What is a critical requirement for the use of inhalation general anaesthesia?

The requirement that oxygen must not be less than 30% is critical in the context of inhalation general anesthesia because maintaining adequate oxygen levels is essential for the safety and well-being of the patient during the procedure. Oxygen is necessary to prevent hypoxia, a condition where the body or a region of the body is deprived of adequate oxygen supply. Inhalation anesthetics, when used in combination with a mixture of other gases, can lead to reduced oxygen levels; therefore, ensuring that the oxygen concentration remains at least 30% helps to support the physiological needs of the patient while minimizing the risk of serious complications that could arise from low oxygen saturation.

Other considerations related to anesthesia practice, such as the concentration of halothane or the order of administering nitrous oxide, are important but do not encompass the fundamental requirement of ensuring sufficient oxygen levels. The duration of inhalation anesthesia being limited to 20 minutes is not a universal rule, as some surgical procedures may necessitate longer periods of anesthesia, provided that proper monitoring and techniques are employed to ensure patient safety.