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vaporizers
| Question | Answer |
|---|---|
| what contributes to the physics of vaporizers? | 1. vapor pressure 2. boiling point 3. specific heat 4. latent heat of vaporization 5. thermal conductivity. |
| vapor pressure is independent of ? | atmospheric pressure |
| what is the importance of vapor pressure in anesthesia? | the amount of anesthetic delivered is dependent upon vapor pressure. |
| vapor pressure is dependent upon? | temperature and physical characteristics of the liquid. |
| how do you increase vapor pressure? | increasing temperature makes more liquid to enter the gas phase or vapor phase. |
| what happens to volatile liquid in a closed container? | liquid molecules escape into the gas/vapor phase until there is a equilibrium between vapor and liquid phase. |
| when vapor/gas molecules bombard the walls of the container creating pressure, this is known as? | saturated vapor pressure. |
| what is boiling point? | is the temperature at which vapor pressure equals to atmospheric pressure. |
| boiling points refers to? | liquid. |
| at atmospheric pressure, what are teh boliing points of volatile anesthetics? | 1. desflurane - 22.8 C 2. isoflurane - 48.5 3. sevoflurane - 58.5 4. enflurane - 56.5 5. halothane - 50.5 |
| what type of volatile anesthetic has vapor pressure that is steeper and shifted versus all others? | desflurane. |
| define latent heat of vaporization? | the number of calories required to change 1 gram of liquid into a vapor or gas phase without a temperature change. |
| in regards to latent heat of vaporization, what happens during vaporization in the absence of outside energy source/ ? | as liquid enters the gas phase, temperature of liquid decreases during vaporization in the absence of outside energy. |
| where does the energy/calorie for vaporization comes from? | the liquid itself or from an outside energy source. |
| what is specific heat of vaporization? | the number of calories needed to increase temperature of 1 gram of substance (solid, liquid, gas) by 1 degree celcius. |
| what are the importance of specific heat in anesthesia? | 1. it is important in designing vaporizers 2. how much heat must be supplied to maintain constant temp when heat is lost during vaporization for inhaled anesthetics.3. companies-metals with high specific heat to minimize temp changes during vaporization |
| how is thermal conductivity important to vaporizers? | manufacturers choose metals with high thermal conductivity which are easier to maintain uniform constant temperature for vaporization |
| list the types of vaporizers available/ | 1. variable bypass 2. flow over 3. temperature compensated 4. agent specific out of circuit |
| what is the most common vaporizer utilized? | variable bypass vaporizers. |
| variable bypass vaporizers are used to deliver what volatiles? except? | 1. isoflurane 2. sevoflurane 3. enflurane 4. halothane 5. but not/except desflurane |
| give a few examples of variable by pass vaporizers | datex - tec 4,5, 7 drager - vapor 19.n, 20.n |
| what is the method of the variable bypass vaporizer work? | method of regulating the concentration of anesthetic agent output from the vaporizer. |
| how is the amount of gas determined with the variable bypass vaporizer? | by the concentration dial. |
| what type of vaporizers allow gas to be channeled to the vapoizing chamber where it flows over liquid anesthetic and becomes saturated with vapor? | flow over vaporizers |
| what determines the ratio of gass flow that goes through the bypass champber versus through the vaporizing chamber? | the concentration dial |
| a vaporizer that is designed to accommodate a single agent and are located outside the breathing circuit? | agent specific out of circuit vaporizer |
| what affects vapor pressure in the chamber of variable bypass vaporizer? | environmental changes in temperature. the higher the temperature the more vapor pressure is produced increasing delivery of anesthethic |
| what is the function of the metalic strip in the variable bypass vaporizer of ohmeda tec? | to create constant vapor pressure irrespective of environmental temperature. increase temperature creates more vapor flow through bypass chamber-the metalic strip tips to the right. strip tips to left with cold temp creating more flow to vaporizing chambe |
| how does the drager maintains constant vapor output with changes in temperature? | contains and expansion element for temperature combensation. |
| if variable bypass vaporizer is tilted or overfilled what may happen? what can minimize this chance/ | liquid anesthetic can spill into the bypass chamber and cause overdose. position of the filler port can mimimize the chance of overfilling. |
| what is the function of the concentration dial of the variable bypass vaporizer/ | regulates flow rates through the bypass and vaporizing chamber located either in the bypass chamber or in the outlet of vaporizing chamber. |
| how much of the gas flow from the flow meter enters the bypass chamber? enters the vaporizing chamber? | 80 % to the bypass chamber. 20% to the vaporizing output. |
