Pulmonary Function Test Guide: Spirometry Explained

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According to the American Thoracic Society, pulmonary function testing is essential for diagnosing and managing respiratory diseases, with spirometry being one of the most commonly performed medical tests worldwide, used to evaluate lung function in over 20 million Americans annually.

A Pulmonary Function Test (PFT) is a non-invasive breathing test that measures how well your lungs are working. These tests evaluate lung size, airflow, and how effectively gases (oxygen and carbon dioxide) are exchanged between your lungs and bloodstream.

The most common and important component of PFT is spirometry, which measures how much air you can breathe in and out and how quickly you can do it. PFTs are essential for diagnosing and managing conditions like asthma, COPD, pulmonary fibrosis, and other respiratory diseases.

Why Are PFTs Important?

Your lungs are complex organs that must:

• Bring in oxygen with each breath
• Transfer oxygen to your bloodstream
• Remove carbon dioxide from your body
• Maintain proper airflow during breathing

PFTs measure these essential functions to detect problems early and monitor treatment effectiveness.

Understanding the PFT procedure helps you know what to expect:

The Technology:

PFT equipment includes:

1. Spirometer: Device measuring airflow and lung volumes
2. Mouthpiece: Disposable piece you breathe through
3. Nose clips: Prevents air from escaping through nose
4. Computer: Records and analyzes breathing patterns
5. Body plethysmogram (for some tests): Sealed booth measuring lung volumes

Types of Pulmonary Function Tests:

1. Spirometry (Most Important)

The core PFT component measuring airflow:

• Duration: 15-30 minutes
• What it measures: FVC, FEV1, FEV1/FVC ratio
• Procedure: Forceful breathing into spirometer
• Reversibility testing: Before/after bronchodilator

2. Lung Volume Measurement

Measures total lung capacity:

• Duration: 10-15 minutes
• Methods: Body plethysmography or gas dilution
• What it measures: TLC, RV, FRC
• Indication: Restrictive lung disease

3. Diffusion Capacity Test (DLCO)

Measures gas exchange:

• Duration: 10-15 minutes
• What it measures: How well oxygen moves into blood
• Procedure: Breathe in trace gas, hold, breathe out
• Indication: Emphysema, pulmonary fibrosis, pulmonary hypertension

4. Bronchoprovocation Test

Tests for airway hyperresponsiveness:

• Duration: 45-90 minutes
• What it measures: Airway response to irritant (methacholine, exercise)
• Indication: Asthma diagnosis when baseline spirometry normal

5. Exercise Challenge Test

Lung function during exercise:

• Duration: 60-90 minutes
• What it measures: Lung function with physical activity
• Indication: Exercise-induced asthma

Doctors recommend PFTs for various respiratory evaluations:

1. Diagnosing Asthma

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According to the American Lung Association, spirometry is essential for asthma diagnosis, with specific criteria including an FEV1/FVC ratio below normal or FEV1 improvement of at least 12% after bronchodilator administration.

Asthma detection:

• Reversible obstruction: Improvement after bronchodilator
• Airway hyperresponsiveness: Positive bronchoprovocation
• Variable airflow: Differences between visits
• Exclusion of other causes: COPD, vocal cord dysfunction

2. Diagnosing COPD

PFT for COPD is the gold standard:

• Irreversible obstruction: No improvement with bronchodilator
• FEV1/FVC < 0.70: Diagnostic criterion
• Severity staging: Based on post-bronchodilator FEV1
• Progression monitoring: Serial measurements over time

3. Evaluating Shortness of Breath

Dyspnea assessment:

• Obstructive pattern: Asthma, COPD, bronchiectasis
• Restrictive pattern: Pulmonary fibrosis, chest wall disease
• Neuromuscular weakness: ALS, muscular dystrophy
• Cardiovascular cause: Normal PFT suggests heart problem

4. Pre-operative Assessment

Surgical risk evaluation:

• Lung resection surgery: Predict postoperative lung function
• Major surgery: Overall risk assessment
• Anesthesia planning: Determine ventilator needs

5. Occupational Health

Workplace exposure monitoring:

• Asbestos exposure: Early detection of asbestosis
• Silica exposure: Silicosis screening
• Chemical exposure: Reactive airways dysfunction syndrome
• Return to work: Fitness for duty determination

6. Disability Evaluation

Functional assessment:

