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A coaxial circle circuit: Comparison with conventional circle and bain circuit

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Abstract

A coaxial system to be used for gas delivery to patients in a closed or low fresh gas flow anaesthetic system is described. The resistance to gas flow, humidity of inspired gases, and static compliance of the circuit are provided and compared with the circle tubing customarily employed or the coaxial Mapleson D (“Bain”) circuit, The resistance to gas flow is highest in the coaxial circle and “Bain” circuits; the resistance of the conventional circle is approximately 40 per cent less. Static compliance of this coaxial circle is 50 per cent greater than the conventional circle. During artificial ventilation humidity of inspired gases is maintained at levels recommended in the literature for all circuits, but during spontaneous breathing only the conventional rubber circle maintains appropriate levels. Advantages of this coaxial circle over the conventional circle include light weight and small size. Advantages of this coaxial circle over the “Bain” circuit include lower fresh gas flows and improved humidity during spontaneous breathing. These advantages make this coaxial circle useful for routine use.

Résumé

On décrit un système coaxial destiné à l’administration de gaz en circuit fermé ou à bas débit de gaz frais. La résistance à l’écoulement des gaz, l’humidité des gaz inspirés et la compliance statique du circuit ont été déterminées et sont comparées avec les tuyaux ordinairement utilisés ou le circuit coaxial de type Mapleson D ("Bain"). La résistance à l’écoulement des gaz est la plus grande dans le circuit coaxial étudié et le circuit Bain; la résistance du circuit circulaire conventionnel est de 40 pour cent moindre. La compliance statique de ce circuit coaxial est de 50 pour cent plus élevée qu’avec le circuit conventionnel. Pendant l’anesthésie, l’humidité des gaz inspiratoires est maintenue au niveau recommandé dans la littérature par tous les circuits en respiration contrôlée; en respiration spontanée, seul le circuit circulaire conventionnel en caoutchouc est adéquat. Les avantages du circuit coaxial étudié comprennent son faible poids et son volume réduit; ses avantages sur le circuit Bain consistent en des besoins moindres en gaz frais et une amélioration de l’humidification en respiration spontanée. Ces avantages en font un circuit utile pour usage courant.

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Correspondence to John Shandro.

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Shandro, J. A coaxial circle circuit: Comparison with conventional circle and bain circuit. Canad. Anaesth. Soc. J. 29, 121–125 (1982). https://doi.org/10.1007/BF03007989

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Key Words

  • Equipment
  • coaxial circle circuit
  • resistance
  • compliance
  • humidification