What are 4 physical properties of O2?
Colorless, odorless, transparent and tasteless
Is O2 flammable?
No but it greatly accelerates combustion
What produces most large quantities of Medical O2?
Fractional distillation
What is Fractional distillation?
Atmospheric air is filtered to remove pollutants, water and CO2. Purified air is liquefied by compression & cooled by rapid expansion (Joule-Thompson Effect). Resulting mixture is heated slowly to allow nitrogen to boil off, leaving just O2
**Simplified:
Who monitors the purity of O2 for medical gas
The Food and Drug Administration (FDA) ensures O2 is 99% pure
What is physical separation O2 production?
Molecular sieves absorb nitrogen, trace gasses and H2O vapor from air, O2 concentrators pull ambient air through semipermeable plastic membrane.
What are physical characteristics of "medical" air?
Colorless, odorless, naturally occurring gas mixture.
(20.95% O2, 78.1% nitrogen & about 1% argon-helium mixture)
How is medical-grade air produced?
by filtering and compressing atmospheric air
What are physical characteristics of "medical" CO2?
Colorless and odorless gas.
Does CO2 support combustion?
Hell no.
What are two common uses for CO2 mixtures?
**Calibration of blood gas analyzers
**Diagnostic purposes in clinical laboratory
What percentage mixture of CO2 has therapeutic purposes?
5-10% CO2/O2 mixtures
What purposes does 5-10% CO2 mixtures (Carbogen) serve?
**Singultus management
**CO2 washout prevention during cardiopulmonary bypass
**Regulate pulmonary vascular pressures in some congenital heart disorders
What are physical characteristics of helium (He)
odorless, tasteless, nonflammable, chemically and physiologically inert
How is He commercially produced?
from natural gas through liquefaction to purity standards of at least 99%
What must He be always mixed with?
20% O2
What is a therapeutic use of He/O2 mixtures (Heliox)
**Manages severe cases of airway obstruction
**Decreases WOB
How does heliox decrease work of breathing?
**Has lower density
**Makes gas flow more laminar
Gas Density simplified
CO2>O2Air>He
Physical characteristics of Nitric Oxide (NO)
Colorless, nonflammable, toxic (Supports combustion)
What can exposure to high concentrations of NO cause?
Methemogloinemia --> tissue hypoxia
What treatments has the FDA approved the use of NO for?
**Treatment of infants with hypoxic respiratory failure
**Pulmonary hypertension
Physical characteristics of Nitrous Oxide (N2O)
colorless gas with slightly sweet odor and taste
What is N2O clinically used for?
Anesthetic agent
What must always be mixed with N2O for clinical use?
Oxygen
What are risks of long term exposure to N2O?
**neropathy
**fetal disorders
**spontaneous abortion
What are gas cylinders used for?
To store and ship compressed or liquid medical gases.
Who is responsible for approving manufacture, transport and use of gas cylinders?
Industrial standards, federal regulations and ESPECIALLY the department of transportation (DOT)
How are cylinders marked and identified?
Color coded and marked with metal stamping on shoulder.
What does the stamping indicate?
Size, normal filling pressure, serial number, ownership and method of manufacturer.
How often are safety tests conducted on gas cylinders?
every 5 or 10 years
How are gas cylinders pressurized to?
5/3 of their service pressure (PSIG)
What is results are measured and stamped on the tank?
Cylinder leakage, expansion, and wall stress.
What are cylinder safety relief valves designed for?
To vent gas to atmosphere if tank is heated.
What do cylinder safety relief valves prevent?
tank pressure from becoming too high.
What mechanisms make up a cylinder safety relief valve?
**Flangible metal disk ruptures at specific pressure
**Fusible plug melts at specific temperature
**Spring loaded valve opens and vents gas at set high pressure
How are gas cylinders filled (Charged) with compressed gases
**normally filled to its service pressure at 70 degrees Fahrenheit
**Can be filled to 10% in excess of service pressure
How are liquefied gas (O2 and N20) cylinders charged?
according to specified filling density
*Filling density is ratio between weight of liquid gas put into cylinder and weight of H2O cylinder could contain if full
How do you measure Gas-filled cylinder contents?
Volume of gas in cylinder is directly proportional to its pressure
How do you measure Liquid Gas cylinder contents?
