# Glossary of Sleep Disorder Terminology

### A-Flex

An algorithm for adjusting CPAP pressure during the later stage of inspiration and during exhalation to improve patient comfort based on a user-defined gain setting.

### AHI

Apnea/Hypopnea Index. A count of apnea and hypopnea events per hour.

### Apnea

An apnea is indicated if there is an 80%/75% (Respironics/ResMed) reduction in airflow for 10 seconds compared to the average airflow over an extended period of several minutes or if there is no airflow detected for 10 seconds.

Apnea/Clear Airway Apnea Detection the the Respironics System One.. An apnea is detected when there is an 80% reduction in airflow from a baseline for at least 10 seconds if there is no airflow detected for 10 seconds. During the apnea, one or more pressure test pulses are delivered by the device. The device evaluates the response of the patient to the test pulse(s) and assesses whether the apnea has occurred while the patient has a clear airway or an obstructed airway. The airway is determined to be clear if the pressure test pulse generates a significant amount of flow; otherwise the airway is determined to be obstructed.

Apnea Detection guidelines per ResMed machines..Apnea...When the respiratory flow decreases by more than 75% for at least 10 seconds.

### ASV

Adaptive Servo-Ventilation. Pertains to a low-pressure, electrically driven ventilator system with electronic pressure control. The device’s pressure controls are adjusted to deliver pressure support for patient ventilatory assistance. The device augments patient breathing by supplying pressurized air through a patient circuit. It senses the patient’s breathing effort by monitoring airflow in the patient circuit and adjusts its output to assist in inhalation and exhalation.

### Auto-CPAP

Continuous Positive Airway Pressure (CPAP) that automatically titrates the pressure up and down based on the varying requirements of the patient.

### AVAPS

Average Volume Assured Pressure Support therapy mode

### Average AHI

The average AHI (Apnea/Hypopnea Index) is the total number of apneas and hypopneas that occurred during sleep divided by the number of therapy hours.

### Average Hours of Use

The total number of hours the patient received therapy divided by the total days of use.

### Average Time in Large Leak Per Day

Displays the average amount of time the patient spent with excessive air leakage that will compromise therapy. This could be the result of poor mask fitting.

### Bi-Flex

A small amount of pressure relief (levels of 1, 2, or 3) applied during the latter stages of inspiration and during active exhalation (the beginning part of exhalation).

### Bi-Level

Two different positive pressure levels (IPAP/EPAP). The dual pressure levels provide a more natural means of delivering pressure support therapy to the patient resulting in improved patient comfort. The pressure toggles between an inspiratory and an expiratory pressure during spontaneous breathing.

### BPM

Breaths per Minute, or beats per minute in the context of Heart Rate/Pulse oximetry.

### C-Flex

A small amount of pressure relief applied during active exhalation (the beginning part of exhalation).

### Cheyne-Stokes Respiration

(pinched from Wikipedia, full link: Cheyne-Stokes respiration)

Cheyne-Stokes respiration is an abnormal pattern of breathing characterized by progressively deeper and sometimes faster breathing, followed by a gradual decrease that results in a temporary stop in breathing called an apnea. The pattern repeats, with each cycle usually taking 30 seconds to 2 minutes. It is an oscillation of ventilation between apnea and hyperpnea with a crescendo-diminuendo pattern, and is associated with changing serum partial pressures of oxygen and carbon dioxide.

Cheyne-Stokes respiration and periodic breathing are the two regions on a spectrum of severity of oscillatory tidal volume. The distinction lies in what we observe happening at the trough of ventilation: if there is apnea, we describe it as Cheyne-Stokes respiration (since apnea is a prominent feature in their original description); if there is only hypopnea (abnormally small but not absent breaths) then we call it periodic breathing. Physiologically and mathematically, the phenomena are less different than they appear, because breaths that are smaller than the anatomical dead space do not actually ventilate the lung and so - from the point of view of gas concentrations in an alveolus - the nadir of hypopnea in periodic breathing may be indistinguishable from apnea.

These phenomena can occur during wakefulness or during sleep, where they are called the Central sleep apnea syndrome (CSAS).

System One calls lumps this together with Periodic breathing..

### cm H2O

Measurement unit of pressure; centimeters of water.

