Our glossary contains vocabulary frequently used to talk about our products and features on our site and aspects of our service.

    A B C E F H I L M N O P R S T U V

    AAV (Anti-Asphyxia Valve)

    The AAV is a safety feature in all ResMed full face masks. If the therapy device stops delivering air for any reason (e.g. in a power failure), the AAV allows you to breathe in fresh air from the room rather than re-breathe exhaled air built up in your mask.

    AHI (Apnea–Hypopnea Index)

    Measured during a sleep study, AHI refers to the number of apneas and hypopneas you have per hour. See also: Apnea; Hypopnea.

    APAP (Automatic Positive Airway Pressure)

    While CPAP (Continuous Positive Airway Pressure) therapy delivers air at one fixed pressure, APAP is a type of therapy delivery that automatically changes throughout the night to deliver only the minimum pressure you need at any given time. ResMed's APAP therapy is delivered in our AutoSet™ range of devices. See also: CPAP; AutoSet


    "Apnea" literally means no breath or stopping breathing for 10 seconds or longer during sleep. See also: Sleep apnea; Obstructive sleep apnea (OSA); Central sleep apnea (OSA); Mixed apnea.

    ASV (Adaptive Servo-Ventilation)

    ASV is a type of positive airway pressure (PAP) therapy that is designed to treat central sleep apnea, including a type of breathing called Cheyne-Stokes respiration (CSR). ASV automatically adjusts to the magnitude of support needed by providing minimal pressure during the overbreathing phase or normal breathing, and increases support during underbreathing (hypopnea or apnea) See also: Apnea; Central sleep apnea; Periodic breathing; Cheyne-Stokes respiration (CSR)


    AutoSet is the name of ResMed's APAP technology, which adjusts the therapy pressure delivered to you as your needs change on a breath by breath basis to deliver the ideal, lowest therapy pressure. As a result, the AutoSet algorithm is clinically proven to increase comfort and compliance.1-3

    • Teschler H, Wessendorf TE, Farhat AA, Konietzko N, Berthon-Jones M. Two months auto-adjusting versus conventional nCPAP for obstructive sleep apnea syndrome. Eur Respir J. 2000 Jun; 15(6):990-5
    • Hukins C. Comparative study of autotitrating and fixed-pressure CPAP in the home: a randomized, single-blind crossover trial. Sleep. 2004 Dec 15;27(8):1512-7. This was an industry supported study by ResMed Australia. Dr. Hukins received research equipment from ResMed Australia.
    • Massie et al. Comparison between automatic and fixed positive airway pressure therapy in the home. Am J Respir Crit Care Med 2003 167:20-23

    Bilevel therapy

    While CPAP (Continuous Positive Airway Pressure) therapy delivers air at one fixed pressure, bilevel therapy delivers two different levels of pressure: • a higher level of pressure when you breathe in; and • a lower level of pressure when you breathe out. This makes it a little easier to breathe out against the air pressure. ResMed's bilevel therapy is delivered in our VPAP range of devices. See also: VPAP; CPAP

    BMI (Body Mass Index)

    Using your height and weight, your BMI is calculated to assess if you are at your ideal weight, or over or underweight, for your gender and height.


    Chest wall disorder

    A chest wall disorder is one that affects the connection between the muscles and bones around the rib cage and the respiratory system (that is, the organs in your body that help you to breathe).

    Climate Control

    This is the name of ResMed's humidification technology. Climate Control is a comfortable humidification system that delivers rainout protection without compromising on humidity delivery. By using one of our ClimateLine™ heated tubes with your Climate Control system, you can also keep the air in the tube warm throughout the night. Humidity and temperature are maintained, even as ambient conditions change. See also: Humidification; Rainout

    CO2 wash-out

    During normal breathing, you breathe in oxygen and breathe out carbon-dioxide (or CO2). All masks need to have a feature that 'washes out' CO2 remaining in the mask.

