Question: What are the key components of a draw-over system?

Answer: The key components are shown in Fig 1.

It is essential to assemble the components of the draw-over apparatus in the correct order for safe patient care.

Dilution of inspired volatile will occur if oxygen is added downstream of the vaporizer.

The non-rebreathing patient inflating valve, e.g. Laerdal or Ambu valve, is unique to draw-over anaesthesia. It automatically allows inspiration during spontaneous breathing or lung inflation during IPPV, prevents rebreathing and prevents air from being drawn in via the exit port during spontaneous breathing.

Dangerously high concentrations of volatile agent are delivered if the SIB/bellows is upstream of the vaporizer, i.e. 'push-over'.