Partitional respirometry in cardio-pulmonary disease.

Respiratory disorders can now be classified by the average laboratory as primary defects of respiratory mechanics or of gas uptake, and the verdict is accepted with reasonable confidence. However, further classification of disordered gas uptake is still a tedious and uncertain business. The aim of partitional respirometry is to meet this challenge, distinguishing three basic components of the gas uptake process (effective dead space, diffusing capacity, and pulmonary perfusion). Inconvenience to the patient is minimal, since all that is required is the breathing of a composite gas mixture containing very low concentrations (300 p.p.m.) of ether, carbon monoxide, and acetylene. The uptake of each gas is determined by infra-red analysis. Ether uptake is dependent mainly on ventilation and slightly on perfusion, carbon monoxide uptake on ventilation and diffusion, and acetylene uptake on perfusion and ventilation. A series of simultaneous equations with terms in ventilation, diffusion, and perfusion are obtained, and it is then a simple matter to partition the gas uptake process into these three independent components. The technique was originally introduced by Hatch and Cook (1955), and some data relating to mine-workers were briefly reported at that time. More recently, simultaneous analysis of the three gases and other refinements have considerably increased the precision of the method, and multiple regression analyses which permit the prediction of normal values have been completed (Shephard, 1958). The main object of the present paper is to evaluate the usefulness of partitional respirometry in a variety of patients studied in some detail by conventional clinical and physiological methods.