Respiratory Physiology for UPSC CMS: Lung Volumes, Compliance and Gas Exchange

Lung Volumes#

Tidal volume (TV): 500 mL. Inspiratory reserve volume (IRV): 3000 mL. Expiratory reserve volume (ERV): 1200 mL. Residual volume (RV): 1200 mL.

Lung capacities: VC = TV + IRV + ERV = 4600. FRC = ERV + RV = 2400.

Compliance#

= Change in volume / Change in pressure. Normal: 200 mL/cmH2O.
Emphysema: compliance increased (floppy lungs).
Fibrosis: compliance decreased (stiff lungs).

O2 Dissociation Curve#

Right shift: increased PCO2, increased H+, increased temperature, increased 2,3-DPG. Left shift: opposite.