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Chem/Phys Med Gases
Kevins - Lecture # 4
| Question | Answer |
|---|---|
| absolute pressure is the sum of | all pressure. It is zero referenced against a perfect vacuum (P absoulte = P gauge + P atm) |
| gauge pressure is | pressure relative to the local atmospheric pressure (Pgauge = P absolute - Patm) |
| Vapor pressure | pressure exerted by the pressure of a subsance in contact with its liquid or solid phase in a sealed container (its a function of temperature not pressure) |
| saturated vapor pressure is | when a substance is in dynamic equilibrium with its gaseous & liquid state at a given temp; in a closed container the number of molecules leaving liquid state = number of molecules entering the liquid state |
| partial pressure | pressure exerted by one of the gas in a mixture of gases |
| workin pressure in a cylinder is | the service pressure (2200 PSI) |
| a mechanical device used to safely control the dischare pressure of a compressed gas from a container | pressure regulator |
| STP = | standard temperature (0 C) & pressure (100kPa) |
| Boiling point | temp at which the vapor pressure is equal to the atmospheric pressure (Dependant on heat & pressure) |
| cryogenic liquid | liquid with a normal boiling point below -150C at 1 atm |
| oxidizing gas | gas that can support & accelerate combustion of other materials |
| 1 atm = | = 1 bar 760 torr = 760mmHg = 14.696 psi = 101.325 kPa |
| 1 psi = ? mmHg | 54 |
| 0C = ?F and ?K | 32F & 273.15K |
| O2 tanks D | 2200 psi & 412 L |
| O2 tank E | 2200 psi & 660 L |
| O2 tank H | 2200 psi & 6900L |
| N2O tanks D | 750 psi & 1590L |
| N20 tank E | 750 psi & 16000L |
| compressed gas | gas or mix of gases that, in a container will have an absolute pressure exceeding 40 psi @ 70F (room temp) or 21.1C or a liquid having VP exceeding 40 psi at 100F or 37.8C |
| nitrous oxide uses | adjuncts to other anesthetic agents, peds minor cases |
| nitrogen uses | powers OR equipments |
| carbon dioxide uses | laproscopic procedures |
| compressed air | piped into anesthesia machine |
| helium | expands atelectasis in apex of lung |
| Who is the big regulator for design, construct, testing, marking, labeling, filling storage, maint, handling & transport of high pressure cylinders | DOT or department of transportation |
| Regulating bodies for compressed gases | DOT, FDA, CGA, JCAHO, NIOSH, OSHA, ASTM |
| 2 classes of anesthetic agents are | nitrous oxide & halogenated agents |
| recommended exposure limits for nitrous | 25ppm or 50ppm for 8 hr work day (time weighted average) |
| recommended exposure limits for halogenated agents | not to exceed 2 ppm for greater than 1 hr. |
| If you run nitrous with halogenated agent the exposure limits for nirous drop to | 5ppm |
| Hydrostatic test, burst test for cylinders | every 10 years, cylinder are pressure tested to 1.66 times their service pressure |
| Tesile strength test for cylinders | cylinder must have up to 10% tensile strength, cylinder is flexible, yet rigid. |
| Storage of cylinders | full cylinders are stored away from empties, large cylinders should be chained to the wall, always secured in upright position which prevents tip-over which could fracture the neck, small cylinders should be placed in nonflammable racks |
| T/F it is okay to refill small cylinders from larger ones | FALSE, it is NEVER ok, you could risk explosion from the heat of compression, and it's illegal |
| What is cracking of the cylinder | the opening of the cylinder momentarily before its use to clear the outlet of any possible dust |
| What must always be attached to the outlet valve on the cylinder? | regulating device |
| PISS | pin index safety system, prevent wrong gas cylinder connections, different pin positions for different gases |
| Air pins are at what positions | 1 & 5 |
| O2 pins are at what positions | 2 & 5 |
| N2O pins are at what positions | 3 & 5 |
| What are the 2 type of connectors at the wall | quick coupler & diameter index safety system which prevent incorrect connections |
| Quick coupler | wall connector, allows for rapid connection and disconnection of fittings & hoses, specific pin positions for specific gases |
| DISS (diameter index safety system) | gas-specific diameter fittings with a non-interchangable thread system |
| Color of medical air tanks | yellow |
| color of medical carbon dioxide tanks | gray |
| color of medical helium tanks | brown |
| color of medical nitrogen tanks | black |
