What is Spirometry?
Spirometry is a test used to measure the amount of air a person can inhale and exhale, and how quickly they can exhale. It is a commonly used test to diagnose respiratory conditions such as asthma, chronic obstructive pulmonary disease (COPD), and interstitial lung disease.
Why is Spirometry Test Performed?
Spirometry is a commonly used test to evaluate lung function in individuals and is performed for several reasons. The most common reasons for spirometry include:
Diagnosis of Respiratory Conditions
Spirometry is often used to diagnose respiratory conditions such as asthma, COPD, and interstitial lung disease. These conditions can cause airflow limitation, which can be easily measured by spirometry. The results of spirometry can also be used to determine the severity of the condition and to monitor its progress over time.
Monitoring the Effectiveness of Treatment
Spirometry is also used to monitor the effectiveness of treatment for respiratory conditions. Regular spirometry can help determine if the treatment is controlling the symptoms and improving lung function. If the results show a decline in lung function, the treatment plan may need to be adjusted.
Pre-employment Screening
Spirometry is often performed as part of pre-employment screening for individuals who will be working in jobs that may pose a risk to their lung health, such as those in the construction or mining industries.
Occupational Exposure
Spirometry is also used to monitor the lung function of individuals who are exposed to workplace hazards, such as dust, fumes, or chemicals. Regular spirometry can help determine if the exposure is affecting lung function and if steps need to be taken to protect the individual's health.
Pulmonary Function Before and After Surgery
Spirometry is sometimes performed before and after surgery, such as lung transplantation or lung resection, to assess lung function and to monitor the recovery process.
How is the Spirometry Test performed?
The spirometry test is performed using a machine called a spirometer. The spirometry test is typically performed by a healthcare provider, such as a respiratory therapist, in a clinic or hospital setting. The procedure involves the following steps:
1.) Preparation: Prior to the test, the patient will be asked to avoid smoking or using bronchodilators (medications that open up the airways) for a certain period of time. The patient will also be instructed on how to perform the test.
2.) Inhale: The patient will be asked to take a deep breath in and then place the mouthpiece of the spirometer in their mouth, making sure to form a tight seal around the mouthpiece with their lips.
3.) Exhale: The patient will then be instructed to blow out as hard and fast as they can into the mouthpiece, expelling as much air as possible. This may be repeated several times to obtain accurate results.
4.) Data collection: As the patient exhales into the spirometer, the device will measure the volume of air they have exhaled, as well as the speed and force of their breath. This data is recorded and can be used to diagnose or monitor respiratory conditions.
The spirometry test is a safe and painless procedure, and typically takes only a few minutes to complete.
What do the Results Mean?
Spirometry test results should be interpreted by a qualified healthcare provider.
The results of the spirometry test are used to calculate several important values that give a comprehensive picture of the patient's lung function. These values include:
A.) Forced Vital Capacity (FVC)
This is the total amount of air that a person can exhale in one breath. The predicted FVC value is based on a person's age, height, sex, and ethnicity, and is used to determine if the person's lung function is normal or abnormal. A low FVC value can indicate a restrictive lung disease, while a high FVC value can suggest an obstructive lung disease.
B.) Forced Expiratory Volume in 1 Second (FEV1)
This is the amount of air that a person can exhale in one second. This measurement is important because it reflects the amount of airway obstruction and can be used to diagnose and monitor COPD. A low FEV1 value in comparison to the predicted value suggests airflow limitation and possible obstruction of the airways.
C.) FEV1/FVC Ratio
This is the ratio of the amount of air exhaled in the first second to the total amount of air exhaled. This ratio is used to determine if there is any obstruction in the airways.
D.) Forced Expiratory Flow 25-75% (FEF25-75%)
This is the average flow rate during the middle half of a forced exhalation.
E.) Peak Expiratory Flow (PEF)
This is the maximum flow rate during forced exhalation. PEF can be used to monitor asthma and is often used in conjunction with other measurements, such as FVC and FEV1, to assess lung function.
The results of spirometry are compared to predicted values based on age, height, weight, and gender. If the measured values fall below the predicted values, it may indicate the presence of an obstructive or restrictive lung disorder.
Obstructive lung disorders, such as asthma and chronic obstructive pulmonary disease (COPD), are characterized by a decreased FEV1/FVC ratio and a decreased FEV1. Restrictive lung disorders, such as pulmonary fibrosis and interstitial lung disease, are characterized by a decreased FVC but a normal FEV1/FVC ratio.
Spirometry results can also be used to monitor the progression of lung disease and the effectiveness of treatment. A follow-up spirometry test may be ordered after treatment to evaluate whether lung function has improved.
Summary
Spirometry is a valuable tool in the evaluation and management of respiratory conditions. It is a simple, safe, and non-invasive test that provides important information about an individual's lung function. If you have been referred for a spirometry test, it is important to follow your doctor's instructions carefully to ensure the best possible results.
