Basic Lung Volumes
| Volume | Full Name | Definition | Value (mL) | Measurable by Spirometer? |
|---|---|---|---|---|
| TV | Tidal Volume | Air moved in a normal breath | ~500 | Yes |
| IRV | Inspiratory Reserve Volume | Extra air forcibly inhaled beyond TV | 2500–3000 | Yes |
| ERV | Expiratory Reserve Volume | Extra air forcibly exhaled beyond normal expiration | 1000–1100 | Yes |
| RV | Residual Volume | Air remaining after maximum forced expiration | 1100–1200 | NO |
Derived Lung Capacities
| Capacity | Formula | Value (mL) | Key Fact |
|---|---|---|---|
| Inspiratory Capacity (IC) | TV + IRV | ~3000–3500 | Max air inspired from FRC position |
| Expiratory Capacity (EC) | TV + ERV | ~1500–1600 | Max air expired from end-inspiration |
| Functional Residual Capacity (FRC) | ERV + RV | ~2100–2300 | Air left after NORMAL expiration |
| Vital Capacity (VC) | TV + IRV + ERV | ~3500–4600 | Max voluntary air movement; excludes RV |
| Total Lung Capacity (TLC) | VC + RV | ~5000–6000 | ALL air in lungs after deepest inspiration |
NEET Trap Comparison
| "Air remaining after..." | Volume/Capacity | Formula |
|---|---|---|
| Maximum FORCED expiration | Residual Volume (RV) | — |
| Normal QUIET expiration | Functional Residual Capacity (FRC) | ERV + RV |
| Deepest inspiration (everything that can be exhaled) | Vital Capacity (VC) | TV + IRV + ERV |
| Deepest inspiration (total air in lungs) | Total Lung Capacity (TLC) | VC + RV |