    CompSA (Complex sleep apnea)

    Complex sleep apnea is a form of sleep apnea where central apneas persist (or emerge) during attempts to treat obstructive apneas with CPAP (continuous positive airway pressure) or bilevel therapy. See also: Apnea; Obstructive sleep apnea; CPAP; Bilevel

    Conducted noise

    Refers to noise that is created from therapy equipment - it's the vibration you might hear or feel in the tube. See also: Radiated noise

    COPD (Chronic Obstructive Pulmonary Disease)

    COPD is a lung disease that develops over time, mainly caused by cigarette smoking, air pollution, chemical fumes, or dust.

    CPAP (Continuous Positive Airway Pressure)

    CPAP is a type of therapy that delivers pressurised air at one prescribed fixed pressure throughout the night to keep your airway open so that you don't stop breathing in your sleep (that is, have an ' apnea'). This is suitable for treating obstructive sleep apnea (OSA). See also: Apnea; Sleep apnea; Obstructive sleep apnea (OSA); APAP; VPAP

    CSA (Central Sleep Apnea)

    While some apneas are caused by a blockage or collapse of your upper airway, central sleep apnea is when your breathing stops but your airway is actually open. Even though the airway may be open, the automatic action of breathing stops because the communication between the brain and the body has been lost. See also: apnea; Obstructive Sleep Apnea (OSA)


    This is a term used to describe how well you are following the recommended usage of your therapy. If you are compliant, it means you are using it as recommended to gain the benefits of treatment. If you are noncompliant, you are not using it as recommended to gain the benefits.


    Easy –Breathe™ technology

    This is the name of ResMed's smooth air delivery technology, which intelligently mimics your natural breathing pattern. It incorporates the Easy-Breathe motor, which reduces the sound of your device to a whisper, so your (and your partner's) sleeping environment is quiet and restful.

    EPR™ (Expiratory Pressure Relief)

    EPR is a feature on ResMed's sleep therapy devices that mildly lowers the pressure delivered to you when you breathe out. This makes it easier to breathe out against the air pressure.


    This is a term used to describe the occurrence of an apnea or hypopnea.


    Refers to breathing out, either naturally or mechanically with the help of a therapy device or ventilator. Also referred to as Exhalation.

    Excessive Daytime Sleepiness (EDS)

    EDS is a condition where you constantly feel tired during the day, and generally lack energy, even though you might feel you have had enough sleep.



    Generally, flow refers to the stream of air entering your airways when you breathe either naturally or with the help of a therapy device.

    Flow limitation

    This refers to any event that limits the flow of air into your body, due to a blockage or collapse of your upper airway.

    Full face masks

    Full face masks are a type of mask used during positive airway pressure therapy. Full face masks cover both the nose and mouth. See also: Nasal pillow masks; Nasal masks.



    During positive airway pressure therapy, humidification warms the air you're breathing as it comes out of the device. This helps you avoid getting a dry nose or throat, keeps your airway moist, and helps you keep your mouth closed while you sleep. Using a humidifier can make a positive difference to your therapy comfort and experience. ResMed's humidification technology is called Climate Control. See also: Climate Control


    Hypopnea is a partial blockage of the airway. During a hypopnea, breathing is shallow at 30%-50% less than your normal breathing for 10 seconds or longer.



    Refers to breathing in, either spontaneously or mechanically with the help of a therapy device or ventilator.

    Inspiration pressure

    Refers to the pressure delivered to you during inspiration. See also: Inspiration; Pressure

    Inspiration time (Ti)

    Refers to the length of time (in seconds) you spend in inspiration i.e how long it takes for air to flow into the lungs. See also: TiControl


    Refers to where a tube is inserted down your throat to provide you with oxygen. See also: Invasive ventilation

    Invasive ventilation; Invasive therapy

    Refers to a method of ventilation that requires something to enter your body to help you breathe. This can be via intubation (where a tube is inserted down your throat), or a tracheotomy (where an incision is made into your throat). See also: Tracheotomy; Intubation; Noninvasive ventilation

    intelligent Volume-Assured Pressure Support (iVAPS)

    iVAPS is a volume assurance therapy mode found in some of ResMed's ventilators. To ensure you receive the right 'volume' of air needed for your therapy, iVAPS intelligently monitors whether air is flowing in or out of your lungs, the amount of air that's flowing through and how much air you need for the next breath. See also: Volume


    Leak; leaking; leaking air or bad leak

    Leak refers to air escaping (or leaking out of) your mask due to issues such as you having the wrong mask size or type, the mask not being assembled or fitted correctly, or the mask is worn out and needs to be replaced.

