Spirometry

Spirometry is a common breathing test that measures how much air you can breathe out and how quickly you can do it. It helps doctors assess your lung function, diagnose certain lung conditions like asthma or chronic obstructive pulmonary disease (COPD), and monitor how well your lungs are working over time or responding to treatment.

What is Spirometry?

Spirometry is a simple, non-invasive breathing test that measures how much air your lungs can hold and how fast you can push air out. It helps your doctor understand your lung function by evaluating key measurements like the total amount of air you exhale and the volume of air you exhale in the first second.

During the test, you breathe into a device called a spirometer. This device records the amount of air you breathe in and out, and the speed of your breath. These measurements provide important information about the health and capacity of your lungs. The main measurements taken during spirometry include forced vital capacity (FVC) and forced expiratory volume in one second (FEV1). FVC is the total amount of air you can forcefully exhale after taking a deep breath. FEV1 is the amount of air you can forcefully exhale in the first second of that breath. Doctors also look at the ratio of FEV1 to FVC (FEV1/FVC ratio). This ratio helps determine if there is any obstruction to airflow in your lungs. By comparing your results to normal values for someone of your age, height, sex, and ethnic background, your doctor can assess your lung health.

Why it's ordered

Your doctor might order a spirometry test to diagnose lung conditions, monitor existing lung diseases, or check how well treatments are working. It is a key tool for identifying conditions such as asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis, and pulmonary fibrosis, which affect how you breathe.

One common reason for spirometry is to help diagnose lung conditions if you have symptoms like shortness of breath, coughing, or wheezing. For example, it can help distinguish between asthma, which often involves reversible airway narrowing, and COPD, a progressive lung disease. If you already have a diagnosed lung condition, spirometry can be used to monitor its progression over time. Regular tests can show if your lung function is stable, getting worse, or improving with treatment. This helps your doctor adjust your care plan as needed. Spirometry can also assess how well your lungs are functioning before certain surgeries or if you are exposed to substances in your workplace that might harm your lungs. It provides a baseline measurement that can be used for future comparisons.

How to prepare

To prepare for spirometry, you will usually need to avoid smoking, drinking alcohol, and eating heavy meals for several hours before the test. It's also important to wear loose, comfortable clothing that doesn't restrict your breathing. Your doctor will provide specific instructions, especially regarding any medications you take.

Your doctor or the clinic staff will give you detailed instructions. Generally, you should avoid smoking for at least one hour before the test and avoid drinking alcohol for at least four hours. Strenuous exercise should also be avoided for about 30 minutes prior to the test. Eating a heavy meal within two hours of the test can sometimes affect your ability to take a deep breath and exhale forcefully. It's best to eat a light meal if you need to eat before your appointment. It is crucial to discuss all your medications with your doctor, especially any bronchodilators (medicines that open your airways) or inhalers. You might be asked to stop taking certain medications for a specific period before the test, as they can affect the results. Do not stop any medication without your doctor's guidance.

What to expect during

During spirometry, you will sit comfortably while a nurse or technician guides you through the breathing process. You will wear a nose clip and breathe into a mouthpiece connected to the spirometer. You will be asked to take a deep breath and then exhale as hard and fast as you can for several seconds.

The test usually takes about 15 to 30 minutes. You will sit upright in a chair. A soft clip will be placed on your nose to ensure all air goes through your mouth. You will then place your lips tightly around a sterile mouthpiece connected to the spirometer. The technician will instruct you to take the deepest breath possible, filling your lungs completely. Then, you will be told to blow out all the air as hard and fast as you can, emptying your lungs completely. You will need to keep exhaling for at least six seconds, or until no more air comes out. You will typically repeat this forceful breathing maneuver three to eight times to ensure accurate and consistent results. The technician will encourage you and ensure you are performing the test correctly. Sometimes, after the initial measurements, you might be given an inhaled bronchodilator medicine and then repeat the test to see if your lung function improves.

Understanding your results

Your spirometry results will show specific measurements of your lung function, which your doctor will compare to predicted normal values for someone like you. These results help your doctor determine if your lung function is normal or if there are signs of an obstructive or restrictive lung condition.

The spirometer provides numbers for your FVC, FEV1, and the FEV1/FVC ratio. These numbers are then compared to "predicted" values, which are averages for healthy people of your age, height, sex, and ethnic background. A result is considered abnormal if it falls significantly below these predicted values. Generally, a low FEV1/FVC ratio suggests an obstructive lung disease, meaning there is difficulty getting air out of your lungs. Conditions like asthma and COPD are examples of obstructive diseases. If both FVC and FEV1 are low, but the FEV1/FVC ratio is normal, it might indicate a restrictive lung disease, where your lungs cannot hold as much air. Pulmonary fibrosis is an example of a restrictive condition. It is important to remember that only your doctor can interpret your spirometry results in the context of your overall health, symptoms, and medical history. They will explain what the numbers mean for you and discuss any further steps or treatment options.

Risks

Spirometry is generally a safe procedure, but some people may experience minor side effects like dizziness, lightheadedness, or coughing during the test. These effects are usually temporary and resolve quickly. Serious complications are rare, but your doctor will assess if the test is safe for you.

Because the test requires forceful breathing, it's common to feel a bit lightheaded or dizzy immediately afterward. Some people may also experience a brief coughing fit. These symptoms typically pass quickly once you stop breathing into the spirometer. Spirometry is usually not recommended for people who have recently had a heart attack or stroke, have unstable angina (chest pain), uncontrolled high blood pressure, or have recently undergone certain types of surgery, such as eye, abdominal, or chest surgery. This is because the forceful breathing could potentially worsen these conditions. Always inform your doctor about any existing medical conditions or recent surgeries before undergoing spirometry. They will review your health history to ensure the test is appropriate and safe for you.

Frequently asked questions

How long does a spirometry test take?

A spirometry test usually takes about 15 to 30 minutes from start to finish. This includes time for preparation, performing the breathing maneuvers multiple times, and sometimes repeating the test after taking a bronchodilator medication.

Do I need to stop my medications before spirometry?

You might need to stop certain medications, especially bronchodilators or inhalers, before a spirometry test. Always discuss all your medications with your doctor, who will provide specific instructions on which ones to stop and for how long. Do not stop any medication without medical advice.

Is spirometry painful?

Spirometry is not painful. You might feel a bit tired or lightheaded from the forceful breathing, and some people cough, but there is no pain involved. The nose clip and mouthpiece are generally comfortable.

Can children do spirometry?

Yes, children can do spirometry, usually starting around age 5 or 6, as long as they can understand and follow the instructions to breathe in and out forcefully. Special child-friendly techniques and encouragement are often used.

What is the difference between spirometry and peak flow?

Spirometry is a comprehensive test that measures several aspects of lung function, including how much air you can exhale and how fast. A peak flow meter only measures your peak expiratory flow (PEF), which is the fastest speed you can blow air out of your lungs. Spirometry provides more detailed information.

How often should spirometry be done?

The frequency of spirometry depends on your individual health needs and your doctor's recommendations. If you have a chronic lung condition, it might be done regularly to monitor your condition. For diagnosis, it's usually a one-time test unless follow-up is needed.

Sources

• MedlinePlus — Spirometry
• Mayo Clinic — Spirometry
• Cochrane Library — Spirometry