• Impairment rating: Based on PFT results
• Disability claims: Objective evidence of lung dysfunction
• Social Security Disability: PFT criteria

7. Monitoring Treatment

Therapy effectiveness:

• Asthma control: Symptom correlation with PFT
• COPD progression: Serial FEV1 decline
• Response to medications: Bronchodilator or steroid response
• Lung transplant: Pre- and post-transplant function

Key Spirometry Values:

Lung Volume Measurements:

DLCO (Diffusion Capacity):

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According to 2024 healthcare pricing data from Healthcare Bluebook, the average cost of pulmonary function testing in the United States ranges from $150 to $1,200 depending on the number and type of tests performed, with complete PFT panels costing significantly more than simple spirometry.

Typical PFT Cost Range (Without Insurance):

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Source: Healthcare Bluebook Fair Price Data, 2024.

With Insurance:

• Most insurance plans cover medically necessary PFTs
• Typical copay: $20-$50 for office visit
• Coinsurance: 10-20% after deductible
• Medicare covers PFT at 80% after Part B deductible
• Prior authorization may be required for comprehensive testing

Why PFT Costs Vary:

• Test components: Spirometry only vs. complete panel
• Number of tests: More tests = higher cost
• Facility type: Hospital vs. clinic vs. office
• Geographic location: Regional price differences
• Physician interpretation: Pulmonologist expertise
• Bronchodilator used: Medication cost included

Before Spirometry:

What to do:

• Wear loose clothing that doesn't restrict breathing
• Eat a light meal (heavy meals can limit breathing)
• Bring inhalers to the appointment
• Bring medication list
• Arrive on time or early

What to avoid:

• Smoking for at least 4-6 hours before
• Heavy exercise for at least 30 minutes before
• Alcohol for at least 4 hours before
• Large meals within 2 hours

Before Complete PFT:

Additional preparations:

• Avoid certain medications as directed:
  • Short-acting inhalers: Hold 4-6 hours
  • Long-acting inhalers: Hold 12-24 hours (if safe)
  • Theophylline: Hold 24-48 hours
• Check with your doctor before holding any respiratory medications
• Wear comfortable clothes for body plethysmography booth

Before Bronchoprovocation:

Additional preparations:

• Hold all bronchodilators as directed (usually 12-24 hours)
• No caffeine for 6-8 hours before
• No smoking for at least 6 hours
• No recent respiratory infections (may need to reschedule)

Special Considerations:

For patients using inhalers:

• Bring all inhalers with you
• Technician may ask when you last used them
• Reversibility testing: May use your bronchodilator during test

For patients with recent illnesses:

• Reschedule if you have cold, flu, or pneumonia
• Wait until recovered for accurate results
• Recent illness can affect results for weeks

Spirometry Procedure:

Step-by-step process:

1. Preparation (5 minutes)

   • Remove restrictive clothing
   • Sit in comfortable chair
   • Nose clip applied
   • Technician explains procedure

2. Baseline Measurement (5 minutes)

   • Practice breaths with mouthpiece
   • Understand "blast out" breathing
   • Learn from technician coaching

3. Spirometry Maneuvers (10-15 minutes)

   • FVC maneuver: Deep breath in, blast out completely, keep going
   • Multiple attempts: 3-8 acceptable maneuvers
   • Quality criteria: Must meet ATS standards
   • Coach encourages: "Blast out!", "Keep going!", "More!"

4. Bronchodilator Administration (if ordered) (15 minutes)

   • Given inhaler medication
   • Wait 15 minutes for effect
   • Repeat spirometry

5. Completion (5 minutes)

   • Remove nose clip
   • Rest briefly if dizzy
   • Return to normal activities

During the Test:

What you'll experience:

• Physical effort: Requires vigorous breathing
• Dizziness: Common after forceful exhalation
• Lightheadedness: Normal, passes quickly
• Coughing: May occur with forceful breathing
• Chest tightness: Rare, report immediately
• Fatigue: From repeated efforts

What the technician does:

• Demonstrates: Shows you proper technique
• Coaches: Encourages maximal effort
• Monitors: watches for acceptable maneuvers
• Assesses: Real-time quality of each effort
• Repeats: Until 3 acceptable maneuvers obtained

Quality Criteria:

Acceptable spirometry requires:

• Good start: No hesitation
• No cough: Especially in first second
• No early termination: Blow until completely empty
• Good reproducibility: Two best FVCs within 150 mL
• Maximal effort: Give it everything you have

Complete PFT Procedure:

Additional tests beyond spirometry:

Body plethysmography:

• Sit in booth: Sealed glass enclosure
• Pant against shutter: Gentle breathing efforts
• Various maneuvers: Lung volume measurements
• Duration: 10-15 minutes

DLCO (Diffusion capacity):

• Breathe in gas mixture: Contains small amount of carbon monoxide
• Hold breath: For 10 seconds
• Breathe out forcefully: Into measuring device
• Repeat: 2-3 acceptable maneuvers

Is a PFT Safe?