    Lower airway

    The respiratory system is made up of all the organs in your body that help you breathe. The windpipe and lungs make up the lower airway. The lower airway is protected by the chest cavity, which also contains the heart. See also: Upper airway; Respiratory system


    Mask leak

    See Leak.

    Minute ventilation

    Refers to the volume of air breathed in or out within any 60 second period.

    Mouth leak

    Refers to air escaping or leaking out of your mouth during positive airway pressure therapy.

    Mixed apnea

    This is a mixture of both obstructive sleep apnea, where there is a blockage or collapse of the upper airway; and central sleep apnea, where no effort is made to breathe. See also: Central sleep apnea (CSA); Obstructive sleep apnea (OSA); Lower airway


    Nasal masks

    Nasal masks are a type of therapy masks used during positive airway pressure therapy. Nasal masks cover only the nose. See also: Nasal pillow masks; Full face masks.

    Nasal pillow masks

    Nasal pillow masks are a type of mask used during positive airway pressure therapy. The nasal pillows rest at the entrance to the nose, gently sealing in the nostrils. These masks are minimalistic and less obtrusive than nasal or full face masks. See also: Nasal masks; Full face masks.

    NMD (Neuromuscular disease)

    NMD refers to a range of diseases and conditions that affect your nerves that control voluntary muscle function. This can be due to the nature of the muscles themselves or the nerves in the muscles.

    Noninvasive ventilation (NIV)

    NIV is a noninvasive way to deliver air to your system in an effort to help you breathe. In NIV, pressurised air is delivered from a device that sits on your bedside table, to a mask that you wear over your face. It does not require any surgery or any equipment to enter your body. See also: Invasive ventilation

    Non-REM sleep

    NREM (non-rapid eye movement) is one of the phases of the sleep cycle which is also referred to as slow wave sleep (SWS). See also: REM

    (NPPV) Non-invasive positive pressure ventilation

    Also known as Non-invasive ventilation. See also: Non-invasive ventilation (NIV)


    OSA (Obstructive Sleep Apnea)

    OSA is the most common type of SDB (sleep-disordered breathing). OSA is where an apnea or hypopnea occurs due to a complete or partial blockage or collapse of the upper airway. See also: apnea; SDB; upper airway; hypopnea


    An oximeter is a small sensor that clips onto your fingertip to calculate your pulse rate and oxygen saturation. See also: Pulse rate; oxygen saturation

    Oxygen therapy

    Is a prescribed therapy which refers to where oxygen is delivered to your airway via a tube, nasal cannula or mask to give you more oxygen.


    Periodic breathing

    Periodic breathing describes a breathing pattern occurring during sleep. In periodic breathing, you will have periods during your breathing cycle where breathing is deep and then shallow. Periodic breathing can be accompanied with central sleep apnea or cheyne stokes respiration. See also: Apnea; Central sleep apnea (CSA)


    Therapy devices measure the force of air delivered to you in units of pressure (i.e. centimetres of water or cm H2O). For example, if your care provider prescribes a therapy pressure of 12cm H2O, then that's the force of air needed to keep your airway open to minimise or avoid apneas. See also: Therapy pressure

    Pressure port

    Refers to places in the mask where oxygen tubes and/or pressure lines can be directly connected to the mask, so that oxygen and pressure can be monitored.

    Pulse rate

    Refers to the number of heart beats in a 60-second time frame. Your pulse rate can be measured by an oximeter which is usually placed on your index finger. See also: Oximeter

    Polysomnography (PSG)

    This is a test used to monitor sleep and breathing. The reading from a PSG can be used to assess the quality of your sleep and the likelihood of having a sleep disorder.


