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Lung Volumes and Capacities

TLC = TV + IRV + ERV + RV. TLC <80% = restrictive. TLC >120% = hyperinflation. RV/TLC >40% = air trapping.

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TLC ~6L in adults RV/TLC 20-35% normal Restrictive: ILD, neuromuscular

Ready to run the numbers?

Why: Distinguishing restrictive vs obstructive patterns guides diagnosis and management.

How: Spirometry measures TV, IRV, ERV. Body plethysmography or gas dilution for RV and TLC.

TLC ~6L in adultsRV/TLC 20-35% normal
Sources:ATS/ERS Standards

Run the calculator when you are ready.

Calculate Lung CapacityUse the calculator below to check your health metrics

Normal Male (40 years)

Healthy adult male with normal lung volumes

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Normal Female (35 years)

Healthy adult female

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Restrictive Pattern

Patient with interstitial lung disease

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COPD/Hyperinflation

Increased TLC and RV in COPD

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Elderly Patient (75 years)

Age-related changes in lung volumes

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Sample Scenarios

Normal Male (40 years)

Healthy adult male with normal lung volumes

Normal Female (35 years)

Healthy adult female

Restrictive Pattern

Patient with interstitial lung disease

COPD/Hyperinflation

Increased TLC and RV in COPD

Elderly Patient (75 years)

Age-related changes in lung volumes

Enter Lung Volume Data

Demographics

Volumes

Clinical

For informational purposes only — not medical advice. Consult a healthcare professional before acting on results.

🏥 Health Facts

📊

RV cannot be measured by spirometry alone.

— Pulmonary function

Understanding Lung Volumes

Lung volumes are divided into four primary volumes (TV, IRV, ERV, RV) that combine to form four capacities (TLC, VC, IC, FRC). Understanding these helps distinguish between obstructive and restrictive lung diseases.

Restrictive Pattern

TLC <80% predicted - all volumes reduced proportionally

Obstructive/Hyperinflation

TLC >120% predicted - increased RV, elevated RV/TLC ratio

The Four Primary Lung Volumes

Tidal Volume (TV)

  • • Volume of normal breath
  • • ~500 mL at rest
  • • Increases with exercise
  • • Measured by spirometry

Inspiratory Reserve Volume (IRV)

  • • Extra air after normal breath
  • • ~2500-3000 mL
  • • Used during deep breaths
  • • Decreases with lung disease

Expiratory Reserve Volume (ERV)

  • • Extra air exhaled after normal breath
  • • ~1000-1200 mL
  • • Reduced in obesity, pregnancy
  • • Measured by spirometry

Residual Volume (RV)

  • • Air remaining after max exhale
  • • ~1200 mL
  • • Cannot be measured by spirometry
  • • Increased in air trapping

The Four Lung Capacities

CapacityFormulaNormal ValueClinical Relevance
TLCTV + IRV + ERV + RV~6000 mLRestrictive vs obstructive
VCTV + IRV + ERV~4600 mLRespiratory muscle/lung parenchyma
ICTV + IRV~3500 mLDyspnea on exertion
FRCERV + RV~2300 mLResting lung position

Measurement Methods

Spirometry

  • • Measures TV, IRV, ERV
  • • Cannot measure RV directly
  • • Calculates VC, IC
  • • Most common test

Body Plethysmography

  • • Gold standard for TLC
  • • Measures FRC directly
  • • Uses Boyle's Law
  • • More accurate in obstruction

Gas Dilution

  • • Helium dilution
  • • Nitrogen washout
  • • May underestimate in obstruction
  • • Measures communicating airways

Normal Values

Adult Male (70 kg, 175 cm)

  • • TV: ~500 mL
  • • IRV: ~3000 mL
  • • ERV: ~1100 mL
  • • RV: ~1200 mL
  • • TLC: ~6000 mL
  • • VC: ~4600 mL

Adult Female (60 kg, 165 cm)

  • • TV: ~450 mL
  • • IRV: ~2400 mL
  • • ERV: ~900 mL
  • • RV: ~1000 mL
  • • TLC: ~4800 mL
  • • VC: ~3750 mL

Restrictive Pattern

  • • Definition: TLC <80% predicted (or below LLN)
  • • All volumes reduced: Proportional decrease in TV, IRV, ERV, RV
  • • VC reduced: May be more pronounced than TLC reduction
  • • RV/TLC ratio: Usually normal or mildly increased
  • • Causes: ILD, chest wall disease, neuromuscular, obesity

