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pulmonary plethysmography; total body plethysmography
Indications:
- measures pulmonary functional residual capacity & total lung volume
- a flow-loop can calculated to assess pulmonary compliance
- restrictive lung disease
- chronic obstructive pulmonary disease
- respiratory muscle weakness
- useful for patients who have air spaces which do not communicate with the bronchial tree
Procedure:
- the patient sits in a small, airtight room known as a body box & breathes against a mouthpiece
- clips are put on the nose to shut off the nostrils
- the mouthpiece may be open at first, & then closed
- breathing changes the pressure of air in the room & against the mouthpiece
- at the end of normal expiration, the mouthpiece is closed
- the patient is then asked to make an inspiratory effort
- the lungs expand, decreasing pressure within the lungs & increasing lung volume
- this increases pressure within the box since it is a closed system & the volume of the box has decreased to accommodate the new volume of the lungs
General
plethysmography
References
- Wikipedia: Plethysmograph
http://en.wikipedia.org/wiki/Plethysmograph
- MedlinePlus: Lung Plethesmography
http://www.nlm.nih.gov/medlineplus/ency/article/007289.htm