EXPERIMENTS DEMONSTRATING THE UPTAKE, DISTRIBUTION AND ELIMINATION OF NITROUS OXIDE IN THE CONTEXT OF OUT-PATIENT ANAESTHESIA : PART I: REBREATHING EXPERIMENTS

Abstract

SUMMARY A series of experiments is described which was designed to illustrate the fundamentals of the uptake, distribution and elimination of nitrous oxide in the context of out-patient anaesthesia. The experiments are grouped under three main headings: (1) Rebreathing experiments (Part I); (2) Non-rebreathing experiments (Part II); and (3) Experiments using the jerkin plethysmograph (Part II). More emphasis is placed upon the practical demonstration of the essential features of the subject than upon precision in measurement, but a comparison with a previous study of the uptake of nitrous oxide using pneumotachography is made (see Part II). The experiments indicate the influence of inspired gas mixture, pulmonary ventilation and cardiac output, upon the alveolar tension and the uptake of nitrous oxide: but they hint that there is more to the induction of anaesthesia than the uptake of anaesthetic and the rise in its arterial tension, and the contributions of cerebral perfusion and narcotic threshold are mentioned. They indicate a potential hazard of respiratory obstruction. They also demonstrate how redistribution of nitrous oxide may speed immediate recovery, yet delay elimination; and how elimination is also dependent upon total uptake.