Sleep Apnea Definitions

    Common CPAP Definitions

    CPAP therapy comes with its own lingo. This is the place to visit if you are wondering what "AHI" means, what "rainout" is, or what the difference is between a CPAP machine and an APAP machine. Please check the FAQ section below for an alphabetized listing of common sleep terms.

    Definitions FAQs

      What is A-Flex?
    A-Flex is a form of exhalation relief which helps the air pressure from an APAP machine mirror a person's breathing. Like C-Flex, A-Flex provides flow-based pressure relief at the beginning of exhalation. Like Bi-Flex, A-Flex softens the pressure transition from inhalation to exhalation to provide additional comfort in an auto-CPAP mode.

    An example of a machine with A-Flex is the PR System One REMStar 60 Series Auto with Bluetooth.

    A-Flex Easy Breathing Technology Visual Graph A-Flex Easy Breathing Technology Visual Graph
      AHI (Apnea Hypopnea Index)
    Apnea Hypopnea Index is the number of apneas and hypopneas per hour. This index, as well as oxygen saturation levels (O2 Sat), is used to determine how severe a case of sleep apnea a patient has.

    To determine AHI add the total number of apnea events, plus hypopnea events and divide by the total number of minutes of actual sleep time, then multiply by 60.

    Example:

    Apnea + Hypopnea divided by actual sleep time, then multiply by 60

    200 Apneas, 200 Hypopnea (400 Total Events)

    420 Minutes Actual Sleep time (7 hours x 60 minutes)

    Divide 400 by 420 =.95 x 60 = 57 AHI (Severe OSA)

    The Severity of OSAHS as defined by the American Academy of Sleep Medicine Task Force (1999) is:

    < 5 per hour = Normal
    5 - 15 per hour = Mild
    15 - 30 per hour = Moderate
    > 30 per hour = Severe
      What is Ambient Tracking Technology?
    Ambient Tracking technology is a rainout reduction feature created by Fisher & Paykel. Ambient Tracking Technology monitors the ambient temperature and adjusts heat to maintain the most effective humidification, given the ambient conditions. The Ambient Tracking Technology uses an auto-adjusting heater plate to maximize humidity delivered while adjusting for room temperature. The level of humidity delivered is dependent on room temperature.

    Effects of Ambient Temperature on Humidification Ambient Temperature

    Here are some heated humidifiers with Ambient Tracking Technology:

    ICON Auto CPAP with Built-In Heated Humidifier and Heated Hose
    DreamStation Heated Humidifier
    PR System One 60 Series Heated Tube Humidifier
      What is an APAP Machine?
    An APAP (Automatic Positive Airway Pressure) machine automatically adjusts on a Breath by Breath basis to blow the Minimum Pressure needed to keep your airway open during sleep. This allows your machine to provide you with your ideal pressure nightly.

    APAPs tend to be more advanced than CPAPs in that they normally offer more therapy tracking information and more comfort features.

    Every APAP machine can be placed in a CPAP mode to blow one straight pressure like a CPAP. However, CPAP machines cannot automatically adjust pressure like an APAP. This DeVilbiss IntelliPAP AutoAdjust is an example of an APAP machine that comes with built-in Smart Code therapy tracking software.
    IntelliPAP AutoAdjust CPAP Machine

    Here are some of our available APAP Machines:

    DreamStation Auto CPAP Machine
    Z1 Auto Travel CPAP Machine
    XT Auto CPAP Machine
    + See More
      Apnea
    Apnea is the cessation of airflow for 10 seconds or more. Apnea is Greek for "without breath."
      Arousal
    An Arousal is an abrupt change from a "deeper" stage of non-REM sleep to a "lighter" stage (Normally to stage 1).

    This is distinct from an awakening, which is an arousal that lasts for more than 15 seconds.
      Automatic Altitude Adjustment
    Auto Altitude Adjustment is the CPAP machine's ability to compensate for changes in altitude automatically.

    The feature allows the patient to travel to different altitudes without having the pressure setting adjusted. Because atmospheric pressure changes with altitude, most machines need adjustment in order to provide the correct pressure at different altitudes.
      Awakening
    An awakening is an arousal that lasts for more than 15 seconds.

