Carl E. Hunt

Obstructive sleep apnea in infants and children

Twenty-two infants and children were found to have clinically significant obstructive sleep apnea. A history suggesting complete or partial airway obstruction during sleep was obtained on all patients, and physical examination of the sleeping patient revealed snoring, retractions, or OSA in 21 patients. Nevertheless, the mean delay in referral for 20 patients first seen after the neonatal period was 23 +15 (+ SD) months. Sixteen of 22 patients (73%) developed serious sequelae: cor pulmonale in 12 (55%), failure to thrive in six (27%), permanent neurologic damage in two (9%), and behavioral disturbances, hypersomnolence, or developmental delays in five (23%). Clinical and radiologic evaluations revealed anatomic abnormalities which narrowed the upper airway in 21 patients; enlarged tonsils and/or adenoids in 14, micrognathia in three,generalized facial abnormalities in three, and cleft palate repair/tonsillar hypertrophy in one. In five patients, upper airway fluoroscopy was performed and was helpful in establishing the site and mechanism of obstruction. Polygraphic monitoring was utilized to quantify the frequency and duration of OSA. Prolonged partial airway obstruction during sleep resulted in significant hypercarbia in 11 patients and hypoxemia in five. Twenty patients improved after surgery which relieved or bypassed the pharyngeal airway obstruction; two cases are pending. Increased awareness of OSA and examination of the sleeping patient should result in earlier treatment and less morbidity for infants and children with OSA.

A diagnostic approach to suspected obstructive sleep apnea in children

Most children with obstructive sleep apnea will benefit from tonsillectomy and adenoidectomy. Although polygraphic monitoring remains the definitive diagnostic technique, we wondered if all children suspected of having OSA require such evaluation. We therefore administered a standardized questionnaire to the parents of 23 children with polygraphically proved OSA related to adenotonsillar hypertrophy, 46 age- and sex-matched normal children, and 23 children subsequently referred because of possible OSA. Significantly increased frequencies of the following symptoms were found in the OSA group compared with the control group: difficulty breathing during sleep, 96% vs 2%; apnea observed by the parents, 78% vs 5%; snoring, 96% vs 9%; restless sleep, 78% vs 23%; chronic rhinorrhea, 61% vs 11%; and mouth breathing when awake, 87% vs 18%. Using discriminant analysis, an OSA score was derived that correctly classified all control subjects and 22 of 23 patients with OSA. Considering the data from all groups, we found that (1) OSA scores greater than 3.5 were highly predictive of OSA requiring adenotonsillectomy; (2) no child with an OSA score less than -1 had OSA; and (3) in children with OSA scores between -1 and 3.5, polygraphic monitoring was required to determine the severity of sleep-related airway obstruction and the need for surgical treatment. Use of the OSA score should decrease the need for polygraphic monitoring and facilitate selection of children for tonsillectomy and adenoidectomy.

Prospective controlled study of parenteral nutrition-associated cholestatic jaundice: effect of protein intake.

The development of transient cholestatic jaundice is a well-recognized complication of prolonged parenteral nutrition. The etiology and long-term significance have not been established. This report describes a prospective controlled study designed to compare the hepatic effects of two different parenteral protein intakes, a lower protein regimen of 2.3 gm/kg/day and a higher protein regimen of 3.6 gm/kg/day. The minimum criterion for ChJ was a direct bilrubin greater than or equal to 2.0 mg/dl. Eighty-two consecutive infants completed the study. No ChJ occurred in the 39 infants who received PN for less than two weeks. In 43 infants requiring PN for at least two weeks, the incidence of ChJ was similar in the two groups, six infants in the LP and seven in the HP group. However, infants prospectively assigned to the HP group developed ChJ earlier than the LP group, 27 +/- 6 days (P less than 0.01), and achieved a significantly greater peak direct bilrubin level, 8.4 +/- 1.6 versus 3.2 +/- 0.3 mg/dl (P less than 0.001). Retrospective comparison of the 13 ChJ infants to the 30 long-term PN infants without ChJ revealed a significantly greater daily dextrose intake in those developing ChJ, 16.2 +/- 1.1 gm/kg/day versus 13.4 +/- 0.9 in the group without ChJ (P = 0.025). Our results indicate that an increased parenteral protein intake is associated with an earlier and increased magnitude of ChJ and suggest than an increased dextrose intake may be associated with an increased frequency of ChJ.

Arousal responses in near-miss sudden infant death syndrome and in normal infants.

