Pulmonary function tests
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Pulmonary function tests are a group of tests that measure how well the lungs take in and release air and how well they move gases such as oxygen from the atmosphere into the body's circulation.
How the Test is Performed
Spirometry measures airflow. By measuring how much air you exhale, and how quickly, spirometry can evaluate a broad range of lung diseases. In a spirometry test, while you are sitting, you breathe into a mouthpiece that is connected to an instrument called a spirometer. The spirometer records the amount and the rate of air that you breathe in and out over a period of time.
For some of the test measurements, you can breathe normally and quietly. Other tests require forced inhalation or exhalation after a deep breath. Sometimes you will be asked to inhale the substance or a medicine to see how it changes your test results.
Lung volume measurement can be done in two ways: * The most accurate way is to sit in a sealed, clear box that looks like a telephone booth (body plethysmograph) while breathing in and out into a mouthpiece. Changes in pressure inside the box help determine the lung volume. * Lung volume can also be measured when you breathe nitrogen or helium gas through a tube for a certain period of time. The concentration of the gas in a chamber attached to the tube is measured to estimate the lung volume.
To measure diffusion capacity, you breathe a harmless gas, called a tracer gas, for a very short time, often for only one breath. The concentration of the gas in the air you breathe out is measured. The difference in the amount of gas inhaled and exhaled measures how effectively gas travels from the lungs into the blood. This test allows the doctor to estimate how well the lungs move oxygen from the air into the bloodstream.
How to Prepare for the Test
Do not eat a heavy meal before the test. Do not smoke for 4 - 6 hours before the test. You'll get specific instructions if you need to stop using bronchodilators or inhaler medications. You may have to breathe in medication before or during the test.
How the Test Will Feel
Since the test involves some forced breathing and rapid breathing, you may have some temporary shortness of breath or lightheadedness. You breathe through a tight-fitting mouthpiece, and you'll have nose clips.
Why the Test is Performed
Pulmonary function tests are done to: * Diagnose certain types of lung disease (such as asthma, bronchitis, and emphysema) * Find the cause of shortness of breath * Measure whether exposure to chemicals at work affects lung function * Check lung function before someone has surgery
It also can be done to: * Assess the effect of medication * Measure progress in disease treatment
Normal Results
Normal values are based upon your age, height, ethnicity, and sex. Normal results are expressed as a percentage. A value is usually considered abnormal if it is less than 80% of your predicted value.
Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
Different measurements that may be found on your report after spirometry include: * Expiratory reserve volume (ERV) * Forced vital capacity (FVC) * Forced expiratory volume (FEV) * Forced expiratory flow 25% to 75% * Functional residual capacity (FRC) * Maximum voluntary ventilation (MVV) * Residual volume (RV) * Peak expiratory flow (PEF). * Slow vital capacity (SVC) * Total lung capacity (TLC)
What Abnormal Results Mean
Abnormal results usually mean that you may have some chest or lung disease.
Some lung diseases (such as emphysema, asthma, chronic bronchitis, and infections) can make the lungs contain too much air and take longer to empty. These lung diseases are called obstructive lung disorders.
Other lung diseases make the lungs scarred and smaller so that they contain too little air and are poor at transferring oxygen into the blood. Examples of these types of illnesses include: * Extreme overweight * Fibrosis of the lungs * Lung cancer * Sarcoidosis and scleroderma
Risks
The risk is minimal for most people. There is a small risk of collapsed lung in people with a certain type of lung disease. The test should not be given to a person who has experienced a recent heart attack, or who has certain other types of heart disease.
Considerations
Your cooperation while performing the test is crucial in order to get accurate results. A poor seal around the mouthpiece of the spirometer can give poor results that can't be interpreted. Do not smoke before the test.
