Polysomnographic values in children 2-9 years old: Additional data and review of the literature

The establishment of normal pediatric polysomnographic parameters is important for both clinical and research interests. Our objectives were to describe respiratory events, paradoxical breathing, periodic limb movements, and sleep architecture of children at the age of peak incidence of obstructive sleep apnea syndrome. We performed a retrospective cross-sectional analysis of a prospective cohort study of 66 children, 2-9 years old, at the Sleep Disorders Center at the Children's Hospital of Philadelphia. Subjects screened by questionnaire underwent a standard polysomnogram. The percent of total sleep time spent in sleep stages 1, 2, 3, 4, and rapid eye movement (REM) were 4 ± 3%, 44 ± 10%, 10 ± 6%, 22 ± 8%, and 21 ± 6%, respectively. The arousal and awakening index was 11.2 ± 4.3/hr. Respiratory events included a central apnea index of 0.08 ± 0.14/hr, obstructive apnea index of 0.01 ± 0.03/hr, and obstructive hypopnea index of 0.3 ± 0.5/hr. The baseline arterial oxygen saturation (SpO ₂) was 97 ± 1%, with a nadir of 92 ± 3%. The index of periodic limb movements in sleep (PLMS) was 1.3 ± 2.2/hr. Paradoxical breathing appeared significantly more frequent with piezo crystal effort belts (40 ± 24% of epochs) than with respiratory inductive plethysmography (1.5 ± 3% of epochs). We describe the occurrence of hypopneas during sleep, arousals and awakenings, and PLMS. We illustrate how different technologies can vary the apparent amount of paradoxical breathing. We also confirm previous data on the frequency distribution of sleep stages, SpO₂, and relative rarity of respiratory events in this age group.