AHI Calculator | Apnea-Hypopnea Index

Created by Łucja Zaborowska, MD, PhD candidate
Reviewed by Anna Szczepanek, PhD
Based on research by
Malhotra, A., Ayappa, I., Ayas, N., Collop, N., Kirsch, D., Mcardle, N., Mehra, R., Pack, A. I., Punjabi, N., White, D. P., Gottlieb, D. J. β€œMetrics of sleep apnea severity: beyond the apnea-hypopnea indexβ€œ Sleep (July 2021)See 1 more source
Boyd, S. B., Upender, R., Walters, A. S., Goodpaster, R. L., Stanley, J. J., Wang, L., Chandrasekhar, R. β€œEffective Apnea-Hypopnea Index ("Effective AHI"): A New Measure of Effectiveness for Positive Airway Pressure Therapyβ€œ Sleep (November 2016)
Last updated: Jul 26, 2022

The AHI calculator is one of the most useful sleep apnea tools.
Along with STOP-BANG and the Epworth sleepiness scale, it allows us to screen and diagnose the severity of blocked and clear airway apnea. πŸ›οΈ

Keep on reading to fully discover the OSA AHI scale, its meaning, and its potential uses.

We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace professional medical advice.

What is AHI?

The Apnea-Hypopnea Index (or AHI) is a widely used tool for assessing the severity of sleep apnea.
It describes the average number of sleep disturbance episodes in one hour.

What's the meaning of AHI?

The severity of sleep apnea (lack of breathing) and hypopnea (shallow breathing) is linked to an increased risk of many serious conditions, such as:

The ability to recognize and adequately treat sleep apnea may not only protect us from these diseases but also considerably increase our quality of life.

Apart from AHI in sleep apnea, we may use a variety of other scales:

  • STOP-BANG β€” scans for risk factors and symptoms of sleep disorders.
  • The adult and pediatric Epworth sleepiness scale β€” for assessing daytime sleepiness, one of the most important symptoms of sleep apnea.

OSA β€” AHI scale and treatment

AHI is a vital score used in the diagnosis of obstructive sleep apnea (OSA). OSA is a disease caused by the relaxation of throat muscles that consequently block the airflow in your airways.

A continuous positive airway pressure (or CPAP) machine is a device worn during the night, designed to increase the air pressure in our airways, decreasing the blockage and allowing oxygen to flow freely to our lungs. We can use a CPAP machine for mild, moderate, and severe apnea.

Now that we are familiar with the meaning of AHI, it is high time to explain how to calculate AHI.

How to calculate AHI events per hour?

Let's enumerate the crucial steps:

  1. Observation β€” the patient is carefully monitored during their sleep.
    We're looking for:

    • Abnormally slow or shallow breathing (hypopnea).
    • The absence of breathing that lasts more than 10 seconds (apnea).
  2. Calculation of AHI score

    • We need to add the number of episodes of both hypopnea and apnea, and then divide the result by the number of hours spent sleeping.
  3. Interpretation of AHI

    The final sleep apnea score informs us about the total number of sleep episodes during one hour. πŸ•’


How to calculate CPAP AHI score?

AHI is a vital sleep apnea score used to evaluate the work of a CPAP (continuous positive airway pressure) machine β€” an automatic device used to treat apnea and hypopnea. An AHI score of 5 or more informs us that the therapy is not working as it should.

To calculate the CPAP AHI score, we need to use the equation for the number of AHI events per hour as featured in Omni's AHI calculator:

AHI = ((apnea episodes + hypopnea episodes) / sleep time) * 60

Where sleep time is given is minutes. 😴

What are the risk factors of high AHI score?

We use the AHI (the Apnea-Hypopnea Index) to assess both central sleep apnea (CSA) and obstructive sleep apnea (OSA).

The risk factors for CSA and OSA AHI scale include:

  • Obesity;
  • Male sex;
  • Family history of apnea;
  • Large neck circumference;
  • Being older;
  • Using recreational drugs, alcohol, or narcotic pain medication;
  • Heart diseases; and
  • History of stroke.

How to interpret the sleep apnea AHI chart?

It's extremely easy! Follow the table below for a full answer:

AHI scoreInterpretation
0–4Normal range
5–14Mild sleep apnea
15–29Moderate sleep apnea
30+Severe sleep apnea

Patients may use a CPAP (continuous positive airway pressure) machine for mild, moderate, and severe sleep apnea.

Łucja Zaborowska, MD, PhD candidate
Apnea episodes
Hypopnea episodes
Actual sleep time
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