During sleep, relaxation of the muscles around the upper airway causes turbulent airflow through narrowed areas and the resultant vibration creates the noise of snoring by causing the engagement of mucosa located in opposite walls.
The effect of the vacuum formed in the channel walls by the flowing air during respiration causes the air passage to collapse and get narrowed, and consequently the respiration decreases and even completely stops as a result of complete blockage of the channel.
A cessation of nasal or oral respiration for more than 10 seconds is referred to as “ apnea ”, and the number of apneas observed during sleep for a period of 1 hour is referred to as “ apnea index ”.
The condition that involves 30-50% decrease in airflow for a period longer than 10 seconds, reduced respiratory movement, deceased oxygen saturation of the blood (O2 saturation), and the resultant awakenings is referred to as hypopnea .
A respiratory arrest due to failure of the brain’s respiratory control center in stimulating the respiration function is referred to as ” central apnea “. In general, this disease is a pathology in the field of neurology.
RDI ( R espiratory D isturbance I ndex), the most commonly used value intended for determining the severity of the respiratory arrest, or apnea-hypopnea index ( AHI ) is the total number of apneas and hypopneas experienced in an hour. But in recent years, the amount of decrease in the blood oxygen saturation during sleep as well as the duration of the decrease have been considered rather than apnea-hypopnea index, for determining the severity of the disorder. Patients’ apnea-hypopnea index values and changes in their oxygen saturation values are determined with an overnight sleep test (polysomnography).