Causes of Restrictive Pattern

Parenchymal

  • • Idiopathic pulmonary fibrosis (IPF)
  • • Hypersensitivity pneumonitis
  • • Sarcoidosis
  • • Drug-induced ILD
  • • Connective tissue disease-ILD

Extra-parenchymal

  • • Obesity (severe)
  • • Kyphoscoliosis
  • • Neuromuscular disease (ALS, myopathy)
  • • Pleural effusion/thickening
  • • Chest wall abnormalities

Hyperinflation Pattern

  • • Definition: TLC >120% predicted
  • • Increased RV: Air trapping due to incomplete exhalation
  • • RV/TLC >40%: Significant air trapping indicator
  • • IC reduced: Contributes to dyspnea on exertion
  • • Causes: COPD, emphysema, severe asthma

Clinical Interpretation Guide

ParameterNormalRestrictiveObstructive
TLC80-120%<80%Normal or >120%
RVNormalDecreasedIncreased
RV/TLC20-35%Normal-slight ↑>40%
FRCNormalDecreasedIncreased

RV/TLC Ratio Significance

  • • Normal: 20-35% (increases slightly with age)
  • • 30-40%: Mild air trapping
  • • >40%: Significant air trapping
  • • Clinical significance: Correlates with dyspnea and exercise limitation
  • • Age effect: Increases ~5% per decade after age 40

Age-Related Changes

  • • TLC: Relatively stable with age
  • • VC: Decreases ~25-30 mL/year after age 20-25
  • • RV: Increases with age (senile emphysema)
  • • ERV: Decreases with age
  • • Closing capacity: Increases, may exceed FRC (airway closure)
  • • Elastic recoil: Decreases (contributes to RV increase)

Factors Affecting Lung Volumes

Increase Lung Volumes

  • • Taller height
  • • Male sex
  • • Obstructive disease (RV, FRC)
  • • High altitude (acclimation)
  • • Standing position

Decrease Lung Volumes

  • • Shorter height
  • • Female sex
  • • Restrictive disease
  • • Obesity (ERV, FRC)
  • • Supine position
  • • Pregnancy

Clinical Pearls

  • • Spirometry alone: Cannot determine TLC - need body plethysmography or gas dilution
  • • Low VC + normal FEV1/FVC: Suggests restriction, but need TLC to confirm
  • • Mixed pattern: Both obstructive + restrictive features possible
  • • Nonspecific pattern: Normal TLC with low VC - submaximal effort or early disease
  • • Air trapping: RV/TLC elevated even when TLC is normal in early obstruction

Inspiratory Capacity and Dyspnea

  • • Dynamic hyperinflation: IC decreases during exercise in COPD
  • • Mechanism: Air trapping increases FRC, reducing IC
  • • Clinical impact: Limited ability to increase tidal volume
  • • IC/TLC ratio: Correlates with dyspnea severity
  • • Bronchodilators: Can improve IC and exercise tolerance

Plethysmography vs Gas Dilution

FeatureBody PlethysmographyGas Dilution
MeasuresAll thoracic gasCommunicating airspaces
In obstructionTrue TLCMay underestimate TLC
EquipmentSpecialized boxSimpler setup
ClaustrophobiaMay be an issueNot an issue

Clinical Scenario Examples

Scenario 1: IPF Patient

TLC 60% predicted, VC 55% predicted, RV/TLC 32%. Classic restrictive pattern with proportional reduction in all volumes. Consider HRCT and DLCO.

Scenario 2: COPD Patient

TLC 130% predicted, RV 180% predicted, RV/TLC 48%. Hyperinflation with significant air trapping. IC reduced - correlates with dyspnea.

Scenario 3: Obese Patient

TLC 85% predicted, ERV markedly reduced, FRC reduced. Low VC but FEV1/FVC normal. Obesity-related restriction affecting mainly ERV and FRC.

