Storage and delivery of medical gas

properties of air

78% nitrogen, 21% oxygen

non-flammable but supports combustion

medical grade air produced by filtering and compressing atmospheric air

compressed air available in cylinders and bulk

properties of oxygen (O2)

20.9% of earth's atmosphere , slightly heavier than air

non-flammable but readily supports combustion

uses for O2

used with a variety of respiratory equipment

primarily to treat hypoxemia

"sub-ambient" for certain heart defects

methods to prepare O2

fractional distillation (large quantities)

physical separation (small quantities)

physical separation

molecular sieve and semipermeable membrane

properties of carbon dioxide (CO2)

1.5 times heavier than air

non-flammable and does not support combustion

does not support life - must be combined with O2 prior to administration

uses for CO2

treatment for singultus (hiccups)

most commonly calibration gas for blood gas analyzers, transcutaneous monitors, and capnographs

pulmonary function tests

properties of helium (He)

occurs naturally in the atmosphere in small quantities

from natural gas or heating uranium ore

very light

does not support life - must be mixed with O2 (i.e 70% He to 30% O)

uses for helium

combined with O2 to treat severe airway obstruction and can carry medications past obstruction

pulmonary function test

nitric oxide (NO)

toxic but powerful pulmonary vasodilator

non-flammable but supports combustion

combined with O2 to treat PPHN, hypoxic respiratory failure and ARDS

not measured in L/min = very expensive

nitrous oxide (NO2)

used as a mild to moderate anesthetic

non-flammable but supports combustion

slightly sweet odor and taste

does not support life - must be combined with O2

gas cylinders

high quality carbon steel, steel alloys, or aluminum

undergo hydrostatic testing every 5-10 years

specific colors to indicate contents but should also match label before use

normal filling pressure

2000 psi for all sizes - safely exceeded by 10%

cylinder colors

air - yellow

CO2 - grey

O - green

He - brown

N - black

NO2 - light blue

NO - silver

heliox - brown and green

gas cylinder regulations

FDA regulates purity

national formulary dictates "recipe"

Department of Transportation regulates manufacture, storage, and transport of compressed gases

cylinder protocols

properly secured at all times (chained or in carts/stands)

full and empty must be separate

caps in place on large cylinders when being moved

valves fully open when in use and closed when not

safety systems

pressure relief valve that responds to either pressure or heat (fire)

cylinder connector safety systems prevents wrong gas delivery (ASSS and PISS)

ASSS and PISS

american standard safety system - for large cylinders (G, H, and K) utilizes different thread sizes

pin index safety system - for small cylinders (E and below) utilizes yoke connections with pins

reducing valves

reduces high pressure gases to a "working" pressure of 50 psi

typically combined with a flowmeter (regulator)

typically allows monitoring of how much gas is in the cylinder

liquid systems

most common way hospitals store O2

maintained below boiling point to liquid state

easier/cheaper to transport and consumes less space

insulated - series of coils allows it to become gas

bulk and portable liquid system

bulk - used by hospitals with pressure reducing valves to maintain 50 psi as gas enters hospital piping system

portable - filled from "base" units, best for mobile patients or home care that requires a lot of oxygen

zoning

allows areas to be isolated in case of fire

accessible shut-off valves, alarm panels with audible and visual signs, and clearly labeled

station outlets

connections for gas delivery devices (flowmeters, ventilators) has check valves that open when device is inserted and automatically close when removed

color coded and labeled

prevents incompatibility through DISS and quick connects

DISS and quick connects

diameter index safety system - non-interchangeable threaded fittings

quick connects - use plunger/springs that are non interchangeable

flowmeters

further reduce 50 psi from wall outlet or reducing valve

provide control of flow rate (liters per minute)

thorpe tube

most common flowmeter

vertical tube with ball float and adjustable knob

standard adjustable from 0-15 L/min

gravity dependent

"pressure compensated"

bourdon gage

not gravity dependent

converts pressure gradient into flow

generally combined with a pressure reducing valve

low flow and high flow flowmeters

low - precise administration of O2 to patients with chronic lung disease or neonates

high - used to power CPAP units or tents

O2 concentrators

used in home care settings

most common type is molecular sieve

sucks in room air and pushes gas through to absorb nitrogen

provides 85-95% O2 at flows of 1-6 L/min

requires electricity (portable on batteries)

air/O2 cylinder factors

E = .28 (.3) H&K = 3.14 (3)

psi X factor / flow = duration in minutes

portable liquid system equation

1L weighs 2.5 lbs and produces 860 L of gaseous O2

lbs X 860 / 2.5 = liquid gas in unit by liter

amount of unit / flow rate = duration in minutes