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Asthma Lung Function Test Results

Study Design And Population

Pulmonary Function Test (PFT) Explained Clearly – Procedure, Spirometry, FEV1

In this observational multi-centre cross-sectional study, we compared patients diagnosed with asthma, patients diagnosed with COPD, and subjects without underlying chronic obstructive lung conditions using data from a previous study, i.e., the Detection, Intervention and Monitoring of COPD program. This program was originally set up to improve early detection of chronic airways disease in general practices. A random sample of 1,749 adult subjects from ten general practices in The Netherlands were invited to participate. At the start of the program, patients with pre-existing asthma, COPD or another airway disease were excluded. In 2007, ten years after the start of the initial DIMCA program, all subjects received an invitation for a comprehensive respiratory assessment consisting of extensive lung function measurements and a myriad of medical history questions. A total of 532 subjects agreed to participate in this follow-up study. The results of the respiratory assessment of these subjects were submitted to two experienced chest physicians who assessed if a chronic airways disease was present or absent using a standardized protocol that was based on the international clinical guideline criteria that applied at the time of the study . The results of the chest physicians assessments were used as the golden standard in the current study.

Here’s What They Say About Pfts

Forced Vital Capacity. This is the total amount of air you can exhale after a full inhalation. You inhale as deep as you can. Then you blow as hard and fast as you can. You exhale until you have no air left to exhale.

Flow Volume Loop. This will appear on the computer as you do this test. The expiratory loop will appear concave if you are having asthma symptoms. This is indicitive of airflow limitation. It means your airways are obstructed. If you are not having asthma symptoms, the expiratory loop will not appear concave. You can see this in the picture above.

Forced Expiratory Volume in one second . The computer uses your FVC to calculate how much air you exhaled in one second. This is the best indicator of asthma. It cannot be faked. Normal is 80% or better. It may be less than 80% if you’re having asthma symptoms. The goal of any asthma treatment program is to keep this above 80%. Your lung function should be normal or close to normal between attacks.

FEV1/ FVC. This is a very senstive calculation. It is a tel-tale indicator of airflow limitation. Normal is 80%. Less than 80% may means airflow limitation or asthma.

Bronchodlator. After performing the test, you will be given a breathing treatment. The most common medicine used is albuterol. It relaxes airway smooth muscles to open airways. This treatment takes 5-10 minutes. After the treatment you will wait about 15 minutes. Then, you will repeat the FVC.

Blood And Sputum Eosinophils

As indicated in the recent ERS/ATS guidelines, the assessment of asthma phenotype may play a crucial role in the management of patients with severe disease . The ideal tool for this purpose is represented by the cell count on BAL during bronchoscopy. The invasive nature of the procedure has obviously limited the number of subjects studied, therefore the scientific community has sought surrogates that allowed the identification of different asthma phenotypes such as eosinophils count in induced sputum and the peripheral eosinophilia.

Based on the sputum analysis, patients with asthma can be grouped in four different inflammatory phenotypes: eosinophilic asthma, neutrophilic asthma, mixed granulocytic asthma, and paucigranulocytic asthma. Eosinophilic asthma defined as a sputum eosinophil count of 23% or higher, represents almost half of the asthmatic population .

Several studies have found higher levels of sputum eosinophils in uncontrolled asthmatics, therefore sputum analysis may be a useful method of objectively monitoring asthma . Moreover, the short-term response to inhaled corticosteroids depends on the amount of eosinophils present in the sputum therefore this technique may be a guide for modulating steroid therapy .

It is difficult for children to collect sputum because they tend to swallow more than expectorate.

Nadif et al. showed that patients with high blood eosinophilia had lower FEV1 values and worse asthma control than those with eosinophils in normal range .

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How Do I Get Ready For Pulmonary Function Tests

Your healthcare provider will explain the procedure to you. Ask him or herany questions you have. You may be asked to sign a consent form that givespermission to do the procedure. Read the form carefully. Ask questions ifanything is not clear.

Tell your healthcare provider if you take any medicines. This includesprescriptions, over-the-counter medicines, vitamins, and herbalsupplements.

Make sure to:

  • Stop taking certain medicines before the procedure, if instructed by your healthcare provider

  • Stop smoking before the test, if instructed by your healthcare provider. Ask your provider how many hours before the test you should stop smoking.

  • Not eat a heavy meal before the test, if instructed by your healthcare provider

  • Follow any other instructions your healthcare provider gives you

Your height and weight will be recorded before the test. This is done sothat your results can be accurately calculated.

How Can Ahr Be Measured

Pulmonary Function Testing in the Diagnosis of Asthma

In considering the concept of 2 components of airway contributing to AHR, structural and variable, 2 classes of activators have been identified and used to measure this feature of asthma . Methacholine and histamine are contractile substances that act directly on airway smooth muscle to elicit contraction. Because of the structural alterations in the airway that may occur in asthma, the sensitivity to and resulting contraction that arises following an inhalation of methacholine or histamine is greater . There are 2 distinct responses that occur in asthma in the response to either methacholine or histamine when compared to events in normal subjects. First, the relative contraction, as reflected in the fall in FEV1, occurs at a lower concentration of agonist, which reflects an increased sensitivity of the airway. Second, in patients with more severe disease, in particular, the overall contractile response is greater and, in contrast to that seen in normal subjects or patients with mild disease, there is not a plateauing of the contractile response. The usual cutoff dose for a positive PC20 of methacholine in asthma is 8 mg/mL. However, in patients with more severe disease, the concentrations of methacholine necessary to elicit these responses are less .