Pressure does not relate to amount of liquid remaining, only weight of cylinder indicates amount of gas inside
What are factors affecting duration of flow
**Gas Flow
**Cylinder size
**Cylinder pressure at start of therapy
Gas flow formulas...
Cylinder factor (L/psig) = Cubic feet (full cylinder) x 28.3 / Pressure (Full Cylinder) in psig
Duration of flow = Content/Flow
--Duration of flow (min) = Pressure (psig) x cylinder factor / Gas Flow (L/min)
What must be known to determine volume of gas in liquid-filled cylinder?
Weight
What is the weight of 1L of liquid O2 and how much O2 gas does it produce?
Weight= 2.5 lbs
Production= 860 L of O2 gas
what are the constant Factors for E & H cylinders?
E cylinder = 0.28
H cylinder = 3.14
What is a regulator?
A mechanism attached to the gas cylinder that steps the initial pressure down to a working pressure (50 PSIG)
**Readable via gauges
How should gas cylinders be stored?
in racks or chained to wall away from heat sources. No smoking signs posted and with cylinder caps in place if not in use.
**Store LIQUID O2 containers in cool, well-ventilated area
What should you avoid when storing gas cylinders.
**storing with combustible material
**storing flammable gases with gases that support combustion
What precautions should be taken when utilizing gas cylinders?
Secure cylinders at patients bedside, do not use flammable materials on regulators, cylinders, fittings or valves, and "crack open cylinder valve slightly to remove dust before attaching regulator.
Post "NO SMOKING" sign when O2 is used
What is bulk O2 used for?
To meet large O2 needs of health care facilities
How much gas is held in bulk O2 systems?
At least 20K cubic feet of gas (in gas or liquid form)
Three types of bulk O2-Gas supply systems are?
1. Alternating supply system (cylinder manifold system)
2. Cylinder supply system with reserve supply
3. Bulk gas system with reserve
If bulk O2 gas supply systems go down what should you do?
utilize individual E cylinders for immediate use until system is functional. (facilities should have back up system in effect)
What does a central piping system do?
Used to deliver compressed gas to all areas throughout the hospital at standard working pressure (50-psi)
What is the purpose of the central piping system main alarm?
warns of pressure drops or interruptions in flow from source.
What are zone valves and what are their purpose?
located throughout the system. Used to turn on/off O2 flow in emergencies (ie fire)
What is the safety indexed connector system for large cylinders and attachments designated to prevent accidental misconnections
American Standard Safety System (ASSS)
What is the safety indexed connector system for Low pressure gas connectors at outlets of pressure reducing valves, outlets of central piping systems and the inlets of blenders, flowmeters and ventilators
Diameter-Index Safety System (DISS)
What is the safety indexed connector system for Small cylinders up to and including E and attachments and yoke type connection. Exact positions of pins and pinholes vary for each gas. (2 & 5 for O2; 1 & 5 for Air)
Pin-Index Safety System (PISS)
What is a reducing valve used for?
To reduce gas pressure to a useable level.
What is a flowmeter used for?
To control flow to patient
What is a regulator used for?
To control both pressure and flow.
What are three types of flowmeters?
**Flow Restrictor
**Bourdon guage
**Thorpe tube
What s a flow restrictor?
The simplest and least expensive flowmeter device, consists of fixed orifice calibrated to deliver specific flow at constant pressure based on the principle of flow resistance.
Term deleted
Lalim "I am not going to test you on this
What is the Bourdon Gauge always used in combination with
adjustable pressure-reducing valve
What is the mechanisms in a Bourdon Gauge and how do they function?
Uses fixed orifice operating under variable pressures, not gravity dependent but not accurate when pressure distal to orifice changes. (Ideal for patient transport)
Integrated O2 cylinders...
Definition deleted per Lalim Principle of Non-Importance
What does a pressure compensated Thorpe Tube do?
Prevents changes in downstream resistance, or back pressure, from affecting meter accuracy
What is a pressure compensated Thorpe Tube calibrated to?
50 PSIG instead of Atmospheric pressure
*
IMPORTANT
*
Why is the pressure compensated Thorpe Tube NOT ideal for patient transport?
Gravity dependent
How is an UNCOMPENSATED Thorpe Tube calibrated?
Calibrated in liters per minute at atmosphere pressure (without restriction)
What controls the meter rate flow of gas in an uncompensated Thorpe Tube from a 50 PSIG source.
Needle valve