Pediatric Polysomnography

Pediatric Polysomnography: General Considerations

As polysomnography (PSG) has become more widely available and used for the assessment of sleep in children, it has become evident that the methods and facilities used for the study of adult patients do not always meet the needs of young children. There are several strategies by which the likelihood of successful pediatric studies can be maximized.

It is essential for sleep laboratories that study young children regularly to prepare a child-friendly environment. Appropriately decorated pediatric rooms containing an additional bed for a parent are optimal. The laboratory should provide age-appropriate distractions and activities that can be used during study setup, such as nonstimulating videos. Stuffed animals, toys, and stickers are useful for both distraction and reward for younger children. Snacks such as crackers, milk, or juice should also be available.

Proper preparation of the laboratory technical staff is also essential. Pediatric studies should always be performed by staff who are comfortable with and oriented toward children. Younger children, children with behavioral or developmental disabilities, and children with significant medical comorbidities may require additional staff for study setup and higher staffing levels during the night. Finally, the laboratory should schedule pediatric studies to coincide as closely as possible with the child’s typical sleep schedule, particularly for younger children with early bedtimes.

Advance preparation of families for the study is also quite important. Children should told what to expect during the study at a level appropriate for age. An advance tour of the sleep laboratory often helps acclimate youngsters to the equipment that will be used. Any potentially uncomfortable aspects of the study such as esophageal pressure (Pes) monitoring should be discussed with parents well in advance of the study.

Standard and Custom Polysomnographic Montages

Figure 17.1 demonstrates a standard recording montage for children that conforms to the recommended specifications of the American Academy of Sleep Medicine (AASM) Manual for the Scoring of Sleep and Associated Events. Electroencephalography (EEG) recording includes frontal (F4, F3), central (C4, C3), and occipital (O2, O1) leads referenced to the contralateral mastoid (M1, M2). Bilateral electro-oculogram (EOG) leads (E2, E1) permit detection of the slow eye movements of light sleep and the rapid movements associated with stage R. Surface electromyography (EMG) over the chin (Chin1-Chin2) permits detection of increased muscle tone with arousals or atonia associated with stage R sleep. Additional EMG leads over the left and right anterior tibialis muscles (LAT1-LAT2, RAT1-RAT2) permit recording of periodic limb movements and other limb movements associated with arousals or sleep-related movement disorders. Electrocardiogram (ECG) channels provide concurrent data reflecting cardiac rate and rhythm.

FIGURE 17.1 Standard pediatric recording montage demonstrating stage N2 sleep in a healthy 5-year-old (30-second epoch).

Standard respiratory monitoring for pediatric PSG includes a snore channel (SNORE), nasal pressure transducer (PFLOW), oronasal airflow (OroNs), thoracic effort (THO), and abdominal effort (ABD). Pulse oximetry (SpO₂) is used for monitoring of baseline oxygen saturation and for detection of desaturations associated with sleep-disordered breathing.

The PSG recording montage for children can be customized depending on the nature of the sleep disorder being investigated. End-tidal carbon dioxide (ETCO₂) or transcutaneous carbon dioxide (TcCO₂) monitoring (Fig. 17.2) during PSG is appropriate for children with neuromuscular disorders, morbid obesity, Chiari I malformation, and other medical conditions associated with increased risk for nocturnal hypoventilation.

FIGURE 17.2 Pediatric polysomnographic montage with supplemental end-tidal CO₂ (ETCO₂) monitoring demonstrating normal CO₂ levels during stage R sleep in a 9-year-old boy (1-minute epoch). ETCO₂ is calculated by measuring peak CO₂ levels at the end of each breath as displayed by the capnogram (CAPN). The channel labeled ETCO₂ displays a rolling average of the peak levels recorded on the capnogram.

Use of Pes monitoring improves the sensitivity of PSG for detection of chronic partial airway obstruction and other findings associated with upper airway resistance syndrome (UARS). The technique uses a small water- or air-filled esophageal catheter attached to a pressure transducer for direct quantitative assessment of Pes fluctuations during each respiratory cycle (Fig. 17.3). Although minimally invasive, Pes monitoring can detect varieties of sleep-related airway obstruction that are often not evident on standard PSG. The technique is well tolerated by most school-age children and has negligible impact on sleep architecture.

