- Spirometry
- Flow volume loop
- Lung volume
- Diffusion study
- Pulse oximetry and arterial blood gas
- Fractional Exhaled Nitric Oxide test (FENO)
- Exercise Challenge Test
- Methacholine challenge Test
They include tests that measure lung size and air flow, such as spirometry and lung volume tests. Other tests measure how well
gases such as oxygen get in and out of your blood. These tests include pulse oximetry and arterial blood gas tests. Another pulmonary
function test, called fractional exhaled nitric oxide (FeNO), measures nitric oxide, which is a marker for inflammation in the lungs.
You may have one or more of these tests to diagnose lung and airway diseases, compare your lung function to expected levels of function,
monitor if your disease is stable or worsening, and see if your treatment is working.
Spirometry measures the rate of air flow and estimates lung size.
- A spirometer measures how much air you inhale, how much you exhale and how quickly you exhale.
Lung volume tests are the most accurate way to measure how much air your lungs can hold.
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These can be measured by nitrogen washout technique or a body plethysmography technique. These can help us assess restrictive lung
disease from lung fibrosis, respiratory muscle weakness or chest wall deformity like kyphosis and scoliosis.
Lung diffusion capacity assesses how well oxygen gets into the blood from the air you breathe and carbon dioxide gets removed from the blood.
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For this test, you will breathe in and out through a tube for several minutes without having to breathe intensely. You also may need to have blood
drawn to measure the level of haemoglobin in your blood. This test is useful for lung fibrosis and COPD.
Pulse oximetry estimates oxygen levels in your blood.
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For this test, a probe will be placed on your finger or another skin surface such as your ear.
It causes no pain and has few or no risks.
Arterial blood gas tests directly measure the levels of gases, such as oxygen and carbon dioxide, in your blood.
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Arterial blood gas tests are usually performed in a hospital, but may be
done in a doctor’s office. For this test, blood will be taken from an
artery, usually in the wrist where your pulse is measured. You may feel
brief pain when the needle is inserted or when a tube attached to the
needle fills with blood.
Fractional Exhaled Nitric Oxide Test
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An exhaled nitric oxide test can help with the diagnosis and treatment of asthma. It measures the level of nitric oxide gas
in an exhaled sample of your breath. This sample is collected by having you breathe into the mouthpiece of a machine that performs
the measurement. Nitric oxide is produced throughout the body, including in the lungs, to fight inflammation and relax tight muscles.
High levels of exhaled nitric oxide in your breath can mean that your airways are inflamed — one sign of asthma.
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Nitric oxide testing is also done to help predict whether or not steroid medications, which decrease inflammation, are
likely to be helpful for your asthma. If you've already been diagnosed with asthma and treated with one of the steroid medications,
your doctor may use an exhaled nitric oxide test during office visits to help determine whether your asthma is under control.
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To do this test, you'll be seated. You will put in a mouthpiece attached to a tube that leads to an electronic measurement device.
Next, you'll breathe in for two or three seconds until your lungs are filled with air. You will then exhale steadily so that the air flows out
of your lungs at a steady rate. You will be watching a computer monitor that registers how much you're breathing out so that you can maintain a
steady exhalation. The entire test generally takes five minutes or less.
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Results :
Higher than normal levels of exhaled nitric oxide generally mean your airways are inflamed — a sign of asthma.
- Levels under about 20 parts per billion in children and under about 25 parts per billion in adults are considered normal.
- More than 35 parts per billion in children and 50 parts per billion in adults may signal airway inflammation caused by asthma.
Nitric oxide test results can vary widely from person to person. When interpreting test results, your doctor will consider a number of other factors. These may include:
- Your asthma signs and symptoms
- Past nitric oxide test results
- Results of other tests, such as peak flow tests or spirometry tests
- Medications you take
- Whether you have a cold or the flu
- Whether you have hay fever or other allergies
- Whether or not you smoke
- Your age
Exercise Challenge Test
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A test that enables your doctor to observe and assess symptoms is an exercise challenge. You will run on a treadmill or use other
stationary exercise equipment that increases your breathing rate. This exercise needs to be intense enough to trigger the symptoms you've
experienced. Spirometry tests before and after the challenge can provide evidence of exercise-induced bronchoconstriction, EIA (asthma)
Methacholine Challenge Test
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This lung function test for asthma is more commonly used in adults than in children. It might be performed if your symptoms and screening spirometry
do not clearly or convincingly establish a diagnosis of asthma. Methacholine is an agent that, when inhaled, causes the airways to contract and
narrow if asthma is present. During this test, you inhale increasing amounts of methacholine aerosol mist before and after spirometry.
The methacholine test is considered positive, meaning asthma is present, if the lung function drops by at least 20%. A bronchodilator is
always given at the end of the test to reverse the effects of the methacholine.
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