    An arousal is an abrupt change from a "deeper" stage of non-REM sleep to a "lighter" stage (Normally to stage 1).
      What is Bi-Flex?
    Bi-Flex is a feature that makes breathing back against CPAP pressure easier to do. Bi-Flex pressure relief technology offers pressure relief at the transition from exhalation to inhalation, at the transition from inhalation to exhalation, and during exhalation to make BiPAP therapy more like natural breathing.

    Bi-Flex Easy Breathing Technology Visual Graph Bi-Flex Easy Breathing Technology Visual Graph

    Here are some machines with Bi-Flex:

    DreamStation BiPAP Auto Machine
    PR System One REMStar 60 Series BiPAP Auto with Bluetooth
      What is a BiPAP or BiLevel machine?
    A BiPAP machine (also referred to as BiLevel or VPAP) delivers two separate and distinct pressures. A higher pressure is need for inhalation, while a lower pressure is needed for exhalation. The machine alternates between the two pressures which are set per the doctor's order or prescription. A prescription for a CPAP machine may not be used to purchase a BiPAP machine.

    PR System One BiPAP Auto

    Here are some of our best selling BiPAP machines:

    PR System One REMStar 60 Series BiPAP Auto with Bluetooth
    DreamStation BiPAP Auto Machine
    RESmart BPAP 25A Auto Bi-Level Machine
    + See More
      Bruxism (Teeth Grinding)
    This is a habit observed in a large number of people occasionally, and in a smaller number, habitually. The mechanism of causation is tension and spasm of the muscles used for mastication. The term also refers to clenching of the teeth, which causes similar problems.

    Often, it occurs during sleep; even a short nap may induce it. In a typical case, the canines and incisors are commonly moved against each other laterally, i.e. a side to side action, which erodes tooth enamel, removing the sharp biting surfaces and flattening the edges of the teeth. Sometimes, there is a tendency to grind the molars together, which can be loud enough to wake a sleeping partner.

    Over time, bruxing shortens and blunts the teeth being ground, and may lead to pain in the joint of the jaw, the temporomandibular joint, or headache. Teeth hollowed by previous decay (caries) may collapse; the pressure exerted by bruxism on the teeth is extraordinarily high.

    The cause, or causes, of bruxism remains unclear. Some dentists believe it is due to a lack of symmetry in the teeth; others, that it reflects anxiety, digestive disturbances or a disturbed sleep pattern.

    The effects of the condition may be quite advanced before sufferers are aware they brux. Eroded teeth may be brought to the sufferer's attention during a routine dental examination. If enough enamel is eroded, the softer dentine will be exposed, and erosion will accelerate. This opens the possibility of dental decay and tooth fracture, so early intervention by a dentist makes sense.
      What is Central Sleep Apnea (CSA)?
    In Central Sleep Apnea (CSA), a person stops breathing throughout the night, not due to a blocked air passage, but because the brain temporarily stops sending signals to the muscles that control breathing.

    BiPAP therapy can be used to assist persons with central sleep apnea. The BiPAP machine provides air pressure in an inhale/exhale pattern helping a person to breathe.
      What is C-Flex?
    C-Flex is a pressure relief feature that makes breathing back against CPAP pressure easier to do by reducing the pressure at the beginning of exhalation and returning to therapeutic pressure just before inhalation. Independent studies conducted by leading universities indicate that patient comfort, and therefore, patient CPAP compliance, is higher with machines that use C-Flex. C-Flex is a technology invented by Respironics, is proprietary, and is not available on other brands of CPAP machines.

    An example of a machine with C-Flex technology is the DreamStation CPAP Machine.

    C-Flex Easy Breathing Technology Visual Graph C-Flex Easy Breathing Technology Visual Graph
      What is C-Flex+?
    C-Flex+ is an improved pressure relief technology over the previous C-Flex technology. Like C-Flex, C-Flex+ reduces the pressure at the beginning of exhalation. Like A-Flex, C-Flex+ softens the pressure transition from inhalation to exhalation to provide additional comfort in fixed-CPAP mode.

