Flow-volume loop interpretation (fixed vs variable, intrathoracic vs extrathoracic obstruction)
Core concept
- Expiration above the axis, inspiration below; volume on the x-axis (TLC at left, RV at right)
- Only the first ~1 second (to peak expiratory flow) is effort-dependent
- The rest of the expiratory limb is effort-independent, limited by dynamic airway compression at the equal pressure point
- -> a patient cannot fake a normal descending limb, but can fake a low PEF
- The inspiratory limb is effort-dependent throughout - negative intrathoracic pressure holds intrathoracic airways open
- -> The pressure gradient across the lesion during each phase determines which limb flattens
3 more sections, plus exam facts
Premium unlocks every note across every specialty, and the full exam fact library behind it.
Get premium access