Flow-Volume Loop — Interactive Teaching Tool

Flow-Volume Loop Normal

FEV₁ · FVC
vs predicted

Patient Predicted normal FEV₁ FEF₂₅ / ₅₀ / ₇₅

Volume–Time Curve read the loop and this together

FEF₂₅₋₇₅–

FEF₅₀–

FIF₅₀–

FEF₅₀/FIF₅₀–

FET–

What the shape suggests

Normal loop

Differential to consider

FEV₁

–

FVC

–

FEV₁/FVC

–

FEV₁ %pred

–

FVC %pred

–

PEF

–

Try a pattern

Patient

Height170 cm

Age40 yr

Sex

Male

Female

Weight70 kg

Predicted FVC–

Predicted FEV₁–

Predicted ratio–

BMI–

Adjust the maneuver

FVC (% predicted)100%

Sets loop width. Low with a preserved ratio → think restriction.

FEV₁/FVC ratio80%

Below ~70% → obstruction. The lower it goes, the deeper the scoop.

Predicted for this patient: 80%

PEF100%

Effort-dependent peak.

PIF85%

Inspiratory depth.

Upper airway lesion

None

Extrathoracic

Intrathoracic

Fixed

Flattening severity0%

No lesion — both limbs unclipped.