Obstructive Reduced (to a lesser extent than FEV1) < 80% of  predicted < 0.7
Restrictive Reduced (< 80% predicted) < 80% of predicted > 0.7
Image of Spirometry trace

Causes of an Obstructive picture

  • Anything that causes obstruction to air flow.  Examples are…
  • Enlarged thyroid
  • Vocal cord dysfunctions
  • Tumours

  • COPD
  • Asthma
  • Bronchiectasis
  • Cystic fibrosis


Causes of a Restrictive picture

  • Scoliosis
  • Kyphosis
  • Ankylosing spondylitis
  • Diaphragm paralysis/elevated hemi-diaphragm
  • Neuromuscular diseases, such as polio, Guillain-Barre syndrome and Myasthenia gravis
  • Obesity

  • Pulmonary fibrosis
  • Drug induced fibrosis, for example with amiodarone or methotrexate
  • Extrinsic allergic alveolitis
  • Sarcoidosis
  • Asbestosis


COPD & Asthma

  • COPD and Asthma are both obstructive lung disease.
  • If there is doubt, consider reversibility spirometry.
  • If high suspicion of asthma, treat and review.  In intermediate suspicion, do reversibility spirometry.
Clinical features
COPD Asthma
Smoker Almost all Maybe
< 35y Rare Often
Chronic productive cough Common Rare
Breathless Persistent and progressive Variable
Night time breathlessness or wheeze Rare Common
Day to day variation Rare Common

Reversibility spirometry

Administer 400mcg of salbutamol and repeat spirometry after 15 minutes

  • Asthma suggested if >=12% FEV1 response
  • COPD excluded if FEV1/FVC & FEV1 returns normal
  • In mixed picture, may only have partial response

Grading COPD severity
< 80% of  predicted

50 – 80%: Mild COPD

30 – 49%: Moderate COPD

<30%: Severe COPD

PEFR logs for asthma
  • Look for daily or diurnal variations
  • > 20% variation is of significance



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