An evaluation of the Samson and Magill (Mapleson A) circuits during anaesthesia

The valveless scavenging circuit of Samson was compared with a standard Magill (Mapleson A) circuit. Replacement of the scavenging unit of the Samson circuit by the Heidbrink valve of the Magill circuit at a given fresh gas flow rate allowed each patient to act as his own control. The minimum and maximum carbon dioxide levels were estimated at varying fresh gas flows related to the body weight of the patient. The carbon dioxide elimination of the two circuits showed no statistical difference and it is concluded that the Samson circuit requires fresh gas flows similar to the Magill circuit. The Samson circuit scavenged adequately during spontaneous breathing, manual ventilation and even when using the emergency oxygen bypass.