Alternative Names
PFTs; Spirometry; Spirogram; Lung function tests http://www.nlm.nih.gov/medlineplus/ency/article/003853.htm http://www.nlm.nih.gov/medlineplus/ency/article/003853.htm
A spirometer is a device for measuring timed expired and inspired volumes, and hence indicates how quickly and effectively the lungs can be emptied and filled. * Spirometry should be used to diagnose airflow obstruction in patients with respiratory symptoms but should not be used to screen for airflow obstruction in people without respiratory symptoms.[1] * Spirometry can also be used to monitor disease progression and also rehabilitation and treatment gains. * There is strong epidemiologic evidence to indicate that reduced expiratory volume in one second (FEV1) is a marker of cardiovascular mortality, independent of age, gender and smoking history.[2] * It is the gold standard for the diagnosis, assessment and monitoring of chronic obstructive pulmonary disease (COPD) and is now the preferred method in adults for demonstrating obstruction of airways in the diagnosis of asthma.[3] * The recommendation of national evidence-based guidelines on asthma[3] and COPD[4] for the use of spirometers in diagnosis and monitoring, together with their required use in the Quality of Outcomes Framework (QOF), has led to a large increase in the use of spirometry in primary care (70-80% of UK practices in 2005[5]).
Poorly performed spirometry produces misleading results and there have been some concerns regarding the validity of some primary care spirometry. However, studies incorporating training have found no differences between test results produced in primary care and in pulmonary function laboratories.[6] Anyone performing spirometry should be fully trained and should undertake regular updates. Quality audits should also be routine.
Types of device
Many remember the large volume-displacement devices with bellows or water sealed bell beloved of physiology laboratories but the spirometers most commonly used in primary care are now electronic, flow-sensing devices: 1. Small, hand-held devices that provide digital readings. These are the cheapest options and will fit into a medical bag but do not provide a graphical display (spirogram) and therefore it may be difficult to judge when an expiration is complete. They also need to be used in combination with predicted charts and a calculator to interpret results. 2. Portable meters with integrated printers. Typically more expensive than (1.) but will provide calculations, spirograms to monitor the blow and a printout including a flow volume loop. 3. Systems designed to work with a computer that will display a graph, make calculations of predicted values and reversibility and provide a printout for records. They also enable tests to be emailed for a second opinion and for electronic storage.
Whatever equipment is used, devices should be regularly calibrated, maintained, cleaned and disinfected according to the manufacturer's instructions. Disposable 'one-way' valved mouthpieces reduce the risk of cross infection (but prevent inspiratory flow-volume loops). Good practice should be to keep a calibration and maintenance log and list of patients tested with the spirometer (eg, to enable contact tracing in case of unwitting testing of a patient with tuberculosis).
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Instructions for spirometry[5] * Prior to testing, the patient's condition should be stable (ideally six weeks since the last exacerbation but spirometry should be performed before hospital discharge for an exacerbation of COPD).[4] * Standing is not mandatory but may provide better results. Sitting is safer for the elderly and infirm; if sitting, then the patient should sit straight up, with their head slightly extended. * Breathe in maximally. * Hold the mouthpiece between the teeth, and then apply the lips for an airtight seal. * Breathe out as hard and as fast as possible. The patient should aim for maximal flow at the moment expiration starts. With handheld devices, watch the vane rotating, and make sure it does not start rotating while the spirometer is brought to the lips, thus avoiding artefacts. * Keep breathing out until the lungs are 'empty'. * Some get the users to practise just emptying their lungs, ie to do a slow vital capacity (SVC - the amount of air that can be breathed out during the largest possible breath when breathing gently) before getting them to repeat the same as quickly as possible. This allows comparison of the SVC with the forced vital capacity (FVC - the maximum amount of air a person can expel from the lungs after a maximum inspiration) and allows the user to discard poor attempts where the FVC is below the expiratory volume. * Limit the total number of attempts (practice and recording) to eight.
Three satisfactory blows should be performed and best values taken for interpretation. Criteria for satisfactory blows are: * The blow should continue until a volume plateau is reached - this may take more than 12 seconds in severe COPD. * FVC and FEV1 readings should be within 5% or 100 ml. * The expiratory volume-time graph should be smooth and free from irregularities.