### Compliance

The consistency and accuracy with which a patient follows the regimen prescribed by a physician or other health professional.

### Compliance Graph

Provides a view of the patient's therapy usage and the patient's compliance.

### CPAP

Continuous Positive Airway Pressure

### CSR

Short for Cheyne-Stokes Respiration

### Daily Events Per Hour

Number of events per hour for one night of therapy.

### Desaturation

An indication that the patient's measured SpO2 is reduced by 3% or more.

### Diagnostic RDI

Diagnostic Respiratory Disturbance Index. The total number of breathing events divided by the total sleep time without therapy.

### DME

Distributor of Durable Medical Equipment

### EPAP

Expiratory Positive Airway Pressure

### Exhaled Tidal Volume

The amount of air passing out of the lungs for each breath.

### FL

Flow Limitation is a partial obstruction of the airway as detected by a change in the shape of the flow signal.

Flow Limitation Detection in Respironics System One..Auto Mode Only scoring only..Straight CPap or Straight BiPap modes does not score this event. The device looks for relative changes in the peak, flatness, roundness, or shape (skewness) of the inspiratory portion of the airflow waveform. These changes are observed both over a short period of time (groups of 4 breaths) and over a long period of time (several minutes). Statistical measures are used to help minimize false event detection while allowing the device to be sensitive to even small changes.

### Flow Limitation Index

Changes in flow limitation are recorded as events. The Flow Limitation Index is calculated by the total number of flow limitation events per night divided by the hours of use. Note: The average is calculated by taking the total number of events divided by the number of therapy days. This can be used to indicate if there has been a significant degradation in the flow signal, resulting in a pressure increase. This value is only reported on auto pressure machines.

### GMT

Greenwich Mean Time (time zone), also known as Universal Coordinated Time (UTC)

### Hours of Usage

Shows patterns of use displayed by date.

### Hypopnea

An hypopnea is indicated if there is approximately 40% reduction in airflow for a duration of between 10 and 60 seconds, compared to the average airflow over an extended period of several minutes. Following a reduction in airflow, the therapy device must see two recovery breaths in order to label the event as a potential hypopnea. (Respironics detection is 40% reduction and ResMed detection is 50% reduction)

### Hypopnea Index

The Hypopnea Index is calculated by the total number of hypopnea events per night divided by the hours of use.

Hypopnea Detection in the Respironics System One..A hyponea is detected when there is an approximately 40% reduction in airflow from a baseline for at least 10 seconds.

Hypopnea Detection per ResMed guidelines...When the respiratory flow decreases to 50% for at least 10 seconds.

### IPAP

Inspiratory Positive Airway Pressure

### Leak

The amount of air leakage in the patient circuit.

### LL

Large Leak

### LPM

Liters per Minute..L/min

### MaP

Minutes at Pressure

### Mean Pressure

Average device pressure multiplied by the time at pressure divided by the total time in the device.

### Minute Vent

The average minute ventilation (tidal volume x rate).

### NRAH Index

Non-Responsive Apnea/Hypopnea Index. A non-responsive apnea/hypopnea flag is generated when a patient has apneas and or hypopneas that do not respond to increased pressure from a pressure therapy device. It is detected when the patient has at least 2 apneas and/or hypopneas, the pressure level of the therapy device increases at least 3 cm H2O, and the patient continues to have apneas and/or hypopneas. Total Events / Total Session Hours = Index.

### Obstructive Apnea

Obstructive Apnea (OA) is a temporary cessation of airflow caused by a collapse of the airway either full or partial without an accompanying cessation of respiratory effort.

### Obstructive Apnea Index

The Obstructive Apnea Index is calculated by the total number of Obstructive Apnea events per night divided by the hours of use.

### OSA

Obstructive Sleep Apnea

### PB

Periodic Breathing is a Respironics data feature defined as a persistent waning and waxing breathing pattrn which repeats itself between 30 and 100 seconds. The nadir of the breathing pattern is characterized by at least a 40% reduction in airflow from an established baseline flow. The pattern must be present for several minutes before it can be identified as periodic breathing. No therapy adjustments are made in response to periodic breathing.

### Patient-Triggered Breaths

Breaths initiated by the patient.

### Peak Average Pressure

The largest average CPAP Pressure in the date range.