Key Formulas

  • TLC: TV + IRV + ERV + RV
  • VC: TV + IRV + ERV (also = TLC - RV)
  • IC: TV + IRV (also = TLC - FRC)
  • FRC: ERV + RV
  • RV/TLC ratio: (RV / TLC) × 100

Lung Capacity Calculator Summary

TLC Formula

TV+IRV+ERV+RV

Restrictive

<80% TLC

Air Trapping

RV/TLC >40%

Normal

80-120% TLC

Documentation Guide

  • • Method: Body plethysmography vs gas dilution
  • • Values: Absolute and percent predicted
  • • TLC interpretation: Normal, reduced (restrictive), elevated (hyperinflation)
  • • RV/TLC: Document air trapping assessment
  • • Quality: Note if technically satisfactory

Key References

ATS/ERS 2005

Standardisation of the measurement of lung volumes. Eur Respir J.

Quanjer et al. 2012

Multi-ethnic reference values for spirometry (GLI-2012). Eur Respir J.

O'Donnell et al. 2015

Dynamic hyperinflation and exercise intolerance in COPD. Am J Respir Crit Care Med.

Memory Aids

  • • "4 volumes, 4 capacities" - TV, IRV, ERV, RV → TLC, VC, IC, FRC
  • • "TLC <80 = Restriction" - Defining criterion
  • • "RV/TLC >40 = Air trapping" - Key ratio for obstruction
  • • "FRC = ERV + RV" - Resting lung volume

Key Takeaways

  • • TLC is the gold standard for distinguishing restriction from obstruction
  • • Spirometry alone cannot measure TLC (need plethysmography or gas dilution)
  • • RV/TLC ratio is key indicator of air trapping
  • • Restrictive: TLC <80% with proportionally reduced volumes
  • • Hyperinflation: TLC >120% with elevated RV
  • • IC correlates with dyspnea on exertion in COPD

Important Disclaimer

This calculator provides estimates based on input volumes. Actual lung volume measurement requires pulmonary function testing with body plethysmography or gas dilution techniques. Clinical interpretation should be performed by qualified healthcare professionals in context of the complete clinical picture.

Mixed Ventilatory Defects

  • • Definition: Both obstructive (low FEV1/FVC) AND restrictive (low TLC) features
  • • Examples: COPD + obesity, COPD + post-surgical resection, sarcoidosis
  • • Interpretation challenge: TLC may normalize if RV elevated but VC reduced
  • • Approach: Consider each component separately
  • • Key point: Cannot diagnose mixed pattern without lung volume measurement

Nonspecific Pattern

  • • Definition: Low VC with normal FEV1/FVC ratio AND normal TLC
  • • Not restrictive: Because TLC is not reduced
  • • Causes: Submaximal effort, early/mild disease, obesity, neuromuscular
  • • Management: Repeat testing, assess effort, clinical correlation
  • • Prevalence: Common finding (up to 10% of PFTs)

Integration with DLCO

  • • Restriction + low DLCO: Suggests parenchymal (ILD)
  • • Restriction + normal DLCO: Suggests extra-parenchymal (chest wall, neuromuscular)
  • • Hyperinflation + low DLCO: Emphysema
  • • Hyperinflation + normal DLCO: Asthma, chronic bronchitis
  • • DLCO corrected for VA: KCO may be elevated in extra-parenchymal restriction

Effect of Obesity on Lung Volumes

  • • ERV: Most affected - markedly reduced
  • • FRC: Reduced (ERV reduction > RV reduction)
  • • TLC: Usually normal or mildly reduced
  • • RV: Usually normal
  • • Mechanism: Abdominal mass restricts diaphragm descent
  • • OHS: Obesity hypoventilation may have additional effects

Lung Volumes in Pregnancy

  • • TLC: Unchanged (diaphragm rise compensated by rib flare)
  • • FRC: Decreases ~20% by term
  • • ERV: Decreases
  • • RV: Unchanged or slightly decreased
  • • IC: Increases (allows maintenance of TV despite FRC decrease)
  • • TV: Increases (progesterone effect)

Anesthesia and Lung Volumes

  • • General anesthesia: FRC decreases ~15-20% (atelectasis risk)
  • • Supine position: Further FRC decrease
  • • Muscle relaxation: Contributes to FRC reduction
  • • Pre-operative assessment: Severe restriction increases risk
  • • Post-operative: Lung volumes remain reduced for days

Effect of Body Position

  • • Standing to supine: FRC decreases ~25-30%
  • • Mechanism: Abdominal contents push diaphragm cephalad
  • • RV: Relatively unchanged with position
  • • VC: May decrease slightly supine
  • • Clinical relevance: Tests standardized in sitting position

