FL Score (Flow Limitation Score)

The FL Score is computed by the WAT (Wobble Analysis Tool) engine. For each inspiration, it takes the samples above 50% of peak flow and computes the variance of that normalized top region. Low variance, a flat top, maps to a higher score; the night’s score is the average across all breaths.

In normal breathing, airflow ramps up and rounds off naturally near the peak, so the top of the breath still varies. In flow-limited breathing, the airflow plateaus because the airway is partially narrowed, so the top of the breath flattens and its variance drops, pushing the score up.

This is an uncalibrated relative index currently under review. Because only the top of each breath is analysed, scores cluster between roughly 50 and 65 even for unobstructed breathing, so a value in the borderline (60-70) band can still occur in normal breathing — the bands are provisional while the metric is under review. Compare trends within your own nights rather than reading the absolute number or a single band, and cross-check against NED and Glasgow, which measure flow limitation differently.