All of the following are used to maintain proper oxygen flow to the patient except:

Placement of nitrogen flowmeter downstream of the oxygen flowmeter "Oxygen is last gas to be added for safety in event of leak from top of rotainotor, so most downstream." The systems used to prevent hypoxia:- Low oxygen pressure alarm It detects oxygen supply failure at the common gas inlet that activates a gas whistle or electric alarm Minimum oxygen/nitrous oxide Prevent delivery of less than 21% oxygen ratio controller device (hypoxic guard) Oxygen must enter the common Prevent hypoxia in event of proximal gas leak. manifold down-stream to other gases Oxygen concentration monitor and Prevents administration of hypoxic gas mixtures in alarm event of a low pressure system leak; precisely regulate oxygen concentration Pin index safety system for cylinders prevents incorrect cylinder attachments. It is a safeguard introduced to eliminate cylinder interchanging and the possibility of accidently placing the incorrect gas on a yoke designed to accomodate another gas.