Define normal lung volumes and lung capacities. Give normal values for an average adult male.
Answer:
There are four basic 'volumes' and four derived 'capacities' that are combinations of these volumes (Fig. 1.1).
VT is the volume of air inhaled or exhaled during normal breathing. Normal VT is 500 mL or approximately 6 to 8 mL per kg.
Inspiratory reserve volume (IRV) is the maximum volume of gas that can be inhaled following a normal inspiration while at rest. Normal IRV is 2,500 to 3,500 mL.
ERV is the maximum volume of gas that can be exhaled after a normal expiration. Normal ERV is 1,200 mL.
RV is the volume of gas remaining in the lungs after a forced exhalation. Normal RV is 1,200 mL.
VC is the maximum amount of gas that can be exhaled after a maximum inhalation. VC is the sum of VT, ERV, and IRV. Normal VC is 4,500 mL or approximately 60 to 70 mL per kg.
Inspiratory capacity (IC) is the maximum amount of gas that can be inhaled from the resting expiratory position after a normal exhalation. It is the sum of VT and IRV. Normal IC is 3,500 mL.
FRC is the remaining lung volume at the end of a normal quiet expiration. It is the sum of RV and ERV. Normal FRC is 2,500 mL or 30 to 40 mL per kg.
TLC is the lung volume at the end of a maximum inspiration. It is the sum of VC and RV. Normal TLC is 5,000 to 6,000 mL for an adult man and 4,000 to 5,000 mL for an adult woman.
Reference(s):
- Barash PG, Cullen BF, Stoelting RK, et al, eds. Clinical Anesthesia. 8th ed. Philadelphia, PA: Wolters Kluwer; 2017:361-383, 1710.
- Jameson JL, Fauci AS, Kasper DL, et al, eds. Harrison’s Principles of Internal Medicine. 20th ed. New York: McGraw-Hill; 2018:1945-1950.
- Lumb AB. Nunn’s Applied Respiratory Physiology. 8th ed. Philadelphia, PA: Elsevier; 2017:26-29.