Two inhalation induction techniques are practised:

• Tidal volume breathing
• Vital capacity breath

They both use either oxygen/volatile agent or oxygen/nitrous oxide/volatile agent mixture. Nitrous oxide may speed induction through the second gas effect.

Question: What is the second gas effect of nitrous oxide?

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Two inhalation induction techniques are practised:

• Tidal volume breathing
• Vital capacity breath

They both use either oxygen/volatile agent or oxygen/nitrous oxide/volatile agent mixture. Nitrous oxide may speed induction through the second gas effect.

Question: What is the second gas effect of nitrous oxide?

Answer: Nitrous oxide is rapidly absorbed from the alveoli when it is administered in a high concentration (e.g. 60 % with oxygen). If it is co-administered with a volatile agent, e.g. sevoflurane, the rapid absorption of nitrous oxide will result in an increased alveolar concentration of the volatile agent (the concentration effect). This will result in a more rapid onset of the volatile agent which is known as the second gas effect. Note that the terms second gas effect and concentration effect are closely related.