1.1 ,For the purpose of this standard, a pressure regulator, also called a pressure-reducing valve, is a device intended for medical or emergency purposes that is used to convert a medical or emergency gas pressure from a high, variable pressure to a lower, more constant working pressure [21 CFR 868.2700 (a)]. Some of these oxygen pressure regulators are a combination of a pressure regulator and cylinder valve. These devices are often referred to as valve integrated pressure regulators, or VIPRs.