FIGURE 17.3 Pediatric polysomnographic montage with supplemental esophageal pressure (Pes) monitoring demonstrating normal Pes fluctuations during stage N3 sleep in a 10-year-old boy (1-minute epoch). The esophageal pressure tracing (labeled EX PES) demonstrates normal fluctuations (0 to −10 cm H₂O, measured from peak to trough) with inspiration.

Sixteen-lead EEG can be performed during pediatric PSG (Fig. 17.4) when sleep-related seizures represent a clinical consideration. Technically satisfactory video recording is particularly important during expanded EEG studies to verify the presence or absence of any clinical symptoms coinciding with EEG findings. Although technically straightforward to perform, interpretation of expanded EEG studies is time consuming and requires that the polysomnographer be experienced in the interpretation of normal and abnormal EEG findings for the pediatric age-group.

FIGURE 17.4 Pediatric polysomnographic montage with 16-lead electroencephalography demonstrating normal stage N2 sleep in a 12-year-old boy (30-second epoch).

Normal Sleep in Infants

The EEG characteristics of sleep for term newborns and younger infants are immature and poorly differentiated compared to the sleep of older children and adults. As a result, sleep staging for this age-group is initially restricted to stage N (undifferentiated non–rapid eye movement [non-REM] sleep, historically called quiet sleep) and stage R (infant REM sleep, historically called active sleep). For healthy term newborns, sleep spindles, slow wave activity, and other markers that distinguish lighter and deeper stages of non-REM sleep become evident beginning at 2 to 3 months postterm, eventually permitting more detailed scoring of non-REM sleep as stages N1, N2, or N3.

Infants often enter sleep with a period of stage R sleep, which constitutes almost half of total sleep time in term infants (Fig. 17.5). In Figure 17.6 the EEG background during stage R sleep for this 2-month-old infant is characterized by mixed frequencies of somewhat higher amplitude than those typical of REM sleep for older children. The rapid eye movements demonstrated in this epoch are not always apparent in younger infants, whereas the reduced EMG activity and irregular respiration demonstrated represent somewhat more consistent findings.

FIGURE 17.5 Hypnogram illustrating sleep cycling for a 5-month-old boy.Typical characteristics of infant sleep include a sleep-onset rapid eye movement period, a high proportion of stage R sleep (49.8% in this study), and shorter sleep cycling time than the 90 minutes typical for older children.

FIGURE 17.6 Infant rapid eye movement (REM) sleep (active sleep, stage R).This 1-minute polysomnographic epoch for a 2-month-old girl with Prader-Willi syndrome demonstrates clearly evident rapid eye movements, muscle atonia with phasic twitches on chin electromyogram, and mixed-frequency electroencephalographic background. The irregular respiratory rate and effort in this epoch are also typical for infant REM sleep.

Stage N sleep during infancy is characterized primarily by high-amplitude delta and theta frequencies associated with deep, regular respiration and less-frequent limb and body movements compared to infant REM sleep (Fig. 17.7, demonstrating findings for the same 2-month-old infant shown in Fig. 17.6).

FIGURE 17.7 Infant non–rapid eye movement sleep (quiet sleep, stage N).This 1-minute polysomnographic epoch for a 2-month-old-girl with Prader-Willi syndrome demonstrates typical findings of quiet sleep, including higher baseline chin electromyographic tone compared to active sleep, deep and regular respiration, and high-amplitude delta and theta frequency electroencephalographic (EEG) background. Immature sleep spindles are apparent in the central EEG channels.

Periodic breathing is a respiratory pattern characterized by cyclical periods of normal breathing interrupted at regular intervals by brief pauses in respiration (Fig. 17.8). This pattern is observed most commonly in premature infants but is occasionally observed in younger term infants as well. Scoring rules established by the 2007 AASM Manual for the Scoring of Sleep and Associated Events specify that periodic breathing may be scored in the presence of more than three episodes of central apnea separated by no more than 20 seconds of normal breathing.