Lung Volumes in Neuromuscular Disease

  • • VC: Most sensitive indicator - decreases early
  • • TLC: Decreases as disease progresses
  • • RV: May increase (expiratory muscle weakness)
  • • FRC: Often normal until advanced disease
  • • Supine VC: Drops >25% from sitting suggests diaphragm weakness
  • • MIP/MEP: More sensitive for early weakness

Lung Volumes During Exercise

  • • TV: Increases significantly (up to ~3L in young fit adults)
  • • IC utilization: Normal subjects use IC reserve
  • • EELV: End-expiratory lung volume decreases (below FRC)
  • • COPD: EELV increases (dynamic hyperinflation) - limits TV increase
  • • IC/TLC ratio: Determines exercise capacity in COPD

Lung Volumes in Asthma

  • • Between attacks: Often normal TLC, RV, FRC
  • • During exacerbation: Air trapping - elevated RV, FRC, TLC
  • • Severe asthma: Chronic hyperinflation possible
  • • Post-bronchodilator: RV may decrease with bronchodilator
  • • Distinguishing from COPD: Better reversibility of hyperinflation

Lung Volumes in Emphysema

  • • TLC: Elevated (loss of elastic recoil)
  • • RV: Markedly elevated (air trapping)
  • • RV/TLC: Elevated >40-50%
  • • FRC: Elevated (new resting point)
  • • IC: Reduced (limits exercise)
  • • DLCO: Reduced (parenchymal destruction)

Lung Volume Reduction Surgery (LVRS)

  • • Goal: Remove hyperinflated emphysematous tissue
  • • Effect on TLC: Decreases towards normal
  • • Effect on RV: Decreases (reduced air trapping)
  • • Effect on IC: Improves (better diaphragm mechanics)
  • • Ideal candidates: Upper lobe predominant emphysema, low exercise capacity

Bronchoscopic Lung Volume Reduction

  • • Methods: Endobronchial valves, coils, vapor ablation
  • • Assessment: Pre-procedure lung volumes mandatory
  • • Outcome measure: RV reduction, IC improvement
  • • Best responders: Significant hyperinflation (RV/TLC >175%)
  • • Fissure integrity: Important for valve placement

Quality Assurance in Lung Volume Testing

  • • Reproducibility: FRC should be reproducible within 5%
  • • Patient cooperation: Critical for accurate measurement
  • • Calibration: Equipment calibration per ATS/ERS standards
  • • Technician training: Proper technique essential
  • • Reference equations: Use appropriate for population

Pediatric Lung Volumes

  • • Growth: Lung volumes increase with height and age
  • • FRC/TLC ratio: Higher in infants, decreases to adult values by age 7
  • • Testing challenges: Cooperation, specialized equipment
  • • Reference equations: Pediatric-specific equations needed
  • • Clinical applications: CF, asthma, neuromuscular disease

Common Questions

Why can't spirometry measure TLC?

Spirometry measures exhaled volumes, but RV cannot be exhaled. TLC = VC + RV, so without RV, you can't calculate TLC. Need plethysmography or gas dilution.

What's the difference between FRC from plethysmography vs gas dilution?

Plethysmography measures all thoracic gas including trapped air, while gas dilution only measures communicating airways. In obstruction, plethysmography gives higher (true) values.

Can someone have both restriction and obstruction?

Yes - mixed ventilatory defect. Examples include COPD + obesity, sarcoidosis, or post-lung resection in COPD patient. Need full PFTs to characterize.

Step-by-Step Lung Volume Interpretation

  1. Review spirometry first (FEV1/FVC ratio)
  2. Check TLC: <80% = restrictive, >120% = hyperinflation
  3. Assess RV: elevated suggests air trapping
  4. Calculate RV/TLC ratio: >40% = significant air trapping
  5. Compare FRC methods if available (pleth vs dilution)
  6. Integrate with DLCO for complete picture
  7. Consider clinical context and compare to prior studies

Final Summary

Lung volumes provide essential information beyond spirometry for complete pulmonary function assessment. TLC measurement distinguishes true restriction from pseudo-restriction due to air trapping. The RV/TLC ratio is a key indicator of air trapping in obstructive diseases. Integration with DLCO helps differentiate parenchymal from extra-parenchymal restriction.

