Pulmonary function testing: Difference between revisions

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Latest revision as of 14:21, 18 July 2025

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==== Helium dilution ====

{{Main|Helium dilution technique}}

The [[helium dilution technique]] for measuring lung volumes uses a closed, rebreathing circuit.<ref name="pmid5475674">{{cite journal | vauthors = Hathirat S, Mitchell M, Renzetti AD | title = Measurement of the total lung capacity by helium dilution in a constant volume system | journal = The American Review of Respiratory Disease | volume = 102 | issue = 5 | pages = 760–70 | date = November 1970 | pmid = 5475674 | doi = 10.1164/arrd.1970.102.5.760 | doi-broken-date = 112 NovemberJuly 20242025 }}</ref> This technique is based on the assumptions that a known volume and concentration of helium in air begin in the closed [[spirometer]], that the patient has no helium in their lungs, and that an equilibration of helium can occur between the spirometer and the lungs.{{cn|date=November 2023}}

==== Nitrogen washout ====

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* <math>MIP_{LLN}</math> = maximum inspiratory pressure lower limit of normal in cmH20

* <math>MEP_{LLN}</math> = maximum expiratory pressure lower limit of normal in cmH20

* <math>age</math> = the patient's age in years<ref>{{cite journal |vauthors=Evans JA, Whitelaw WA |date=October 2009 |title=The assessment of maximal respiratory mouth pressures in adults |url=https://pubmed.ncbi.nlm.nih.gov/19796415/ |journal=Respiratory Care |volume=54 |issue=10 |pages=1348–1359 |pmid=19796415}}</ref>

== References ==