Compliance of lung is measured by

The extent to which the lungs will expand for each unit increase in transpulmonary pressure is called the lung compliance. The total compliance of both lungs together in the normal adult human being averages about 200 milliliters of air per centimeter of w ater transpulmonary pressure. That is, every time the transpulmonary' pressure increases 1 centimeter of water, the lung volume, after 10 to 20 seconds, will expand 200 milliliters. The characteristics of the compliance diagram are determined by the elastic forces of the lungs. These can be divided into twro parts: (I) elastic forces of the lung tissue and (2) elastic forces caused by surface tension of the fluid that lines the inside walls of the alveoli and other lung air spaces, The elastic forces of the lung tissue are determined mainly by elastin and collagen fibers