Compass is still being developed and is effectively in beta. Some content and features may be incomplete, change, or not work as expected.

Content is anchored to trusted sources where available, but Compass has not yet been clinically reviewed. It provides general information rather than medical advice.

Feedback helps us identify gaps, errors, usability problems and opportunities to improve Compass over time.

How Compass is developedGive feedback

Tests and measurements

Peak cough flow

A measure of how fast air moves when you cough, used to judge whether a cough is still strong enough to clear the chest.

What it means

You cough into a small hand-held meter and it records the fastest flow. Because clearing mucus depends on speed rather than effort, the number gives a team something to track over time rather than relying on how a cough sounds.

Why you might hear it

  • It is usually measured at the same visit as other breathing tests.
  • It often comes up when cough support is being considered.

People who may help

Where Compass goes into this

About this explanation

These are plain explanations of words you may come across, not advice about your own situation. Where a word matters to a decision, the question pages go into it properly, and your own team is the place to take it.