Hypercarbic and hypoxic arousal responses were measured in 22 normal and 11 near-miss sudden infant death syndrome infants during natural sleep. End-tidal PCO2, (PACO2), transcutaneous PO2, electrocardiogram and heart rate, and thoracic and abdominal circumference were continuously recorded. The essential behavioral criteria for arousal were eye opening and crying. For each hypercarbic arousal test, step increases in FICO2 were made until arousal occurred or until PACO2 reached 65 mm Hg. For each hypoxic arousal, step decreases in FIO2 were made until arousal occurred or until FIO2 = 0.15 had been maintained for 20 minutes. The hypercarbic arousal threshold was significantly higher in near-miss SIDS than in normal infants, 54.9 +/- 2.3 vs 48.4 +/- 1.4, respectively ((P less than 0.05). An arousal response to hypoxia occurred in only 9% of near-miss SIDS infants compared to 70% of normal infants (P less than 0.01). The level of respiratory chemostimulation required to produce an arousal response from sleep is significantly greater in near-miss SIDS than in normal infants. We speculate that deficient arousal responsiveness, especially to hypoxia, may prevent potential SIDS victims from responding appropriately to apneic asphyxia.

Sudden infant death syndrome: 1987 perspective

The pathophysiology of SIDS remains unknown. Although a multifactorial cause appears plausible on the basis of available data, new data are needed to determine which components of this multifactorial hypothesis are most important and whether other factors need to be added. We need to better understand control of breathing in the newborn infant and the manner in which maturation of cardiorespiratory control progresses during infancy. The unique period of vulnerability for SIDS, in which risk is less in the neonate than at 2 to 6 months of age, remains unexplained. Is there a worsening in some aspect of cardiorespiratory control in infants destined to die of SIDS? An improved understanding of the increased risk in black infants, preterm infants, and infants with intrauterine drug exposure, although only a small percentage of all SIDS deaths, should contribute substantially to our understanding. Appropriately designed and well-controlled prospective studies are needed in asymptomatic infants at risk, to determine the true contemporary nonintervention rate of SIDS and the extent to which any assessment or intervention lowers this rate. Prospective pneumogram screening studies have demonstrated significant group differences in respiratory patterns in normal infants compared with later SIDS victims, but have failed to achieve sufficient sensitivity and specificity to be useful for populationwide prospective screening. To assess aspects of brainstem cardiorespiratory control in addition to those assessed by a conventional pneumogram, future studies will need to be based on an expanded or modified technology. On the basis of both physiologic considerations and available technology, addition of an oxygen saturation channel offers the most promise for providing a more comprehensive assessment of cardiorespiratory control. If there is an underlying deficiency in asphyxic arousal responsiveness, for example, with or without other respiratory control deficits, continuous monitoring of oxygen saturation as part of a second-generation pneumogram system currently has the greatest promise for providing a modified pneumogram assessment of greater clinical use. The use of continuous oxygen saturation as a home monitoring technique should also be investigated. Power spectrum analysis of cardiorespiratory variability also appears to have potential advantages over conventional pneumogram analyses, and needs to be evaluated in prospective studies. The following statements summarize our current knowledge regarding SIDS, apnea, pneumograms, and home monitors: The cause(s) of SIDS remains unknown.(ABSTRACT TRUNCATED AT 400 WORDS)

Radiologic evaluation of adenoids and tonsils in children with obstructive sleep apnea: Plain films and fluoroscopy

Twenty-six children with obstructive sleep apnea were evaluated by lateral neck radiographs during wakefulness, and by polygraphic monitoring and upper airway fluoroscopy during natural sleep. Children with craniofacial abnormalities, palatal surgery, and central nervous system disease were excluded from the study. Moderate or marked enlargement of tonsils and adenoids was noted on lateral neck radiographs of 18 of 26 patients. An objective measure of adenoidal enlargement, the adenoidal-nasopharyngeal ratio, correlated well with subjective judgment of adenoidal size but was not generally more useful than subjective estimation. Upper airway fluoroscopy demonstrated the site and mechanism of obstruction in all patients. Because all children with moderate to marked adenotonsillar enlargement demonstrated obstruction at the adenoidal or tonsillar level on fluoroscopy, we now screen children with suspected sleep apnea with lateral airway radiographs and polysomnography. Fluoroscopy is reserved for children with mild adenotonsillar enlargement, craniofacial dysplasia, prior cleft palate repair, or neuromuscular disorders. These results suggest that the pathogenesis of obstructive sleep apnea in children involves anatomic factors which narrow the upper airway, sleep-related hypotonia of pharyngeal dilator musculature, and compensatory mechanisms to prevent or alleviate asphyxia.