    C-Flex+ Easy Breathing Technology Visual Graph C-Flex+ Easy Breathing Technology Visual Graph

    Here are some machines with C-Flex+:

    PR System One REMStar 60 Series Pro CPAP Machine with Bluetooth
    DreamStation Pro CPAP Machine
      What is Climate Control Technology?
    Climate Control technology is a rainout reduction feature created by RedMed. Air is delivered at the temperature requested while five sensors, including one close to the mask, monitor multiple conditions to provide optimal humidification to avoid condensation.

    Climate Control Technology Fact Sheet

    Here are some machines that have Climate Control Technology:

    AirSense™ 10 AutoSet CPAP Machine with HumidAir™ Heated Humidifier
    AirSense™ 10 AutoSet For Her CPAP Machine with HumidAir™ Heated Humidifier
    AirSense™ 10 Elite CPAP Machine with HumidAir™ Heated Humidifier
    AirSense™ 10 CPAP Machine with HumidAir™ Heated Humidifier
      What is CPAP therapy?
    CPAP stands for Continuous Positive Airway Pressure. CPAP therapy is the most commonly recommended, and the most effective, treatment for obstructive sleep apnea.

    A CPAP machine provides air at a constant prescribed pressure. The air is delivered to the person through a tube and a CPAP mask. CPAP therapy provides a constant airflow which keeps the airway open so uninterrupted breathing is maintained during sleep. The air stream eliminates Sleep Apnea events and allows the person to get a restful sleep.

    The level of air pressure required to maintain your airway is determined during your sleep study. Your doctor will write a prescription for a CPAP machine set at that pressure.

    CPAP therapy is delivered through a nasal mask that seals around the nose, nasal pillows which seal at the nasal opening, or nasal prong masks that seal inside the nares. Full face masks are available for a person who breathes through both the nose and mouth. Many innovative and comfortable options are available and advances in the delivery of CPAP therapy are continually occurring.

    For instance: Some machines offer a comfort feature such as FLEX or EPR technology. It provides exhalation relief, a slight drop in pressure at the time of exhalation to help make therapy more natural. APAP, BiPAP and BiLevel machines offer various levels of pressure throughout the night.
      DME (Durable Medical Equipment Provider)
    The purest definition of DME is a provider who accepts payment in exchange for CPAP Equipment and Service. Traditional DMEs and Online Providers fall into this category.

    As referenced in cpaptalk.com culture, DME usually refers exclusively to traditional, local providers that accept insurance in exchange for CPAP Equipment and Services. Many who recount their experience with these local providers complain of poor service and high prices. Thus the use of "DME" or "evil DME" is prominent on the sleep apnea forum CPAPtalk.com.
      What is EPR with Easy-Breathe?
    EPR (Expiratory Pressure Relief) is a pressure relief feature developed by ResMed. EPR reduces pressure during exhalation in order to make breathing more comfortable. Easy-Breathe technology applies a smooth waveform that helps make breathing feel more natural.

    EPR with Easy Breath Manufacturer Fact Sheet

    Here are some machines with the EPR with Easy-Breathe feature:

    AirSense™ 10 AutoSet CPAP Machine with HumidAir™ Heated Humidifier
    AirSense™ 10 AutoSet For Her CPAP Machine with HumidAir™ Heated Humidifier
    AirSense™ 10 Elite CPAP Machine with HumidAir™ Heated Humidifier
    AirSense™ 10 CPAP Machine with HumidAir™ Heated Humidifier
      What is exhalation relief?
    Exhalation relief is a comfort feature which reduces the air flow at the time of exhalation, making the breathing process more natural.

    The following are the different types of exhalation relief names by manufacturer.

    • Philips Respironics = C-Flex, C-Flex+, A-Flex and Bi-Flex
    • Resmed = EPR (Expiratory Pressure Relief)
    • 3B Medical = RESlex
    • Apex Medical = PVA (Pressure Variation Algorithm) Pressure Relief
    • Curative Medical = EUT (Expiratory Unloading Technology)
    • DeVilbiss = SmartFlex
    • Fisher & Paykel = SensAwake Technology
    • Human Design Medical = Z-Breathe
    • Somnetics = EZEX

    Here are some machines with an exhalation relief feature:

    Transcend Auto miniCPAP™ Machine with EZEX
    PR System One REMStar 60 Series Auto with Bluetooth
    AirSense™ 10 AutoSet CPAP Machine with HumidAir™ Heated Humidifier
    + See More
      What is humidification?
    Humidification adds moisture to the CPAP air, reducing irritation to the nasal passages caused by the increased airflow.

