A to Zzz of SLEEP DEFINITIONS AND ABBREVIATIONS

ACTIGRAPHY

A wrist watch device to assess movement and sleep/wake cycles.

AHI (Apnoea/Hypopnoea Index)

The number of Apnoea/Hypopnoea Events per hour.

AI (Apnoea Index) 

The number of Apnoea events per hour.

APAP

Automatic Positive Airway Pressure Machine (Automatic CPAP), which automatically adjusts the level of pressure needed on a breath-by-breath basis.   (Useful for people on high pressures or who find it difficult to tolerate the pressure needed and used for identifying correct pressures).

APNOEA

Without Breath (also spelt Apnea in some countries). Therefore, Sleep Apnoea means pauses in breathing whilst sleeping.

AROUSAL

Going from sleep to wakefulness, or from a deeper to lighter stage of sleep.

ASV (Adaptive Servo Ventilation)

A non-invasive ventilator machine, that is used to treating central sleep apnoea, mixed sleep apnoea and other conditions.  These machines support regular breathing with a back-up rate to ensure people continue breathing during central events.

BiPAP

Bi-level Pressure Machine with 2 pressures – a lower pressure for exhalation and a higher pressure for inhalation.  (Useful for people who find it difficult to exhale against the pressure). 

BRUXISM

Teeth grinding during sleep.

COMPLEX SLEEP APNOEA

A combination of Central and Obstructive Sleep Apnoea. (Also known as Mixed Sleep Apnoea).

CPAP

Continuous Positive Airway Pressure Machine with one fixed pressure giving constant same-pressure therapy to keep the airways open.

CSA (Central Sleep Apnoea)   

Absence of breath caused by irregularity in the brain’s control of breathing.

EPAP

Expiratory Positive Airway Pressure prescribed for the expiratory (breathing out) phase of a person on NIV therapy, such as BiPAP/ASV.

FL (Flow Limitation)

Partial closure of the upper airway impeding the flow of air into the lungs.

GERD (Gastroesphageal Reflux Disease)

Flow of stomach acid upwards into the oesophagus that can cause arousals and disrupt sleep.

HST (Home Sleep Study)

A sleep study that can be taken in a person’s own home.

HYPERSOMNIA

Excessive daytime sleepiness

HYPNOTICS

Sleep-inducing medication.

HYPOPNOEA

Shallow breathing, often accompanied by oxygen desaturation.

HYPOVENTILATION

Decreased rate of breathing.

INSOMNIA

Difficulty in falling and/or staying asleep.

IPAP (Inspiratory Positive Airway Pressure)

Pressure prescribed for the inspiratory phase of a person on Bi-level CPAP therapy

LAUP (Laser Assisted Uvulopalatoplasty)

Surgery using a laser to make some small cuts in your soft palate to make it firmer and hopefully reduce snoring. 

MICROSLEEP

Sleep episode lasting from a fraction of a second up to 30 seconds – normally as a result of sleep deprivation and sadly responsible for many traffic accidents!

MIXED SLEEP APNOEA

A combination of Central and Obstructive Sleep Apnoea. (Also known as Complex Sleep Apnoea).

MSLT (Multi Sleep Latency Testing)

Hospital tests via recurrent naps to check for sleep onset and REM, which is useful for identifying narcolepsy and other sleep issues.

NARCOLEPSY

A sleep disorder that causes excessive sleepiness and frequent daytime sleep attacks. 

NIV (Non-Invasive Ventilator)

A term used for machines such as BiPAP, VPAP and ASV, when people need more ventilation support for breathing.

NOCTURIA

Excessive, sometimes frequent, urination during the night.

OSA (Obstructive Sleep Apnoea)

Sleep disorder where the sufferer stops breathing for at least 10 seconds, caused by an obstruction, such as the uvula or tongue blocking the windpipe, soft palate dropping etc.

OSAS (Obstruction Sleep Apnoea Syndrome)

As for OSA (above) although some people refer to OSAS meaning suffering with daytime symptoms.  However, it is rarer to have untreated OSA without daytime symptoms!

An episode of overly shallow breathing or an abnormally low respiratory rate, which is different from an apnoea as there does remain some flow of air.   It is also caused by the same obstructions as OSA.

The number of times per hour oxygen levels dip (desaturate) below the baseline by 3% – often coinciding with apnoeas/hypopnoeas.

A slang term for CPAP, APAP and BiPAP machines.

PSG (Polysomnography)

Sleep Study Testing for sleep apnoea and other disorders.

Includes all respiratory events per hour (apnoeas, hypopnoeas and RERA’s).

The deep sleep stage where there is rapid eye movement (hence its name) and where there is loss of body movement, more brain activity and dreaming occurs.  Most apnoeas happen during REM sleep.

A tingling, aching, crawling and itching of the limbs which can last for hours when ‘at rest’ and usually gets worse at night, preventing the sufferer from getting the sleep they need. There is an almost irresistible urge to move the legs to ease the discomfort.  During sleep this is called PMLD (as above).

Registered Polysomnography Technologist or ‘Sleep Tech’ for short.

A build-up (often accumulated over many years) of sleep deprivation, which the body requires to be paid back in order for healing and restoration to take place.  This debt does not usually start to get paid back until the sufferer is on successful therapy.

Titration carried out during sleep with a CPAP or NIV – adjusting the pressures as needed to eliminate events, and to ensure the patient is on the correct pressures.