Sleep apnea A-Z

AHI (apnea-hypopnea index)

The apnea-hypopnea index (AHI) plays a central role in the diagnosis and determination of the severity of sleep apnea. The AHI indicates the number of apneas and hypopneas per hour of sleep. Apneas are breathing interruptions of at least 10 seconds, while hypopneas are partial blockages of the airways that lead to a reduction in breathing. A high AHI of over 30 indicates a more severe form of sleep apnea, while lower values indicate moderate (AHI 15-30) or mild sleep apnea (AHI 5-15). An AHI below 5 does not indicate sleep apnea.

APAP (Automatic Positive Airway Pressure)

Automatic Positive Airway Pressure (APAP) is a treatment method for sleep apnea. In contrast to the CPAP device, which provides a constant air pressure, the air pressure provided by the APAP device automatically adapts to individual breathing patterns during the night. This means that the device only increases the pressure when necessary.


Apnea is a cessation of breathing during sleep for at least 10 seconds. This can be caused by various reasons such as a blockage of the airways (obstructive apnea) or an impairment of the respiratory muscles (central apnea). During apnea, the oxygen level in the blood drops and the body sounds the alarm to restore breathing, often triggering a brief but unnoticed wake-up reaction.


Arousal is the activation of the brain from sleep or a relaxed state. In the context of sleep medicine, arousal refers to a brief awakening response that often occurs as a result of oxygen deprivation. Although arousals are important for reactivating breathing, they can fragment sleep and cause it to lose its restorative effect.

BiPAP (Bilevel Positive Airway Pressure)

Bilevel Positive Airway Pressure (BiPAP or BPAP) is a treatment method for sleep apnea. Unlike CPAP machines, which deliver a constant air pressure, BiPAP offers two different pressure levels: a higher pressure during inhalation and a lower pressure during exhalation. These different pressure levels make it easier for some people to fully exhale and provide additional support during inhalation, which can be particularly beneficial for people with certain conditions.

Cheyne-Stokes respiration (CSA)

Cheyne-Stokes respiration is a periodic breathing pattern in which breathing increases and decreases repeatedly in a cyclical pattern during sleep. Breathing becomes shallower and shallower, often to the point of complete apnea, then gradually deepens again, peaking with extremely labored breaths before decreasing again. This pattern is repeated several times during sleep. Cheyne-Stokes respiration often occurs in people suffering from heart failure, after a stroke or with other neurological disorders.

CPAP (Continuous Positive Airway Pressure)

Continuous Positive Airway Pressure (CPAP) is the most commonly used treatment method for sleep apnea. In this therapy, a slight positive pressure is continuously fed into the airways via a mask during sleep. This positive pressure prevents the airways from collapsing, making it easier to breathe during sleep and reducing breathing interruptions. CPAP therapy is adjusted individually to determine the optimum pressure. Most CPAP devices are small, quiet and portable, which makes them easier to use in everyday life.

Epworth Sleepiness Scale (ESS)

The Epworth Sleepiness Scale (ESS) is a questionnaire used to assess daytime sleepiness. It consists of eight questions in which the probability of falling asleep in various everyday situations is rated on a scale from 0 to 3. The total score ranges from 0 to 24, with higher scores indicating greater daytime sleepiness. The ESS is often used in the diagnosis and monitoring of sleep disorders such as sleep apnea.

Mixed sleep apnea

Mixed sleep apnoea is a sleep disorder that has characteristics of both obstructive and central sleep apnoea. This means that breathing pauses can occur during sleep, which can be caused by a blockage in the airways or by a lack of respiratory drive in the brain.


Hypopnoea refers to a partial blockage of the airways during sleep, which leads to reduced or shallow breathing. In contrast to apnoea, in which breathing stops completely, breathing is impaired but not completely interrupted in hypopnoea. Nevertheless, hypopnoea can also lead to a reduced oxygen supply to the body.