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According to the American Thoracic Society, pulmonary function testing is very safe with serious complications being extremely rare (<0.1%). The most common adverse effects are temporary dizziness, lightheadedness, or shortness of breath that resolve quickly.

PFT safety profile:

• Non-invasive: Nothing enters your body
• No radiation: Uses airflow measurement only
• Minimal risks: Very safe when performed properly
• No recovery time: Return to normal activities immediately
• Safe for most: Including children and elderly

Potential Risks:

Common and minor:

• Dizziness: From hyperventilation (forceful breathing)
• Lightheadedness: Especially after forceful exhalation
• Shortness of breath: Temporary during testing
• Coughing: From forceful exhalation
• Chest discomfort: Muscle fatigue from effort
• Fainting: Very rare, from dizziness

Rare but serious:

• Bronchospasm: Asthma attack triggered by testing
• Pneumothorax: Collapsed lung (very rare, usually in patients with bullous disease)
• Chest pain: From exertion in patients with heart disease
• Syncope: Fainting from effort

Who Should Be Cautious?

Extra precautions for:

• Recent heart attack: Usually wait 4-6 weeks
• Unstable angina: Chest pain at rest
• Severe aortic stenosis: Heart valve problem
• Recent eye/abdominal surgery: Increased pressure from straining
• Recent respiratory infection: May affect results or trigger bronchospasm
• Active asthma: May need bronchodilator first

Contra-indications:

• Recent heart attack (within 1 month)
• Unstable cardiovascular disease
• Active respiratory infection (may need to postpone)
• Pneumothorax history (caution with body plethysmography)

Interpreting Spirometry:

Normal Spirometry:

• FVC: ≥80% predicted
• FEV1: ≥80% predicted
• FEV1/FVC: ≥0.70 (70%)
• Good effort: Acceptable maneuvers

Obstructive Pattern (Asthma, COPD):

• FEV1/FVC: <0.70 (reduced ratio)
• FEV1: <80% predicted (may be reduced)
• FVC: May be normal or reduced
• Reversibility: Improvement after bronchodilator (asthma) or not (COPD)

Restrictive Pattern (Pulmonary Fibrosis, chest wall disease):

• FVC: <80% predicted (reduced)
• FEV1: <80% predicted (reduced proportionally)
• FEV1/FVC: Normal or elevated (≥0.70)
• TLC: Reduced (if lung volumes measured)

Interpreting Bronchodilator Response:

Significant reversibility (suggests asthma):

• FEV1 increase: ≥12% AND ≥200 mL
• FVC increase: May also improve
• Improvement: In symptoms

Poor reversibility (suggests COPD):

• FEV1 increase: <12% OR <200 mL
• Persistent obstruction: Despite bronchodilator

Severity Classification:

COPD severity (based on post-bronchodilator FEV1):

Asthma severity (based on symptoms and FEV1):

• Intermittent: Symptoms <2 days/week, FEV1 normal
• Mild persistent: Symptoms >2 days/week, FEV1 ≥80%
• Moderate persistent: Daily symptoms, FEV1 60-80%
• Severe persistent: Continual symptoms, FEV1 <60%

Getting Your Results:

• Preliminary: Technician can't interpret
• Quick review: May discuss briefly after testing
• Official report: Within 1-3 business days
• Physician review: Discusses findings and treatment plan

Can I use my inhaler before a pulmonary function test?

Inhaler use before PFT:

For baseline spirometry:

• Check with ordering doctor: Generally hold short-acting inhalers
• Short-acting bronchodilators (albuterol): Hold 4-6 hours before
• Long-acting bronchodilators: May hold 12-24 hours (if safe)
• Inhaled corticosteroids: Usually continue as prescribed

Important:

• Don't stop medications without doctor approval
• Bring all inhalers with you to appointment
• Reversibility testing: Bronchodilator given during test

When in doubt, call ahead to ask for specific instructions.

