THE IMPORTANCE OF THE EXPIRATORY PAUSE - COMPARISON OF THE MAPLESON-A, MAPLESON-C AND MAPLESON-D BREATHING SYSTEMS USING A LUNG MODEL

A physical lung model simulating spontaneous respiration was used to i nvestigate the influence of the respiratory pattern on the efficiency of the Mapleson A, C and D breathing systems. It is shown that the Map leson A system is always the most efficient breathing system and that its performance is relatively independent of the respiratory pattern. When the expiratory pause is minimal, the Mapleson C system is almost as efficient as the Mapleson A, but becomes ever less efficient as the expiratory pause increases. The Mapleson D system is very inefficient when the expiratory pause is short. With a longer expiratory pause, t his system's efficiency approaches that of the Mapleson A. The experim ental results are compared with predictions generated by a mathematica l model. There is good agreement between the two, validating the mathe matics used.