The polysomnographic (PSG) technologist performing studies on an infant population in no small measure provides this service not only with prior extensive experience in the field of PSG, in general, but also with expertise specifically in pediatric PSG with a knowledge base of the factors that can positively and negatively affect the scoring and interpretation of a polysomnogram on an infant. The consequences of both positive and negative production aspects can be significant in the diagnosis of the infant. This chapter seeks to provide the biologic, environmental, interpersonal, and technical underpinnings necessary to provide the technologist performing PSG on an infant population with the information necessary to achieve and maintain a positive and rewarding experience not only for the technologist themselves but as a critical member of a team of infant specialists providing other medical providers and caregivers accurate and helpful information most expeditiously.

Chapter 60 (Pediatric Polysomnography) also addresses aspects of infant PSG such as age classifications that can determine how and when an infant’s PSG can and should be done and interpreted, as well as general PSG knowledge. These areas are addressed only tangentially within this chapter, and the reader is encouraged to seek additional information to gain a comprehensive understanding of infant PSG. It is further recommended for a new technologist to seek a mentoring relationship with a provider who is well versed in infant PSG. Although studying the sleep of infants can be more challenging than studies of an adult, working with infants can be a highly rewarding aspect of one’s career.

An understanding of why most infants undergo PSG testing is critical to the technologist’s approach to the study. Infants being tested fall into the following two main categories:

Technologists working with the infant population should want to work with this population. Many PSG technologists enjoy working with this population and seek out these younger patients. However, technologists who, for whatever reason, clearly do not desire to work with this population should not be forced to. The results of an infant sleep study are directly dependent on the role and effort invested by the technologist. The technologist should be thoroughly dedicated to working with this potentially challenging population, maintain the knowledge necessary to produce an optimal PSG on an infant, and possess the desire and ability to work diligently to produce an artifact-free recording. Just imagine trying to accurately evaluate a PSG on an infant with artifactual oxyhemoglobin saturation data and/or no airflow signal. Without the technologist’s full dedication to ensuring the integrity of each channel, the recording will be suboptimal and the scoring and interpretation will not be accurate.

Infants are not a population where guesswork should be employed. For an accurate diagnosis, only a PSG technologist invested in the study can consistently perform at this level of expertise. PSG technologists working with this age group must be certified in infant and pediatric cardiopulmonary resuscitation (CPR). This kind of work is not for all PSG technologists and that aspect should be recognized by management—even as early as the hiring process.

Producing PSGs on the infant population certainly has its own challenges, and working with the infant’s parent or parents can, at times, be challenging. Caregivers often bring a level of stress to the situation, and this stress can manifest itself in difficult interactions with the technologist. However, with a few simple strategies, these stressors can be minimized or eliminated. Most, if not all, of these difficult interactions are because of occurrences that have little or nothing to do with the technologist but are related to other aspects of care of their infant. Emotions can be heightened for many reasons; some of these include complications during the birth, fear and alarm following the witnessing of an apparent life-threatening event (ALTE) or a brief resolved unexplained event (BRUE) that may or may not have the required contacting emergency medical professionals, the loss of some control over the care of their newborn by medical staff, and birth order of the infant where the first-born infant can elicit additional anxiety. The PSG may be seen as a stressful medical procedure caused by unfamiliarity with the process and the perceived or real consequences of a positive study.

Although there can be many more reasons for heightened anxiety of the caregiver, the PSG technologist can work to reduce these anxieties by clearly understanding the patient’s history and what is to be ruled out with a sleep study and exhibiting sensitivity for the caregiver’s state of mind. To address the caregiver’s anxiety, it is important to thoroughly review with the caregivers the exact procedures that will occur during the study and the technologist’s role. Explaining the procedures and function before touching the infant and checking the caregivers’ complete understanding is essential. Keep the initial explanation on a basic level unless the caregivers ask for a more in-depth explanation, which the technologist can provide if requested. Remember that results are not available until the study is completely scored and evaluated by the medical staff and that the technologist cannot make any statements about whether the findings are abnormal or normal. Remind caregivers that your primary purpose is to obtain an optimal study according to the protocols set forth by the medical director of the sleep center.

Technologists should be knowledgeable regarding the clinic’s policies and procedures so that they can be cited quickly and with authority. For example, if your laboratory has a cosleeping policy for infants, the policy should be stated to the caregivers during the initial instructions and not at the time of lights out. Another example is a policy about when and how to feed the infant during the study. In this regard, the technologist should retain sensitivity to the mother and infant while still being able to describe the clinical picture for the clinicians and scoring personnel.