Agents that can be used to detect airway hyper-responsiveness and classification as to effects of direct versus indirect.

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Other Things To Know About Spirometry

Your doctor will tell you how to prepare for the test. They may ask you to:4

  • Wear comfortable and loose clothing
  • Avoid vigorous exercise and large meals before the test
  • Avoid smoking and alcohol before the test
  • Stop taking certain medicines before the test

Before taking a spirometry test, tell your doctor if you have any heart conditions.2,5

You may need to do spirometry tests at least every 1 to 2 years. This can help see how lung function changes over time. Your doctor may also have you do spirometry whenever you start a new treatment or symptoms worsen. Pregnant women with asthma may do a spirometry test at every prenatal visit.2

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 also might have some coughing. You breathe through a tight-fitting mouthpiece and you will have nose clips. If you are claustrophobic, the part of the test in the booth may feel uncomfortable.

Follow instructions for using the mouthpiece of the spirometer. A poor seal around the mouthpiece may cause results that aren’t accurate.

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Risks And Side Effects

Spirometry is a straightforward test and is generally considered very safe. Some people may feel dizzy, faint, shaky, sick or tired for a short period afterwards.

Most people are able to have a spirometry test safely. But the test increases the pressure inside your head, chest, stomach and eyes as you breathe out, so it may need to be delayed or avoided if you have a condition that could be made worse by this.

For example, spirometry may not be safe if you have, or have recently had, unstable angina, a heart attack, uncontrolled high blood pressure, or an operation to your head, chest, stomach or eyes.

Page last reviewed: 18 August 2021 Next review due: 18 August 2024

What Does Checking Feno Levels Do

Pulmonary Function Tests – PFT Interpretation Explained (Pulmonology)

If you have already been diagnosed with asthma, tracking your FeNO levels:

  • Determines if your current management plan is working properly and how your medicines may need to be increased or reduced
  • May identify what type of asthma you have
  • Can track your airway inflammation over time
  • Can tell your doctor if you have been taking your medicines correctly

If you have not been diagnosed with asthma, a FeNO test:

  • Can support your asthma diagnosis
  • Helps your doctor know how well you may respond to corticosteroids
  • Can rule out other conditions that have symptoms similar to asthma

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Asthma And Other Diseases Can Have The Same Symptoms

When you have asthma, the lining of the airways in the lungs swells and the muscles around the airways get tight. Then the airways get narrow.

When you breathe, you have trouble moving air out of your lungs. As a result, you may cough, wheeze, feel short of breath, or have tightness in your chest. Exercise or cold air may make the symptoms worse.

However, those same symptoms can also be a sign of other lung problems, such as a common cold, bronchitis, or pneumonia. They can even be symptoms of heart disease and other diseases.

It is important to know the cause of your symptoms to make sure you get the right treatment. The treatment for asthma is very different from the treatment for pneumonia or heart disease.

What Are The Risks Of Pulmonary Function Tests

Because pulmonary function testing is not an invasive procedure, it is safeand quick for most people. But the person must be able to follow clear,simple directions.

All procedures have some risks. The risks of this procedure may include:

  • Dizziness during the tests

  • Asthma attack brought on by deep inhalation

In some cases, a person shouldnt have PFTs. Reasons for this can include:

  • Recent eye surgery, because of increased pressure inside the eyes during the procedure

  • Recent belly or chest surgery

  • Chest pain, recent heart attack, or an unstable heart condition

  • A bulging blood vessel in the chest, belly, or brain

  • Active tuberculosis or respiratory infection, such as a cold or the flu

Your risks may vary depending on your general health and other factors. Askyour healthcare provider which risks apply most to you. Talk with him orher about any concerns you have.

Certain things can make PFTs less accurate. These include:

  • The degree of patient cooperation and effort

  • Use of medicines that open the airways

  • Use of pain medicines

  • Stomach bloating that affects the ability to take deep breaths

  • Extreme tiredness or other conditions that affect a persons ability to do the tests

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Does Reversibility Of Air Flow Obstruction Exist In Asthma Even With Normal Lung Functions

The American Thoracic Society has defined reversible airway disease as showing an improvement in FEV1 of 12% with a minimum volume improvement of 200 mL. For patients with reduced baseline lung functions, this degree of improvement in the FEV1 is often seen. Greater improvements in FEV1 values are more often to be found in patients with a greater degree of air flow obstruction. In fact, in many clinical trials where the mean FEV1 is less than 80%, predicted FEV1 improvement is frequently greater than 12% and frequently achieves improvement well over 20%.

