The apnea -hypopnea index ( AHI) referred to in sleep medicine, the average number of apnea - hypopnea episodes per hour and sleep. It is an indication of the severity of a "sleep -related breathing disorder " and is also used in the control of therapeutic intervention.
Calculation of the AHI
To determine the AHI is the sum of the number of apneas and hypopneas is formed, multiplied by 60 and the total sleep time ( "total sleep time", one in minutes ) divided. The number of respiratory events apnea ( pauses in breathing ) and hypopnea ( times with reduced respiratory flow ) are determined in the sleep laboratory in a study using polysomnography.
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.
Use of the AHI
For the diagnosis of certain "sleep -related breathing disorders " such as the obstructive sleep apnea syndrome (OSAS ), in addition to other characteristics laid down specific values for the AHI.
In the review of the treatment is determined whether the number of respiratory events in question shall be reduced proportionately by the treatment.
Severity according to AHI
There is no uniform classification of severity using the AHI. The American Society of Sleep Medicine ( AASM ) has published detailed guidelines for the determination of AHI, are with respect to the severity of OSAS as a gradation to:
- " Mild": AHI 5-15,
- " Moderate": AHI 15-30,
- " Severe ": AHI greater than 30
And combines the statement with references to the tendency to fall asleep during the day in certain situations.
According to the Medical guideline " non -restorative sleep - sleep " OSAS " from an AHI > 15 and < 30" is " classified as seriously as an AHI > 30 " as moderate, and.
Other authors use terms such as light, moderate and heavy and draw boundaries with an AHI of 20 or 40 or use mathematical and technically precise limits appearing with words such as " less than" without the ranges overlap. Given the fact that treatment recommendations not only depend on the severity and the measurement results from night to night anyway fluctuate, but this is not significant.