Introduction Obstructive Sleep Apnea (osa) Is a Commonly Encountered Condition Characterized by Repeated Events of Partial or Complete Upper- Airway Obstruction during Sleep, Resulting in Disruption of Normal Ventilation, Hypoxemia,

OBSTRUCTIVE SLEEP APNEA (OSA) IS A COMMONLY ENCOUNTERED CONDITION CHARACTERIZED BY REPEATED EVENTS OF PARTIAL OR COMPLETE UPPERAIRWAY OBSTRUCTION DURING SLEEP, RESULTING IN DISRUPTION OF NORMAL VENTILATION, HYPOXEMIA, AND SLEEP FRAGMENTATION. A transient return to the waking state (arousal) restores airway patency. OSA is estimated to affect between 1% and 3% of young children, and its potential consequences include behavioral disturbances and learning deficits, pulmonary and systemic hypertension, and growth impairment. Sleep is of particular importance to the pediatric age group, as evidenced by their longer sleep-duration requirements. Furthermore, OSA in children is distinctly different from the disorder seen in adults, in particular with respect to sex distribution, clinical manifestations, and polysomnography (PSG) findings and treatment. In adults, OSA is suggested by heavy snoring, obesity, and excessive daytime sleepiness—especially in adult men. In contrast, OSA in children is equally common in both sexes and not necessarily linked to obesity. OSA is most often seen in the 2to 8-year-old age range when the tonsils and adenoids are largest relative to the underlying airway size. The only currently accepted method for diagnosis of OSA is overnight PSG; unfortunately, the scarcity of pediatric sleep laboratories and the relatively high medical costs associated with such tests make it likely that pediatric OSA is widely underdiagnosed. As a consequence, there is a need for simpler measurements to aid in the diagnosis of OSA. Such methods have been explored; these include subject history, otolaryngologic examination, and audio recordings of snoring, and all have been shown to have low diagnostic sensitivity and specificity. Methods such as nighttime videotaping, pulse oximetry, and nap PSG have a good true positive detection rate, albeit at the expense of many false negatives, ie, a negative result might still require full PSG to rule out a suspected case. Based on previous preliminary observations in children and our extensive experience in electrocardiogram (ECG)-signal analysis in adults with OSA, we explore here the feasibility of ECG timeand frequency-based interval analysis for diagnostic purposes in snoring children suspected of having OSA. It is useful to briefly review the known clinical observations relating to sleep-disordered breathing and heart rate. In 1984, Guilleminault et al published the first paper in this area, noting that obstructive apneas were often associated with a bradycardia during the apneic period, followed by a tachycardia as breathing is resumed. They termed these patterns cyclical variations in heart rate. Since apneas typically occur on a timescale of 10to 20-seconds duration, the net effect (on average) is to introduce a frequency component in the RR interval tachogram correspond-