Two people. Same PAP machine, same pressure settings, same 40% flow limitation. One wakes up exhausted. The other feels fine. If flow limitation drives symptoms, why doesn't everyone with the same FL% feel the same?
The answer is individual sensitivity. Not everyone responds to flow limitation the same way. And until now, there was no way to figure out whether your flow limitation is actually causing your symptoms.
The Missing Piece in Flow Limitation Analysis
AirwayLab already measures flow limitation from multiple angles: the Glasgow Index scores your overall breathing shape, FL Score quantifies inspiratory flatness, NED detects per-breath flow drops, and IFL Symptom Risk combines them into a single percentage. These metrics tell you how much flow limitation you have.
But they can't tell you whether that flow limitation is actually causing your symptoms. A 45% IFL Risk might mean debilitating fatigue for one person and nothing noticeable for another. The metrics measure the airway. They don't measure the person attached to it.
The IFL Sensitivity Hypothesis
Dr. Avram Gold's research suggests that flow limitation activates a stress response via pressure-sensing nerves in the upper airway. But the magnitude of that stress response varies between individuals. Some nervous systems react strongly to mild airflow restriction. Others tolerate significant flow limitation without noticeable symptoms. This individual variation is what makes population-level thresholds unreliable for predicting your experience.
Tracking Your Own Correlation
The only way to know if your flow limitation is driving your symptoms is to track both simultaneously and look for patterns. That's the idea behind AirwayLab's symptom self-report: a simple 1-5 rating of how you feel each morning, stored alongside your flow limitation data.
1
Terrible
2
Poor
3
Fair
4
Good
5
Great
One tap, every morning. No questionnaires, no scales to decode. Just: how do you feel today? Over time, the pattern tells you what no single metric can.
Three Patterns That Tell You Something
When AirwayLab has both your flow data and your symptom rating for a night, it can cross-reference them. Three patterns are particularly informative:
High IFL + Feeling Bad
Your flow limitation is elevated and you feel it. This is the most actionable pattern: your FL metrics are correlating with your symptoms, which means reducing flow limitation (through pressure adjustments, positional changes, or other interventions) is likely to improve how you feel. Discuss with your clinician.
High IFL + Feeling Fine
Your flow limitation is elevated but you're not symptomatic. This is genuinely useful information. It suggests you may have lower sensitivity to flow limitation, which means aggressive pressure increases to chase a "perfect" FL score may not improve your quality of life. Not all flow limitation requires intervention.
Low IFL + Feeling Bad
Your flow limitation is minimal but you still feel terrible. This points away from flow limitation as the cause of your symptoms. Consider other factors: sleep fragmentation from non-respiratory causes, medication side effects, sleep hygiene, comorbid conditions, or factors captured in your Night Notes (caffeine, alcohol, congestion, stress).
None of these patterns are diagnostic on their own. But tracked over weeks, they build a picture of your individual sensitivity that no single-night analysis can provide. And they give your clinician concrete data to work with.
How You Compare to Others Like You
Individual tracking is valuable. But context makes it more valuable. When you opt in to data contribution, AirwayLab can show you how other people with similar IFL Risk levels rate their sleep quality.
What Gets Shared
Your symptom rating (1-5), IFL Risk percentage, a few key metrics (Glasgow, FL Score, NED), your pressure range, PAP mode, and device model. No dates, no names, no timestamps, no raw waveforms. The data is anonymised with a one-way hash — it cannot be traced back to you. If you're not comfortable sharing, the symptom rating still works entirely locally.
Seeing that 70% of people with your IFL Risk level rate their sleep as Good or Great gives you genuinely useful context: maybe your symptoms aren't coming from flow limitation. Seeing that most people in your range feel similarly bad validates your experience and gives weight to a conversation with your clinician about pressure optimisation.
How to Get the Most Out of Symptom Tracking
Rate consistently
Rate how you feel within the first hour of waking, before caffeine. The rating is subjective by design — your internal reference point is what matters, not an absolute scale.
Use Night Notes alongside
Logging caffeine, alcohol, congestion, and stress helps separate FL-driven symptoms from confounders. A bad morning after evening caffeine and high stress tells a different story than a bad morning with clean Night Notes.
Look for patterns over 2+ weeks
Single nights are noisy. Look for trends: does your rating consistently drop on nights with higher IFL Risk? Does it improve when FL metrics are lower? The correlation over time is more informative than any single data point.
Share with your clinician
A PDF report or forum export that includes both FL metrics and symptom ratings gives your sleep physician something concrete: not just "I feel tired" but "my IFL Risk averaged 52% and I rated 2/5 on those nights vs. 4/5 when it dropped below 25%."
Why This Matters
The PAP community has spent years chasing optimal flow metrics. Pressure titrations, mask changes, positional therapy — all aimed at getting FL numbers down. And for many people, that works. But for some, the numbers improve and the symptoms don't. For others, the numbers stay elevated and they feel great.
Individual sensitivity explains this gap. And the only way to understand your sensitivity is to systematically track both sides of the equation: what your airway is doing, and how you actually feel.
That's what AirwayLab's symptom rating is for. Not a replacement for clinical assessment, but a daily data point that, over time, helps you and your clinician understand whether your flow limitation is the thing to fix — or whether the answer lies elsewhere.
References
Gold AR, Dipalo F, Gold MS, O'Hearn D. (2003). "The symptoms and signs of upper airway resistance syndrome: a link to the functional somatic syndromes." Chest, 123(1):87-95.
Mann DL, Staykov E, Georgeson T, Azarbarzin A, Kainulainen S, Redline S, Sands SA, Terrill PI. (2024). "Flow Limitation Is Associated with Excessive Daytime Sleepiness in Individuals without Moderate or Severe Obstructive Sleep Apnea." Annals of the American Thoracic Society, 21(8):1186-1193.
Stoohs RA, Philip P, Andries D, Finlayson EV, Guilleminault C. (2009). "Reaction time performance in upper airway resistance syndrome versus obstructive sleep apnea syndrome." Sleep Medicine, 10(7): 750-756.
Find Out If Your Flow Limitation Matters
Upload your ResMed SD card, rate how you feel, and let the pattern emerge over time. All analysis runs in your browser — your data never leaves your device.
AirwayLab is not a medical device and is not FDA or CE cleared. Symptom ratings are subjective self-reports, not clinical assessments. Always discuss results with your sleep physician before making therapy changes.