    CPAP air is an irritant - to one degree or another - to everyone. In some cases the irritation dries out the nasal passages and may cause bleeding. It may also cause swelling, excess mucous, congestion or sneezing. The irritation may create a very fertile ground for infections to begin. The irritation may be cumulative, building up over time. The only way to reduce the irritation is to add moisture.

    Humidification is therefore a critical part of CPAP Therapy.


    There are two types of humidifiers:

    Heated Humidifiers
    Cold (Passover) Humidifiers
      Hypopnea
    A hypopnea is a decrease in airflow by at least 50% for ten seconds or more, with a 3% desaturation of blood oxygen level.
      Manual Altitude Adjustment
    Manual Altitude Adjustment is a machine feature which allows the CPAP user to adjust the pressure of their CPAP as it is exposed to different altitudes. Atmospheric pressure changes make it difficult for CPAP machines to provide the correct pressure; therefore, requiring a manual adjustment. With this feature, the manual setting gives the user the opportunity to reset the pressure as needed due to atmospheric changes.

    Most machines will operate on altitudes up to approximately 8,000-9,000 feet. If you live in altitudes above this, you will need to increase your CPAP pressure setting.
      What is Mixed Sleep Apnea (MSA)?
    In Mixed Sleep Apnea, the patient has a combination of both Central Sleep Apnea and Obstructive Sleep Apnea. Treatment is usually a combination of medication and CPAP use. There are now some advances in technology with some recent BiPap or BiLevel machines on the market made specifically to treat the special needs of those afflicted with MSA.
      What is Obstructive Sleep Apnea (OSA)?

    Apnea is Greek for "without breath." Obstructive Sleep Apnea (OSA) is a condition in which a person's muscles and tissues in the throat and air passage relax while sleeping. The tissues impede the flow of air into the lungs due to the blockage of the airway. This can occur many times per night in the sleep cycle, especially during the REM sleep stages.

    The scientific standard for an apneic event is when you stop breathing for at least 10 seconds. There must be an overall blood oxygen desaturation level of 3 to 4 percent along with certain potential changes in EEG frequencies and data. If a person has 5 or more of any type of event per hour of sleep, then they are clinically diagnosed with sleep apnea.

    The body responds to the lack of oxygen by arousing, or waking, from sleep. This cycle leads to the person being unable to get the needed quantity of restful sleep and may result in:

    • Constant Fatigue
    • Difficulty Focusing
    • Irritability

    Untreated Sleep Apnea is potentially fatal and frequently results in the following serious health problems:

    • Heart Attack
    • Stroke
    • High Blood Pressure
    • Diabetes

      What is a passover humidifier?
    A passover humidifier uses a chamber of room temperature water with the CPAP to add moisture to the airflow and reduce irritation to the nasal passages.

    Air flows from the CPAP through a short hose to the humidifier chamber where the air "passes over" the water to pick up whatever moisture it can. The air then flows into the six foot hose to the mask.

    Passover humidifiers may provide sufficient moisture with CPAPs set at lower-end pressures. However, if the moisture is not sufficient there is no way to increase the amount of moisture added. The water is room temperature. In cold climates, the water temperature will drop causing the CPAP air to become very cold, and causing the amount of moisture to be reduced.
      What is rainout?
    Rainout is the accumulation of water in a CPAP tube due to warm moist air cooling and condensing on its way from your CPAP machine to your CPAP mask.

    The image below from Fisher & Paykel explains how rainout is formed. Warm, moist air leaves the heated humidifier and travels through the CPAP tube. As air flows through the tube, the temperature of the room causes the tube to cool. As the tube cools, the air inside releases its moisture, and creates condensation in the hose.

    Solutions to rainout include:
    • Raise the temperature of your bedroom.
    • Keep your CPAP machine at the same level as your bed.
    • Insulate your tubing with a hose cover like Snugglehose.
    • Reduce the temperature setting on your heated humidifier.
    • Purchase a CPAP machine with a rainout reduction comfort feature.
    • Some machine systems offer a compatible heated CPAP hose which maintains the temperature from the machine all the way to the mask, reducing the occurrence of rainout. The list of available heated hoses can be found here: Hoses With Heating Coils.
    • If your machines uses a standard hose, consider the Hybernite Heated Rainout Control System.