Restrictive

TLC <80%

Hyperinflation

TLC >120%

Air Trapping

RV/TLC >40%

Gold Standard

Plethysmography

Additional Resources

  • • ATS/ERS Guidelines for Lung Volume Measurement
  • • Global Lung Initiative (GLI) Reference Equations
  • • American Thoracic Society - thoracic.org
  • • European Respiratory Society - ersnet.org
  • • Pulmonary Function Laboratories Society

Quick Reference Card

  • • 4 Volumes: TV, IRV, ERV, RV
  • • 4 Capacities: TLC, VC, IC, FRC
  • • TLC = TV + IRV + ERV + RV
  • • Restrictive: TLC <80% predicted
  • • Hyperinflation: TLC >120% predicted
  • • Air trapping: RV/TLC >40%
  • • Normal RV/TLC: 20-35%
  • • Gold standard: Body plethysmography

Severity Classification

SeverityTLC % PredictedDescription
Normal80-120%Within normal limits
Mild restriction70-79%Mild reduction
Moderate restriction60-69%Moderate reduction
Moderately severe50-59%Moderately severe
Severe restriction35-49%Severe reduction
Very severe<35%Very severe restriction

Helium Dilution Method

  • • Principle: Closed-circuit rebreathing with helium
  • • Formula: FRC × He(initial) = (FRC + spirometer) × He(final)
  • • Equilibration: Patient breathes until helium equilibrates
  • • Advantage: Simple equipment, well-tolerated
  • • Limitation: Underestimates in severe obstruction (trapped gas)

Nitrogen Washout Method

  • • Principle: Open-circuit breathing 100% O2
  • • Formula: FRC = Total N2 washed out / Alveolar N2 concentration
  • • Endpoint: Exhaled N2 <1.5-2%
  • • Advantage: Can assess ventilation distribution
  • • Limitation: Requires 100% O2, may underestimate in obstruction

Body Plethysmography Technique

  • • Principle: Boyle's Law (P1V1 = P2V2)
  • • Procedure: Panting against closed shutter
  • • Measures: FRC (thoracic gas volume)
  • • Calculation: TLC = FRC + IC; RV = FRC - ERV
  • • Advantage: Measures all intrathoracic gas including trapped
  • • Disadvantage: Equipment cost, claustrophobia

Lung Volumes in ILD Evaluation

  • • Diagnosis: TLC <80% confirms restriction
  • • Severity: TLC % predicted helps grade severity
  • • Progression: Serial TLC decline indicates disease progression
  • • Prognosis: Lower TLC associated with worse outcomes in IPF
  • • Treatment response: TLC stability or improvement with therapy

Pre-operative Lung Volume Assessment

  • • Lung resection: Predicted post-operative TLC/FEV1
  • • High-risk: PPO-FEV1 or PPO-DLCO <30% predicted
  • • Marginal: PPO-FEV1 30-60% - consider CPET
  • • Thoracic surgery: Restrictive patients at higher risk
  • • Non-thoracic surgery: Severe restriction increases risk

Lung Volumes in Transplant Evaluation

  • • Referral criteria: TLC decline >10% over 6 months
  • • IPF: TLC <60-65% may indicate need for transplant evaluation
  • • COPD: Severe hyperinflation with poor quality of life
  • • Donor-recipient matching: Size matching based on TLC
  • • Post-transplant: TLC normalizes in successful transplant

Lung Volumes in Disability Assessment

  • • Social Security: Uses spirometry primarily, but TLC may be relevant
  • • VA disability: FEV1, FVC, and DLCO primarily used
  • • Workers' compensation: May require full PFTs including lung volumes
  • • Impairment rating: TLC reduction contributes to impairment class
  • • Occupational lung disease: Lung volumes help characterize pattern

Clinical Workflow

  1. Perform spirometry (most common first test)
  2. If low VC with normal FEV1/FVC, order lung volumes
  3. If obstruction present, lung volumes assess air trapping
  4. Add DLCO to complete assessment
  5. Compare to prior studies if available
  6. Integrate with clinical picture and imaging
  7. Generate comprehensive interpretation

Final Memory Card

  • • "Low TLC = Restriction" - The defining criterion
  • • "High RV/TLC = Air Trapping" - Key ratio in obstruction
  • • "Pleth > Dilution" - In severe obstruction
  • • "IC limits exercise" - In COPD with hyperinflation
  • • "Position matters" - Supine decreases FRC

Final Clinical Summary

Lung volume measurement is essential for complete pulmonary function assessment. TLC is the gold standard for distinguishing true restriction from pseudo-restriction. The RV/TLC ratio quantifies air trapping in obstructive diseases. Body plethysmography is preferred in obstruction as it measures all thoracic gas. Integration with spirometry and DLCO provides a complete picture of pulmonary function.