An infant is defined as a child from birth to 2 years of age. Age difference from birth to 2 years, although comparatively short over the life span, shows many differences even within a matter of a few months or even weeks or days. Therefore, it is important for the technologist to report the gestational age (GA) along with chronologic age (CA) to derive the infant’s corrected age. The infant’s GA is the age of the child at birth expressed in weeks from the first day of the mother’s last normal menstrual period to the day of birth. The CA is the amount of time since the birth. From the GA and CA, the corrected age is derived. Obtaining the corrected age of the infant assists the clinician in determining the maturity of the CNS, and this maturity is linked to the electroencephalogram (EEG) waveforms obtained during the polysomnogram.

Since EEG features, both normal and abnormal, are closely linked to the corrected age of the infant, reporting the corrected age will affect the production and interpretation of the infant polysomnogram. The age of the infant can influence many facets of the study. An infant born at less than 36 weeks GA is considered preterm, an infant born between 36 and 40 weeks CA is considered term, and an infant born at 40 weeks is considered full-term. Since infants at less than 4 months corrected age sleep (<53 weeks corrected age) demonstrate an ultradian rhythm (repeated cycles across a 24-hour period) rather than a circadian rhythm (cycles driven by environmental cues), a sleep study on an infant can be performed at any time day or night. After 4 months corrected age, the infant begins to have more consolidated night sleep with a series of naps, and environmental cues begin to have an effect.

Neonates cycle through REM and non-REM (NREM) sleep differently than an older child or adult (1). In the first few months of life, they have not yet become fully entrained on a day-night cycle, and more of the control of sleep is internal. Full-term infants can spend as much as 50% of their total sleep time in REM sleep. At this age, this is often referred to as “active sleep” (1). The infant often enters the sleep cycle in REM. By about 4 months of age, as the infant approaches the adult mode of sleep-state cyclicity, sleep-state progression matures and NREM sleep typically precedes REM sleep. Breathing abnormalities, including obstructive sleep apnea syndrome (OSAS), may be exacerbated or only seen in REM sleep. For this reason, sleep staging is an important aspect of infant PSG evaluation to assess the sleep-state dependence of breathing abnormalities and to ensure that all stages have been documented during the study (2).

Normally, brief arousals occur as the sleeper transitions between each stage of sleep, usually without a return to full wakefulness (1). These endogenous transitional arousals are common as sleep begins to differentiate in the REM and NREM progression of the infant both quantitatively and qualitatively as the infant matures. As an individual transitions to REM through the lighter phases of NREM sleep during the night, a continuum of behaviors, including stretching, brief vocalizing, crying, or changing of position, are common. Cortical arousals during infant PSG are scored because these may also be the consequences of abnormal breathing events during sleep, but the significance of cortical arousals in infants remains uncertain because there is the suggestion that apnea in children may not always be terminated with frank cortical arousal (2).

The data used for the staging of infant sleep include the combined measurement of the EEG to record brain activity, the electrooculogram (EOG) to record bilateral eye movements, and the electromyogram (EMG) to record facial and intercostal muscle tone. The placement of the EEG leads should always be on the basis of the International “10-20” system of electrode placement so that the clinician can determine the maturity of the CNS as well as the exact location of any abnormalities. EEG placement for scoring sleep in infants is similar to that used in an adult population. For a sleep study, electrodes are placed at M1, M2, F3, F4, C3, C4, O1, and O2 for ease of sleep staging due to the increased amplitude obtained in referential lead derivations. The exploratory leads are referenced to the opposite mastoid. The central leads show activity at the vertex such as vertex sharp waves and sleep spindles, which develop by about 2 to 3 months postterm and K-complexes that do not start to develop until about 5 to 6 months postterm and are usually not fully formed until around 2 years of age. In infants, sleep spindles migrate to the vertex where they generally start more anteriorly and are often asymmetric until they are seen consistently centrally and become symmetric to both hemispheres. Activity in both hemispheres changes rapidly in the first months of life until around 4.5 to 6 months when the infant approaches the adult pattern of sleep-state cyclicity.

Even infants have a posterior dominant rhythm (PDR) seen mainly in the occipital channels, which in younger children starts at about 4 Hz and gradually increases as the child ages. The PDR in infants typically contains intermixed slower EEG activity (3). This frequency provides information to the clinician to help determine wakefulness versus sleep. Children with developmental delays may retain a slower PDR longer than typically developing children. Because of the special criteria used to define sleep states in infants younger than 6 months and the unique EEG features for this population, an extended EEG montage, or PSG channel derivation, is preferred. This extended montage should include bilateral EEG electrodes, utilizing the addition of bipolar channels to more accurately evaluate the EEG of the two hemispheres of the brain. EEG features specific to infants, such as tracé alternant and “delta brushes,” as well as certain epileptiform activity can provide useful information regarding the maturity of the brain and alert clinicians to potential problems in brain activity.

