NBRC SDS key terms

A comprehensive overnight recording of sleep that combines EEG, EOG, chin EMG, airflow, respiratory effort, oximetry, ECG, and body position to stage sleep and identify respiratory and other sleep disorders.

The average number of apneas plus hypopneas per hour of sleep, calculated by dividing the total event count by total sleep time; it is the primary metric for grading obstructive sleep apnea severity.

A partial reduction in airflow lasting at least 10 seconds that meets scoring criteria, typically a 30 percent or greater drop in flow with an accompanying oxygen desaturation or arousal depending on the rule set applied.

A complete cessation of airflow for at least 10 seconds caused by upper airway collapse, distinguished from central apnea by continued or increasing respiratory effort during the event.

A cessation of airflow for at least 10 seconds accompanied by absent respiratory effort, reflecting a failure of the brainstem to generate breathing rhythm rather than airway obstruction.

A sequence of increasing respiratory effort leading to an arousal from sleep without meeting apnea or hypopnea criteria, contributing to sleep fragmentation and daytime symptoms in some patients.

An abrupt shift in EEG frequency during sleep lasting at least 3 seconds, often triggered by respiratory events, that fragments sleep and can cause daytime sleepiness even when total sleep time appears adequate.

The process of classifying each 30-second epoch as wake, N1, N2, N3, or REM using EEG, EOG, and EMG criteria, which determines sleep architecture and the denominator for respiratory event indices.

A sleep stage marked by rapid eye movements, low-voltage mixed-frequency EEG, and muscle atonia, during which obstructive events often worsen because of reduced tone in upper airway dilator muscles.

The distribution and proportion of sleep stages and awakenings across the night, typically displayed as a hypnogram, used to assess sleep quality and the effects of therapy or disease.

The number of times per hour of sleep that oxygen saturation falls by a specified threshold, commonly 3 or 4 percent, below baseline; it is a surrogate marker of respiratory event frequency.

Noninvasive estimation of arterial oxygen saturation using light absorption through a finger or earlobe probe; in sleep testing it documents desaturation events and helps distinguish sustained hypoxemia from intermittent drops.

A method of estimating carbon dioxide tension through skin using a heated electrode, used during sleep studies to detect hypoventilation, especially in patients with obesity hypoventilation or neuromuscular disease.

Insufficient alveolar ventilation producing elevated carbon dioxide during sleep, often defined as a rise in CO2 above a threshold for a sustained portion of sleep, requiring bilevel or volume-targeted support.

A cyclic breathing pattern of crescendo-decrescendo airflow separated by central apneas, commonly seen in heart failure, and frequently treated with adaptive servo-ventilation or optimized cardiac therapy.

A flattening of the inspiratory airflow contour indicating increased upper airway resistance short of frank obstruction; it guides positive airway pressure titration and can cause arousals without desaturation.

The resistance to airflow through the nose and pharynx, increased by anatomical narrowing, obesity, or reduced muscle tone, which predisposes to snoring, hypopneas, and obstructive events during sleep.

A disorder characterized by repetitive upper airway collapse during sleep, causing intermittent hypoxemia, arousals, and daytime symptoms; diagnosis requires symptom assessment plus a qualifying apnea-hypopnea index.

A condition combining obesity, daytime hypercapnia, and sleep-disordered breathing after other causes of hypoventilation are excluded; treatment often requires bilevel positive pressure with attention to ventilation rather than CPAP alone.

A family of therapies that deliver pressurized air through a mask to splint the upper airway open during sleep, including CPAP, bilevel, and automatic or adaptive modes used to treat sleep-disordered breathing.

A single fixed pressure delivered continuously throughout the respiratory cycle to prevent upper airway collapse; it is first-line therapy for moderate to severe obstructive sleep apnea in most adults.

Noninvasive ventilation delivering a higher inspiratory pressure and lower expiratory pressure, useful for patients needing ventilatory support, high pressures, or treatment of central and hypoventilation syndromes.

A servo-controlled positive pressure mode that adjusts support breath by breath to stabilize ventilation and suppress central apneas and periodic breathing, commonly used in heart failure with Cheyne-Stokes respiration.

The supervised process of adjusting pressure levels during a sleep study to eliminate apneas, hypopneas, snoring, and flow limitation across sleep stages and positions while maintaining comfort and adequate oxygenation.

A single-night protocol in which the first portion is diagnostic and the remainder is used for PAP titration, chosen when the diagnostic findings already meet criteria for treatment initiation.

An unattended recording of limited channels, such as airflow, effort, and oximetry, performed outside the laboratory to diagnose obstructive sleep apnea in appropriately selected adults with a high pretest probability.

The patient-contacting component of PAP therapy, available as nasal, nasal pillow, or oronasal designs; correct sizing and fit are central to comfort, leak control, and long-term adherence.

The degree to which a patient uses prescribed PAP therapy, commonly measured as average hours per night and percentage of nights used; adequate adherence is required to realize clinical benefit.

Persistent respiratory events during PAP therapy despite treatment, detected by device data or repeat testing; causes include inadequate pressure, mask leak, positional worsening, or central apnea emergence.

The designed exhalation flow through vents in a PAP mask or circuit that clears carbon dioxide; distinguishing it from unintentional leak is essential when interpreting device leak and event data.

Use of a custom mandibular advancement device to enlarge the upper airway by positioning the jaw forward, an alternative for mild to moderate obstructive sleep apnea or for patients who cannot tolerate PAP.

Strategies that keep a patient off the supine position during sleep, used when respiratory events occur predominantly when lying on the back and are substantially less frequent in other positions.

Repeated brief awakenings or arousals that interrupt sleep continuity, reducing restorative sleep and contributing to daytime sleepiness, mood changes, and impaired cognition independent of total sleep duration.

An inability to stay awake and alert during the day that interferes with daily activities, a cardinal symptom of sleep-disordered breathing assessed with tools such as the Epworth Sleepiness Scale.

A cyclical pattern of alternating hyperventilation and hypoventilation or apnea, most often central in origin, seen in heart failure and at high altitude and targeted by servo-ventilation or other ventilatory support.

Obstructive events concentrated during REM sleep because of atonia of pharyngeal dilators, sometimes producing a low overall apnea-hypopnea index that underestimates clinically important disease.