Control of Carbon Dioxide in Modified Mapleson A and D (Hafnia) Anaesthetic Systems. An Experimental Model |
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| Authors: | P. K. Andersen M.D. |
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| Affiliation: | Department of Anaesthesia, Odense University Hospital, Odense, Denmark |
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| Abstract: | The effects of varying ventilations (Ve) and fresh gas flows (FGF) on end-expiratory CO2 (F eco 2) levels were investigated in an experimental model lung, employing the Hafnia modification of the Mapleson A and D anaesthetic systems during CO2-absorption and CO2-wash-out (rebreathing). Identical results were found in both systems: F eco 2 was constant and independent of FGF with CO2-absorption and constant Ve, whereas rebreathing resulted in increasing F eco 2 levels as FGF was decreased. As control of F eco 2 in the rebreathing systems by regulating FGF could only take place within F eco 2 levels higher than that determined by Ve at complete CO2-absorption, e. g. for the Hafnia A and D rebreathing systems, control of FGF necessitates relative hyperventilation. F eco 2 with constant FGF decreased with increasing Ve during CO2-absorption, as well as during rebreathing, although this decrease was less in the rebreathing systems. Thus a decrease in F eco 2 with rising Ve can be avoided and hypocapnia prevented. The results agree with those obtained in clinical studies. |
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