. Although subtle abnormalities may be detected by sophisticated polygraphic monitoring studies, they are not predictive of recurrent apnea or death. Home monitoring may be useful in detecting the infant at risk for recurrent life-threatening apnea and in providing some safeguard for that infant.

An experimental study of visual perceptual training and reading achievement in first grade

To determine the effects of perceptual training upon selected measures of reading achievement in first grade, 12 experimental classrooms received a 29-day adaptation of the Frostig program for the development of visual perception while 13 control classrooms added comparable time to regular reading instruction. Analysis of the data revealed significant differences between treatment groups in certain post-training perceptual capabilities without concomitant effects on dependent measures. Additional findings strongly suggest need for further research.