Certain normal features of the infant EEG, such as rudimentary sleep spindles, are better seen using an extended EEG montage that includes some derivation referencing frontal to central to parietal to occipital leads in a bipolar array. The addition of T3-T5 and T4-T6 can provide more complete information regarding the maturity and function of the temporal lobes. This is referred to as a bilateral parasagittal montage with the addition of the temporal leads bilaterally and should be considered the minimum number of EEG leads. Other options would include a transverse EEG montage or the more inclusive “double banana” used more often during formal EEG evaluation. Because developing sleep spindles may not be symmetric and begin to develop more anteriorly migrating to the vertex as the infant matures, the bilateral parasagittal with midtemporal leads derivation provides a more comprehensive monitoring of both hemispheres of the brain. Two more aspects in monitoring the EEG of infants are that the lead placement should be precise and the head accurately measured, and EEG lead placement should not be “estimated” or “eyeballed.” In an infant, imprecise placements can and often do yield erroneous information. Additionally, no matter how young and fragile the infant appears, gentle prep of each site, using a mild abrasive, and avoiding the more abrasive preps that are commercially available, the technologist can and should obtain balanced impedances of less than 5 kΩ (3). To expect an accurate representation of the infant’s EEG, without performing these two critical functions, is tantamount to doing a disservice to the patient.

The accurate scoring of sleep stages also requires the proper application of EOG sensors bilaterally to monitor REMs that normally occur during the phasic portion of REM sleep, as well as the slow eye movements that occur with the onset of sleep seen even at younger ages. The REMs of an infant appear more pronounced than those of older children or adults, and the placement of both leads at the outer canthi bilaterally rather than offsetting them is left up to the discretion of the technologist. The placement of eye leads should be as close to the sclera as possible, as long as the tape used does not encroach on the sclera or the lashes of the eye. The EOG leads are referenced to the same mastoid to more easily discern true eye movements from the higher voltages produced by the CNS and picked up in the EOG leads and the mastoid, a site felt to be electrically neutral but known to produce signal voltages sufficient to have an effect on the recording channel once amplified. The impedances for these leads should be at or below 5 kΩ, and the more abrasive skin prep should certainly be avoided around this sensitive area (3).

An EMG recording of facial muscle tone assists the clinician in more accurately determining the presence of REM sleep when skeletal muscle tone, particularly the muscles of the face, is normally inhibited. For infants, chin EMG leads should be placed adjacently and close together on the anterior aspect of each cleft of the chin following sufficient prep. In this manner, the channel will accurately represent the atonia of REM sleep in this population. Since oral and nasal secretions are common in this age group, covering the chin EMG
leads with a moisture-resistant tape will usually assure the integrity of the channel and is removed easily following the study.

To comprehensively assess the adequacy of respirations and ventilation and identify and differentiate between central and obstructive apnea and its severity, the recording should also include effort movements of the chest wall and abdomen with ideally a summation channel output, airflow at the nose and mouth, transcutaneous oxygen saturation data with a validating plethysmograph waveform from the monitor (also known as a “pleth wave” or pulse wave), and end-tidal carbon dioxide (EtCO₂) measures (3).

A summation channel is simply an output representing the combination of the chest and abdominal effort channels and acts as a fourth airflow signal should airflow or EtCO₂ sensors become dislodged during the study. A pulse waveform assists to assess the reliability of oxygenation data because oxygen saturation monitors can yield artifactual data at times usually when the infant is feeding or moving. It may be difficult to attach an oxyhemoglobin probe to infant digits, and this recording can be difficult to obtain. On small infants, the oxyhemoglobin probe may be placed on the side of the foot. If the technologist notices a poor output from the oxyhemoglobin sensor, a second probe may be added allowing the technologist to choose the signal that is most optimal without waking the infant. Capnography, a graphic representation of EtCO₂, is recommended for infant PSG because it can assess airflow and ventilation simultaneously. It detects the retention of CO₂ associated with sleep-related breathing abnormalities in this population (3). Calibrated EtCO₂ measurements can effectively detect CO₂ retention associated with apnea or prolonged hypoventilation.

Standard PSG also includes additional parameters that can provide important information relevant to the patient’s electrophysiologic status. An electrocardiogram (ECG) monitors cardiac rate and rhythm and is useful in evaluating the consequences of breathing disorders on the heart. An EMG recording of the intercostal muscles detects expansion of the chest wall to assess for the presence of respiratory effort to help differentiate between central versus obstructive apnea. An infant PSG could include EMG of the anterior tibialis muscles to identify periodic limb movement disorders, although these disorders are rare in infants and leg EMG channels are not routinely monitored in children younger than about 2 years unless specified by the medical director or ordering physician. Limb movements in infants are generally a startle response to exogenous stimuli or endogenous stimuli and unrelated to low ferritin levels or known nervous conditions. Further, treatment modalities used for these disorders in the adult populations would be inappropriate for infants.