What type of gas is commonly used in combination with oxygen for anesthesia?

Nitrous oxide is commonly used in combination with oxygen for anesthesia due to its anesthetic properties and analgesic effects. It is a colorless and non-flammable gas that acts quickly to induce sedation and pain relief. When administered with oxygen, it enhances the effectiveness of anesthetics, allowing for lower doses of other anesthetic agents while still achieving a desirable level of sedation and analgesia. This combination is particularly useful in various medical and dental procedures because it provides rapid onset and recovery, which is important in maintaining patient safety and comfort.

In contrast, carbon dioxide is not used for anesthesia; instead, it is a byproduct of respiration and plays a role in maintaining acid-base balance in the body. Helium, while useful in certain medical treatments (such as in respiratory therapy), does not provide the necessary anesthetic effects and is not commonly used in anesthesia protocols. The phrase "airtight gas" is not a recognized category of medical gases and does not refer to any specific gas used in conjunction with oxygen for anesthesia. Therefore, nitrous oxide stands out as the most effective and widely utilized gas in this context.