| what happens to gas flow diverted into the vaporizing chamber of variable bypass? | becomes partially saturated with liquid volatile anesthetic and is dependent on both temperature and vapor pressure of agent. |
| the final concencentration of inhaled anesthetic is? | the ratio of flow of inhaled anesthetic to total gas flow at the vaporizer outlet. |
| at 20 degree celcius the vapor pressure of isoflurane is 238 and at 35 degrees is 450. this means that? | vapor pressure and subsequent anesthetic delivered depends on temperature. |
| depsite ambient temperature, what other factors influence vaporizer output? | 1. flow rate, 2. back pressure (pumping effect) 3. carrier gas compositiopn |
| how is the vaporizer output affected by extremes of flow rate in a variable bypass vaporizer? | 1. flow rate less then 250ml, vaporizer output is less then the dial setting due to high density of volatile. turbulence produced by low flow is ineffective to advance flow. 2. high flow rate > 15L/min - output less then dial b/c incomplete volatile mixi |
| how does high flow > 15 L /min affect vaporizer output of variable bypass? | 1. incomplete mixing and vaporization 2. resistance of the bypass and vaporizer chambers vary decreasing output concentration |
| how does the variable bypass compensate for vaporizer output due to temperature changes? | 1.bimetallic strip (other expansion strip) 2. wicks on metal walls to replace heat used in vaporization 3. metals that have high specific heat and thermal conductivity to minimize heat loss from vaporization. |
| what causes the pumping effect (intermittent back pressure) of the variable bypass vaporizers? | 1. created by rapid RR, HIGH PEAK AIRWAY PRESSURE FROM OXYGEN FLUSH/POSITIVE PRESSURE VENTIlation. 2. leads to higher vaporizer output then in the dial setting. 3. back pressure from circuit to vaporizer during inspiration of positive pressure ventila |
| the pumping effect of variable bypass is more pronounced in what settings? | low flow rates, low dial settings, low levels of liquid anesthetic in the vaporizing chamber. |
| what types of variable bypass vaporizers are not subject to the pumping effect? | 1. tec 4 2. dragger vapor 19 because of their very small vaporizing chamber size limiting amount of vapor transfer from the vaporizer to the bypass. |
| explain the pumping effect of variable bypass vaporizers. | back pressure from circuit during inspiration/mechanical ventilation cause back pressure towards vaporizer and bypass chambers, during expiration phase back pressure cause forward pumping of anesthetic gas. |
| how does the carrier gas influence the vaporizer output in variable bypass? | due to solubility difference in carrier gas. when oxygen switched to nitrous oxide there is a transient decrease in ouput followed by slow increase to a new steady state value of vaporizer output |
| what contributes to hazards of vaporizers? | 1. incorrect filling 2. contamination 3. tipping 4. overfilling 5. leaks 6. simultaneous inhaled anesthetic administration. |
| what is the most common source of vaporizer leak? | loose filler cap. |
| list the safety features of vaporizers ? | keyed filling devices which prevents wrong filling agent, filling ports for reduction of overfilling, attachement to mimimize tipping, interlock system to prevent administering more then one agent at atime. |
| what kind of vaporizer is used for desf;urane? | tec 6 |
| what serves as a reservoir for desflurane vapor in the vaporizer? | the heated sump assembly. and downstream is the shut off valve which downregulates pressure |
| the vaporizer circuit of desflurane in the vaporzier is______________ | electrically heated to 39 degrees which is above desflurane boiling point. |
| the desflurane vaporizer must be ________ to ensure controlled vaporization. | tec 6 is electrially heated to 39 degrees and pressurized. |
| the desflurane vaporizer has __________ gas circuits arranged in _______. they are : | tec 6 has 2 gas circuits in parallel; the fresh gas and vaporizer circuit kept separated until vapor flow joins gas flow at R1 |
| vapor pressure at 39 degrees in the sump of tec 6 is? | 1300mmHg or 2 atmosphere. |
| what originates at the desflurane sump? | the vapor circuit which is heated and pressurized. |
| desflurane output (tec 6) is adjusted where? | at the concentration control valve (R2), which is a variable resistor. |
| WHAT IS DOWNSTREAM FROM THE SHUT OFF VALVE OF TEC 6? | THE PRESSURE REGULATOR VALVE WHICH FUNCTION TO DECREASE PRESSURE TO 1.1 ATM. AT FRESH GAS FLOW RATE OF 10L/min |
| what is the safety feature of tec 6? | vaporizer faults such as tipping, low volatile fluid, tilting, power failure, etc. will close the "shut off valve" which is located downstream from the sump. |
| the equation in order to calculate the volume of gas produced from vaporizer output? | VO = (CG X SVP)/(BP-SVP) CG - carrier gas must be in cc/min SVP - saturated vapor pressure = fraction of atmospheric pressure (760/y) BP = barometric pressure=atm pressure 760 |
| question asking what flow will be delivered from the vaporizer? | use the vaporizer output equation. |
Created by:
michelledaryanani