Hypoxia is a condition in which the oxygen supply in the body falls below a normal level. This can lead to tissues and organs not being adequately supplied with oxygen, which can cause various health problems. In the case of sleep apnea, apnea and sometimes also hypoxia trigger hypoxia.

Laser-assisted uvulopalatoplasty (LAUP)

Laser-assisted uvulopalatoplasty (LAUP) is a minimally invasive surgical procedure for the treatment of obstructive sleep apnea. In this procedure, a laser is used to remove excess tissue from the soft palate and uvula. This increases the diameter of the airway and improves airflow during sleep. LAUP is often performed on an outpatient basis and usually does not require general anesthesia.


Obstruction occurs when the airway collapses or narrows completely or partially, restricting the flow of air during breathing. This can be caused by various factors such as slackening of the throat muscles, narrowed airways, e.g. due to obesity, a receding tongue or anatomical features such as large tonsils or a large uvula.

Obstructive sleep apnea (OSA)

Obstructive sleep apnoea (OSA) is a common sleep disorder in which breathing pauses (apnoeas) or reduced breathing (hypopnoeas) occur repeatedly during sleep. These are caused by a temporary blockage or narrowing of the airways and lead to a reduced oxygen content in the blood. In order not to suffocate, the body sounds the alarm, which reactivates breathing. However, this often triggers brief but unnoticed wake-up reactions that interrupt restful sleep. If left untreated, OSA can lead to serious health problems, including cardiovascular diseases such as heart attacks and strokes.

Polygraphy (PG)

Polygraphy (PG) is a diagnostic procedure for detecting sleep disorders such as sleep apnoea. During polygraphy, various parameters such as respiratory flow, blood oxygen saturation, heart rate, snoring sounds, breathing movements of the chest and abdomen and body position are recorded. This procedure is usually performed at home and uses a portable device that can be easily attached to the body. Polygraphy is a less extensive and less expensive alternative to polysomnography (PSG), which involves more comprehensive monitoring of sleep in a sleep laboratory.

Polysomnography (PSG)

Polysomnography (PSG) is a diagnostic procedure used to monitor various physiological parameters during sleep. It enables a detailed assessment of sleep behavior and is suitable for the diagnosis of sleep disorders, including sleep apnea. Polysomnography is carried out in specially equipped sleep laboratories. During polysomnography, various bodily functions such as brain activity, heart rate, muscle activity, eye movements, respiratory flow, breathing movements of the chest and abdomen and oxygen saturation in the blood are continuously monitored and recorded. The results are evaluated by a sleep physician and help with diagnosis and therapy adjustment.

Respiratory event

A respiratory event refers to a deviation from the normal breathing pattern during sleep. This can include apneas, hypopneas or other respiratory disturbances. Respiratory events can result in the body's oxygen supply being compromised and sleep being disturbed. Respiratory events are important in the diagnosis of sleep disorders such as sleep apnea and are detected by monitoring breathing patterns during sleep.

Sleep apnea

Sleep apnoea is a sleep disorder characterized by recurrent pauses in breathing during sleep. There are different types of sleep apnea, the most common being obstructive sleep apnea (OSA), in which the airways become partially or completely blocked during sleep. Sleep apnea can lead to symptoms such as daytime sleepiness, concentration problems and reduced quality of life. Early diagnosis and treatment are important to reduce the risk of serious health problems such as cardiovascular disease and stroke.

Sleep-related breathing disorders (SBAS)

Sleep-related breathing disorders (SBAS), also known as sleep disordered breathing (SDB), is the umbrella term for the various possible forms of breathing disorders that can occur during sleep. This primarily includes obstructive sleep apnea (OSA), which accounts for the majority of SBAS. Sleep-related breathing disorders (SBAS) are characterized by abnormal breathing patterns or pauses in breathing as well as insufficient ventilation during sleep. This often leads to sleep fragmentation, daytime sleepiness and reduced quality of life.


