Longitudinal assessment of hemoglobin oxygen saturation in healthy infants during the first 6 months of age. Collaborative Home Infant Monitoring Evaluation (CHIME) Study Group.

Limitations in home monitoring technology have precluded longitudinal studies of hemoglobin oxygen saturation during unperturbed sleep. The memory monitor used in the Collaborative Home Infant Monitoring Evaluation addresses these limitations. We studied 64 healthy term infants at 2 to 25 weeks of age. We analyzed hemoglobin oxygen saturation by pulse oximetry (SpO(2)), respiratory inductance plethysmography, heart rate, and sleep position during 35, 127 epochs automatically recorded during the first 3 minutes of each hour. For each epoch baseline SpO(2) was determined during >/=10 s of quiet breathing. Acute decreases of at least 10 saturation points and <90% for >/=5 s were identified, and the lowest SpO(2) was noted. The median baseline SpO(2) was 97.9% and did not change with age or sleep position. The baseline SpO(2) was <90% in at least 1 epoch in 59% of infants and in 0.51% of all epochs. Acute decreases in SpO(2) occurred in 59% of infants; among these, the median number of episodes was 4. The median lowest SpO(2) during an acute decrease was 83% (10th, 90th percentiles 78%, 87%); 79% of acute decreases were associated with periodic breathing, and >/=16% were associated with isolated apnea. With the use of multivariate analyses, the odds of having an acute decrease increased as the number of epochs with periodic breathing increased, and they lessened significantly with age. We conclude that healthy infants generally have baseline SpO(2) levels >95%. The transient acute decreases are correlated with younger age, periodic breathing, and apnea and appear to be part of normal breathing and oxygenation behavior.

Influence of increased survival in very low birth weight, low birth weight, and normal birth weight infants on the incidence of sudden infant death syndrome in the United States: 1985-1991.

OBJECTIVE: To examine the relationship between infant survival and the rates sudden infant death syndrome (SIDS) in very low birth weight (VLBW), low birth weight (LBW), and normal birth weight (NBW) infants from 1985 to 1991. METHODS: The National Center for Health Statistics Birth Cohort Linked Birth/Infant Death Data Sets were used to determine birth weight, age at death, and cause of death for US-born singleton infants with birth weights of 500 g or more. RESULTS: Increasing infant and postneonatal survival rates were greatest in VLBW infants. In contrast, SIDS rates did not change in VLBW infants (3.66 to 3.69; P = .70) but declined in both LBW (3.51 to 3.32; P = .041) and NBW (1.07 to 1.03; P = .008) infants. Postneonatal SIDS rates (per 1000 neonatal survivors) did not change in VLBW (4.93 to 4.58; P = .58) or LBW (3.36 to 3.22; P = .07) infants but declined in NBW infants (1.00 to 0.97; P = .018). Although there were differences among the slopes of survival rates, there was no statistical evidence of differences in the slope of SIDS rates among the three groups. CONCLUSIONS: The marked increase in survival of VLBW infants increased the pool of babies at potential risk for SIDS. VLBW infants' SIDS rates have not changed while they have declined in NBW and LBW infants.

Assessment of compliance with home cardiorespiratory monitoring in infants at risk of sudden infant death syndrome. Collaborative Home Infant Monitoring Evaluation (CHIME).

OBJECTIVES: Documented monitoring was used to evaluate prospectively (1) the level of compliance among infants in whom cardiorespiratory monitoring was clinically indicated and (2) factors that might influence compliance: diagnosis, socioeconomic status, maternal age and education, and alarms. STUDY DESIGN: Sixty-seven infants (51% female, 49% term) were sequentially enrolled, and monitoring was prescribed for the following indications: siblings of sudden infant death syndrome victims (16%), apnea of prematurity (45%), and apparent life-threatening events or apnea of infancy (39%). Demographic data, alarm and event data, and a summary report of monitor use from the first monitor download were obtained. RESULTS: Maternal age, education, and insurance status did not differ significantly by indication for monitoring. The median number of monitor alarms per 10 hours of use was 0.7 for apnea or bradycardia and 0.6 for loose lead alarms. Monitors were available for use in the home from 2 to 106 days (median, 11 days). Median hours of monitor use per full day in the home was 15.5 hours. Of 67 infants, 58 used the monitor for at least part of every day in the home. The number of hours of monitor use per day did not differ significantly by diagnostic category, chronologic age, alarms, maternal age, education, or insurance type. This study population of infants at increased risk of sudden infant death syndrome had excellent compliance; 75% of the infants were monitored more than 10.5 hours per day, and 25% were monitored more than 21 hours per day. CONCLUSIONS: Documented monitoring provides an objective measure of compliance. These data provide a potential goal for level of compliance with home cardiorespiratory monitoring.

