The mnemonic
Vital Capacity = IRV + TV + ERV
What each word stands for
- IRVInspiratory reserve volume
- TVTidal volume
- ERVExpiratory reserve volume
Why it matters clinically
Vital capacity falls in restrictive disease and neuromuscular weakness.
Where it stops being reliable
Residual volume is excluded, so it cannot give FRC or TLC.
Teaching aid, still awaiting independent review. Confirm facts in a standard source.