oxygen therapy

This term is a technical medical designation used primarily in clinical settings, such as hospitals or home-care environments. It carries a neutral, professional tone and describes a specific therapeutic intervention rather than a general state of breathing.

Because it refers to a specific medical protocol, it is treated as an uncountable noun. One does not refer to "an oxygen therapy" or "oxygen therapies" in standard medical discourse; instead, practitioners refer to the administration of the therapy or a course of therapy.