ANALYSIS OF RESPIRATORY GASES

A simple and rapid method of analyzing respired air for carbon dioxide and oxygen is still needed in medicine. In investigations on the expenditure of energy in muscular exercise, many samples of expired gas must be analyzed daily. The number of such analyses has been further increased by the widespread adoption of routine clinical determinations of metabolic rates involving the respiratory exchange. An improvement in the technic of obtaining such data might also be applied to studies of the composition of alveolar air and possibly to the estimation of lung volumes. Accordingly it has seemed worth while to apply to the requirements of the medical profession the method of gas analysis by thermal conductivity which has proved of value along different lines to chemists and engineers. Although gas analysis by thermal conductivity was shown to be feasible as early as about 1880, it was not developed in medicine, until recently and then only for the determination of carbon dioxide. In 1922, A. V. Hill (1) reported in the Proceedings of the Physiological Society the possibilities of the "katharometer " for the rapid determination of carbon dioxide in expired air. In 1926 Rabinowitch and Bazin (2) gave a more detailed account of this apparatus as produced by the Cambridge Instrument Company, and described its application for obtaining basal metabolic rates. They used a "katharometer" in conjunction with a gas meter, getting in that way the data from which they calculated the metabolic rate by the method previously described by King (3). A similar apparatus, manufactured b