# AHI severity & Medicare 90-day CPAP compliance calculator

Your Apnea-Hypopnea Index (AHI) is the number of breathing pauses and shallow breaths per hour of sleep. Enter the events and sleep time from your sleep study report to see your severity tier, then check whether your CPAP use meets the 70% four-hour rule that Medicare and many insurers use.

Use the tool on the [web page](https://sleepstudies.fyi/tools/ahi-cpap-compliance-calculator). It works without JavaScript.

## How to use it

1. Enter apneas and hypopneas recorded.
2. Enter total sleep time.
3. Enter nights with 4 or more hours of cpap use.
4. Read the result.

## How it works

AHI is the apneas plus hypopneas divided by the hours of sleep, rounded to one decimal. A home sleep apnea test divides by monitoring time instead of measured sleep, so it can read lower than an in-lab study for the same night.

Severity tiers for adults follow the American Academy of Sleep Medicine: under 5 is normal, 5 to 14.9 is mild, 15 to 29.9 is moderate and 30 or more is severe. Children are scored on a different scale; ask a pediatric sleep specialist.

Compliance follows the Medicare rule for continued CPAP coverage (CMS National Coverage Determination 240.4 and the DME local coverage policy): use on 70% of nights, at least 4 hours a night, in 30 consecutive days within the first 3 months. That is 21 of 30 nights. Commercial insurers and DOT medical examiners for commercial drivers often use the same threshold.

The calculator counts only the nights you enter. Your supplier's download from the machine is the record your insurer reads, and Medicare also needs a face-to-face follow-up visit with your clinician between day 31 and day 91 that notes your benefit from therapy.

> For information only, not medical advice or a coverage decision. Your sleep physician interprets your study, and your insurer or Medicare contractor decides coverage from your device data.

## Questions

### What AHI counts as sleep apnea?

For adults, an AHI of 5 or more events per hour with symptoms, or 15 or more without symptoms, meets the usual definition of obstructive sleep apnea. Your sleep physician makes the diagnosis from the full report.

### What is the Medicare CPAP compliance rule?

Medicare keeps paying for CPAP after the first 3 months if you used it at least 4 hours a night on 70% of nights in any 30 consecutive days during those 3 months, and your clinician documents at a follow-up visit that it helps.

### What happens if I miss the 70% rule?

Medicare may stop paying for the device. To requalify you usually need a new face-to-face evaluation and, often, a repeat sleep study in a lab. Talk to your clinician and supplier early if the mask or pressure is a problem.

### Is AHI the same as RDI?

No. The Respiratory Disturbance Index (RDI) adds respiratory effort-related arousals to the apneas and hypopneas, so it is the same as or higher than the AHI.