    Conventional Humidification
      What is ramp?
    The ramp button on a machine is a feature that allows for a gradual pressure build-up to your prescribed pressure. The feature is enjoyed by those with high pressures because it eases up to their pressure.
      RERAs
    Respiratory event-related arousals. Episodes that are not apneas or hypopneas, often related to loud snoring, that generally do not cause a decrease in oxygen saturation.
      What are reusable foam filters?
    Foam filters are designed to collect larger dirt particles and animal fur. If two filters are used in a machine, the foam filter should be on the outside.

    An example of a reusable foam filter is shown below.
    M Series Filters
      Supine
    Supine is a sleep position: Sleeping on back. Non-supine means to sleep in a position not on your back.
      What is System One Humidity Control?
    System One Humidity Control technology is a rainout reduction feature created by Philips Respironics. System One Humidity Control technology analyzes ambient room temperature, relative humidity, and air flow from the tube to the CPAP user. Then, it adjusts heat to deliver an optimal level of humidification that avoids rainout conditions. The heated tube maintains the humidification all the way from the machine to the mask.

    System One Humidity Control Technology System One Humidity Control Technology
      What is ThermoSmart Technology?
    ThermoSmart technology is a rainout reduction feature created by Fisher & Paykel. ThermoSmart technology is a unique heated hose which maintains the warm environment for the airflow to prevent condensation.

    With conventional humidification, as air flows from the heated humidifier through the CPAP hose, the surrounding air cools the air inside the CPAP hose. As the air cools, it releases moisture in the tube and mask. The heated hose creates a continuous heated environment to help the air hold its moisture and be delivered effectively to the user.

    Conventional Humidification Conventional Humidification ThermoSmart Technology ThermoSmart Technology

    Here are some of the Fisher & Paykel machines with ThermoSmart Technology:

    ICON Auto CPAP Machine with Built-In Heated Humidifier and ThermoSmart Heated Hose
    SleepStyle 234 CPAP Machine with Built In Heated Humidifier
    ICON Premo CPAP Machine with Built-In Heated Humidifier and ThermoSmart Heated Hose
      Total # of PLMs
    Total # of PLMs: The number of periodic leg movements in sleep that last greater than 0.5 seconds.
      Total arousal index
    Total arousal index: Total number of all arousals multiplied by the number of hours of sleep.
      TRT (Total Recording Time)
    TRT is the amount of time that is recorded during a Polysomnogram. This statistic can be used to compare how long it takes a patient to fall asleep, and Totals Sleep Time (TST).
      TST (Total Sleep Time)
    TST is the actual time a patient spends asleep during a Polysomnogram. This statistic can be used to determine sleep architecture.
      Spontaneous arousal index
    Spontaneous arousal index: The number of spontaneous arousals (e.g. arousals not related to respiratory events, limb movements, snoring, etc) multiplied by the number of hours of sleep.
      What Does CPAP Stand For?

    "CPAP" is an acronym, standing for the words "Continuous Positive Airway Pressure". CPAPs work by gently pressurizing the outside air, and blowing it through a long tube, connecting to the nose or mouth using a CPAP mask. CPAP machines are the most common form of Sleep Apnea treatment available on the market today.

      What is Positive End Expiratory Pressure (PEEP)?

    Positive End Expiratory Pressure (PEEP) refers to a type of ventilation where airway pressure is maintained as one breathes out by using a mechanical device, such as a valve, within a circuit. Why would someone want to do this? The purpose is to increase the volume of gas in the lungs as the person breathes out, and is meant to improve the exchange of oxygen and carbon dioxide in the lungs.

    PEEP is not an alternative to CPAP and the two devices perform very different functions. Typically, PEEP is used by EMTs during emergencies and to help combat acute respiratory failure to allow reduction in the level of oxygen during respiration.

    Did You Know?, Definitions

    • Apnea in Greek, literally translates to "without breath."
    • Oximeters can detect the oxygen saturation in your blood, so you can know how your therapy is going.
    • Manometers test the pressure output of machines. This lets you know if you are getting the prescribed treatment.
    • You can share and get information at the CPAPtalk.com Wiki.


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