### Pressure

Pressure settings and average delivered pressures are indicated as colored lines on reports.

### 90% & 95% Pressure reports

90% Pressure.. PR System One..The pressure at which the device spent 90% of the time at OR below. 95% Pressure.. ResMed S9..The pressure at which the device spent 95% of the time at OR below.

### Pressure Pulses

Data available on the Respironics System One machines. Small test probes or puffs of air to help the machine decide if the apnea event is obstructive in nature or clear airway in nature. This number can vary widely and is of no real critical consequence to therapy.

### Pressure Support

Difference between IPAP and EPAP pressure on bi-level machines.

### Ramp

During ramp time, a patient starts therapy at a pressure lower than the prescription. The pressure is incrementally increased over time while the patient is falling asleep.

### Ramp Time

The time over which the pressure increases from the initial low-value, to the prescription value.

### RERA

Respiratory Event Related Arousal... a sequence of breaths characterized by increasing respiratory effort leading to an arousal from sleep, but which does not meet criteria for an apnea or hypopnea.”

RERA Detection in the Respironics System One data..Respiratory effort-related arousal..defined as an arousal from sleep that follows a 10 second or longer sequence of breaths that are characterized by increasing respiratory effort, but which does not meet criteria for an apenea or hypopnea. Snoring, though usually associated with this condition need not be present. The RERA algorithm monitors for a sequence of breaths that exhibit both a subtle reduction in airflow and progressive flow limitation. If this breath sequence is terminated by a sudden increase in airflow along with the absence of flow limitation, and the event does not meet the conditions for an apnea or hypopnea, a RERA is indicated.

### RDI

Respiratory Disturbance Index

### REMstar Auto Flags

Measurements recorded in 30 second intervals for the following measures: NR = Non-Responsive Apnea/Hypopnea event OA = Obstructive Apnea event H = Hypopnea event FL = Flow Limitation event S = Snoring event AHI = Apnea/Hypopnea Index (the sum of the Apneas and Hypopneas during the night divided by the number of therapy hours).

### RR

Respiration Rate Frequency of breathing, expressed as the number of breaths per minute

### S/T

Spontaneous/Timed therapy mode

### SD Card

A SD Card (Secure Digital Card) is an integrated circuit which is housed in a compact, rugged plastic enclosure. SD Cards are designed to store data and to enable the transfer of data between devices equipped with SD Card slots.

### Session

A length of time in which therapy has been delivered with breaks lasting no more than one hour.

### Sigh

A breath that is delivered every 100 mandatory or assisted breaths at 150% of the normal volume.

### Sleep Therapy Flags

Measurements recorded in 30 second intervals for the following measures: OA = Obstructive Apnea event H = Hypopnea event S = Snoring event AHI = Apnea/Hypopnea Index (the sum of the Apneas and Hypopneas during the night divided by the number of therapy hours).

### SmartCard

A type of memory card inserted in some therapy devices that records the patient's device usage information. The SmartCard can be removed for easy download of the data into EncorePro.

### SmartCard Reader/Writer

The SmartCard reader/writer is used to download compliance data from a SmartCard.

### Snore

A loud upper airway breathing sound during sleep, without episodes of apnea.

Snore detection in Respironics System One..Vibratory snore is detected when a specific frequency is detected during the inspiratory portion of the patient's breath. Vibratory snore is disabled at pressures greater than 16 cm H2O.

### Split Night

A mode that enables the auto CPAP algorithm to be delayed by a pre-selectable time interval.

### Ti

Ti...ResMed..Duration of inspiration (ie, the respiratory flow into the lungs), expressed in seconds (5 breath moving average).

Ti Max...ResMed...Maximum inspiration time in seconds.

Ti. Min..ResMed..Minimum inspiration time in seconds.

### Tidal Volume

The amount of air passing in and out of the lungs for each breath (mL).

### Total AHI

The sum of the Apneas and Hypopneas divided by the number of therapy hours.

### VAPS

Volume Assured Pressure Support, breath by breath correction towards a target tidal volume.

### Vibratory Snore (VS) Index

The Vibratory Snore Index is the total number of vibratory snoring events per night divided by the hours of use.

### VTE

Estimated average exhaled tidal volume.