Use of nasal continuous positive airway pressure as treatment of childhood obstructive sleep apnea.

OBJECTIVE: To determine the safety and efficacy of nasal continuous positive airway pressure (CPAP) for obstructive sleep apnea (OSA) during childhood and the effects of growth and maturation on CPAP requirements. DESIGN: Retrospective study with use of a written questionnaire administered to pediatric practitioners treating sleep disorders. SETTING: Nine academic pediatric sleep disorders centers. RESULTS: Data were obtained for 94 patients. Three percent of patients receiving CPAP were less than 1 year, 29% were 1 to 5 years, 36% were 6 to 12 years, and 32% were 13 to 19 years of age; 64% were boys. The longest duration of CPAP use was 4 years. Indications for CPAP included OSA associated with obesity (27%), craniofacial anomalies (25%), idiopathic OSA persisting after adenoidectomy and tonsillectomy (17%), and trisomy 21 (13%). Continuous positive airway pressure was effective in 81 patients (86%), in one patient it was unsuccessful, and in 12 patients compliance was inadequate. The median pressure required was 8 cm H2O (range, 4 to 20 cm H2O); pressure requirements were independent of age or diagnosis. Twenty-two percent of patients eventually required a modification of CPAP levels. Complications of CPAP were minor. Sixty-four percent of centers reported difficulty in obtaining funding for CPAP. CONCLUSIONS: Continuous positive airway pressure is safe, effective, and well tolerated by children and adolescents with OSA. Experience in infants is limited. As pressure requirements change with patient growth, we recommend that CPAP requirements be regularly reevaluated over time. The marked center-to-center variability in CPAP use suggests that specific indications for this therapy require clarification.

Prolonged cardiorespiratory monitoring of children more than twelve months of age: characterization of events and approach to discontinuation.

We assessed children referred to our apnea program who were > or = 12 months of age, beyond the at-risk period for sudden infant death syndrome (SIDS), but for whom home cardiorespiratory monitoring had continued. Our objectives were to (1) determine reasons for initiation and continuation of monitoring, (2) apply documented monitoring of transthoracic impedance, electrocardiographic signals, and, in a subset of patients, pulse oximetry, to determine the types of cardiorespiratory events that these children experienced, and (3) describe how documented monitoring was applied for eventual discontinuation of monitoring. Among 45 patients (median age, 22 months), 263 disks were collected, representing 2982 monitor days. Indications for initiation of monitoring included an apparent life-threatening event in 51.1% of patients, apnea of prematurity in 35.5%, history of SIDS or apparent life-threatening event in a relative in 9%, and intrauterine drug exposure in 4.4%. Continuation of monitoring had been based on continued alarms and, in 31% of patients, documented apnea, bradycardia, or hemoglobin desaturation. In 40 of 45 patients, 2292 episodes of apnea (17.5% of all events) were recorded (range, 16 to 31 seconds). Five patients had 223 episodes of bradycardia (1.7% of all events). Of all 13,075 recorded events, 76.8% resulted in audible alarms, but only 3.9% of these alarms were for apnea and 2.2% were for bradycardia. Of 19 patients studied with pulse oximetry, 18 had 663 episodes of hemoglobin desaturation <90%. All children were thriving at the time of referral. Discontinuation of monitoring was based on a child's ability to resume breathing spontaneously or on normalization of heart rate or hemoglobin saturation before the audible alarm sounded, for a minimum of 2 to 3 months. By extension of the audible apnea alarm to 25 or 30 seconds, lowering of the cutoff point for bradycardia alarm, or lowering of the cutoff point for the oximetry alarm, a recommendation to discontinue monitoring could be made for 41 patients. Of these, no child had a recurrence of cardiorespiratory events or died of SIDS. Documented monitoring proved to be a useful clinical tool for investigation of the clinical and physiologic importance of these cardiorespiratory events in children beyond the at-risk period for SIDS; recommendations about discontinuation of monitoring could be made knowledgeably and safely.

Congenital central hypoventilation syndrome: diagnosis, management, and long-term outcome in thirty-two children.