Many patients with underlying asthma have normal lung functions, and this relationship is recognized in asthma guidelines. Asthma guidelines define mild persistent asthma with lung function 80% predicted. In children, the presence of normal lung functions is especially frequent despite active, symptomatic asthma. In the Childhood Asthma Management Program , lung functions on entry to the study in the recruited patients were normal , but yet many had improvement in these normal values following the administration of an inhaled 2 agonist.

What Is A Peak Flow Test


A peak flow test is similar to a spirometry test. During the test, you will be asked to take your deepest breath and then exhale as hard as possible into a small machine called a peak flow meter. This test measures how quickly you can force air out of your lungs, which is a sign of how well your lungs are able to work.1-2

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Obstructive Vs Restrictive Lung Disease Testing

Asthma is an obstructive lung disease. In obstructive lung disease, the airflow through the small airways is blocked . The blockage makes it difficult for the air to get out of your lungs. Chronic bronchitis and emphysemaknown together as chronic obstructive pulmonary diseaseare two other obstructive lung diseases.

Spirometry results distinguish obstructive lung disease from restrictive lung disease.3 People with restrictive lung disease have a hard time getting enough air into the lungs to fill them fully. This usually happens because the lungs have gotten stiff and they cannot expand enough. It can also happen when there are problems with the muscles in the chest. For example, fibrosis due to asbestos exposure or radiation can cause restrictive lung disease.

Challenge tests and chest x-ray may also used to rule out conditions that mimic asthma.

What Is A Nitric Oxide Test

Nitric oxide testing is a little less common than the other types of lung function tests. This test measures the amount of nitric oxide that is produced by your lungs by analyzing the air you exhale into a small machine. If you have higher levels of nitric oxide in your lungs, it can be a sign that there is inflammation in your airways caused by asthma.1-3

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Tests For Allergies Gerd And Other Conditions

Multiple conditions can cause coughing and other symptoms that are similar to asthma. Sometimes, these conditions occur alongside asthma and can make your asthma worse. Your doctor will want to run tests for these conditions. The exact tests youll have will depend on your exact symptoms, and the results of your lung function tests. Possible additional tests include:

  • Gastroesophageal reflux assessment. The diagnosis of GERD in people with asthma is often a clinical diagnosis, based on the presence of classic symptoms. For people with symptoms that are suspicious for GERD but who do not have the classic symptoms, the next step would be to refer them to a gastroenterologist for evaluation and workup.
  • Blood tests. There are no blood tests that can determine the presence or absence of asthma or gauge its severity. However, a complete blood count with differential white blood cell analysis to look for cells called eosinophils may be helpful in certain cases. Also, having a low amount of red blood cells can cause shortness of breath that is unresponsive to asthma therapies and would require further evaluation to determine the cause. Certain blood tests can also look for allergies or infections that might be the cause of your symptoms.

Comorbidities And Risk Factors

Pulmonary Function Tests (PFT): Lesson 2 – Spirometry

Both for adults and children, the detection of potentially modifiable risk factors for exacerbations may be useful in asthma monitoring and includes the exposure to specific allergens, smoking, high SABA use, poor adherence to therapy and incorrect inhaler technique. As already mentioned, GINA guidelines state that a previous sever exacerbation in last 12 months and a history of access into an intensive care or intubation are major independent risk factors for exacerbations .

Moreover, the asthma monitoring cannot be separated from an early identification and management of associated comorbidities .

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Spirometry And Bronchodilator Reversibility Test

Spirometry is a breathing or lung function test. It measures how much air you can breathe out in a set timeand how narrow your airways are. This helps your GP or asthma nurse work out how likely or not it is that you have asthma.

This test is suitable for adults, young people, and children over five. Spirometry is safe and quite easy to do, but some people can feel a bit dizzy or faint afterwards.

How is a spirometry test done?

You may be asked to do a relaxed breath first – it is often described as a big sigh into the machine.

Your GP or asthma nurse will then ask you to take a deep breath and breathe out as fast and as hard as you can, for as long as you can, through a mouthpiece linked to a spirometer machine.

You will have to blow a few times so your GP or asthma nurse can get an accurate result.

Bronchodilator reversibility test

If the spirometry test shows that your airways are narrowed, you may need to do a bronchodilator reversibility test. This involves taking some asthma reliever medicine through a spacer. Reliever medicine is a bronchodilator which means it opens up the airways.

Youll be asked to wait 15-20 minutes and then blow into the spirometry machine a few times again. This is to see whether theres been a change in your airways after taking the medicine. If your airways become much less narrow after the reliever medicine, it makes it more likely that you have asthma.

When is a spirometry test used?

What do the results show?

Patterns On A Spirometry Reading

A spirometry reading usually shows one of three main patterns. These depend on how much air you can breathe out and what proportion you can get out in the first second.

Source: British Thoracic Society

The normal range is calculated by the spirometer based on your height, age, sex and ethnicity. If your lungs and airways are healthy, you can blow out most of your breath in the first second. This pattern tells your doctor that your spirometry test is normal when compared to the expected results for you.

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