Lung function test normal range

Lung function tests measure how well the lungs work. They check how much air you can inhale, how much you can exhale, and how well oxygen moves into your blood. As per studies conducted by NCBI, these tests help diagnose and monitor lung diseases like asthma, COPD ( chronic obstructive pulmonary disease), and infections.
 

Why lung function tests are important

In India, air pollution is a major health concern. Millions of people suffer from breathing problems. Early diagnosis of lung issues can prevent severe complications. Lung function tests help doctors understand the condition of the lungs and decide on treatment. Lung diseases are common in both urban and rural areas. City dwellers are exposed to pollution, while people in villages face risks from cooking smoke and dust. Early detection through lung function tests can improve treatment outcomes.

There are several types of lung function tests. Each test provides different information about lung health.

• Spirometry measures how much air you can breathe in and out and checks how fast you can exhale. It is one of the most common tests for diagnosing asthma and COPD.
• Peak flow test: This measures how quickly you can blow air out of your lungs. It is helpful for asthma patients. A peak flow meter can also be used at home to monitor lung function over time.
• Lung volume test: checks the total air the lungs can hold. This is useful for detecting restrictive lung diseases like pulmonary fibrosis.
• The diffusion capacity test measures how well oxygen moves from the lungs into the blood. This test can detect conditions like interstitial lung disease and pulmonary hypertension.
• Pulse oximetry: Though not a lung function test, pulse oximetry measures oxygen levels in the blood. Low oxygen levels may indicate a lung problem.
   

Normal range of lung function tests

normal lung function depends on age, gender, height, and ethnicity. In India, lung capacity may be lower than Western standards due to genetic and environmental factors. Here are the normal ranges:

• Forced vital capacity (FVC): 80-120% of the predicted value
• Forced expiratory volume in one second (FEV1): 80-120% of the expected value
• FEV1/ ratio: above 70%
• Peak expiratory flow (pdf): varies by age and gender but usually above 80% of the predicted value
   

Factors affecting lung function in India

include many factors that influence lung health. Pollution, smoking, occupational hazards, and indoor air quality play a significant role.

• Air pollution: Cities like Delhi and Mumbai have high pollution levels. Fine dust particles reduce lung function over time, and high pollution exposure leads to chronic respiratory conditions like asthma and bronchitis.
• Smoking: tobacco use damages lung tissue and lowers lung capacity. Smoking is a leading cause of COPD in India. Passive smoking is also a concern, especially for children and women in households where men smoke.
• Occupational exposure: Factory workers, miners, and construction workers inhale harmful particles daily, which affects lung function. Prolonged exposure to dust, chemicals, and toxic fumes can lead to lung diseases like pneumoconiosis and silicosis.
• Indoor pollution: Many homes use biomass fuels for cooking. The smoke from these fuels affects lung health, especially in rural areas. Women and children are the most affected, as they spend more time indoors.
• Genetic factors: some people may have inherited conditions that affect lung function, such as alpha-1 antitrypsin deficiency.
   

Symptoms that require a lung function test

Anyone experiencing the following symptoms should get a lung function test:

• frequent coughing
• shortness of breath
• wheezing
• chest tightness
• recurring lung infections
• difficulty in physical activity due to breathlessness
• unexplained fatigue
• blue lips or fingertips (a sign of low oxygen levels)
   

How to prepare for a lung function test

Preparing for a lung function test is simple but essential:

• Avoid heavy meals before the test.
• Do not smoke for at least 4-6 hours before testing.
• Wear loose clothing to allow free breathing.
• Avoid caffeine before the test as it may affect results.
• Follow the doctor’s instructions about stopping medications before the test.
• Stay relaxed and breathe normally before the test to avoid affecting results.
   

How lung function tests are done

The tests are painless and take only a few minutes. For spirometry, you will be asked to take a deep breath and blow forcefully into a tube. The machine records the results. Other tests may require breathing in special gases or sitting inside a chamber to measure lung volume. Sometimes, multiple tests are done to get a complete picture of lung health.
 

