REBREATHING IN THE MAPLESON-A, MAPLESON-C AND MAPLESON-D BREATHING SYSTEMS WITH SINUSOIDAL AND EXPONENTIAL FLOW WAVE-FORMS

The degree of rebreathing in Mapleson A, C and D breathing systems for sinusoidal and exponential flow waveforms is analysed mathematically. The effects of altering the I:E ratio and of introducing an expirator y pause are investigated. The results for sinusoidal waveform closely resemble those for a square wave. Exponential flow waveforms produce r esults similar to triangular flow waveforms. The Mapleson A system is always the most efficient. The Mapleson C system is efficient when the I:E ratio is 1:1, becoming less efficient with longer expiration and very inefficient with an expiratory pause. The Mapleson D system becom es efficient when the expiratory pause is long.