Lung Capacity Calculator

Calculate predicted lung volumes and capacities based on age, height, gender, and ethnicity using standardized prediction equations.

Personal Information

years

For ethnicity-specific corrections

About Lung Volumes

TLC: Total lung capacity - maximum air lungs can hold

FVC: Forced vital capacity - maximum air exhaled forcefully

FEV1: Volume exhaled in first second of forced breath

RV: Residual volume - air remaining after maximal exhalation

Normal Ranges

FEV1/FVC Ratio:

Normal: >70% (>0.70)

Obstruction: <70%

RV/TLC Ratio:

Normal: 20-35%

Hyperinflation: >35%

Important Note

These are predicted values based on population norms. Actual lung function should be measured via spirometry. Consult a healthcare professional for proper diagnosis.

Understanding Lung Volumes

Lung volumes and capacities are key measurements of respiratory function used to diagnose and monitor lung diseases.

Key Volumes:

  • TLC: Total volume of air in lungs after maximal inspiration
  • VC: Maximum volume that can be exhaled after maximal inspiration
  • RV: Volume remaining in lungs after maximal exhalation
  • FRC: Volume in lungs at end of normal exhalation
  • IC: Maximum volume that can be inhaled from resting level

Clinical Significance

Abnormal lung volumes can indicate various respiratory conditions:

  • Reduced FEV1/FVC (<70%): Obstructive diseases (COPD, asthma)
  • Reduced TLC and VC: Restrictive diseases (fibrosis, obesity)
  • Increased RV/TLC: Air trapping (emphysema)
  • Reduced FVC with normal ratio: Restrictive pattern
  • Normal predicted values: Vary by age, height, gender, ethnicity

Spirometry Patterns

Normal Pattern:

  • FEV1/FVC > 70%
  • FVC > 80% predicted
  • FEV1 > 80% predicted
  • TLC within normal range

Obstructive Pattern:

  • FEV1/FVC < 70%
  • Reduced FEV1
  • Normal or increased TLC
  • Increased RV/TLC ratio
  • Examples: COPD, asthma

Restrictive Pattern:

  • FEV1/FVC normal or high
  • Reduced TLC (<80%)
  • Reduced FVC
  • Proportionally reduced FEV1
  • Examples: Fibrosis, obesity

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