Diagnostic Criteria

The diagnostic criteria used for adults with OSA cannot be used reliably in children (5,49,62,63). The diagnosis of SDB is based on the history, physical findings, and supportive data. Laboratory testing should be, ideally, tailored to the clinical question. For example, if there are concerns about excessive daytime sleepiness, a multiple sleep latency test (MSLT) may be indicated (64). The MSLT is ideally performed in subjects who are at least eight years old.

The polysomnogram in a child uses the same technology and the same type of information as recorded in adults. Airflow, respiratory effort, and pulse oximetry comprise the breathing measurements usually monitored. Breathing can be measured with different techniques, ranging from qualitative techniques such as nasal thermocouples which use the temperature difference between inhaled and exhaled air to record individual breaths, to quantitative and invasive measures such as esophageal pressure measurements. The latter technique is less tolerable than others but is particularly helpful to distinguish central from obstructive apneas. End-tidal CO2 monitoring is another technique that can help detect transient episodes of hypoventilation. Currently, the technique that balances need for quantification with tolerability is measuring airflow using a nasal pressure cannula (65,66). This technique allows for the identification of more subtle breathing episodes but can be harder to interpret than earlier techniques, in particular when a child is mouth breathing.

This nasal pressure cannula has facilitated the measurement of an additional abnormal respiratory event, RERA, which is an acronym for respiratory event-related arousal. The term respiratory disturbance index (RDI) may now include the total number of apneas, hypopneas, and RERAs divided by the total sleep time. The RDI should be distinguished from the AHI. However, some sleep study reports may equate the RDI with the AHI if the sleep study did not measure RERAs.

The clinician needs to be aware that these terms may be used interchangeably, potentially causing confusion.

The multitude of available techniques to measure breathing makes it difficult to compare the results from different studies. Along with the absence of controlled studies, another problem with understanding pediatric SDB is that definitions for key terms vary. OSAs are defined as lasting at least 10 seconds in adults. However, since children have faster respiratory rates clinically significant apneas can occur in less time (Fig. 1). Apneas as brief as three or four seconds may have oxygen desatu-rations. There is no universally accepted definition of hypopneas in children. The clinician needs to know how apneas and hypopneas are defined and scored when interpreting a polysomnogram report. The most recent edition of the International Classification of Sleep Disorders (ICSD-2) defines OSA in children as having an AHI > 1 (67). In adults a higher AHI of five is required. Unfortunately it is not uncommon for an adult cutoff value to be used in children (68). There is also controversy as to when the adult cutoff value should be applied; the onset of puberty or the age of 18 years is often debated.

FIGURE 1 Polysomnogram of a 10-year-old girl depicting several obstructive apneas and hypop-neas during a 60-second epoch of rapid eye movement (REM) sleep, accompanied by esophageal pressure "crescendos," intermittent snoring (as detected by the Chin EMG and Mic), and oxygen desaturations. Note the rapid respiration rate consistent with that of a child. Abbreviations: C3-A2, C4-A1, O1-A2, Fp1-A2, electroencephalogram electrodes placed centrally (C3, C4), occipitally (O1), and fronto-parietally (Fp1), and referenced to the right (A2) or left (A1) ear; Chin EMG, elec-tromyogram recorded from chin muscles; LOC, left eye electro-oculogram; ROC, right eye electro-oculogram; EKG, electrocardiogram; LAT and RAT, electromyogram recorded from the left and right anterior tibialis muscles, respectively; SaO2, pulse oximetry; Mic, microphone to detect snoring; Nasal, nasal pressure measured by pressure transducer; Oral, oral airflow measured by thermistor; Chest and Abdomen, impedance bands to measure thoracic and abdominal movement, respectively; Pes, esophageal pressure to measure transmitted intrathoracic pressure. Source: Courtesy of Clete A. Kushida, MD, PhD.

FIGURE 1 Polysomnogram of a 10-year-old girl depicting several obstructive apneas and hypop-neas during a 60-second epoch of rapid eye movement (REM) sleep, accompanied by esophageal pressure "crescendos," intermittent snoring (as detected by the Chin EMG and Mic), and oxygen desaturations. Note the rapid respiration rate consistent with that of a child. Abbreviations: C3-A2, C4-A1, O1-A2, Fp1-A2, electroencephalogram electrodes placed centrally (C3, C4), occipitally (O1), and fronto-parietally (Fp1), and referenced to the right (A2) or left (A1) ear; Chin EMG, elec-tromyogram recorded from chin muscles; LOC, left eye electro-oculogram; ROC, right eye electro-oculogram; EKG, electrocardiogram; LAT and RAT, electromyogram recorded from the left and right anterior tibialis muscles, respectively; SaO2, pulse oximetry; Mic, microphone to detect snoring; Nasal, nasal pressure measured by pressure transducer; Oral, oral airflow measured by thermistor; Chest and Abdomen, impedance bands to measure thoracic and abdominal movement, respectively; Pes, esophageal pressure to measure transmitted intrathoracic pressure. Source: Courtesy of Clete A. Kushida, MD, PhD.

Controversy exists over whether a diagnosis of OSA, or the larger spectrum of SDB, should be routinely made without a formal polysomnogram. While some have suggested that this diagnosis can be made in patients using either the history and physical, or the history, physical, and an audio- or videotape, others have found an inability of clinical history alone to distinguish primary snoring from OSA in children (69). The situation is further complicated by the description of UARS in children, which may have been missed in the studies cited above. Therefore, a sleep study is the most definitive test for SDB (70,71). Currently, some otolaryngologists who treat SDB in children may make the surgical recommendation based on clinical findings of airway obstruction, sometimes reviewing an audio- or videotape (72,73). The clinicians must be aware of the potential pitfalls to this practice. Certainly there are individual cases in which a diagnostic sleep studies are not available, but ideally they should be the exception. The challenge we face in sleep medicine is providing easily-accessible and cost-effective care working within a multidisciplinary model. We do not know, for certain, how accurate clinical diagnosis is without objective testing. Until we have a better answer, the diagnostic gold standard should not be disregarded particularly in a tertiary care setting. The American Thoracic Society, American Academy of Sleep Medicine, and AAP all support the use of sleep studies (70,74,75).

SDB is not the only sleep disorder a child may have. Clinical impression may have both false negatives and positives resulting in possible misdiagnosis or unnecessary surgery. For example, without confirmatory testing, a child with symptomatic periodic limb movements might be misdiagnosed with SDB and may have unnecessary surgery. Periodic limb movements of sleep and restless legs syndrome may not be rare in children (76). These syndromes can have a vague or difficult history to elicit.

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