AHI - Prone Position Test

This measure captures the apnea hypopnea index during sleep spent in the prone position, meaning lying face down. As with other AHI metrics, it counts apneas and hypopneas per hour that are associated with at least a 3 percent decrease in blood oxygen levels. Oxygen desaturation signals that airflow limitation is affecting oxygen delivery to the body.

Prone sleeping is less common in adults but can reduce airway collapse in some individuals by changing head and neck alignment and reducing backward displacement of the tongue. A relatively low prone AHI compared with supine values can support the diagnosis of positional obstructive sleep apnea and suggests that airway mechanics improve when gravitational forces on the upper airway are altered.

However, prone AHI should be interpreted cautiously because many sleep studies include limited prone sleep time. Short sampling can make the number less reliable and may not reflect typical nightly sleep. Neck rotation and pillow use in the prone position can also affect airway patency, adding variability to this measure.