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{{Infobox diagnostic
| Name = Pulmonary function testing
| Image =
| Alt =
| Caption =
| DiseasesDB =
| image = Body plethysmograph box.jpg
| caption = Plethysmograph "body box"
| ICD10 =
| ICD9 =
| ICDO =
| MedlinePlus = 003853
| eMedicine =
| MeshID = D012129
| LOINC =
| HCPCSlevel2 =
| OPS301 = {{OPS301|1-71}}
| Reference_range =
}}
{{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==
Pulmonary function testing is a diagnostic and management tool used for a variety of reasons, such as:
* Diagnose lung disease.
* Monitor the effect of chronic diseases like [[asthma]], [[Chronic obstructive pulmonary disease|chronic obstructive lung disease]], or [[cystic fibrosis]].
▲* Monitor the effect of chronic diseases like [[asthma]], [[Chronic obstructive pulmonary disease|chronic obstructive lung disease]], or [[cystic fibrosis]].
▲* Detect early changes in lung function.
* Identify narrowing in the airways.
* Evaluate airway bronchodilator reactivity.
* Show if environmental factors have harmed
* Preoperative testing<ref>{{Cite web |title=Pulmonary Function Tests |url=https://www.thoracic.org/patients/patient-resources/resources/pulmonary-function-tests.pdf |access-date=June 15, 2022 |website=American Thoracic Society}}</ref>
===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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{{Main|Spirometry}}
[[File:DoingSpirometry.JPG|left|thumb|Spirometry]]
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.{{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
==== Helium
{{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
{{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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===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}}
Several calculations are needed for what a normal maximum inspiratory (MIP) and expiratory pressure (MEP) is. For males this found by:▼
<math>MIP=120-(0.41 \times age)</math>▼
and▼
<math>MEP=174-(0.83 \times age)</math>▼
To find the lower limit of what is acceptable in males the equations are:▼
<math>MIP_{LLN}=62-(0.15 \times age)</math>▼
and ▼
<math>MEP_{LLN}=117-(0.83 \times age)</math>▼
For females, the equations are slightly different. For the normal values this is used:▼
<math>MIP=108-(0.61 \times age)</math>▼
and▼
<math>MEP=131-(0.86 \times age)</math>▼
For find the lower limit of what it should be without impairment this form of the equations is used:▼
<math>MIP_{LLN}=62-(0.50 \times age)</math>▼
and▼
<math>MEP_{LLN}=95-(0.57 \times age)</math>▼
where ▼
* <math>MIP</math> = maximum inspiratory pressure in cmH20▼
* <math>MEP</math>= maximum expiratory pressure in cmH20▼
* <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 |last=Evans |first=John A. |last2=Whitelaw |first2=William A. |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 |issn=0020-1324 |pmid=19796415}}</ref>▼
===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 ===
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
===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 ==
Pulmonary function testing is a safe procedure; however, there is cause for concern regarding untoward reactions and the value of the test data should be weighed against potential hazards. Some complications include dizziness, shortness of breath, coughing, pneumothorax, and inducing an asthma attack.<ref>{{Cite web |date=2019-11-19 |title=Pulmonary Function Tests |url=https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/pulmonary-function-tests |access-date=2022-06-15 |website=www.hopkinsmedicine.org |language=en}}</ref><ref>{{Cite web |title=Pulmonary function tests: MedlinePlus Medical Encyclopedia |url=https://medlineplus.gov/ency/article/003853.htm |access-date=2022-06-15 |website=medlineplus.gov |language=en}}</ref>
== Contraindications ==
There are some indications against a pulmonary function test being done. These include a recent heart attack,
==
=== Preparation ===
Subjects have
=== Quality control ===
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.
==Clinical significance==
Changes in lung volumes and capacities from normal are generally consistent with the pattern of lung impairment.▼
Spirometry is required for a diagnosis of COPD
==Interpretation of tests==▼
{| class="wikitable" style = "float: right
|+Classification of COPD based on spirometry<ref name=":1">{{Cite book |last=Global Initiative for Chronic Obstructive Lung Disease |url=https://goldcopd.org/2022-gold-reports-2/ |title=Pocket Guide to COPD Diagnosis, Management, and Prevention |page=11}}</ref>
!Severity
!FEV1 % predicted
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|<30
|}
{{See also|Spirometer#History - Interpreting Spirometry}}▼
▲Changes in lung volumes and capacities from normal are generally consistent with the pattern of lung impairment.
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 |
=== COPD ===
▲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>
The [[Global Initiative for Chronic Obstructive Lung Disease]] provides guidelines for the diagnosis, severity, and management of [[Chronic obstructive pulmonary disease|COPD]].<ref>{{Cite web |title=About Us |url=https://goldcopd.org/about-us/ |access-date=2022-06-16 |website=Global Initiative for Chronic Obstructive Lung Disease - GOLD |language=en-US}}</ref> To determine obstruction in a patient's lungs, the post-bronchodilator FEV1/FVC needs to be <0.7.<ref name=":0" /> Then, the FEV1 percentage of predicted result is used to determine the degree of obstruction where the lower the percent the worse the obstruction.<ref name=":1" />
=== Maximum respiratory pressures ===
▲Several calculations are needed for what a normal maximum inspiratory (MIP) and expiratory pressure (MEP) is. For males this found by:
▲<math>MIP=120-(0.41 \times age)</math>
▲and
▲==Interpretation of tests==
▲{{See also|Spirometer#History - Interpreting Spirometry}}
▲<math>MEP=174-(0.83 \times age)</math>
▲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|last1=Mohanka|first1=Manish R.|last2=McCarthy|first2=Kevin|last3=Xu|first3=Meng|last4=Stoller|first4=James K.|title=A Survey of Practices of Pulmonary Function Interpretation in Laboratories in Northeast Ohio|journal=Chest|date=April 2012|volume=141|issue=4|pages=1040–1046|doi=10.1378/chest.11-1141|pmid=21940775}}</ref>
▲To find the lower limit of what is acceptable in males the equations are:
▲<math>MIP_{LLN}=62-(0.15 \times age)</math>
▲<math>MEP_{LLN}=117-(0.83 \times age)</math>
▲For females, the equations are slightly different. For the normal values this is used:
▲<math>MIP=108-(0.61 \times age)</math>
▲and
▲<math>MEP=131-(0.86 \times age)</math>
▲For find the lower limit of what it should be without impairment this form of the equations is used:
▲<math>MIP_{LLN}=62-(0.50 \times age)</math>
▲and
▲<math>MEP_{LLN}=95-(0.57 \times age)</math>
▲* <math>MIP</math> = maximum inspiratory pressure in cmH20
▲* <math>MEP</math>= maximum expiratory pressure in cmH20
▲* <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>{{
== References ==
{{reflist}}
{{Respiratory system procedures}}
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