The diagnosis, management, and long-term outcome of 32 patients with congenital central hypoventilation syndrome are summarized. Sleep hypoventilation was severe in all cases, resulting in an alveolar carbon dioxide pressure (mean +/- SEM) of 62 +/- 2.5 mm Hg and a hemoglobin saturation of 65% +/- 3.3% without ventilatory or arousal response. Awake hypoventilation on initial assessment was present in 12 of the 32 patients, resulting in an alveolar carbon dioxide pressure of 58 +/- 2.2 mm Hg and a hemoglobin saturation of 59% +/- 7%. Associated conditions included pulmonary hypertension or cor pulmonale or both (78%), heart block and sick sinus syndrome requiring a cardiac pacemaker (two patients), mild atrophy by cranial imaging evidence (40%), seizures (72%), normal brain-stem auditory evoked responses in all but one patient tested, ganglioneuroblastomas (one patient), Hirschsprung disease (16%), and ophthalmologic abnormalities (60%). Growth was deficient in 44% of patients; hypotonia or major motor delay or both were apparent in all. Twenty-two patients are living; 12 of them require continuous ventilatory support and 10 breathe spontaneously while awake and require ventilatory support while asleep. Ten patients have died. Autopsy performed in six cases indicated diffuse central nervous system astrocytosis, gliosis, and atrophy but no primary brain-stem abnormality. Although these data support a diffuse central nervous system process, the specific cause and the mode of inheritance remain unclear. With early diagnosis and careful ventilatory management, the sequelae of hypoxia and morbidity should be minimized and long-term outcome improved.

Neuropsychologic abnormalities in children with congenital central hypoventilation syndrome.

We hypothesized that intellectual, neurodevelopmental, and visual-motor tests would be able to characterize the scope and nature of central nervous system involvement in children with congenital central hypoventilation syndrome. Age-appropriate intellectual (Brazelton Neonatal Behavioral Assessment, Bayley Scales of Infant Development, Wechsler Preschool and Primary Scale of Intelligence-Revised and Wechsler Intelligence Scale for Children--Revised), neurodevelopmental (Halsted-Reitan neuropsychologic battery), and visual-motor (Beery visual-motor integration test) tests were given to 17 children with congenital central hypoventilation syndrome (age 0.1 to 14.3 years). We found a broad range in IQ and developmental quotient, from greater than the 85th percentile to less than the 5th percentile, with discrepancies noted between verbal and performance measures. Multiple asymmetries and deficiencies of motor performance, not consistently related to handedness, were also found. Significant eye-hand coordination deficits were uncommon, but general performance was well below average. Full, verbal, and performance IQs and developmental quotients greater than or equal to 70 and less than 70 were compared by chi-square analysis with other associated conditions, including hours of ventilatory support, duration of initial hospitalization, growth, pulmonary hypertension, seizures, brain atrophy, central and peripheral hearing deficits, and ophthalmologic abnormalities; no statistically significant associations were found. These results lend support to the hypothesis that congenital central hypoventilation syndrome is a diffuse central nervous system process. However, the effects of transient hypoxia and associated conditions on neurodevelopmental test results cannot be excluded with certainty.

Assessing clinical significance of apnea exceeding fifteen seconds with event recording.

Using event recording, we determined how often apnea exceeding 15 seconds in duration was associated with bradycardia and how often patients with apnea resumed breathing spontaneously. Of 1306 documented apnea events exceeding 15 seconds (54 patients), 926 lasted 16 to 20 seconds, 262 lasted 21 to 25 seconds, and 118 exceeded 25 seconds. Of these episodes, 75.3% were isolated and 14.9% were associated with pulse deceleration, 4.4% with irregular transthoracic impedance, and 5.4% with bradycardia. Event recording provided data supporting discontinuation of monitoring in 50 of 54 patients: 36 spontaneously resumed breathing before the auditory alarm and 14 had a decreased incidence of apnea with maturation. Follow-up of 51 patients (three not located) showed that none had subsequent apparent life-threatening events or sudden infant death syndrome. Our results in these older infants and children (median age 6.7 months) provide substantiation that such patients with apnea of less than 20 seconds without bradycardia do not require continued monitoring. Further, these data suggest that in selected older infants, longer isolated apnea may be well tolerated; however, hemoglobin saturation during sleep and the ability to resume breathing after the apnea alarm delay is prolonged should be verified. Our patient population had a wide age range and heterogeneity of diagnoses, and was typically free of symptoms, so these results should not be extrapolated uncritically to premature infants, infants with chronic lung disease, and patients with symptomatic apnea.

Assessing validity of infant monitor alarms with event recording.

We evaluated the performance of an event recorder system in a large, consecutive series of referred monitored patients to determine the relative incidence of true apnea and true bradycardia, false alarms, and alarms for movement or a loose lead. In addition, we developed an event classification system based on the reason for the event being recorded. The recorder stored transthoracic impedance and electrocardiogram signals on a floppy disk before, during, and after each monitor alarm. These events on 302 disks from 83 patients were analyzed and classified as true, false, or movement-loose lead. Of 14,131 events, only 8% were caused by apnea or bradycardia (true events). Of true events, 70% were triggered by apnea and 30% by bradycardia. These true events occurred in 48% of the patients. False alarms constituted 23%, and movement-loose lead 69%, of all events. Even when movement-loose lead events were excluded, nearly three of four events were found to be false. Event recording proved helpful clinically, allowing discontinuation of the monitor in 49% of patients, modification of monitor alarm settings, or reassurance and counseling for parents.

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.