😴 AHI Severity Scoring Simulator

Reading a Normal Airflow Waveform

Polysomnography records airflow as a continuous scrolling trace.

• <5: Normal AHI (events per hour)
• 30 sec: Recording epoch (per scored page)
• Nasal + oral: Airflow sensor (thermistor / pressure)
• PSG: Study type (gold-standard sleep study)

What the trace shows

A rhythmic rise and fall marks each breath cycle.

Why baseline matters

Every apnea and hypopnea is scored against this baseline.

Channels recorded

Airflow, chest effort, and oxygen saturation run together.

Scoring an Apnea Event

An apnea is a flat line lasting ten seconds or longer.

• 10 sec: Minimum duration (AASM scoring rule)
• ≥90%: Airflow drop (from baseline amplitude)
• Effort continues: Obstructive type (chest still moves)
• No effort: Central type (brain signal absent)

Visual signature

The waveform collapses to a near-flat segment.

Obstructive vs central

Effort belts distinguish a blocked airway from no drive.

Counting rule

Each qualifying flat segment counts as one apnea.

Scoring a Hypopnea Event

A hypopnea is a partial airflow drop paired with desaturation.

• ≥30%: Airflow drop (from baseline amplitude)
• 10 sec: Minimum duration (sustained reduction)
• ≥3%: Desaturation (SpO2 drop required)
• ≥4% drop: Alternative rule (no arousal needed)

Visual signature

The waveform shrinks but never fully flattens.

Desaturation pairing

An oxygen dip confirms the reduction was significant.

Arousal alternative

A brain-wave arousal can substitute for desaturation.

Calculating the Apnea-Hypopnea Index

AHI totals every scored event per hour of actual sleep.

• (A+H)/hrs: AHI formula (events over sleep time)
• Sleep time: Denominator (not total recording time)
• 6–8 hrs: Typical study length (overnight PSG)
• Sleep technologist: Scored by (epoch by epoch)

The core equation

Apneas plus hypopneas, divided by hours slept.

Why sleep time, not clock time

Wake periods would falsely dilute the rate.

Related index

RDI adds respiratory-effort arousals to the count.

Classifying OSA Severity from AHI

The AHI score sorts patients into standard severity bands.

• <5: Normal (events per hour)
• 5–15: Mild OSA (events per hour)
• 15–30: Moderate OSA (events per hour)
• >30: Severe OSA (events per hour)

Mild range

Often managed with lifestyle change or a dental device.

Moderate range

CPAP therapy is typically recommended here.

Severe range

CPAP is strongly indicated to cut cardiovascular risk.