Comparison of respiratory inductive plethysmography and thoracic impedance for apnea monitoring

Thoracic impedance apnea monitors may fail to detect obstructive apnea, may falsely alarm when the infant is breathing, and may confuse cardiac artifact with respiratory impedance. Therefore, we compared the performance of a respiratory inductive plethysmograph and a thoracic impedance monitor with a reliable measure of airflow, either nasal CO2 or pneumotachograph, during 29 studies in 28 patients referred for sleep laboratory evaluation. Sleep time averaged 72 +/- 37 (SD) minutes. The inductance plethysmography and the impedance monitor detected 99.6% +/- 0.6% and 98.3% +/- 3.0% of breaths, respectively. However, in two studies, the impedance monitor detected many extra breaths, once because of cardiac-induced impedance changes and once because of partial airway obstruction-induced impedance changes. In 11 studies, cardiac artifact was sometimes misinterpreted as a breath by the impedance monitor. The impedance monitor, but not the inductance plethysmograph, missed breaths following sighs in 16 of 29 studies. Both monitors detected all 60 episodes of central apnea. The inductance plethysmography detected 35 of 38 episodes of obstructive apnea, but the impedance monitor identified only two such events. Apnea was detected falsely four times by the inductance plethysmograph and 14 times by the impedance monitor. These results suggests that a respiratory inductive plethysmograph would have significant advantages over impedance monitoring, including the ability to detect obstructive apnea, and freedom from cardiac artifact.

Fundamental considerations in pacing of the diaphragm for chronic ventilatory insufficiency: A multi-center study

Records were reviewed of 477 patients who had diaphragm pacemakers implanted for treatment of chronic hypoventilation. Three groups were established for comparison. (1) Center group: 165 patients operated on in six medical centers participating in a cooperative study; (2) Noncenter group, sufficient data available: 203 patients operated on by surgeons with experience limited to a few cases; (3) Nonstudy group, minimal data available: 109 patients operated on as in group 2; vital statistics only were contributed. The protocol for data gathering was comprised of 154 major variables. Basic data on age, sex, diagnosis and etiology were analyzed for homogenicity of data among the groups. A comprehensive analysis of the pacing methods, complication and results fom the Center group yielded information on the early experience with diaphragm pacing important to its future application.

Abnormalities of breathing control and airway maintenance in infants and children as a cause of cor pulmonale.

SummaryRespiratory control abnormalities may result in cor pulmonale. This report summarizes the clinical history, diagnostic evaluation, treatment, and outcome of 16 infants and children presenting with cor pulmonale subsequently found to be due to sleep-dependent hypoventilation. Eleven patients had cardiomegaly and electrocardiographic evidence of right ventricular hypertrophy (RVH) while 5 had only severe RVH or biventricular hypertrophy (BVH). Four infants with central hypoventilation syndrome (CHS)—absence of sleep-related ventilatory drive—had severe sleep-dependent asphyxia and resultant acute respiratory failure; all were ultimately treated with phrenic nerve pacing. One patient with alveolar hypoventilation syndrome (AHS)—a partial deficit in ventilatory drive during sleep—presented with severe pulmonary hypertension and ultimately died despite symptomatic relief with respiratory stimulants. Eleven patients presented with obstructive sleep apnea (OSA) and sleep-dependent asphyxia secondary to intermittent complete or to prolonged partial upper airway obstruction. Localized airway obstruction due to an anomalous innominate artery in 1 child was corrected by arteriopexy. Four children underwent adenotonsillectomy (T&A) with disappearance of symptoms in 1, clinical improvement in 2 and no clinical improvement in another. This unimproved patient and the 6 remaining OSA children improved dramatically after tracheostomy to bypass the sleep-dependent airway obstruction; none presently has evidence of cor pulmonale. In summary, early recognition and appropriate treatment of respiratory control disorders will improve sleep ventilation, eliminate asphyxia during sleep, and prevent the development of cor pulmonale.

Intralipid alterations in pulmonary prostaglandin metabolism and gas exchange

To assess the role of Intralipid as a prostaglandin (PG) precursor, we infused Intralipid into 40 rabbits with long-term arterial and venous catheters; 24 other rabbits received a control saline infusion. One-half of the rabbits in both experimental and control groups had oleic acid-damaged lungs, and at least 5 in each of the 4 groups (Intralipid/saline in normal/damaged lungs) received indomethacin. Two vasodilating PGs (E2 and 6KF1α) and one vasoconstricting PG (F2α) were measured. Triglyceride levels increased significantly in all Intralipid groups, averaging 580 mg/dl. Intralipid-related alterations in PG levels and arterial oxygen tension (Pao2) were significant only in the lung-damaged group. The mean (± sem) decrease in Pao2 was 12 ± 1.5 torr (p < .001). For both vasodilating PGs, Intralipid infusion increased the pulmonary arteriovenous gradients for PG E2 and PG 6KF1α by 960 pg/ml (p < .05) and 697 pg/ml (p < .10), respectively. Both the Pao2 decrease and the vasodilating PG increases were blocked by indomethacin. In summary, Intralipid infusion in lung-damaged rabbits increased pulmonary production of vasodilating PGs and associated hypoxemia, presumably caused by an unblocking of hypoxic vasoconstriction and resultant increase in intrapulmonary right-to-left shunt.