Important Safety Note

This calculator provides educational estimates based on entered values. Clinical lung volume measurement requires specialized equipment (body plethysmograph or gas analyzers) and trained personnel. Results should be interpreted by qualified healthcare professionals in the context of the complete clinical picture. Follow ATS/ERS guidelines for standardized measurement and interpretation.

Interpretation Algorithm

Step 1: Is FEV1/FVC reduced?

Yes → Obstruction present

No → Go to Step 2

Step 2: Is TLC reduced (<80% or below LLN)?

Yes → Restriction confirmed

No → Normal or nonspecific

Step 3: If obstruction, is RV/TLC >40%?

Yes → Air trapping present

No → Minimal air trapping

Step 4: If TLC normal but FEV1/FVC low + TLC low?

Mixed ventilatory defect

Reference Equations

  • • GLI-2012: Multi-ethnic spirometry equations (most current)
  • • ECSC 1993: European Community for Steel and Coal
  • • Quanjer 1993: Lung volumes reference values
  • • Crapo 1981: Traditional reference equations
  • • NHANES III: US-based spirometry reference

Ethnicity Considerations

  • • Caucasian: Standard reference values
  • • African: Generally 10-15% lower than Caucasian
  • • Asian: Generally 10-15% lower than Caucasian
  • • Hispanic: Variable, often use Mexican-American equations
  • • GLI-2012: Includes ethnicity-specific adjustments

Altitude Effects on Lung Volumes

  • • Acute exposure: Minimal change in TLC
  • • Acclimatization: FRC and RV may increase slightly
  • • Native highlanders: Larger lung volumes, larger chest
  • • Testing: Standard BTPS corrections apply
  • • Clinical relevance: Consider altitude for reference values

Effects of Smoking on Lung Volumes

  • • Early changes: RV/TLC may increase before TLC elevation
  • • Progressive: RV increases, FRC increases
  • • Emphysema: TLC elevation, RV markedly elevated
  • • Reversibility: Some improvement with cessation
  • • Screening: LDCT for cancer, PFT for COPD

Interpretation Checklist

  • • ☐ Review spirometry (FEV1, FVC, FEV1/FVC)
  • • ☐ Assess TLC (% predicted and vs LLN)
  • • ☐ Calculate RV/TLC ratio
  • • ☐ Compare plethysmography to gas dilution if both available
  • • ☐ Review DLCO if available
  • • ☐ Compare to prior studies
  • • ☐ Correlate with clinical presentation
  • • ☐ Consider imaging findings
  • • ☐ Generate comprehensive interpretation

Summary Reference Table

  • • TV: ~500 mL (normal breath)
  • • IRV: ~2500-3000 mL (extra inhale)
  • • ERV: ~1000-1200 mL (extra exhale)
  • • RV: ~1200 mL (air remaining)
  • • TLC: ~6000 mL (TV + IRV + ERV + RV)
  • • VC: ~4600 mL (TV + IRV + ERV)
  • • IC: ~3500 mL (TV + IRV)
  • • FRC: ~2300 mL (ERV + RV)
  • • Normal RV/TLC: 20-35%

Clinical Decision Points

Order Lung Volumes When:

  • • Low VC with normal FEV1/FVC
  • • Suspected mixed defect
  • • Assessing air trapping in COPD
  • • Pre-operative assessment
  • • ILD evaluation and monitoring

Key Thresholds:

  • • TLC <80%: Restriction
  • • TLC >120%: Hyperinflation
  • • RV/TLC >40%: Air trapping
  • • Pleth-Dilution >0.5L: Trapped gas
  • • IC/TLC <25%: Severe IC limitation

Final Disclaimer

This educational calculator provides estimates based on user-entered lung volume data. Actual clinical assessment requires proper pulmonary function testing with calibrated equipment and trained technicians. Interpretation should be performed by qualified healthcare professionals considering the complete clinical context including symptoms, imaging, and laboratory findings. Follow ATS/ERS guidelines for standardized testing and interpretation.

Quick Reference Values

  • • Normal TLC: 80-120% predicted
  • • Restrictive: TLC <80% or below LLN
  • • Hyperinflation: TLC >120%
  • • Air trapping: RV/TLC >40%
  • • Normal RV/TLC: 20-35%
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