Abstract
In establishing a complete mixture of air within the lungs with other air several factors come into play. Some of these factors play a minor role and may be varied within rather wide limits before any appreciable influence on the results is observed. Others are of more importance, but their variations can be kept within narrow limits and therefore neglected. There are, however, three factors, which mainly govern the procedure of mixing: first, the number of times rebreathing takes place; second, the depth of the respirations; and third, the amount of air left in the lungs after expiration, that is, the amount of air which can be mixed through diffusion only. The methods where mixture is used, or the subjects on whom these methods are applied, often prevent us from choosing the magnitude of these which would be most suitable for obtaining a complete mixture. In a series of experiments, an example of which are reported in this paper, we have investigated the quantitative influence of variations in these three factors.
Technique. All our experiments are performed on two normal, well trained subjects. We have, for the sake of convenience, exclusively used hydrogen plus oxygen, but earlier experience makes it highly probable that the results can be extended to oxygen, to carbon monoxide, and to nitrous oxide.
A certain varying amount of hydrogen plus oxygen was introduced into a bag or into a Krogh spirometer. The subject started to inspire with a known amount of air left in his lungs. The minimum amount of air left within the lungs was of course the residual air. By starting from different points a known fraction of the reserve air or even of the complimentary air could be added to the residual air.
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