Physiology of Diving

Abstract

The significant subdivisions of lung or respiratory system volume are functional residual capacity, residual volume, and total lung capacity; these are shown in figure III-1. Functional residual capacity (FRC) is the volume of gas in the respiratory system at the end of a normal expiration. Residual volume (RV) is the gas volume in the system at maximal expiration, and total lung capacity (TLC) is the gas volume at maximal inspiration. Vital capacity (VC), the maximum amount of gas an individual can move, is the difference between TLC and RV. The determinants of these subdivisions of lung volume are shown for a young man in figure III-2, which plots the passive pressure-volume characteristics of the lung, the chest wall, and the total respiratory system.