Which gas is generally considered safe for medical use but must be carefully controlled in terms of pressure and temperature?

Oxygen is well-regarded for its essential role in medical applications, primarily for its use in respiratory therapies and surgical procedures. However, it requires careful management regarding pressure and temperature because of its highly reactive nature, especially when under pressure in storage cylinders or when used in high concentrations.

At elevated pressures, oxygen can support combustion, which poses risks in environments where there are flammable materials. Additionally, fluctuations in temperature can affect the stability of oxygen systems. It's vital to ensure that oxygen is stored in controlled environments that regulate both pressure and temperature to maintain safety and efficacy.

The other gases listed may have medical applications, but they do not share the same safety considerations associated with oxygen. For example, while nitric oxide is used in specific therapeutic settings, it is more related to managing pulmonary hypertension and has additional complications regarding toxicity and handling requirements. Helium is primarily used in certain diagnostic and therapeutic procedures but does not carry the same risks as oxygen. Carbon dioxide is utilized for insufflation in surgeries but is not subject to the same pressures and temperature controls as oxygen. Thus, the emphasis on oxygen safety underscores its critical importance in medical settings.