A new method of measuring the impedance of the human respiratory system at moderate frequencies

Abstract

The stability of aircrew breathing equipment depends not only on the stability of the oxygen regulator, but also on the impedance of the system it feeds, which includes the user's respiratory system. A method of measuring the human respiratory impedance, in the range 5-90 c/s, by comparing oscillating pressures at two points in an external reference system, is described; and results are given for nose and mouth, heavy and light, breathing. The effect of altitude, and of increased external resistance to breathing are briefly discussed. The importance of correct representation of man's impedance in dynamic testing of oxygen equipment is illustrated by reference to the characteristics of a present-day simulator and system, and an improved type of simulator is suggested.