Hypopnea

In a more or less long complete cessation of breathing one speaks of an apnea. These events occur in the context of respiratory regulation disorders, such as sleep apnea or Cheyne -Stokes respiration.

Measurement and evaluation

In order to detect hypopneas, the nasal respiratory pressure by means of pressure sensors and pressure transducers is measured. Additionally, the measured values ​​of an oximeter are needed because the oxygen saturation of the blood enters into the evaluation of these respiratory events. To detect apneas, however, fulfill temperature sensors.

Measurement and evaluation are carried out in the sleep laboratory in the context of polysomnography and depend on the current recommendations of the American Society of Sleep Medicine ( AASM ).

As a feature of a hypopnea following cases are distinguished in the definition:

• A reduction in airflow by at least 30 % of the initial value at least 4% reduced oxygen saturation or
• A reduction in airflow at least 50% of the initial value, when either the oxygen saturation of at least 3% of reduced or event is associated with an arousal.

The duration of the event, must be at least ten seconds, the said value must be at least 90 % of this time.

Apnea - hypopnea index

The number of these events and of apneas per hour of sleep is used as an apnea -hypopnea index ( AHI) in assessing the severity of a "sleep -related breathing disorder ."

Due to differences in the assessment of hypopneas by older rules and the two now valid, alternatively apply rules there are significant differences in the determination of AHI with an impact on the comparability of study results.