Distinguish between (a) IRV and ERV (b) Inspiratory capacity and Expiratory capacity. (c) Vital capacity and Total lung capacity.

Inspiratory reserve volume (IRV) vs expiratory reserve volume (ERV)

IRV is the extra air you can forcefully inhale after a normal resting inhalation. Typical value ≈ 1900–3300 mL in healthy adults

ERV is the additional air you can forcefully exhale after a normal resting exhalation. Normal value ≈ 700–1200 mL

Inspiratory capacity (IC) vs expiratory capacity (EC)

IC is the maximum air you can inhale starting from the end of a normal exhalation; calculated as IC = TV + IRV. Typical adult IC ≈ 3000–3800 mL

EC (not commonly used) refers to the air you can exhale starting from the end of a normal inhalation; calculated as EC = TV + ERV. Reflects maximal expiratory volume post-inhalation

Vital capacity (VC) vs total lung capacity (TLC)

VC is the total air exhaled after maximal inhalation; sum of IRV + TV + ERV. Normal adult VC ≈ 4800 mL

TLC is the maximum air the lungs can hold after full inhalation; sum of VC + residual volume (RV). Typical adult TLC ≈ 6000 mL