Most PAP analysis focuses on events: apneas, hypopneas, AHI. The Glasgow Index looks at what happens between events -- in breaths that your machine never flagged.
What Is the Glasgow Index?
The Glasgow Index measures the shape of your inspiratory flow curve -- the pattern your breath traces during inhalation while you sleep. It characterises whether each breath has a normal, rounded inspiratory waveform or shows features associated with upper airway narrowing: flattening, irregular peaks, unusual timing, variable amplitude.
How the Score Is Calculated
AirwayLab scores each inspiratory breath in your session using nine independent waveform features:
Skew
Whether peak flow occurs early or late in the breath
Spike
Sharp, narrow peaks in the flow trace
Flat top
Flattening of the waveform crest rather than a smooth curve
Top heavy
Flow concentrated in the first portion of inhalation
Multi-peak
More than one peak rather than a single rounded arc
No pause
Absence of a natural inspiratory pause
Inspiration rate
Abnormally fast or slow inhalation
Multi-breath
Irregular cycles spanning more than one breath
Variable amplitude
Significant variation in breath height across the night
Each component scores 0 (feature absent) or 1 (feature present). The overall Glasgow Index for the night is the sum, averaged across all scored breaths. A higher score means more breath shape irregularities were detected.
AirwayLab's implementation is an open-source port of the DaveSkvn/GlasgowIndex algorithm (GPL-3.0). The code is publicly auditable -- you can verify exactly what it calculates.
Where to Find It in AirwayLab
Open the Glasgow tab after loading your ResMed SD card data. You will see your overall nightly score, a component-level breakdown showing which features were elevated, and a trend view across multiple nights if your SD card contains more than one session.
What the Glasgow Index Does NOT Tell You
The Glasgow Index is a data description of your breathing waveform shapes. It is not a clinical finding, a diagnosis, or a trigger for therapy changes. A high score does not confirm any specific condition. Flow shape scoring is one dimension among many in PAP data -- your clinician sees the full picture.
Discuss your data with your clinician for clinical interpretation.
See Your Glasgow Index
Upload your ResMed SD card data to see your Glasgow Index score, component breakdown, and trend across nights. Free, built on an open-source engine, and 100% private -- nothing leaves your browser.
Related reading
What Is NED (Negative Effort Dependence)? -- a breath-by-breath measure of airway resistance during PAP therapy.
What Is the WAT Score in CPAP Data? -- FL Score, regularity, and periodic breathing in one bundle.
AirwayLab Glossary -- definitions of all metrics used in AirwayLab.
see all four metrics AirwayLab tracks -- how the Glasgow Index fits alongside the other metrics AirwayLab measures.
Source
AirwayLab implements an open-source port of the DaveSkvn/GlasgowIndex algorithm (GPL-3.0). The algorithm was developed to score nine features of the inspiratory flow waveform. Code is publicly auditable on GitHub.
AirwayLab is a free tool for analysing PAP flow data, built on an open-source analysis engine. Your data never leaves your browser. Nothing on this page constitutes medical advice -- always discuss your results with a qualified sleep specialist.