EFFICIENCY OF BREATHING SYSTEM-A AND VITAMIN-D IN THE CARDEN-VENTMASTA VENTILATOR

We have compared the efficiency of the enclosed Magill attachment (Sys tem A) and the co-axial System D (Bain) in the Carden Ventmasta ventil ator using both systems, each under five different ventilatory conditi ons, in each of five anaesthetized patients. Efficiency was assessed i n terms of the effective alveolar ventilation as a fraction of the fre sh gas flow. For System A, efficiency increased from a mean of 0.37 wh en the total ventilation was only 50% of the fresh gas flow, to a mean of 0.74 when ventilation was 2.3 times the fresh gas flow. The effici ency was substantially and significantly less with System D: 75% of th at for System A at the smaller total ventilation (95% CI 65-85%) and 6 5% at the larger (95% CI 59-71%). A critical examination is made of co nflicting definitions and terminology of the efficiency of breathing s ystems.