Understanding your sleep study results

What do AHI, REI, and RDI mean?

AHI · Apnea-hypopnea index

The number of apneas and hypopneas per hour of sleep. It describes frequency, not the total number across the night. [1]

REI · Respiratory event index

Many home tests use monitoring time because they do not measure sleep with brain-wave sensors. Time awake and differences in what the device measures can affect the result. [2]

RDI · Respiratory disturbance index

Can include breathing-effort-related arousals in addition to apneas and hypopneas. Ask which index and scoring method your report uses before comparing it with another report. [2]

Adult AHI severity ranges

These are adult categories. They do not apply to children, and they do not describe every part of an individual’s condition. Your sleep physician also considers symptoms, the rest of the study, and medical history. “Mild” does not automatically mean that symptoms or treatment needs are unimportant. [3]

How to read oxygen findings

Your report may show average oxygen saturation, the lowest recorded value, the frequency of drops, or time spent below a stated level. These measurements describe different things. Ask your sleep physician what the pattern means rather than using the lowest number alone to judge the whole study. [1]

What kind of events were recorded?

Obstructive events involve blockage of the upper airway. Central events involve a problem with the signals that control breathing. The total event count does not tell you which pattern was present. Ask whether your report shows obstructive events, central events, or a mixture, and what that means for care. [4]

What a report may not settle

A home test may underestimate breathing-event frequency because of limited sleep/wake measurement, events it cannot detect, or poor sensor signals. A negative, inconclusive, or inadequate home test requires follow-up with the ordering clinician. [5]

If the findings do not match your experience, ask your sleep physician what needs further evaluation.

Questions to bring to your results visit

• Which index does my report use, and what did the test measure?
• What types of breathing events were present?
• Were there important oxygen findings or recording limitations?
• How do these findings relate to my symptoms and health history?
• Which treatment options fit my situation, and how will we check the result?

Bring the full report to a treatment consultation, along with a list of treatments you have tried and what was difficult about them.

Common questions