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{{Pulmonary function}}
'''Pulmonary function testing''' ('''PFT''') is a complete evaluation of the [[respiratory system]] including patient history, physical examinations, and tests of pulmonary function. The primary purpose of pulmonary function testing is to identify the severity of pulmonary impairment.<ref>{{cite journal | vauthors = Burrows B | title = Pulmonary terms and symbols:
==Indications==
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===Neuromuscular disorders===
Pulmonary function testing in patients with neuromuscular disorders helps to evaluate the respiratory status of patients at the time of diagnosis, monitor their progress and course, evaluate them for possible surgery, and gives an overall idea of the prognosis.<ref name="pmid19420147">{{cite journal |
[[Duchenne muscular dystrophy]] is associated with gradual loss of muscle function over time. Involvement of respiratory muscles results in poor ability to cough and decreased ability to breathe well and leads to [[atelectasis|collapse of part or all of the lung]] leading to impaired gas exchange and an overall insufficiency in lung strength.<ref name="pmid15302625">{{cite journal | vauthors = Finder JD, Birnkrant D, Carl J,
==Tests==
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Spirometry includes tests of pulmonary mechanics – measurements of FVC, FEV<sub>1</sub>, 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.
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
==== 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
==== Nitrogen Washout ====
{{Main|Nitrogen washout}}
The nitrogen washout technique uses a non-rebreathing open circuit. The technique is based on the assumptions that the nitrogen concentration in the lungs is 78% and in equilibrium with the atmosphere, that the patient inhales 100% oxygen and that the oxygen replaces all of the nitrogen in the lungs.<ref>{{cite journal | vauthors = Boren HG, Kory RC,
===Plethysmography===
{{Main|Plethysmograph|Lung volumes}}
The plethysmography technique applies [[Boyle's law]] and uses measurements of volume and pressure changes to determine total lung volume, assuming temperature is constant.<ref name="pmid13295396">
There are four lung volumes and four lung capacities. A lung's capacity consists of two or more lung volumes. The lung volumes are [[tidal volume]] (V<sub>T</sub>), [[inspiratory reserve volume]] (IRV), [[expiratory reserve volume]] (ERV), and [[Lung volumes|residual volume]] (RV). The four lung capacities are [[total lung capacity]] (TLC), inspiratory capacity (IC), [[functional residual capacity]] (FRC) and [[vital capacity]] (VC).
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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>{{
===Diffusing capacity===
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=== Bronchodilator responsiveness ===
When a patient has an obstructive defect, a bronchodilator test is given to evaluate if airway constriction is reversible with a short acting beta-agonist. This is defined as an increase of ≥12% and ≥200 mL in the FEV1 or FVC.<ref>{{
===Oxygen desaturation during exercise===
The six-minute walk test is a good index of physical function and therapeutic response in patients with [[chronic lung disease (disambiguation)|chronic lung disease]], such as [[COPD]] or [[idiopathic pulmonary fibrosis]].<ref name="pmid12890299">{{cite journal |
===Arterial blood gases===
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In order for the forced vital capacity to be considered accurate it has to be conducted three times where the peak is sharp in the flow-volume curve and the exhalation time is longer than 6 seconds.
Reproducibility of the PFT is determined by comparing the values of forced vital capacity (FVC) and forced expiratory volume at 1 second (FEV1). The difference between the highest values of two FVCs need to be within 5% or 150 mL. When the FVC is less than 1.0 L, the difference between the highest two values must be within 100 mL. Lastly, the difference between the two highest values of FEV1 should also be within 150 mL. The highest FVC and FEV1 may be used from each different test. Until the results of three tests meet the criteria of reproducibility, the test can be repeated up to eight times. If it is still not possible to get accurate results, the best three tests are used.<ref>{{
==Clinical significance==
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Spirometry is required for a diagnosis of COPD where the post-bronchodilator FEV1/FVC is <0.7 indicating airflow limitation.<ref>{{Cite web |title=2022 GOLD Reports |url=https://goldcopd.org/2022-gold-reports-2/ |access-date=2022-06-15 |website=Global Initiative for Chronic Obstructive Lung Disease - GOLD |language=en-US}}</ref>
==Interpretation of tests==
{{See also|Spirometer#History - Interpreting Spirometry}}
Professional societies such as the [[American Thoracic Society]] and the [[European Respiratory Society]] have published guidelines regarding the conduct and interpretation of pulmonary function testing to ensure standardization and uniformity in performance of tests. The interpretation of tests depends on comparing the patients values to published normals from previous studies. Deviation from guidelines can result in false-positive or false negative test results, even though only a small minority of pulmonary function laboratories followed published guidelines for spirometry, lung volumes and diffusing capacity in 2012.<ref>{{cite journal |
== References ==
{{reflist}}
{{Respiratory system procedures}}
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