Lung Volumes

What is a lung volume test?

Lung volume testing measures the total amount of air the lungs, and how much air is left after the child has breathed out as far as possible.

What’s it used for?

Lung volume test helps us to determine if the child’s lung condition is restrictive or obstructive:

  • Obstructive lung disease: This leads to narrowed airways and child’s lungs has more air than normal after the child breathes out. Examples of obstructive conditions are asthma, cystic fibrosis and bronchiectasis.
  • Restrictive lung disease: This leads to loss of elasticity which restricts the lungs from expanding fully. Hence, the child cannot fill the lungs completely with air. Examples of restrictive conditions are diffuse lung diseases, interstitial lung diseases, kyphoscoliosis and obesity.

What happens during a lung volume test?

The lung volume testing be done by using two methods:

  • Body Plethysmography
  • Helium Dilution Method

The method used to measure lung volumes may vary depending on your condition or the equipment that is available at your hospital.

What will the results look like?

The results are available as total lung capacity (TLC) is based on your age, height, sex and ethnicity. Normal results typically range between 80-120% of the prediction.

If the lung volume (TLC) is high it suggest an obstructive lung disease while low lung volumes (TLC) suggests restrictive lung disease.