Use of Helium as a New Therapeutic Gas

With an atomic weight of 4 and a density of 0.138, helium is the lightest of all the gases except hydrogen. The explosive possibilities of the latter render it too dangerous for clinical use. When helium is substituted for nitrogen in the air, the specific gravity of the mixture (21% oxygen and 79% helium) is 0.341, as compared to that of air. 1. The helium-oxygen mixture is 66% lighter. Since work is in general proportional to the density, the pressure required to move helium-oxygen mixtures in and out of the lung should be decidedly less than nitrogen-oxygen mixtures.

An “artificial lung” was constructed by using a spirometer in which the bell was moved up by a motor running at constant speed and pressure, and lowered by constant weights. The spirometer “breather” (was filled by) different mixtures of gases from a Douglas bag or from another spirometer. The volume of air entering and leaving the spirometer (the tidal air) was graphically recorded on a kymographic drum. The pressure of the air within the spirometer, corresponding to a theoretical intra-pulmonary pressure, was obtained by making a leak-tight connection into the spirometer bell and connecting it to a water manometer, which then recorded the lifting or inspiratory pressure and the compressing or expiratory pressure. When the helium-oxygen mixture was “respired”, the tidal air was increased from 23% to 50%, with a reduction in pressure of from 2% to 21%.

The effect on patients with compensated heart disease of breathing through a slightly narrowed orifice was measured. The inspiratory and expiratory pressures in the pulmonary air-ways were obtained by connecting a water manometer to the tube which came from the patient's mouth. They were then graphically recorded.