Reversibility testing
Reversibility - an increase of >400 ml from baseline in FEV1 is suggestive of asthma. Smaller increases are less discriminatory.[3] * Perform baseline spirometry first. * Bronchodilator reversibility testing: before undertaking bronchodilator testing, the patient should stop short-acting beta2 agonists for 6 hours, long-acting bronchodilators for 12 hours and theophyllines for 24 hours. Administer bronchodilator (at least 400 micrograms salbutamol) and repeat spirometry after 15 minutes. * Steroid reversibility testing: a steroid trial (30 mg prednisolone daily for 2 weeks or 200 micrograms beclometasone or equivalent inhaled corticosteroid for 6-8 weeks) is undertaken. http://www.patient.co.uk/doctor/spirometry-pro What Is Spirometry?
Spirometry measures both how much and how fast air moves through your lungs. It's is much more reliable than peak flows and spirometers are required to meet certain standards from the American Thoracic Society. Depending on which specific tests are ordered, spirometry may take anywhere from 10 to 30 minutes.
From the patient perspective, spirometry is similar to a peak flow except: * It is preformed in a doctor's office * A machine, called a spirometer, collects data as you maximally inhale and forcefully exhale
Why Would My Asthma Provider Order Spirometry?
Spirometry may be useful to your asthma care provider in the following situations. Spirometry: * Cannot by itself diagnose asthma, but may help your asthma care provider make an asthma diagnosis * Aids in asthma management * Helps monitor the progression of your asthma over time
Spirometry results cannot be considered alone, but will help support or exclude your asthma diagnosis. After taking a thorough history and preforming a physical exam, spirometry may help establish an asthma diagnosis. Over time, spirometry measurements will indicate if your asthma is getting better or worse.
What Does Spirometry Measure?
Spirometry allows your asthma care provider to measure several aspects of your lung function that are important in determining both the severity and control of your asthma including: * Vital capacity * Peak expiratory flow rate (PEFR) * Forced expiratory volume (FEV1)
How is Spirometry Preformed?
Spirometry is preformed with a device called a spirometer. It consists of a mouthpiece that is connected via tubing to a machine that records results and displays them graphically as you breathe in and forcefully exhale. In order to perform spirometry, a technician will ask you to: 1. Apply a nose clip to prevent you from exhaling through the nose 2. Have you breathe normally for a short time and then 3. Inhale as deeply as possible 4. Closes their mouth tightly around the tube and 5. Exhale forcefully and completely through the mouth piece for as long as possible while maintaining a tight seal around the mouth piece
Spirometry will often be repeated three times to get your best and maximum effort. Your provider may also repeat the test after having you take a short acting bronchodilator like Albuterol.
What Do My Spirometry Results Mean?
Your FEV1 value expressed as a percentage of predicted can be used to classify the amount of obstruction occurring with your asthma: * FEV1 greater 80% of predicted= normal * FEV1 60% to 79% of predicted = Mild obstruction * FEV1 40% to 59% of predicted = Moderate obstruction * FEV1 less than 40% of predicted = Severe obstruction
Alternatively, if your doctor is unsure if you have asthma, an improvement in your FEV1 of 12% or more with a rescue medication helps your asthma care provider confirm a diagnosis.
Sources:
National Heart, Lung, and Blood Institute. Accessed: January 1, 2009. Expert Panel Report 3 (EPR3): Guidelines for the Diagnosis and Management of Asthma
Clinical Pulmonary Function Testing, Exercise Testing, and Disability Evaluation. In Chest Medicine: Essentials Of Pulmonary And Critical Care Medicine. Editors: Ronald B. George, Richard W. Light, Richard A. Matthay, Michael A. Matthay. May 2005, 5th edition.
Suggested Reading * What Is Asthma? * What Do I Do in a Asthma Attack? * How Is Asthma Treated?
Other Questions? * How Long Will My Inhaler Last? * Is Antibiotic Use Related to Asthma? * What Is a Health Information Prescription
Related Articles * Adult Asthma- Developing Asthma Symptoms After Childhood * Asthma -- Everything You Need To Do To Treat Asthma * What You Need To Do To Control Asthma * New Treatment Guidelines for Pregnant Women with Asthma * Asthma Screening Quiz Results [pediatrics] http://asthma.about.com/od/adultasthma/a/art_AA_spiro.htm * What Is a Lung Plethysmography?