| color of medial nitrous oxide tanks | blue |
| color of medical oxygen tanks | green |
| what particular markings need to present on cylinder | regulating body (DOT), specification of cylinder construction material, service/working pressure in psi, serial number, registered owner symbol, date of manufacture, manufacat symbol, manufact manual, retest markings, neck ring identifcation |
| cylinder neck ring identification | displays current own of the cylinder (ex Paul & Andy's sympbol) |
| retest markings on cylinder format | month-facility-year- + rating -stamp (+ rating indicates that cylinder qulifies for 10% overfill, & stamp indicates cylinder meets requirements for 10 year re-test) |
| THis particular valve is required on all medical gas cylinders | pressure relief valve |
| purpose of pressure release valve on the cylinder | a mechanism to vent the cylinder's contents before it explodes from excessive pressure (extreme temp could cause this) |
| Types of pressure relase valves (3) | fusible plug, frangible disc assembly, safety release valve |
| Fusible plug | pressure release valve on the cylinder, has woodsmetal implanted into the valve assembly that has a low melting point which alls the escape of the gas in case of a fire. (woodsmetal will melt allowing gas to escape, not explode) |
| Frangible disc assembly | pressure release valve; a metal disc that is designed to break when a certain pressure is exceeded, allowing gas to escape through a discharge vent versus exploding |
| Safety release valve | release valve on cylinder; spring loaded mechanism that opens a discharge pressure relief valve if pressure becomes too high, and remains open until the pressure falls below the valve's opening threshold |
| What size cylinder is found on the back of the anesthesia maching | E cylinder |
| When does an O2 E tank need to be replaced | before it's completely empty, around 250-300 PSI |
| What is the service pressure for E cylinder of O2 | 1900PSI |
| Universal Gas Law can be used to explain how gas escapes from a cylinder by | pressure in the cylinder decreases as the number of mole of gas decrease, keep in mind that the tank has a constant volume |
| Critical temperature | temp below at which a gas boils under pressure, when gas boils it becomes a liquid! |
| When N20 is placed under a pressure of 750 PSI it becomes a liquid at | room temp |
| Nitrous E cylinders are filled to | 90-95% capacity |
| Nitrouse oxide is in an equilibrium between its vapor and liquid state called | saturated vp |
| T/F the pressure gauge can be used to determined the amount of remaining N20 | false, the tank will read 745-750 until all of the liquid below the gas has been vaporized. Once all the liquid is vaporized you will then see a large decrease in the PSI |
| The frostline from the Joule Thompson effect, of decreasing pressure, and loosing heat correlates with | where the liquid is left |
| What is lost during vaporization of a liquid | HEAT, this is called latent heat vaporization |
| The vaporization causes a drop in the tank temperature called the | Joule-thompson efffect (explained by guy lussacs law), the tank will then cool and almost frost |
| H cylinders are | larger, used for small or infrequently used pipelines, intermediate to long term use. Are stored in bulk as a back up for the hospital |
| Reducing valves convert | high pressures to "workin pressures", 50PSI |
| Pressure regulators include (2) | Bourdon gauge & Flowmeters:Thorpe |
| Bourdon gauge | pressure regulator that works with high pressure readings, works regardless of position of the tank |
| Thorpe gauge | work for low pressure readings, 50PSI, only works in an upright position (what we use clinically on the wall) |
| Bulk suppy systems 3 main components | 1) central supply of gas 2) pipelines to transport the gases 3) appropriate end point connectors |
| If a higher vapor pressure agent is placed in a vaporizer designed for a lower vapor pressure, the concentration delievered will be lower/higher than the dialed setting? | HIGHER than the dialed setting |
| If a lower vapor pressure agent is placed in a vaporizer designed for a higher vapor pressure, the concentration delievered will be lower/higher than the dialed setting? | LOWER than the dialed setting |
| If isoflurane is added to a halothane vaporizer the delivered concentration will be | about the same, (bc VP H is 243, and VP of I is 239) |
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asaranita