THE EFFECTS OF INHALATION OF HELIUM MIXED WITH OXYGEN ON THE MECHANICS OF RESPIRATION 1

Abstract

Experiments were conducted on normal human subjects and on dogs to determine the effect of He mixed with O on certain types of dyspnea. When normal individuals breathed through a constricted orifice, such as 3/32 of an inch, respiration slowed in rate and increased in tidal vol. The air pressure in the trachea or in a tubal extension of the pulmonary airway was markedly increased. If 100% O was substituted for air, no distinct changes were observed either in the physical measurements or in the sensation of air-hunger. When, however a mixture of 80% He and 20% O was inhaled, the pressure in the pulmonary airway was lowered approximately 50%, the respiratory rate was increased toward the normal, and the tidal volume was generally decreased. The sensation of dyspnea was partially relieved. When normal subjects were made to breathe violently, with markedly increased tidal volumes, increased pressures were present in the pulmonary airway, which were reduced between 30-50% by the inhalation of 20% O and 80% He. In dogs subjected to breathing through narrowed orifices for 3-6 hrs., the influence of He-0 mixtures was compared to that of air and of 100% O. The inhalation of 20% O and 80% He was followed by significant decreases in the intrapleural, intra-abdominal and intratracheal pressures. During the later stages of the expt., the dogs developed marked congestion and edema of the lungs incident to the maintenance of high neg. intrapleural pressures. Inhalation of He 80% and O 20% in some instances resulted in both a reduction in intrapleural pressure and an increase in tidal volume. Inhalation of 100% O under these circumstances improved the condition of the animal by slowing the respiratory and cardiac rates. A mixture of 30 to 35% O with 65 to 70% He seemed to be of greater benefit than other combinations. In summary, He decreased the effort of the respiratory musculature and, as a physical function, lowered intrapleural pressure. O administered in increased concentrations decreased the pulmonary ventilation, and, as a chemical factor, lessened the work of respiration. The presence of N was detrimental in that it was useful neither physically nor chemically. The application of these findings to clinical conditions, chiefly asthma and obstructive lesions in the trachea and larynx, as well as their more general bearing on the concept of dyspnea, was discussed.