    Radiated noise

    Refers to the sound in your room you hear that comes from the therapy equipment . See also: Conducted noise


    Rainout refers to water droplets or moisture in your tubing or mask. If your bedroom gets too cold at night, the amount of water vapor that can be held by the air decreases, causing condensation-o r rainout-in the tube. This can create issues during PAP therapy. Using a humidification solution like ResMed's Climate Control can help minimize rainout. See also: Humidification; Climate Control


    Designed to make therapy more comfortable, Ramp helps you ease into therapy each night. It's where your PAP device is set to start at a lower pressure than prescribed and slowly ramps up to your full therapy pressure over a maximum of 45 minutes. You can set your own time to fall asleep, or get used to breathing with your equipment on before your pressure reaches the prescribed setting. See also: Therapy pressure

    REM sleep

    The sleep cycle is made up of two recurring sleep states: REM (rapid eye movement) and NREM (non-rapid eye movement).Adults spend about 20-25% of their total sleep time in REM sleep, which is characterized by rapid, random movements of the eyes and muscle paralysis. It’s during this sleep that vivid dreams can occur. Both phases are important for different functions within our body. See also: Non-REM

    Respiratory system

    The respiratory system is made up of all the organs in your body that help you breathe. It is made up of the upper and lower airways. See also: Upper airway; Lower airway

    Respiratory rate

    Refers to the frequency of breathing, measured as the number of breaths per minute


    SDB (Sleep-Disordered Breathing)

    SDB is a term used to describe a group of conditions where a person has trouble breathing or stops breathing while they're asleep. Obstructive sleep apnea s the most common of this disorder See also: Sleep apnea

    Seal (or good seal)

    Your mask needs to seal well on your face for you to get the full benefit of therapy. A good seal means that the air pressure being delivered to you is distributed evenly and comfortably and is not leaking out from your mask. You will know it's a good seal because your mask will feel firm but not tight on your face and around the headgear. If you hear or feel any air escaping from your mask (i.e. 'leaking') your mask may not be sealing well and you should adjust it. Check also that you have the right mask type for your face, the right mask size, and that you are fitting your mask correctly using the fitting guide.

    Settling time; Ramp

    See Ramp.

    Sleep apnea

    This is the general name given to a group of conditions where you stop breathing while you're asleep. See also: SDB

    Snore index

    A snore index is recorded and reported during a sleep study. It's based on the strength of the pressure waves that your snoring makes during the study


    Therapy pressure

    Your therapy pressure is prescribed by your sleep physician. It is measured in centimeters of water (or H2O). The setting prescribed determines the force of air being delivered to you through your therapy device. For example, if your sleep physician prescribes a therapy pressure of 12 cm H2O, then that's the force of air needed to keep your airway open to minimize or avoid apneas. See also: Pressure


    This is the name of a unique feature of ResMed's VPAP™ bilevel devices. TiControl™ allows your care provider to set minimum and maximum inspiratory time limits to accommodate your individual respiratory needs. See also: Inspiration time (Ti)

    Tidal volume

    Refers to the volume of air that you breathe in and out in one breath, when you are in a resting, inactive state.


    This is a surgical procedure, where an incision (cut) is made into your throat to make way for a tube to be placed into your throat to deliver air directly into your airway.


    Upper airway

    The nose, throat and larynx make up the upper airway. See also: Lower airway; Respiratory system


    Usage refers to the length of time recorded on your device, that shows how long you have used and received therapy from your device. This can be used when assessing your compliance to therapy. See also: Compliance



    Ventilation is the movement of air into and out of the lungs, that is inhalation and exhalation. This is done either spontaneously, that is, through the automatic action of breathing, or mechanically, with the help of a ventilator. Using a ventilator, air enters your lungs-either non-invasively (via a mask worn over your mouth and/or nose) or invasively (via a tracheotomy). See also: Invasive ventilation; Non-invasive ventilation; Tracheotomy


    VPAP is the name of ResMed's bilevel technology, which delivers therapy pressures at two different levels. See also: Bilevel; Therapy pressure


    Volume refers to the amount of air delivered to you in units of millilitres (mL) or liters (L).