Chapter 41 – Storage and Delivery of Medical Gases

Vocabulary flashcards covering essential terms, devices, safety systems, and calculations related to the storage and delivery of medical gases in Chapter 41.

Laboratory Gas

Medical gas used primarily for equipment calibration and diagnostic testing.

Therapeutic Gas

Gas administered to relieve symptoms and improve oxygenation in hypoxemic patients.

Anesthetic Gas

Gas mixed with oxygen to provide anesthesia during surgical procedures.

Oxygen (O₂) – Key Characteristics

Colorless, odorless, tasteless gas; density 1.429 g/L; non-flammable but greatly accelerates combustion.

Fractional Distillation

Most common, least-expensive process for large-scale O₂ production by liquefying and distilling atmospheric air.

Joule–Thompson Effect

Cooling that occurs during rapid gas expansion, used in fractional distillation to liquefy air.

Molecular Sieve

Physical separation device that absorbs nitrogen and water vapor to concentrate oxygen.

Oxygen Concentrator

Portable unit that pulls ambient air through a semipermeable membrane to deliver concentrated O₂.

Medical-Grade Air

Filtered, compressed atmospheric air containing 20.95 % O₂, 78.1 % N₂, ~1 % trace gases.

Carbon Dioxide (CO₂) – Key Characteristics

Colorless, odorless gas; specific gravity 1.52; non-combustible; used to calibrate blood-gas analyzers.

Helium (He) – Key Characteristics

Odorless, inert gas; density 0.1785 g/L (lighter than air); must be mixed with ≥ 20 % O₂ for clinical use.

Heliox

Therapeutic mixture of helium and oxygen used to decrease work of breathing in severe airway obstruction.

Nitric Oxide (NO)

Colorless, toxic gas approved as a pulmonary vasodilator for term and near-term infants with hypoxic respiratory failure.

Nitrous Oxide (N₂O)

Colorless gas with sweet odor; anesthetic agent that must be mixed with oxygen; long-term exposure risks neuropathy and fetal disorders.

DOT-3A Cylinder

Seamless carbon-steel gas cylinder classification by U.S. Department of Transportation.

DOT-3AA Cylinder

High-strength alloy-steel gas cylinder tempered for higher service pressure.

Cylinder Safety Relief Valve

Device that vents gas to atmosphere to prevent dangerous pressure buildup in a cylinder.

Frangible Disk

Safety device that ruptures at a specified pressure to relieve cylinder over-pressure.

Fusible Plug

Safety insert that melts at a preset temperature to vent cylinder contents if heated.

Spring-Loaded Relief Valve

Valve that opens at a set high pressure and reseats when pressure normalizes.

Filling Density

Ratio of liquid gas weight added to a cylinder to the water weight the cylinder would hold if filled.

Cylinder Factor

Conversion constant (L/psig) used to calculate remaining gas volume for a given cylinder size (e.g., E = 0.28, H = 3.14).

Duration-of-Flow Formula (Gas Cylinder)

Minutes = [Pressure (psig) × Cylinder Factor] ÷ Flow (L/min).

Liquid Oxygen Conversion

1 L of liquid O₂ weighs 2.5 lb and expands to 860 L of gaseous oxygen.

ASSS (American Standard Safety System)

Threaded connector system that prevents misconnections on large high-pressure cylinders.

DISS (Diameter-Index Safety System)

Threaded, low-pressure connector system for outlets of regulators, piping, and ventilators.

PISS (Pin-Index Safety System)

Safety yoke with unique pin positions for small cylinders (e.g., O₂ = pins 2-5, Air = 1-5).

Reducing Valve

Device that lowers high cylinder or pipeline pressure to a safe, usable level.

Flowmeter

Instrument that sets and controls the gas flow rate delivered to a patient.

Regulator

Combined reducing valve and flowmeter that controls both pressure and flow.

Flow Restrictor

Simplest flowmeter; fixed orifice delivers a preset flow at constant 50 psig source pressure.

Bourdon Gauge

Fixed-orifice, variable-pressure flowmeter paired with a pressure-reducing valve; not gravity dependent; ideal for transport.

Thorpe Tube

Variable-orifice, constant-pressure flowmeter attached to 50 psig source; measures true flow.

Pressure-Compensated Thorpe Tube

Thorpe tube calibrated at 50 psig with control valve distal to flow tube; accurate despite downstream back-pressure.

Uncompensated Thorpe Tube

Thorpe tube calibrated at atmospheric pressure with control valve proximal to flow tube; reads low under back-pressure.

Central Piping System

Hospital piping network delivering gases at a standard working pressure of 50 psig to wall outlets.

Zone Valve

Shut-off valve in a central piping branch used for maintenance or fire isolation.

Cylinder Manifold System (Alternating Supply)

Banked cylinders that automatically switch to a reserve bank when primary pressure drops.

Bulk Gas System with Reserve

Large facility O₂ supply using a main liquid tank plus reserve source for economy and safety.

Bulk Oxygen – Key Advantages

Lower long-term cost, fewer interruptions, reduced cylinder handling, no individual pressure reducers, lower working pressure.

Grab ‘n Go System

Integrated oxygen cylinder with built-in regulator and flow selector, eliminating external gauges and keys.

"Cracking" a Cylinder

Briefly opening the cylinder valve before regulator attachment to clear dust and debris.

NO SMOKING Signage

Required warning posted wherever oxygen is stored or administered to prevent ignition sources.

Standard Working Pressure (U.S. Hospitals)

50 psig — the regulated pressure for medical gas delivery equipment.