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% or 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