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spirometry definition
spirometry definition
Spirometry is a standard test used to measure lung function. The test works by measuring airflow into and out of the lungs. Spirometry tests are used to diagnose these conditions:
COPD
asthma
restrictive lung disease (such as interstitial pulmonary fibrosis)
other disorders affecting lung function
For the purpose of PEMs only FEV testing is performed.
spirometry contraindications
spirometry contraindications
Spirometry must not be performed if the candidate confirms any of the following:
unstable cardiovascular status, unstable angina, recent myocardial infarction (within one month) or pulmonary embolism
haemoptysis of unknown origin (blood in vomit)
recent pneumothorax
thoracic, abdominal or cerebral aneurysms
recent thoracic, abdominal or eye surgery
acute disorders such as nausea or vomiting
severe respiratory distress
physical limitations
cognitive impairment
Procedure
Procedure
Have the client sitting upright in chair. NOTE: Standing during spirometry is contraindicated.
Enter the client data (client number, name, date of birth, weight, height, sex, ethnicity).
Set up the testing equipment (insert USB handpiece, insert spirette into handpiece and filter onto end of spirette).
Provide instruction to client: "The idea of this test is determine how much air you have in your lungs and how well you can blow this air out. I am going to get you to take a big, deep breath right to the tope of your lungs. You will know you are at the top of your lungs when your head and neck start to shake uncontrollably. Once you have taken this breath, you will put the mouthpiece in your mouth making a seal around the mouth piece. Do not stick your tongue into the hole as it will impact the test and prevent the air from exiting. I then need you to blow our hard and fast. The idea is to try to get as much air out within the very first second. I will then ask you to keep blowing as I am measuring how well you can empty your lungs completely. This will last for at least 6 seconds. It may feel like you have no more air in your lungs, however it is important to keep blowing until I tell you to stop (even if you don't think anything is coming out). If you need to cough, cough into the mouthpiece, it won't affect the test. We need 3 tests with consistent results, sometimes it will take several attempts to get this."
Explain to the client that coughing, dizziness/light headedness is common. Fainting is not common. Advise the client that should they feel as though they are going to faint, to stop immediately and inform you of such.
Provide demonstration (without actually using mouthpiece).
Perform test to achieve 3 results within 150ml (0.15) of the best and worst of those 3 attempts.
Refer to 'PEM Criteria for GP Referral' for spirometry referral guidelines.
Acceptable Criteria
Acceptable Criteria
patient followed instructions
a continuous maximal expiratory maneuver was achieved through the test and was initiated from full inspiration
no evidence of hesitation during the test
the test was performed with a rapid start
no premature termination
no leaks
no coughs within the 1st second
no obstruction of the mouthpiece
no evidence of additional breath during expiratory maneuver
best practice is achieved (3 acceptable curves + 3 repeatable results)
interpretation
interpretation
FVC measurement
FVC measurement
FVC (Forced Vital Capacity) is the greatest total amount of air you can forcefully breathe out after breathing in as deeply as possible. If your FVC is lower than normal, something is restricting your breathing.
Normal: FVC is equal or greater than the lower limit normal
Abnormal: FVC is less than the lower limit of normal
An abnormal FVC could be due to restrictive or obstructive lung disease, and other types of spirometry measurements are required to determine which type of lung disease is present. An obstructive or restrictive lung disease could be present by itself, but it’s possible to have a mixture of these two types at the same time.
FEV1 measurement
FEV1 measurement
The second key spirometry measurement is Forced Expiratory Volume in one second (FEV1). This is the amount of air you can force out of your lungs in one second. It can help your doctor evaluate the severity of your breathing problems. A lower-than-normal FEV1 reading shows you might have a significant breathing obstruction.
Your doctor will use your FEV1 measurement to grade how severe any abnormalities are. The following chart outlines what’s considered normal and abnormal when it comes to your FEV1 spirometry test results, according to guidelines from the American Thoracic Society:
FEV1/FVC ratio
FEV1/FVC ratio
Doctors often analyze the FVC and FEV1 separately, and then calculate your FEV1/FVC ratio.
The FEV1/FVC ratio is a number that represents the percentage of your lung capacity you’re able to exhale in one second. The higher the percentage derived from your FEV1/FVC ratio, in the absence of restrictive lung disease that causes a normal or elevated FEV1/FVC ratio, the healthier your lungs are. A low ratio suggests that something is blocking your airways:
5-18 years old: < 85%
Adults: < 70%
Spirometry graph
Spirometry graph
Spirometry produces a graph that shows your flow of air over time. If your lungs are healthy, your FVC and FEV1 scores are plotted on a graph that could look something like this:
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