Snoring is a common phenomenon in which sounds are produced during sleep when breathing in, caused by vibrations of the soft tissues in the throat. Snoring can be caused or aggravated by various factors such as relaxed muscles in the throat, enlarged tonsils, obesity or alcohol consumption before going to bed. Although snoring is often harmless, it can lead to sleep disturbances for the person affected or their sleeping partner. In some cases, it can also be a symptom of obstructive sleep apnea, a serious condition in which the airways become blocked during sleep.


Screening is the early detection or identification of diseases or health risks in people who may not yet show symptoms. The aim of screening is to identify potential problems at an early stage so that treatment or intervention can begin in good time, thereby reducing the risk of complications.


Microsleep refers to the sudden and involuntary falling asleep for a few seconds. Those affected are often unaware that they have fallen asleep. Microsleep often occurs in people who suffer from a severe lack of sleep or who spend long periods of time doing monotonous activities such as driving. In road traffic, this can lead to serious accidents. Microsleep can be a direct result of excessive daytime sleepiness associated with sleep apnea.

Daytime sleepiness

Excessive Daytime Sleepiness (EDS) refers to excessive sleepiness during the day that goes beyond normal levels and can interfere with daily functioning. People with daytime sleepiness tend to fall asleep in everyday situations, such as reading or watching TV, or feel the urge to take a nap. Despite getting enough sleep, they often feel tired, listless and have difficulty staying focused. Daytime sleepiness can have various causes, including sleep disorders such as sleep apnea, but also insufficient sleep hygiene, depression or other medical problems.

Tonsillectomy (TE)

Tonsillectomy is a surgical procedure to remove the palatine tonsils (tonsils). This procedure is often performed to treat recurrent tonsillitis, but can also be considered for sleep apnea caused by enlarged tonsils.

Mandibular advancement splint (UKPS)

The mandibular advancement splint is used to treat obstructive sleep apnoea and snoring. The mandibular advancement splint is worn at night and gently moves the lower jaw forward to open the airway and improve airflow. This helps to reduce the risk of breathing pauses and snoring by stabilizing the soft tissues in the throat area and preventing the airways from collapsing. The mandibular advancement splint is individually fitted and is an effective alternative treatment option for people with sleep apnoea who cannot cope with CPAP therapy.

Uvulopalatopharyngoplasty (UPPP)

Uvulopalatopharyngoplasty (UPPP) is a surgical procedure for the treatment of obstructive sleep apnea. In this procedure, parts of the soft tissue in the throat (the posterior soft part of the palate and the uvula) are tightened to enlarge the airway and reduce tissue collapse. A UPPP is often performed in combination with a tonsillectomy (TE).

Central sleep apnea (CSA)

Central sleep apnea (CSA) is a sleep disorder in which breathing pauses occur during sleep that are not caused by an obstructive blockage of the airways, but by a failure of the respiratory drive in the brain. In central sleep apnoea, the brain sends no or insufficient signals to the respiratory muscles during sleep, which leads to temporary pauses in breathing. Central sleep apnea can have various causes, including heart failure, stroke or other neurological diseases.

Tongue pacemaker

A tension pacemaker or hypoglossal nerve stimulation (HNS) is a treatment option for obstructive sleep apnea. In this procedure, a small device is implanted under the skin that sends electrical impulses to the hypoglossal nerve, which controls the tongue muscles. This stimulation stabilizes the tongue muscles during sleep, preventing the tongue from falling back into the throat. You can control the tongue pacemaker yourself by switching the device on before going to bed and switching it off again when you wake up.

Tongue suspension

Tongue suspension is a surgical procedure for the treatment of obstructive sleep apnoea that prevents the tongue from falling back during sleep. In this procedure, the tongue is stabilized with a small implant to prevent it from falling into the throat during sleep and blocking the airways. However, there are not yet many reliable study results for this method.
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