Glasgow Index
A composite breath-shape scoring system that evaluates 9 flow limitation characteristics per breath on a 0-9 scale. Lower scores indicate better therapy.
What Is Glasgow Index?
The Glasgow Index is a comprehensive breath shape scoring system originally developed by DaveSkvn as an open-source flow limitation analyser (GPL-3.0), ported and validated for AirwayLab. It scores each inspiration across 9 independent shape characteristics: skewness, spikiness, flat-top pattern, top-heaviness, multi-peak pattern, no-pause pattern, inspiratory rate variability, multi-breath pattern, and variable amplitude.
Each component is scored from 0 to 1 based on the proportion of breaths exhibiting that characteristic. The overall Glasgow Index is the sum of all 9 components, yielding a 0-9 scale where lower is better. In practice, typical scores range from 0 to about 3, and scores above 3 are rare, indicating very significant flow limitation problems.
The Glasgow Index is a holistic breath-shape score. Unlike NED, which specifically measures peak-to-mid flow drops, or FL Score, which detects flat-topped breathing patterns, the Glasgow Index catches many types of waveform abnormality including unusual timing patterns, variable amplitude, and multi-peak breathing. For multi-session nights, AirwayLab uses duration-weighted averaging to combine scores accurately.
Normal Ranges
How AirwayLab Measures This
The Glasgow Index engine segments each inspiration from the raw 25 Hz flow signal using zero-crossing detection. It then computes 9 shape descriptors per breath and aggregates them into per-component scores (0-1 each) and an overall Glasgow Index (0-9 scale). Multi-session nights use duration-weighted averaging. Results appear on the Glasgow tab in the dashboard with a radar chart showing all 9 components.
Try it with your dataFrequently Asked Questions
What is a good Glasgow Index score?
A Glasgow Index below 1.0 indicates well-controlled therapy with minimal flow limitation. Scores between 1.0 and 2.0 are borderline and worth monitoring. Scores above 2.0 suggest significant flow limitation that may warrant discussion with your clinician about pressure or settings adjustments.
Why does my Glasgow Index disagree with my FL Score?
Glasgow and FL Score detect flow limitation using different methods. Glasgow scores 9 breath-shape characteristics holistically, while FL Score measures population-level flatness. A high FL Score with low Glasgow can happen when breaths are moderately flat-topped but do not show the specific shape distortions Glasgow targets. Using all three metrics together gives the most complete picture.
What are the 9 Glasgow Index components?
The 9 components are: Skew (asymmetry of the inspiratory waveform), Spike (sharp peaks), Flat Top (plateau pattern), Top Heavy (concentration of flow in early inspiration), Multi-Peak (multiple peaks per breath), No Pause (absent expiratory pause), Inspiratory Rate (breathing rate variability), Multi-Breath (inter-breath pattern changes), and Variable Amplitude (inconsistent breath sizes).
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Medical Disclaimer
AirwayLab is not a medical device and is not FDA-cleared or CE-marked. It is provided for educational and informational purposes only. The analysis results should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult qualified healthcare providers regarding your sleep therapy and any changes to PAP settings.