Respiratory function tests

 

1.FEV1/FVC

·      Obstruction: <0.7

·      Restriction: >0.7 with ↓FVC

2a.Obstruction

Severity = FEV1 (mainly for COPD)

·      Mild: >80%

·      Moderate: 50-80%

·      Severe: 30-50%

·      Very severe: <30%

Cause:

·      Asthma = reversible (↑FEV1 >12% and 200mL)

Other:

·      ↓PEFR

·      ↓FEF25-75

2b.Restriction

Severity = FVC

·      Mild: 50-80%

·      Mod: 30-50%

·      Sev: <30%

Cause:

·      If ↓DLCO: pulmonary interstitial

·      If ↔DLCO: neuro, muscular, skeletal

3.Transfer

Severity = DLCO

·      Mild: 60-80%

·      Mod: 40-605

·      Sev: <40%

Cause:

·      If ↓KCO: interstitial pathology (fibrosis, oedema, PHTN), anaemia

·      If ↔KCO: low lung volume