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Lung Function Tests
Lung Function Tests
Pulmonary function tests including spirometry, flow-volume loops, lung volumes and diffusion capacity can be used to diagnose and grade obstructive or restrictive lung disease.

Total Lung Capacity



  • The total lung capacity refers to the volume of air within the lungs after a maximal inspiration.
      • Normal Range

      • 80 - 120% predicted

Increased Total Lung Capacity

  • Increased TLC (>120% predicted) indicates hyperinflation.
    • Causes of Increased Total Lung Capacity

    • Emphysema
    • Asthma
    • Acromegaly
    • Athletes

Reduced Total Lung Capacity

  • Reduced TLC (<80% predicted) indicates restrictive disease.
    • Causes of Reduced Total Lung Capacity

    • Parenchymal disease - pulmonary fibrosis, sarcoidosis, atelectasis
    • Pleural disease - pleural effusion, pneumothorax
    • Chest wall deformity - kyphosis, scoliosis, morbid obesity
    • Neurologic / neuromuscular / muscular disorder - motor neurone disease, Guillain-Barre, muscular dystrophy, myaesthenia gravis
Last updated on November 25th, 2019

Associated Diseases

Neuromuscular Junction
Interstitial Lung Disease