Medical Gas Systems Vocabulary

Vocabulary flashcards covering essential terms and concepts from the Medical Gas Systems lecture/quiz.

Therapy Gas Oxygen Requirement

All therapeutic medical gas mixtures (e.g., heliox) must contain at least 20–21 % oxygen to support life.

Fractional Distillation of Air

Most common and least expensive industrial method for producing high-purity oxygen by liquefying air and separating its components by boiling point.

FDA Oxygen Purity Standard

The U.S. Food and Drug Administration requires medical-grade oxygen to be at least 99 % pure.

Molecular Sieve Oxygen Concentrator

Device that uses zeolite pellets to adsorb nitrogen, physically separating room air into 90-95 % oxygen.

Electrolysis of Water

Process that generates oxygen (and hydrogen) by passing an electric current through water; not commonly used commercially.

Small Diaphragm/Turbine Air Compressor

Compact compressor capable of powering devices like small-volume medication nebulizers and intermittent positive-pressure breathing devices.

Helium (He) Low Density

Property that reduces turbulent airflow and airway resistance, making helium useful in heliox therapy.

Heliox

Therapeutic mixture of helium and oxygen; must contain at least 20 % oxygen for patient safety.

Nitric Oxide (NO)

Inhaled gas used to treat hypoxic respiratory failure, especially in neonates, by improving pulmonary vasodilation.

Seamless Steel Cylinder

Material from which most high-pressure compressed-gas cylinders are manufactured to withstand thousands of psig.

Hydrostatic Pressure Test

DOT-mandated cylinder test (typically every 5 years) that checks for leaks and permanent expansion under pressure.

Pressure-Relief Device

Safety valve on every compressed-gas cylinder that vents gas to prevent dangerous over-pressurization.

psig

Pressure measurement in pounds per square inch gauge; indicates pressure relative to atmospheric pressure.

Cylinder Pressure vs. Contents

For a compressed gas, remaining volume is proportional to pressure (e.g., 2200→550 psig means the cylinder is one-quarter full).

Liquid Gas Cylinder Monitoring

Amount of gas remaining in a cylinder containing liquefied gas is determined by weighing the cylinder, not by pressure gauge.

Standard Working Pressure

Pressure (≈50 psig) to which bulk oxygen or air is reduced before distribution to hospital pipeline or equipment.

Thorpe Tube Flowmeter

Gravity-dependent, pressure-compensated flowmeter used at bedside wall outlets to set precise gas flow rates.

Bourdon Gauge Flowmeter

Pressure-based flowmeter often paired with a regulator; functions in any position, ideal for portable oxygen systems.

Cracking a Tank

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

Hypoxic Hypoxia

Low arterial oxygen tension (PaO₂) due to inadequate oxygen entering the blood, causing tissue hypoxia.

Circulatory (Stagnant) Hypoxia

Hypoxia that results from insufficient blood flow to tissues despite normal arterial oxygen content.

Anemic Hypoxia

Hypoxia caused by reduced hemoglobin concentration or impaired hemoglobin ability to carry oxygen.

Histotoxic Hypoxia

Hypoxia in which cells cannot use delivered oxygen because of metabolic poisoning (e.g., cyanide).

Oxygen Cylinder Color (U.S.)

Green (white internationally) identifies cylinders and outlets containing medical oxygen.

Air Cylinder Color (U.S.)

Yellow identifies cylinders and outlets containing compressed medical air.

Pin Index Safety System (PISS)

Alignment of gas-specific pin positions on small cylinders (sizes A–E) to prevent regulator misconnections.

PISS Pin Positions for Oxygen

Holes 2 and 5 on the cylinder valve correspond to medical oxygen.

PISS Pin Positions for Air

Holes 1 and 5 on the cylinder valve correspond to medical air.

American Standard Safety System (ASSS)

Threaded safety system for large cylinders (sizes F and larger) that uses gas-specific threads and pitch to prevent misconnections.

Diameter Index Safety System (DISS)

Low-pressure (50 psig) gas connector system using different thread diameters, pitches, and nipple seats to prevent cross-connections.

Medical Air Quality Requirements

Hospital pipeline air must be particle-free, oil-free, and dry to protect patients and equipment.