Principles of anaesthetic vaporizers

Vaporizers are an integral part of modern-day anaesthesia, allowing the delivery of safe concentrations of volatile anaesthetic agent. Over time, vaporizer design has improved to be closer to the ideal. Today, vaporizers can be classified as ‘variable bypass’, where a portion of the fresh gas flow passes through the vaporizing chamber, or ‘measured flow’, where the flow of volatile agent is separately measured as it passes under pressure into the fresh gas flow. Understanding the operation of vaporizers, and the basic principles and designs behind this, is important to enable correct usage, handling and maintenance of vaporizers in everyday anaesthesia.