There are certain measurements spirometry alone can’t take, such as the amount of air that stays in your lungs after you’ve exhaled. So, we use other techniques to measure these amounts — or volumes — which can help figure out how well your lungs are functioning.

What is Measurement of Lung Volumes?

This test can check to see if your lungs have sustained damage due to your work or home environment, lifestyle habits or past or current health conditions. If you have a chronic disease and are receiving treatment, lung volume measurements can track effectiveness and determine if a change is needed.


Lung volume measurements can include plethysmography, which calculates volume through pressure. During plethysmography, you’ll sit inside a transparent tube and breathe into a mouthpiece connected to a machine. The pressure in the tube and at your mouth will then be measured.

Nitrogen Washout

Another technique for measuring lung volume is nitrogen washout, which calculates volume by how much nitrogen stays in your lungs. During this test, you’ll breath in 100% oxygen for a short amount of time until nitrogen is “washed out” of your lungs. The remaining nitrogen you exhale will then be measured.

How to Prepare for Your Test

It’s important to:

  • Stop smoking at least one hour before your test

  • Avoid drinking alcohol at least four hours before

  • Wear loose clothing to allow for chest expansion (no tight belt or vest)

  • Avoid having a large meal two hours prior to your test

Your appointment may be rescheduled if you haven’t prepared according to these criteria.
Call us ahead of time if you:

  • Have an inability to follow instructions*

  • Have had a heart attack in the last month

  • Have chest or abdominal pain

  • Have excessive pain while using a mouthpiece

  • Have stress incontinence, or an unintentional loss of urine during movement or physical activity

  • Have had recent eye surgery (1 week to 6 months, depending on surgery)

  • Have had recent brain surgery or an injury (3 to 6 weeks)

  • Have had a collapsed lung (2 weeks)

  • Are spitting up blood

*If a patient is unable to follow instructions due to a confused state, young age or dementia, then a parent, caregiver or guardian may call on their behalf.

Need More Information?

A white woman with blond hair sits upright in a hospital bed and breathes into a lung diagnostic tool

Download additional information on your test procedure

If you have any questions about your test, please call us: 

Adult Testing

(559) 459-3947 

Pediatric Testing  

(559) 459-2327

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