What is body plethysmography?

Body plethysmography is a simple, painless test that takes lung volume measurements. Lung volume is the amount of air you inhale and exhale. The test involves sitting in an airtight booth and blowing into a mouthpiece while a computer records measurements. Body plethysmography helps diagnose respiratory diseases with similar symptoms, including asthma, pulmonary fibrosis, and chronic obstructive pulmonary disease (COPD). 

Body plethysmography is only one method used to diagnose and manage respiratory diseases. Discuss all your testing options with your doctor to understand which tests are best for you.  

Other procedures that may be performed

Body plethysmography is a type of pulmonary (lung) function test. Your doctor will likely recommend one or more other pulmonary function tests to diagnose and monitor your respiratory disease. Pulmonary function tests include:

  • Arterial blood gas test to measure oxygen and carbon dioxide blood levels and other factors 
  • Bronchoprovocation tests to measure lung function after exposure to factors that commonly trigger asthma. This includes a methacholine challenge test to help diagnose asthma. Some bronchoprovocation tests are done at the same time as body plethysmography using the same equipment.
  • Lung diffusion capacity to measure how well oxygen moves into your blood from your lungs. Lung diffusion capacity may be done at the same time as body plethysmography using the same equipment.
  • Peak expiratory flow to measure the speed of exhaling and lung constriction. People with asthma often use this test routinely to monitor their asthma control.
  • Pulse oximetry to measure oxygen levels in the blood
  • Spirometry to measure the rate and the amount of air that you inhale and exhale. Spirometry may be done at the same time as body plethysmography using the same equipment.

Why is body plethysmography used? 

Body plethysmography is the most accurate method and sometimes the only way to take certain lung volume measurements. Lung volume is the amount of air you breathe in and out of your lungs. There are many kinds of lung volume measurements, which are measured using various pulmonary function tests, such as spirometry. 

Body plethysmography can diagnose respiratory diseases earlier than spirometry. It also helps your doctor determine if your symptoms are due to a restrictive or an obstructive disease. 

Restrictive lung diseases make it hard for you to fully expand your lungs and fill them with air. They include: 

  • Asbestosis, which is chronic inflammation and fibrosis of the lungs due to asbestos exposure
  • Neuromuscular diseases including muscular dystrophy and amyotrophic lateral sclerosis (ALS or Lou Gehrig’s disease)
  • Pulmonary fibrosis, which is lung scarring from growth of excessive fibrous tissue in the lungs
  • Sarcoidosis, which is inflammation of the body’s organs, leading to the formation of lumps (granulomas) in the lungs
  • Scoliosis, which is abnormal sideways curving of the spine 

Obstructive lung diseases make it hard for you to exhale all the air out of your lungs. They include:

  • Asthma, which is a chronic lung disease marked by acute flare-ups of inflammation and swelling of the lung’s airways 
  • Bronchiectasis, which is permanent inflammation and widening of the airways leading to mucus blockage
  • Chronic obstructive pulmonary disease (COPD), which includes emphysema and chronic bronchitis
  • Cystic fibrosis, which is a genetic disorder that causes thick, sticky mucus build-up in the lungs and other organs

Who performs body plethysmography?

A pulmonary function technologist usually performs body plethysmography. A pulmonary function technologist has specialized training and education to perform pulmonary function tests safely and accurately. 

The following physician specialists order and interpret body plethysmography tests:

  • Allergist/immunologists are internists or pediatricians with specialized training in the diagnosis and treatment of allergies, asthma, and immune deficiency disorders.
  • Pulmonologists are internists or pediatricians with specialized training in treating diseases and conditions of the chest. Examples include pneumonia, asthma, tuberculosis, emphysema, or complicated chest infections.