There are two types of nitrous oxide-oxygen delivery systems: portable tanks on yoke stands that can be wheeled between operatories and larger, fixed-tank systems that are connected with a manifold system that can serve several operatories.2 Nitrous oxide-oxygen delivery systems are typically limited to a maximum of 70% nitrous oxide and 30% oxygen delivery; this helps ensure that the patient is receiving at least 9% more oxygen than is found in ambient room air.2
Although there is an inherent safety margin for administration of nitrous oxide-oxygen sedation, there are at least 12 delivery system audio and visual safety features that have been developed to help avoid adverse events during administration (Table).2 Practitioners should know how to maintain these features and to immediately remove the patient’s face mask to allow for breathing of room air when any of these safety features is suspected of failing.2
Table. Safety Features of Nitrous Oxide-Oxygen Delivery Systems2
Safety Feature and Brief Description
Alarms
— Audio and/or visual alarms (e.g., low- or high-oxygen and nitrous oxide pressure alarms)
Color Coding
— Gas tanks, knobs, and hoses are coded by color (standardized nationally, but not necessarily internationally)
Diameter index safety system
— A standard for noninterchangeable, removable connections for use with medical gases helps ensure that the appropriate gas flows through the appropriate tubing and cannot be interchanged
Emergency air inlet
— An inlet designed to remain closed as long as gases are being administered to the patient; however, when the oxygen fail-safe system turns the gases off, ambient air is allowed to enter the system so that the patient can continue to breathe through the nasal hood or face mask
Locks
— According to national fire codes, nitrous oxide and other compressed gases must be kept in locked rooms; many manufacturers supply additional locks for the machines at the tanks, the manifold, or the mixer level to prevent staff members from accessing nitrous oxide inappropriately
Oxygen fail-safe system
— The oxygen fail-safe system is designed so that the nitrous oxide supply will be turned off automatically when oxygen delivery is compromised or depleted; delivery systems are required to provide a minimum oxygen liter flow that ensures that 2.5 to 3.0 liters of oxygen per minute is the minimum amount being administered and that concentrations of oxygen never fall below 30% during gas delivery
Oxygen flush button
— A mechanism that allows for 100% oxygen to be administered through a reservoir bag in the event of an emergency; when the button is pressed, the oxygen flush valve engages, and the system delivers oxygen straight from the pipeline or tank regulator at 45 to 50 psi at a flow rate between 35 and 75 L/min
Pin-index safety system
— Pins protruding from the gas tank yokes have a unique configuration that fits into corresponding holes in the tank valves that help prevent the accidental attachment of a nonoxygen tank to the oxygen attachment portal
Quick connect for positive-pressure oxygen
— In an emergency situation in which positive-pressure oxygen is required (e.g., to augment cardiopulmonary resuscitation), quick-connect compatibility helps ensure immediate access to positive-pressure oxygen anywhere in the office
Reservoir bag
— An inflatable rubber reservoir bladder into which fresh gas entering the circuit is conveyed; the bag is filled gradually as gases enter the circuit and is deflated with inhalation