Can I drink coffee before a pulmonary function test?

Caffeine and PFT:

For routine spirometry:

• Coffee generally allowed in moderation
• Avoid excessive caffeine (4+ cups)
• Caffeine is mild bronchodilator: May slightly affect results

For bronchoprovocation:

• Avoid caffeine for 6-8 hours before
• Can affect test results: Reduces airway responsiveness
• Strict requirement: For accurate test results

General advice:

• One cup is usually fine for routine testing
• Avoid energy drinks: High caffeine content
• Ask your doctor: For specific instructions

Can a pulmonary function test detect COPD?

PFT is the gold standard for COPD diagnosis:

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According to the Global Initiative for Chronic Obstructive Lung Disease (GOLD), COPD diagnosis requires spirometry showing post-bronchodilator FEV1/FVC < 0.70, confirming persistent airflow limitation that is not fully reversible.

PFT findings in COPD:

• FEV1/FVC ratio: <0.70 (key diagnostic criterion)
• Airflow obstruction: Reduced FEV1
• Poor reversibility: Minimal improvement with bronchodilator
• Increased lung volumes: Especially RV and TLC (air trapping)
• Decreased DLCO: Especially in emphysema

PFT also:

• Stages COPD severity: Based on post-bronchodilator FEV1
• Monitors progression: Serial measurements over time
• Assesses treatment response: Bronchodilator effectiveness

No other test can definitively diagnose COPD - PFT is essential.

Can you fail a pulmonary function test?

"Failing" a PFT means abnormal results:

What abnormal results mean:

• Obstructive pattern: Asthma, COPD, bronchiectasis
• Restrictive pattern: Pulmonary fibrosis, chest wall disease
• Mixed pattern: Both obstruction and restriction
• Neuromuscular weakness: ALS, muscular dystrophy

What causes "failure":

• Lung disease: COPD, asthma, fibrosis
• Poor effort: Can cause false abnormality
• Poor technique: Not blowing forcefully enough
• Recent illness: Cold, flu can affect results

Abnormal PFT:

• Not truly "failing": Shows lung function
• Diagnostic information: Helps identify problem
• Not your fault: Lung disease is not passing/failing

If poor effort/technique:

• Technician will coach: Helps improve quality
• May be repeated: For accurate results

Can a pulmonary function test detect asthma?

PFT can help diagnose asthma:

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According to the National Asthma Education and Prevention Program, spirometry demonstrating reversible airflow obstruction (FEV1 increase ≥12% and ≥200 mL after bronchodilator) confirms asthma diagnosis.

PFT findings in asthma:

• Reversible obstruction: Improvement with bronchodilator
• Normal PFT between episodes: Often normal when asymptomatic
• Variable obstruction: Different results at different times
• Positive bronchoprovocation: If baseline PFT normal

If baseline PFT normal but asthma suspected:

• Bronchoprovocation test: Methacholine challenge
• Exercise challenge: If exercise-induced symptoms
• Home PEF monitoring: Peak flow variability
• Repeat PFT: During symptoms

PFT essential for asthma diagnosis and management.

Why do they make you blow so hard during PFT?

Forceful effort is critical for accurate results:

Why maximal effort matters:

• FEV1 measurement: First second requires maximal effort
• FVC measurement: Must completely empty lungs
• Accuracy: Submaximal effort underestimates true lung function
• Reproducibility: Need consistent maximal effort
• ATS standards: Require "good start" and maximal effort

What "blowing hard" achieves:

• Open airways: Maximal effort opens small airways
• Accurate measurement: True lung capacity measured
• Valid results: Meets quality criteria
• Normal vs. abnormal: Correct classification

The coach encourages:

• "Blast out!": Rapid exhalation
• "Keep going!": Continue until empty
• "More!": Even when you think you're done
• Effort matters: Results depend on maximal effort

Poor effort = poor results - give it your all!

What should you not do before a pulmonary function test?

