Relationship Between Compliance and FRC of the Lungs in Cats, and Measurement of Resistance to Breathing

Abstract

In anesthetized, tracheotomized cats, the compliance of the lungs and lung-thorax system varied between 3.6 and 10 ml/cm, water. The lung vol. was 65[image] 110 ml. There was a linear correlation between the compliance and the lung vol.. The vol. elasticity of the distensible part of the lung-thorax was approx. 0.1 ml./cm. water for 1 ml. lung vol.. It is important to measure the Functional Residual Capacity (FRC) in communication with the ambient atmosphere when measurements of lung compliance are made. The resistance of the lung-thorax system at flows below 20 ml./sec. was 0.01[image] 0.03 cm. water/ml./sec. The resistance of spontaneously breathing cats was more than 50% higher than during artificial ventilation with positive pressures. During artificial ventilation, the resistance increased in proportion to the flow at higher flows. The proportionality constant varied inversely to the inflation pressure between 0.00007 and 0.0005 cm. water/(ml. sec.)2._.