Pulmonary function testing: Difference between revisions

Revision as of 00:22, 29 November 2023

Revision as of 00:42, 29 November 2023

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{{Main|Spirometry}}

[[File:DoingSpirometry.JPG|left|thumb|Spirometry]]

Spirometry includes tests of pulmonary mechanics – measurements of FVC, FEV₁, FEF values, forced inspiratory flow rates (FIFs), and MVV. Measuring pulmonary mechanics assesses the ability of the lungs to move huge volumes of air quickly through the airways to identify airway obstruction.{{cn|date=November 2023}}

The measurements taken by the spirometry device are used to generate a pneumotachograph that can help to assess lung conditions such as: asthma, pulmonary fibrosis, cystic fibrosis, and chronic obstructive pulmonary disease. [[Physician]]s may also use the test results to diagnose bronchial hyperresponsiveness to exercise, cold air, or pharmaceutical agents.<ref>{{cite web | title = Pulmonary Function Test in New York | date = June 2010 | vauthors = Gafanovich M | url = http://www.mynycdoctor.com/pulmonary-function-testing }}</ref>

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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 = 1 August 2023 }}</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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===Maximal respiratory pressures===

{{main|Respiratory pressure meter}}

Measurement of maximal inspiratory and expiratory pressures is indicated whenever there is an unexplained decrease in vital capacity or respiratory muscle weakness is suspected clinically. Maximal inspiratory pressure (MIP) is the maximal pressure that can be produced by the patient trying to inhale through a blocked mouthpiece. Maximal expiratory pressure (MEP) is the maximal pressure measured during forced expiration (with cheeks bulging) through a blocked mouthpiece after a full inhalation. Repeated measurements of MIP and MEP are useful in following the course of patients with [[neuromuscular]] disorders.{{cn|date=November 2023}}

===Diffusing capacity===

{{Main|Diffusing capacity}}

Measurement of the single-breath diffusing capacity for [[carbon monoxide]] (DLCO) is a fast and safe tool in the evaluation of both restrictive and [[obstructive lung disease]].{{cn|date=November 2023}}

=== Bronchodilator responsiveness ===

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===Arterial blood gases===

[[Arterial blood gas]]es (ABGs) are a helpful measurement in pulmonary function testing in selected patients. The primary role of measuring ABGs in individuals that are healthy and stable is to confirm hypoventilation when it is suspected on the basis of medical history, such as respiratory muscle weakness or advanced [[COPD]].{{cn|date=November 2023}}

ABGs also provide a more detailed assessment of the severity of hypoxemia in patients who have low normal oxyhemoglobin saturation.{{cn|date=November 2023}}

== Risks ==

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==Technique==

=== Preparation ===

Subjects have measurements of height and weight taken before spirometry to determine what their predicted values should be. Additionally, a history of smoking, recent illness, and medications is taken.{{cn|date=November 2023}}

=== Quality control ===