Pulmonary Function Tests (PFTs): Results Explained Test: Normal Range, High/Low Meaning | WellAlly

What are Pulmonary Function Tests?

Pulmonary Function Tests (PFTs) are a group of breathing tests that measure how well your lungs work. They assess lung size, airflow, and how effectively oxygen moves into your bloodstream.

Think of PFTs as a stress test for your lungs. Just as a treadmill test evaluates your heart's response to exertion, PFTs evaluate your lungs' capacity to move air and exchange gases.

What PFTs measure:

Spirometry (most common test):

FVC (Forced Vital Capacity): Total air you can exhale forcefully

FEV1 (Forced Expiratory Volume in 1 second): Air exhaled in first second

FEV1/FVC ratio : Comparison of these values (identifies obstruction)

PEF (Peak Expiratory Flow): Maximum speed of exhalation

Lung volume measurements:

TLC (Total Lung Capacity): Total air in lungs

RV (Residual Volume): Air remaining after full exhalation

FRC (Functional Residual Capacity): Air in lungs at rest

Diffusion capacity:

DLCO (Diffusing capacity of lung for carbon monoxide): How well oxygen moves into blood

Why PFTs Matter

PFTs diagnose and monitor lung diseases like asthma, COPD, pulmonary fibrosis, and many others. They detect lung problems before symptoms become severe and help guide treatment decisions. PFTs are essential for evaluating chronic cough, shortness of breath, and abnormal chest imaging.

Understanding Your Results

Spirometry: The Core Test

Spirometry is the most important and commonly performed PFT. It measures how much air you can exhale and how quickly.

Normal results:

FVC and FEV1 : ≥80% of predicted value (based on age, gender, height, ethnicity)

FEV1/FVC ratio : 70-75% or higher

Test procedure:

Breathe in deeply until lungs are completely full

Blast air out as fast and hard as possible

Continue exhaling until lungs are empty (6+ seconds)

Repeat 3 times to ensure consistent results

Patterns of Abnormality

PFT results show specific patterns that help identify the type of lung problem:

Understanding Your Results ( FEV1/FVC ratio )

FEV1 and FVC both normal, normal ratio—no obstruction

FEV1 reduced more than FVC—airflow obstruction (asthma, COPD)

Both FEV1 and FVC reduced proportionally—can't fully inflate lungs

Both obstruction and restriction present

Obstructive Pattern

What it means : Airways are narrowed or blocked, making it hard to exhale air quickly. Air gets trapped in lungs.

Typical findings:

FEV1 : Reduced (＜80% predicted)

FVC : Normal or mildly reduced

FEV1/FVC ratio : Low (＜70%)

Common causes:

Causes of Obstructive Pattern

Factor

Effect

What to Do

Always tell your doctor about medications, supplements, and recent health events before testing.

Restrictive Pattern

What it means : Lungs can't fully expand. Reduced lung volume makes it hard to breathe deeply.

Typical findings:

FVC : Reduced (＜80% predicted)

FEV1 : Reduced proportionally

FEV1/FVC ratio : Normal or elevated (＞70%)

Common causes:

Causes of Restrictive Pattern

Factor

Effect

What to Do

Always tell your doctor about medications, supplements, and recent health events before testing.

Bronchodilator Reversibility Testing

After baseline spirometry, you inhale a bronchodilator medication (albuterol) and repeat the test after 15-20 minutes.

Significant reversibility:

FEV1 increases ≥12% AND ≥200 mL : Suggests asthma

Reversible obstruction improves with bronchodilator treatment

No significant reversibility:

COPD, fixed obstruction

Other causes of obstruction

When Are PFTs Ordered?

When Your Doctor Might Order PFTs

PFTs are ordered for various respiratory concerns.

You have chronic cough or shortness of breath

PFTs identify the cause of chronic respiratory symptoms. They distinguish between asthma, COPD, restrictive lung disease, and other causes.

You have a known or suspected lung disease

PFTs diagnose asthma, COPD, pulmonary fibrosis, and many other lung diseases. They also monitor disease progression and response to treatment.

You're being evaluated for surgery

Preoperative PFTs assess surgical risk, especially for lung surgery, chest surgery, or abdominal surgery in people with lung disease.

You have occupational exposure to lung irritants

PFTs screen for occupational lung disease in people exposed to asbestos, silica, coal dust, chemicals, or other respiratory hazards.

