AHI or Apnea Hypopnea Index is a system used to measure the severity level of Sleep Apnea on a scale from normal to severe. It counts the number of Hypopnea events that occur per hour.

• Normal – less than 5 events per hour
• Mild – 5-15 events per hour
• Moderate – 16-30 events per hour
• Severe – over 30 events per hour