Lung (or pulmonary) plethysmography is a test used to measure how much air you can hold in your lungs. Lung plethysmography helps healthcare providers assess patients with lung diseases, which are often associated with a decrease in total lung capacity (TLC).
Although another test called spirometry is the standard test for measuring lung volumes, lung plethysmography has been found to be more reliable. It can measure a person’s TLC, which is the total volume of air in the chest after they have inhaled as deeply as possible.
Plethysmographic measurements are based on Boyle’s Law, a principle that describes the relationship between the pressure and volume of a gas.
How Is the Test Performed?
Lung plethysmography can be done in pulmonary function laboratories, cardiopulmonary laboratories, clinics, and pulmonology offices. In most cases, the test is performed by a respiratory care technician, who will monitor you at all times.
You will sit or stand in a small, airtight chamber and breathe or pant against a mouthpiece. Clips will be put on your nose to shut off air to your nostrils. You’ll be asked to breathe against the mouthpiece when it’s both opened and closed. This will provide your doctor with important information.
As your chest moves while you breathe or pant, it changes the pressure and amount of air in the chamber and against the mouthpiece. From these changes, your doctor can get an accurate measure of TLC, the amount of air in your lungs.
The mouthpiece may feel uncomfortable against your mouth. If you typically struggle in tight spaces, sitting in the chamber might make you anxious. However, you’ll be able to see outside the chamber at all times, and the test usually takes only three minutes to perform. A tracer gas such as carbon dioxide may be included in the air you breathe during the test.
 Lung plethysmography can be done in pulmonary function laboratories, cardiopulmonary laboratories, clinics, and pulmonology offices. In most cases, the test is performed by a respiratory care technician, who will monitor you at all times.
You will sit or stand in a small, airtight chamber and breathe or pant against a mouthpiece. Clips will be put on your nose to shut off air to your nostrils. You’ll be asked to breathe against the mouthpiece when it’s both opened and closed. This will provide your doctor with important information.
As your chest moves while you breathe or pant, it changes the pressure and amount of air in the chamber and against the mouthpiece. From these changes, your doctor can get an accurate measure of TLC, the amount of air in your lungs.
The mouthpiece may feel uncomfortable against your mouth. If you typically struggle in tight spaces, sitting in the chamber might make you anxious. However, you’ll be able to see outside the chamber at all times, and the test usually takes only three minutes to perform. A tracer gas such as carbon dioxide may be included in the air you breathe during the test.
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 How to Prepare for the Test
Be sure to let your healthcare provider know if you’re taking any medications, especially those for breathing problems. You may have to temporarily stop taking certain medications before the test.
You’ll be more comfortable if you wear loose clothes during the test. Avoid smoking, strenuous exercise, and heavy meals for six hours before the test, as these can all affect your ability to take deep breaths.
 Be sure to let your healthcare provider know if you’re taking any medications, especially those for breathing problems. You may have to temporarily stop taking certain medications before the test.
You’ll be more comfortable if you wear loose clothes during the test. Avoid smoking, strenuous exercise, and heavy meals for six hours before the test, as these can all affect your ability to take deep breaths.
Read more

 What Are the Risks?
Risks associated with lung plethysmography include: * dizziness or lightheadedness * shortness of breath * anxiety for those who are uncomfortable in tight spaces * too much carbon dioxide (hypercapnia) or too little oxygen (hypoxia) in your blood can occur if you’re in the chamber for a longer than typical amount of time, which is uncommon * transmission of infection is possible if the equipment (mouthpiece) is not properly cleaned before you use it
 Risks associated with lung plethysmography include: * dizziness or lightheadedness * shortness of breath * anxiety for those who are uncomfortable in tight spaces * too much carbon dioxide (hypercapnia) or too little oxygen (hypoxia) in your blood can occur if you’re in the chamber for a longer than typical amount of time, which is uncommon * transmission of infection is possible if the equipment (mouthpiece) is not properly cleaned before you use it
Read more

 Why Is the Test Performed?