You're being assessed for disability

PFTs provide objective measurement of lung function for disability evaluations related to respiratory impairment.

You have abnormal chest imaging

PFTs evaluate the functional significance of chest X-ray or CT abnormalities. They determine if imaging findings affect lung function.

Your Action Plan Based on Results

If PFTs are completely normal:

No evidence of lung dysfunction

Continue healthy respiratory habits: Don't smoke (or quit if you smoke) Avoid lung irritants when possible Stay physically active Get recommended vaccinations (flu, pneumonia)

Don't smoke (or quit if you smoke)

Avoid lung irritants when possible

Stay physically active

Get recommended vaccinations (flu, pneumonia)

No further PFTs needed unless symptoms develop

If you have obstructive pattern (asthma):

Confirm reversibility with bronchodilator testing

Start asthma treatment: Inhaled bronchodilators (albuterol for quick relief) Inhaled steroids for long-term control Avoid asthma triggers

Inhaled bronchodilators (albuterol for quick relief)

Inhaled steroids for long-term control

Avoid asthma triggers

Monitor with peak flow meter at home

Repeat PFTs to assess treatment response

If you have obstructive pattern (COPD):

Confirm diagnosis (no significant reversibility)

Start COPD treatment: Smoking cessation if you smoke (essential!) Bronchodilators (long-acting inhaled medications) Pulmonary rehabilitation Vaccinations (flu, pneumonia, COVID-19)

Smoking cessation if you smoke (essential!)

Bronchodilators (long-acting inhaled medications)

Pulmonary rehabilitation

Vaccinations (flu, pneumonia, COVID-19)

Annual PFTs to monitor progression

Oxygen therapy if indicated (based on oxygen saturation)

If you have restrictive pattern:

Further evaluation to identify cause: High-resolution CT chest Autoimmune testing if indicated Occupational exposure history Physical examination for chest wall abnormalities

High-resolution CT chest

Autoimmune testing if indicated

Occupational exposure history

Physical examination for chest wall abnormalities

Treatment depends on underlying cause

May need referral to pulmonologist

If PFTs are borderline or inconclusive:

Repeat testing may be recommended

Additional testing: Bronchial provocation testing (methacholine challenge) for suspected asthma Lung volume measurements (body plethysmography) Diffusion capacity (DLCO) measurement Exercise testing

Bronchial provocation testing (methacholine challenge) for suspected asthma

Lung volume measurements (body plethysmography)

Diffusion capacity (DLCO) measurement

Exercise testing

When PFT Abnormalities Require Urgent Evaluation

FEV1 <50% predicted with respiratory symptoms

Sudden change in lung function (asthma exacerbation)

PFTs with resting oxygen saturation <88%

Known lung disease with sudden worsening

Restrictive pattern with rapid progression

⚠️ These findings warrant prompt referral to a pulmonologist. Severe lung dysfunction requires comprehensive evaluation and treatment. Acute worsening of asthma or COPD may need urgent care or emergency evaluation.

Preparing for Your PFT

Before the test:

No smoking for at least 1 hour before test (preferably 4-6 hours)

No heavy exercise for 30 minutes before test

Avoid large meals before test (full stomach limits breathing)

Wear loose clothing that doesn't restrict chest movement

Follow your doctor's instructions about holding respiratory medications Short-acting bronchodilators (albuterol): Usually hold 4-6 hours Long-acting bronchodilators: Usually hold 12-24 hours Inhaled steroids: Usually continue as prescribed

Short-acting bronchodilators (albuterol): Usually hold 4-6 hours

Long-acting bronchodilators: Usually hold 12-24 hours

Inhaled steroids: Usually continue as prescribed

During the test:

You'll sit upright and wear nose clips

You'll breathe through a mouthpiece

The technician will coach you through each maneuver

Effort matters—give your best effort for accurate results

You may feel lightheaded or temporarily short of breath (normal)

After the test:

You can return to normal activities immediately

Results are usually available the same day

Your doctor will review results with you

Common Questions

How often should I have PFTs?

Can PFTs diagnose asthma?

What's the difference between asthma and COPD?

Can I improve my lung function?

Do PFTs hurt?

Why are my PFT results expressed as percentages?

Disclaimer : This information is for educational purposes only and does not constitute medical advice. Always consult your healthcare provider to interpret your PFT results and determine appropriate management.

Track Your Pulmonary Function Tests Results

Monitor your levels over time, identify trends, and share your history with your doctor.