by How Spirometry Works
A spirometer is a simple medical device used to measure lung function. It works by having the patient breathe into a mouthpiece that is connected to the spirometer. As the patient breathes in and out, the spirometer measures:
– Forced vital capacity (FVC): The total amount of air that can be forcibly exhaled from the lungs after taking the deepest breath possible. Normal FVC depends on a person’s age, height, and sex.
– Forced expiratory volume in 1 second (FEV1): The amount of air that can be forcibly blown out in the first second of exhaling. FEV1 is one of the most important measurements for detecting lung diseases.
– FEV1/FVC ratio: This compares FEV1 to FVC and is expressed as a percentage. It helps determine if airflow is blocked throughout the lungs.
As the patient breathes in and out through the mouthpiece, the Spirometer measures these parameters and displays them digitally or prints them out on a paper strip for the doctor to analyze. The whole test takes about 15 minutes to perform.
Detecting Lung Diseases
Spirometry is most commonly used to diagnose and monitor chronic obstructive pulmonary disease (COPD) such as emphysema and chronic bronchitis. In COPD, the airways become damaged and narrowed over time, obstructing airflow and causing shortness of breath.
During spirometry, patients with COPD will have a low FEV1 and FEV1/FVC ratio, as their lungs can’t empty properly due to blockages in the airways. Spirometry allows doctors to determine the severity of COPD and track if it is getting worse over time.
Asthma can also be diagnosed with spirometry. During an asthma attack, airways become inflamed and narrowed, restricting airflow. Patients often have a reduced FEV1 reading that improves after using an inhaler. Spirometry helps monitor asthma control and determine how well current treatment is working.
It can also detect restrictive lung diseases that make lungs stiff and unable to expand fully, like pulmonary fibrosis. These patients will have a low FVC reading. Other conditions that can be picked up include lung cancer, pneumonia, and bronchiectasis.
What the Readings Mean
A normal spirometry test shows all lung function measurements are within the predicted range for the patient’s age, height, sex, and ethnicity. Readings below the lower limit of normal range may indicate a lung disease:
– Reduced FEV1 often indicates airway obstruction from asthma, COPD, or other obstructive lung diseases.
– Reduced FVC often indicates restrictive lung disease that hinders full lung expansion, like pulmonary fibrosis.
– Reduced FEV1/FVC ratio below 70 percent (in adults) suggests airway obstruction.
– An increased FEV1 after using an inhaler suggests reactive airways from asthma.
It’s also important to track changes in spirometry readings over time. A progressive loss of FEV1 or FVC may indicate a lung disease is getting worse. Improvements after treatment would be a positive sign.
Repeating Spirometry Testing
A spirometry test provides an important snapshot of lung function on a given day. However, lung function can vary depending on a patient’s condition, medications, and other factors.
For this reason, it’s common to repeat spirometry testing:
– As part of regular checkups for lung diseases like COPD or asthma to monitor changes.
– Before and after starting new respiratory medications to gauge effectiveness.
– If shortness of breath symptoms change significantly to see if lung function is declining.
– Yearly testing may be advised for high-risk patients or those with a family history of lung disease.
Comparing current readings to past ones allows doctors to track disease progression more accurately over prolonged periods. Seeing a consistent downward trend in readings could indicate a need to adjust treatment.
Spirometry is an essential test used routinely in pulmonary medicine. It provides objective measurements of lung volumes and airflow to detect respiratory diseases, determine severity, and monitor response to treatment long-term. Understanding spirometry results plays an important role in properly managing lung health conditions.
