Medical Gas Storage & Delivery

Air

• 78% Nitrogen, 21% Oxygen, trace gases

• Non-flammable but supports combustion

• Produced by filtering/compressing atmospheric air

• Delivered via cylinders or bulk supply

• Used to power equipment (nebulizers, ventilators)

Oxygen (O₂)

• 20.9% of atmosphere, slightly heavier than air

• Non-flammable but strongly supports combustion (danger with oil/grease)

• Production:

  • Fractional distillation (large amounts; liquid storage)

  • Physical separation (small amounts; concentrators)

• Main use: treat hypoxemia

• Must be monitored for fire safety

Carbon Dioxide (CO₂)

• 1.5x heavier than air, non-flammable, no combustion support

• Uses:

  • Calibration gas (ABG analyzers, capnography)

  • Pulmonary function tests

  • Prevent CO₂ washout during bypass

• Must mix with O₂ for administration (does not support life)

Helium (He)

• Inert, very light

• Combined with O₂ (Heliox) to bypass severe airway obstruction

• Also used in PFTs

• Must mix with O₂ to support life (heliox)

Nitric Oxide (NO)

• Potent pulmonary vasodilator

• Used for: PPHN, hypoxic respiratory failure, ARDS (off-label)

• Byproduct: Nitrogen Dioxide (toxic)

• Non-flammable but supports combustion

Nitrous Oxide (N₂O)

• Mild-moderate anesthetic

• Sweet odor/taste

• Non-flammable but supports combustion

• Must be mixed with O₂ (does not support life)

Gas Cylinders

• Made from steel or aluminum

• Hydrostatic testing: every 5–10 years

• Normal fill: 2000 psi (can reach 2200 psi safely)

• Label is the only reliable identifier! (colors may vary)

• Sizes: E (portable), H/K (large, bulk supply)

Cylinder Color Codes

• Air = Yellow

• CO₂ = Gray

• O₂ = Green

• Helium = Brown

• Nitrogen = Black

• Nitrous Oxide = Light Blue

• Nitric Oxide = Silver

• Heliox = Brown/Green

Regulation & Safety

• FDA: purity

• DOT: manufacture, storage, transport

• NF (National Formulary): standards

Safety

• Always secure cylinders (chain, cart, stand)

• Keep full/empty cylinders separate

• Keep caps on large cylinders during transport

• Open valves fully when in use, closed when not

Pressure relief valves

prevent explosions from heat/pressure

American Standard Safety System

• Large cylinders (G, H, K)

• Different thread sizes

Pin Index Safety System

• Small cylinders (E and below)

• Yoke connections with specific pin positions

Diameter Index Safety System

• Station wall outlets

• Non-interchangeable threaded fittings

Quick Connects

• Spring/plunger connections, not interchangeable

Reducing Valves

lower cylinder pressure to 50 psi “working pressure

Regulator

• combines reducing valve + flowmeter

• Built-in pressure gauge + safety “pop-off” valve

Liquid O₂

• Stored below boiling point (-183°C)

• 1 L liquid O₂ → 860 L gaseous O₂

• Advantages: saves space, cheaper transport

• Hospitals use bulk tanks; portable systems for home/mobile patients

Medical Air

• Bulk supply for hospitals

• Portable compressors for home use

Piping Systems

• Carries gas to outlets at 50 psi

• Zoning: shut-off valves, alarm panels, labeling

• Outlets: color coded + safety system (DISS/Quick Connect)

• Check valves prevent backflow

Thorpe Tube Flowmeter

• Vertical tube with ball float

• Gravity-dependent (must stay upright)

• Standard: 0–15 L/min (flush >30 L/min)

• Pressure compensated = accurate under back pressure

Bourdon Gauge

• Not gravity dependent (works in any position)

• Measures pressure → converts to flow

• May read higher than actual flow if back pressure present

Specialty Flowmeters

• Low-flow: precise delivery for neonates, COPD

• High-flow: CPAP, tents

O₂ Concentrators

• Home use: pulls nitrogen from air via molecular sieve

• Output: 85–95% O₂ at 1–6 L/min

• Requires electricity (portable versions: battery)

• Always need cylinder back-up

Safety Reminders

• Always verify label (never rely only on color)

• Secure cylinders at all times

• Never use oil/grease near O₂

• Separate full & empty cylinders

• Use proper regulators and safety systems