| Definition | Comments |
Events |
Apnea | >90% decrease in airflow signal that lasts ≥90% of the duration of at least two normal breaths, as determined from the baseline breathing pattern. | - Apnea is obstructive if there is continued or increased inspiratory effort during the entire period of decreased airflow.
- Apnea is central if inspiratory effort is absent during the entire period of airflow cessation*.
- Apnea is mixed if there is absent respiratory effort during one portion of the event and the presence of inspiratory effort in another portion, regardless of which portion comes first.
|
Hypopnea | ≥30% decrease in airflow signal that lasts ≥90% of the duration of at least two normal breaths, as determined from the baseline breathing pattern. The decreased airflow is associated with an arousal or at least 3 percent oxyhemoglobin desaturation. | - Hypopneas may be classified as either obstructive or central, depending on the presence or absence of snoring, flattening of nasal pressure signal, or paradoxical thoracoabdominal breathing.
- However, in practice, accurate classification of the etiology of hypopneas is challenging and usually not performed. In a patient who has clear OSA, hypopneas are usually assumed to have an obstructive basis.
|
RERA | Respiratory event (increasing respiratory effort, flattening of the inspiratory portion of the nasal pressure waveform, snoring, or an elevation in the end-tidal PCO2) that leads to arousal and does not qualify as an apnea or hypopnea¶. | - RERAs can be detected with routinely used sensors on in-laboratory PSG or by addition of esophageal manometry.
- UARS was previously used to describe presence of RERAs in the absence of apneas or hypopneas. UARS is now subsumed into the category of OSA.
|
Sleep-related hypoventilation | End-tidal or transcutaneous CO2 >50 mmHg for more than 25% of the total sleep time. | - Some children with breathing disturbance due to increased upper airway resistance have hypoventilation but not discrete apneas or hypopneas.
- Obstructive hypoventilation is now subsumed into the category of OSA.
|
Additional events | Arousals, snoring, changes in body position, and limb movements. | |
Summary measures |
AHI | The number of apneas plus hypopneas that occur per hour of sleep. | - Concern for clinically significant OSA generally starts with an AHI >1 or RDI >1.
- An AHI ≥1.5 events per hour was considered abnormal based on a study of a group of healthy children not suspected of having sleep-related breathing disorders, in whom the mean AHI was 0.2±0.6 events per hour[1].
|
RDI | The number of apneas, hypopneas, and RERAs per hour of sleep. | - Concern for clinically significant OSA generally starts with an AHI >1 or RDI >1.
- Some experts have advocated slightly higher RDI thresholds, such as 1.5, 2, or 3 events per hour.
- An RDI >5 events per hour of sleep is often used to identify an abnormal RDI in adults but is insufficiently sensitive for children.
|