Spirometry | Lung Function Test

Authored By: Dr. Leonard Leng
Last updated: Jul 3, 2025

Spirometry is a lung function test that measures how much air you can breathe in and out, and how quickly you can exhale. It is commonly used to help diagnose and monitor respiratory conditions such as asthma, chronic obstructive pulmonary disease (COPD), and other disorders that affect breathing.

The test involves taking a deep breath and forcefully exhaling into a mouthpiece connected to a spirometer. The device records key measurements that provide insight into how well your lungs are functioning. Spirometry helps detect early changes in lung health, guide treatment decisions, and monitor disease progression over time.

Spirometry may be recommended for several reasons, including:

• Diagnosing chronic lung conditions such as asthma, COPD, or other respiratory diseases.
• Evaluating ongoing respiratory symptoms like chronic cough, wheezing, or shortness of breath.
• Monitoring disease progression and treatment response in individuals with known lung conditions.
• Assessing lung function before surgery to evaluate pre-operative risk.
• Screening individuals in high-risk occupations who are exposed to dust, fumes, or other airborne irritants.

The frequency and purpose of spirometry depend on your individual health status and the recommendations of your doctor.

A spirometry test typically involves sitting upright and breathing into a disposable mouthpiece connected to a spirometer. A nose clip may be used to ensure all air is exhaled through the mouth. The test usually takes about 15 to 30 minutes. The typical steps include:

1. Taking a deep breath in.
2. Sealing your lips tightly around the mouthpiece.
3. Blowing out as hard and fast as possible until your lungs feel empty.
4. Repeating the process several times to obtain consistent readings.

A doctor or healthcare professional will guide you through each attempt and ensure the technique is performed correctly to help achieve accurate results.

Spirometry results are assessed using key measurements, primarily FEV₁, FVC, and the FEV₁/FVC ratio:

• FEV₁ (Forced Expiratory Volume in 1 Second) – The volume of air you can forcefully exhale in the first second of the test. This is a key indicator used to assess the severity of airflow obstruction.
• FVC (Forced Vital Capacity) – The total volume of air exhaled after taking a full, deep breath.
• FEV₁/FVC Ratio – The proportion of your lung capacity exhaled in the first second, used to detect airflow limitation and help differentiate between obstructive and restrictive lung conditions.

These values are compared against reference ranges based on your age, sex, height, and ethnicity to determine if your lung function is within expected limits.

A low FEV₁ or FEV₁/FVC ratio may indicate obstructive lung diseases such as asthma or COPD. In contrast, a reduced FVC with a normal or elevated FEV₁/FVC ratio may suggest a restrictive lung condition.

Your doctor will interpret the results in the context of your symptoms, medical history, and, if needed, other diagnostic tests.

Spirometry is generally considered low risk when performed by trained professionals, but it may not be suitable for everyone. Some individuals may experience brief lightheadedness, dizziness, or fatigue due to the effort required during forceful exhalation.

The test may be avoided or postponed in certain situations, such as:

• Recent chest, abdominal, brain, or eye surgery.
• Cardiac conditions such as a recent heart attack, severe arrhythmias, decompensated heart failure, or uncontrolled high blood pressure.
• Infectious diseases such as active tuberculosis or COVID-19, due to the risk of transmission during the test.
• Conditions affected by increased internal pressure, such as cerebral or aortic aneurysms.
• Late-term pregnancy, where spirometry may place additional strain.

Always inform your doctor of any existing health conditions before undergoing the test, so they can determine whether spirometry is appropriate for you.

At ATA Medical, we provide spirometry testing and treatment for asthma at the following rates:

We also offer workplace health screening services for corporate clients, which may include spirometry testing depending on the nature of the job and industry requirements.

Our occupational health doctors are experienced in assessing lung function for work-related risk management and fitness-to-work evaluations.

Contact us to learn more or discuss a customised screening package for your organisation.

To help ensure accurate results, it is important to follow certain preparation guidelines:

• Wear loose, comfortable clothing.
• Avoid eating a heavy meal before the test.
• Refrain from smoking, consuming alcohol, or engaging in vigorous exercise for at least a few hours beforehand.
• You may also be advised to temporarily stop using certain inhaled medications, depending on your doctor’s instructions.

It is best to follow your doctor’s specific instructions for the test, as recommendations may vary based on your individual health needs.