What are the two common N₂O:O₂ mixtures?

The correct answer is based on the recognition that Entonox® and Nitronox® are recognized mixtures of nitrous oxide (N₂O) and oxygen (O₂) that are commonly used in medical settings, particularly for analgesia and sedation.

Entonox® is a well-known gas mixture of 50% nitrous oxide and 50% oxygen, often used in emergency medicine and labor to provide pain relief. The combination allows patients to achieve sedation while maintaining adequate oxygenation.

Similarly, Nitronox® is another formulation offering a similar mixture, often available for patients requiring fast-acting analgesia.

Both of these mixtures leverage the properties of nitrous oxide as an anesthetic and analgesic agent while using oxygen to ensure patient safety and reduce the risk of hypoxia.

The other options listed do not represent standard mixtures of nitrous oxide and oxygen used in clinical practice. Heliox® is a combination of helium and oxygen, while Carbogen® is a mix of carbon dioxide and oxygen. The inclusion of substances like nitrogen and carbon dioxide alongside oxygen does not pertain to the common medical applications of nitrous oxide and oxygen mixtures.