The purpose of a vaporiser is to add anaesthetic vapor into the fresh gas flow in a way that the output of the vaporiser delivers the set concentration of anaesthetic agent accurately.
Fresh gas enters the inlet of the vaporiser and is divided into two flow pathways. The splitting valve, depending on the setting of the control dial, adjusts how much goes through each of the pathways. The fresh gas that is sent along the "by pass" pathway doesn't get into contact with any vapor. On the other hand, the fresh gas that is sent to the vaporising chamber becomes fully saturated with vapor. At the exit end of the vaporiser, the by pass gas (vaporless) meets the chamber gas (fully saturated with vapor) and the two mix. The resultant output depends on how much of fresh gas went though each of the pathways.
The image below shows you that if you dial a high anaesthetic concentration requirement, the splitting valve sends more fresh gas via the vaporising chamber and less through the by pass pathway.
Similarly, the image below shows you that if you dial a low anaesthetic concentration requirement, the splitting valve sends less fresh gas via the vaporising chamber and more through the by pass pathway.
Click on button to learn about splitting ratios
The image below shows that if you set the dial to zero to make vaporiser deliver no anaesthetic vapor, the splitting valve sends all the fresh gas via the by pass pathway and nothing through the vaporising chamber.
The basic vaporiser discussed above has a very simple design. Unfortunately, this simple design has some problems and these will be explained in more detail in later sections.
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