What abnormal results mean

If lung function test results are not within the normal range, it could indicate different conditions:

1.  FEV1 (Forced Expiratory Volume in 1 Second) & FVC (Forced Vital Capacity)

• Indicates: Possible restrictive or obstructive lung disease.
• Normal Value: ≥ 80% of predicted (Liters or % predicted).
• Severity Levels (FEV1 % Predicted):
  • Mild: 70–79%
  • Moderate: 50–69%
  • Severe: 30–49%
  • Very Severe: < 30%
     

2. FEV1/FVC Ratio

• Indicates: Obstructive lung disease if low.
• Normal Value: ≥ 70%
• Severity Levels (Based on GOLD Criteria for COPD):
  • Mild (GOLD 1): ≥ 80%
  • Moderate (GOLD 2): 50–79%
  • Severe (GOLD 3): 30–49%
  • Very Severe (GOLD 4): < 30%
     

3.  DLCO (Diffusing Capacity of the Lungs for Carbon Monoxide)

• Indicates: Impaired gas exchange if low.
• Normal Value: ≥ 75–140% of predicted (ml/min/mmHg or % predicted).
• Severity Levels (DLCO % Predicted):
  • Mild: 60–74%
  • Moderate: 40–59%
  • Severe: < 40%
     

4. TLC (Total Lung Capacity) & RV (Residual Volume) – Lung Volume Abnormalities

• High Values: Indicate air trapping/hyperinflation (e.g., Emphysema).
• Low Values: Indicate restrictive lung disease (e.g., Pulmonary fibrosis).
• Normal Values:
  • TLC: 80–120% of predicted.
  • RV: 75–120% of predicted.
• Severity Levels (TLC % Predicted for Restrictive Disease):
  • Mild: 65–79%
  • Moderate: 50–64%
  • Severe: < 50%
     

5.  Airway Resistance (RAW)

• Indicates: Narrowed airways if increased.
• Normal Value: < 2.5 cmH₂O/L/s.
• Elevated Values: Seen in Asthma, Chronic Bronchitis, and Upper Airway Obstruction.

6. Bronchodilator Response (Reversibility Test for Asthma vs. COPD)

• Indicates: Reversible airway obstruction if positive.
• Normal Response: Increase in FEV1 or FVC by ≥ 12% and ≥ 200 ml after bronchodilator administration.
• Interpretation:
  • Significant Response (Reversible Airway Obstruction): Suggests Asthma.
  • Minimal or No Response: Suggests COPD or fixed obstruction.
     

Treatment and lifestyle changes for better lung function: 

Doctors may suggest medications, lifestyle changes, or therapies to improve lung function. Here are some ways to keep your lungs healthy:

• Quitting smoking: This is the most crucial step for better lung health.
• Exercise regularly: Walking, swimming, and breathing exercises improve lung capacity.
• Avoid pollution: Wearing masks in polluted areas and using air purifiers at home helps protect the lungs.
• Eat a healthy diet: Foods rich in antioxidants like fruits, vegetables, and nuts support lung health.
• Stay hydrated: Drinking enough water keeps mucus in the lungs thin and easy to clear.
• Practice breathing techniques: Yoga and pranayama help strengthen the lungs.
• Get vaccinated: Flu and pneumonia vaccines prevent lung infections.
   

Lung function tests in India

Many hospitals and clinics offer lung function tests. Major cities have advanced facilities, but rural areas still lack access. Awareness about lung health is growing, and more people are getting tested. Government programs are helping improve respiratory health care.
 

Final thoughts

Lung function tests are an essential tool for detecting lung diseases early. Pollution, smoking, and occupational hazards make regular testing vital in India. People can maintain good lung health and prevent serious illnesses by taking preventive measures, staying active, and getting tested on time.

FAQs

What is the typical lung function range?  

Younger, taller, and male individuals generally have higher expected values. Peak expiratory flow (PEF) is recorded in litres per minute. Adults' normal peak flow scores typically fall between approximately 400 and 700 litres per minute. Although scores may be lower, they are still considered normal for older women.  

What constitutes a good lung function test result?  

Normal spirometry results indicate an FEV1/FVC ratio exceeding 0.70, with both FEV1 and FVC above 80% of the predicted value. If lung volumes are measured, a total lung capacity (TLC) greater than 80% of the expected value is deemed normal. A diffusion capacity above 75% of the predicted value is also considered normal.  

What does having 50% lung function imply?  

When a glass is filled to the top, it is 100% full. Conversely, if it is only half full, that represents 50% of its capacity. Similarly, if your FEV1 is at 50%, it means your lungs can only manage half of the air they should be able to accommodate.  

What is the typical lung capacity range?  

The average lung capacity in healthy adults is around 6 liters. Factors such as age, gender, body composition, and ethnicity influence the varying lung capacity ranges among individuals.  

What oxygen level is considered safe in lung disease?  

An oxygen level between 88% and 92% is considered safe for someone with moderate to severe COPD. Oxygen saturation levels falling below 88% can be hazardous, and you should contact your doctor if it drops below that threshold. If oxygen levels drop to 84% or lower, it is advisable to seek emergency medical attention.