How are lung volume and capacity measured?

Spirometry

Spirometry is the most common method for measuring lung volume and capacity. It involves blowing into a mouthpiece connected to a spirometer, which measures the volume and flow of air that is inhaled and exhaled.

Body plethysmography

Body plethysmography is a method for measuring lung volume by using a sealed chamber. The person sits inside the chamber and breathes through a mouthpiece. The pressure changes inside the chamber are measured and used to calculate lung volume.

Nitrogen washout

Nitrogen washout is a method for measuring lung volume by using a gas mixture that contains nitrogen. The person breathes in this gas mixture and then breathes out into a spirometer. The amount of nitrogen that is washed out of the lungs is measured and used to calculate lung volume.

Helium dilution

Helium dilution is a method for measuring lung volume by using a gas mixture that contains helium. The person breathes in this gas mixture and then holds their breath. The concentration of helium in the lungs is measured and used to calculate lung volume.