Before your PFT, avoid:

Smoking:

• No smoking for 4-6 hours before test
• Smoking affects airways: Can cause bronchospasm
• Better results: After not smoking

Heavy meals:

• Avoid large meals within 2 hours
• Full stomach: Limits diaphragm movement
• Light meal OK: Don't go hungry

Exercise:

• Avoid vigorous exercise for 30 minutes before
• Fatigue affects effort: Rest before testing
• Light activity OK: Walking, stretching

Alcohol:

• Avoid alcohol for 4 hours before
• Can affect breathing: Alcohol affects respiratory center

Medications (as directed):

• Short-acting inhalers: May need to hold 4-6 hours
• Long-acting inhalers: May need to hold 12-24 hours
• Theophylline: May need to hold 24-48 hours
• Check with doctor: Before stopping any respiratory medication

DO:

• Wear loose clothing
• Bring inhalers to appointment
• Bring medication list
• Arrive on time
• Be ready to give maximal effort

Can I drive after a pulmonary function test?

Yes, you can usually drive yourself home:

After routine PFT:

• No sedation given
• Dizziness resolves quickly
• Return to normal activities immediately
• Driving is safe

After bronchoprovocation:

• Usually can drive once symptoms resolve
• May be given bronchodilator to reverse bronchospasm
• Wait until breathing normal before driving
• Most people fine within 30-60 minutes

After exercise challenge:

• Usually can drive after recovery
• Wait until recovered from exercise
• Most people fine within 30-60 minutes

If you're unsure, ask the technician or arrange a ride.

How often should you have pulmonary function tests?

PFT frequency depends on your condition:

Healthy individuals:

• Not routinely needed
• Work requirements: Some occupations require periodic testing
• Baseline before: Starting medications affecting lungs

Asthma:

• At diagnosis: Establish baseline
• After treatment change: Assess response
• Periodic monitoring: Based on severity
• Before/after bronchodilator: To assess reversibility

COPD:

• At diagnosis: Establish baseline
• Annually: Monitor progression
• After exacerbation: Assess recovery
• Before starting new medication: Assess response

Pulmonary fibrosis:

• At diagnosis: Establish baseline
• Every 3-6 months: Monitor progression
• Before/after treatment: Assess response

Occupational monitoring:

• Baseline: Before starting job
• Periodic: Based on exposure (annually for asbestos)
• After exposure change: Assess for disease

Follow your doctor's recommendations for monitoring frequency.

Your doctor may recommend a PFT when you have:

Respiratory symptoms:

• Chronic cough
• Shortness of breath (dyspnea)
• Wheezing
• Chest tightness
• Exercise intolerance
• Sputum production

Known respiratory conditions:

• Asthma (diagnosis and monitoring)
• COPD (diagnosis and staging)
• Pulmonary fibrosis (diagnosis and monitoring)
• Sarcoidosis (diagnosis and monitoring)
• Occupational lung disease (screening and monitoring)

Risk factors:

• Smoking history
• Occupational exposures (asbestos, silica, chemicals)
• Family history of lung disease
• Recurrent respiratory infections
• Connective tissue disease (scleroderma, rheumatoid arthritis)

Pre-operative assessment:

• Lung surgery
• Cardiothoracic surgery
• Major abdominal surgery
• Organ transplantation

Don't ignore respiratory symptoms - early detection improves outcomes.

A Pulmonary Function Test (PFT) is a valuable, safe, and non-invasive tool for evaluating how well your lungs are working. Whether performed to diagnose asthma or COPD, assess shortness of breath, or monitor lung disease progression, PFTs provide essential information for respiratory care.

Understanding what to expect during your PFT procedure, how to prepare (especially holding certain inhalers), and what your results mean can help reduce anxiety and ensure accurate results. The effort you put into the test directly affects the quality of the results - so give it your all when the technician says "blast out!"

Work closely with your healthcare provider to understand your PFT results and develop an appropriate treatment plan if lung disease is detected. Early diagnosis and appropriate management are key to maintaining optimal lung function and quality of life.

Medical Disclaimer: This content is for educational purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider for diagnosis and treatment recommendations.

Sources:

• American Thoracic Society (ATS). "Pulmonary Function Testing: Guidelines." 2024.
• American Lung Association. "Understanding Your Lung Function Tests." 2024.
• Mayo Clinic. "Pulmonary Function Tests: What You Can Expect." 2024.
• Global Initiative for Chronic Obstructive Lung Disease (GOLD). "COPD Diagnosis and Assessment." 2023.
• Healthcare Bluebook. "Fair Price Data: Pulmonary Function Tests." 2024.