Your healthcare provider may order lung plethysmography to: * help diagnose restrictive lung disease * evaluate obstructive lung diseases, such as bullous emphysema and cystic fibrosis * follow the course of a disease and its response to treatment * measure your resistance to airflow * measure your response to bronchodilator medications * assess whether your lung capacity will be affected by such treatments as methacholine, histamine, or isocapnic hyperventilation
Lung plethysmography should not be performed if you: * are mentally confused * experience muscle incoordination (poor muscle control causing jerky or unpredictable movements) * have a condition that prevents you from entering the chamber or properly performing the required steps * are claustrophobic * require continuous oxygen therapy that cannot be discontinued, even temporaril
What Do the Results Mean?
Your doctor will assess whether or not your results are normal. Normal values depend on many factors, such as age, height, ethnic background, and gender.
Abnormal results indicate that there is a problem in your lungs. Although lung plethysmography cannot determine the cause of the problem, it can help your doctor narrow down the possibilities, which include a breakdown of the lung structure, a problem with the chest wall and its muscles, or an inability of the lungs to expand or contract. http://www.healthline.com/health/lung-plethysmography#Results Lung plethysmography
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Lung plethysmography is a test used to measure how much air you can hold in your lungs.
How the Test is Performed
You will sit in a small, airtight room known as a body box. You will breathe or pant against a mouthpiece. Clips will be put on your nose to shut off your nostrils. Depending on the information your doctor is looking for, the mouthpiece may be open at first, and then closed.
You will be breathing against the mouthpiece in both the open and closed positions - they give different information to the doctors. As your chest moves while you breathe or pant, it changes the pressure and amount of air in the room and against the mouthpiece. From these changes, the doctor can get an accurate measure of the amount of air in your lungs.
Depending on the purpose of the test, you may be given some medication before the test.
How to Prepare for the Test
Let your doctor know if you are taking any medications, especially ones for breathing problems. You may have to temporarily stop taking certain medications before the test.
Wear loose clothes that allow you to breathe comfortably.
Avoid smoking and heavy exercise for 6 hours before the test.
Avoid heavy meals before the test. They can affect your ability to take deep breaths.
How the Test Will Feel
The test involves rapid and normal breathing, and should not be painful. However, you may feel short of breath or light-headed. You will be monitored at all times by a technician.
The mouthpiece may feel uncomfortable against your mouth.
If you have trouble in tight spaces, the box might make you anxious. However, it is clear and you can see outside at all times.
Why the Test is Performed
The test is done to see how much air you can hold in your lungs during rest. It can help your doctor determine if a lung problem is due to damage to the lung structure, or a loss of the lungs' ability to expand (get bigger as air flows in).
Normal Results
Normal values depend on your age, height, weight, ethnic background, and gender.
What Abnormal Results Mean
Abnormal results point to a problem in the lungs. This problem can be due to a breakdown of the lung structure, a problem with the chest wall and its muscles, or a problem with the lungs being able to expand and contract.
Lung plethysmography will not find the cause of the problem. However, it will help the doctor narrow down the list of possible problems.
Risks
* Dizziness * Light-headedness * Shortness of breath
Considerations
Although this test is the most precise way to measure how much air you can hold in your lungs, it is not often used because of its technical difficulties.
Alternative Names
Pulmonary plethysmography; Static lung volume determination; Whole-body plethysmography
References
Hegewald MJ, Crapo RO. Pulmonary function testing. In: Mason RJ, Broaddus VC, Martin TR, et al, eds. Murray and Nadel’sTextbook of Respiratory Medicine. 5th ed. Philadelphia, Pa: Saunders Elsevier; 2010:chap 24.
Reynolds HY. Respiratory structure and function: mechanisms and testing. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 85.
Update Date: 8/30/2012
Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Denis Hadjiliadis, MD, Assistant Professor of Medicine, Division of Pulmonary, Allergy and Critical Care, University of Pennsylvania, Philadelphia, PA. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Health Solutions, Ebix, Inc.
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http://www.nlm.nih.gov/medlineplus/ency/article/007289.htm