Chronic obstructive pulmonary disease (COPD) is a condition that obstructs airflow. A spirometry test shows how a person’s lungs are functioning and can help diagnose and grade the severity of COPD.
Spirometry is a valuable tool in the diagnosis of several conditions that affect breathing.
It measures the amount of air a person can exhale after a deep inhalation. It is not painful and often takes
Keep reading to learn about spirometry and the diagnosis of COPD. This article also looks at how doctors may use it to track disease progression and determine treatment.
Spirometry is the standard breathing test for the diagnosis of COPD.
Doctors use it to:
- detect COPD in people with exposure to risk factors, mainly tobacco smoke, whether they have symptoms or not
- confirm an airway obstruction
- determine the severity of airflow obstruction in COPD
- help establish treatment goals
- monitor response to therapy
- help predict outcomes and long-term survival
In a spirometry test, a person blows air into a mouthpiece with tubing. The tubing attaches to a small, computerized machine.
The technician who administers the test instructs the person to inhale deeply and fully and then exhale hard and fast. They repeat this multiple times. Afterward, the person may feel tired or lightheaded.
The machine shows the amount of air the person blows out, as well as the speed with which they blow it. These measurements reveal accurate information about their lung function.
A full inhalation followed by a forced exhalation allows the spirometer to take the following measurements:
- Forced vital capacity (FVC): This is the volume of air that a person can forcibly exhale in one breath. It is a different measurement from vital capacity, which is the maximum air that someone can exhale after a full inhalation, whether they forcibly exhale or not.
- Forced expiratory volume in 1 second (FEV1): This is the volume of air an individual can exhale in the first second of a forced exhalation.
- Ratio of FEV1 to FVC (FEV1/FVC): This ratio, along with FVC and FEV1, are the key measurements that doctors use to make a diagnosis of COPD.
To diagnose COPD, a doctor considers a person’s symptoms, medical history, and the results of their spirometry and other tests.
Some symptoms of COPD include:
- a chronic cough
- shortness of breath
- a blue tinge of the lips and fingernails
- frequent respiratory infections
- the production of sputum or phlegm
The medical history involves the doctor asking questions about:
- smoking or exposure to secondhand smoke
- exposure to chemicals or air pollution
- whether or not family members have had COPD
Besides spirometry, some other diagnostic tests include chest X-rays, which produce an image of the lungs and other structures in the chest, and arterial blood gas, which is a measurement of oxygen in the blood.
The new guidelines for staging COPD take into account two factors: airflow obstruction and symptom history. Doctors can assess airflow obstruction using a spirometer to measure FEV1.
The staging system provides a number to demonstrate the severity of the airflow obstruction:
|GOLD 1||above 80|
|GOLD 4||below 30|
Doctors also assess a person’s symptom history and assign them a letter using either the Modified Medical Research Council (mMRC) questionnaire or the COPD assessment test (CAT):
|Moderate or severe exacerbation history|
|2 (or above) or 1, leading to hospital admission||C||D|
|0 or 1, not leading to hospital admission||A||B|
CAT below 10
|mMRC above 2|
CAT above 10
For example, if someone with an FEV1 of below 30 has a CAT score of below 10 and has experienced one or more moderate exacerbations, a doctor would describe their stage as GOLD 4 group C.
According to the research article, spirometry can lead to an early diagnosis because it shows evidence of COPD before any symptoms appear. The earlier a person receives a diagnosis, the sooner a doctor can optimize treatment.
If a person’s spirometry test indicates that they have COPD, the most important thing they can do is quit smoking and take steps to avoid secondhand smoke, according to the
Doctors also recommend pulmonary rehabilitation, which is a personalized program involving diet, exercise, and energy conservation techniques.
In addition, the CDC lists the following medication options for treatment:
- Bronchodilators: These relax muscles in the airways, which opens them and makes it easier for a person to breathe.
- Steroids: These reduce swelling in the airways.
- Antibiotics: These treat respiratory infections.
Some treatments for severe COPD include oxygen therapy and surgery. Oxygen therapy helps people with severe COPD, who have low oxygen levels, breathe better. Surgery may involve a lung transplant or the removal of the diseased parts of the lung.
When a person has respiratory symptoms and a compatible medical history, a doctor may use spirometry to help diagnose COPD.
Spirometry also shows how the person’s COPD is progressing. This, along with symptom and exacerbation history, helps guide doctors in their treatment recommendations.