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Valley Machines
Valley Anesthesia Delivery Systems: Machines
| Question | Answer |
|---|---|
| What 11 components of an anesthesia machine are required? | 1. Gas Inlet, 2. Pressure Regulators, 3, O2-pressure failure devices, 4. Flow-contol valves and flowmeters, 5. Vaporizers 6. Fresh Gas Outlet 7. Spirometers 8. Circuit Presure gauge, 9. Vent, 10. waste-gas scavenger 11. O2 analyzers |
| What are the componets of the low pressure system of the anesthesia machine | 1. Flow indicators 2. Vaporizers 3. Vaporizer circuit control valves 4. Back pressure safety devices 5. low-pressure safety devices 6 common gas outlet |
| *****List the 9 parameters that the anesthesia machine must monitor in order to comply with ASTM F1850-00 | 1. Continuous breathing system pressure 2. exhaled TV 3. Ventilatory CO2 concentration 4. anesthetic Vapor concentration 5. Inspired O2 concentration 6.Arterial O2 Concentration 7. O2 supply pressure 8. arterial blood pressure 8. Continuous ECG |
| *****Describe 3 functions of teh interlock system on the anesthesia machine | Vaporizers are secured to anesthesai machine in manfolds that hold 2-3 untis. The vaporizer exclusion system prevents only 1 vaporizer being turned on at a time and prevents leaks |
| What gas machines generally have machine outhlet check valves, Drager or Ohmeda? | Most Ohmeda machines have machine outlet check valves. |
| Where is the machine outlet check valve located? When is it open? when is it Closed? | Outlet check vlve is loc downstream from vaps and upstream from O2 flush. Outlet chek vlve is open in lack of back press Gas flow freely to comon outlet Vlve clos when back press is exert on it Back pressure is created by intemittent pos pres & O2 flush |
| *****What is the purpose of the check valve found at the cylinder inlet to the gas machine? | The Single check valve between the machine and cylinder prevents retrograde flow of gases from the machine to the atmosphere when there is no cylinder yoke. |
| List 3 functions of the anesthesia machine check valve | (1) prvents "back-flow" from high pressure sides (prevents "pumping action of gases), (2) allows for an empty cylinder to be exchanged for a full one with minimal loss of gas (3) minimizes leakage form an open cylinder to the atmosphere |
| The check valve found between cylinders that are double yoked has what purpose? | In the case of cylinders that are double-yoked, check valve prevents transfer of gas from the cylinder with higher pressure to the cylinder with lower perssure. In addition, one of the double-yoked cylinders can be changed while the other is in use. |
| *****Early vaporizer designs were susceptible to a "pumping effect." Descrie this pumping effect. | Intermittent fluctuating press in breathing sys, like that generated by pos press vent or by itermittent press and releas of O2 flush, caused by fluctuating back press to be transmitted into the low-press system Pumping effect is more pronounced at ↓ flow |
| *****What was the result of pumping effect in terms of anesthesia delivery | The result of this pumping effect was an increased concentration of the anesthetic delivered |
| *****How is the pumping effect (see previous question) prevented in more modern anesthetic vaporizers? | New anesthetic vaporizers incorporate mech that ↓ the size of the vaporizing chamber relative to bypass channel & increase the volume of the inflow channel. Vapor-sat gas can't make its way back into the bypass channel thus the pumping effect is prevented |
| *****What system prevents filling a vaporizer with the incorrect agent? | The keyed filling port system on modern vaporizers prevent filling with the wrong agent. |
| *****What is the transport (T) dial setting on the Drager Vapor 20.n gas machine? What is the equivalent of this on other gas machines? | The Dragor Vapor 20.n gas machine has a transport ("T") dial setting the helps prevent tipping-related problems. This function is provied by vaporizer casette systems on other moder gas machines |
| *****What typer of anesthesia machines should be tested with a negative-pressure leak test? | Machines with check valves should be tested with a neg-pressure leak test. In 1993, the FDA implemented a universal neg-pressure leak test that can be used on all contemporary anesthesia machines, regardless of the presence or absence of check valves |
| *****Where and how is the negative pressure leak test performed on the anesthesia machine during check-out? | To perform a neg-pressure leak test, a suction bulb is attached to the common fresh gas outlet and squeezed repeatedly until the bulbe is fully collapsed. The anesthesia machine is leak-free if the bulb remains collapsed for at least 10 seconds |
| Where is the valve of the scavenging system located? | Waste gas scavengers dispose of gases that have been vented from breathing circuit by a pressure release valve located in the breathing circuit or the vent. Either of these valves is connected to hoses leading to the scavenger system |
| To What is the outlet of the scavenging system connected? | The outlet of teh scavenging system can be a direct line to the outside (passive scavenging), or a conncection to the hospital's vacuum system (active scavenging) |
| The vacuum control valve should be adjusted to allow the evacuation of what volume of waste gas per minute? | 10-15L/min |
| What is the purpose of pressure relief valves? | negative and poitive pressure relief valves protect the patient from the negative pressure of teh vacuum system or positive pressure from an obstruction in the disposal tubing |
| What is the purpose of each of teh two pressure relief valves of the scavenger system? | One relief valve is for negative pressure and one is for positive pressure |
| When does the positive pressure relief valve of the scavenger system open? | If flow of waste gases into the vacuum source is insufficient and the reservoir bag distends, the positive pressure valve opens and vents some of the exhaled gases into the room |
| When does the negative pressure relief valve of the scavenger system open? | If the flow of waste gases into the vacuum system is too high and the bag collapses, the negative valve oens and lets in room air |
| What would happen if there was too much suction applied to the scavenging system? Too Little Suction? | Excessive suction manifests as collapse of the gas reservoir bag. Inadequate suction allows excessive pressure in the breathing system leading to barotrauma |
| How frequently does the scavenging system need to be checked? | The scavenging system needs to be checked daily as outlined by the FDA in 1986 |
| Name 5 Components of the scavenging system | 1. The gas-collecting system 2. The transfer tubing 3. the scavenging interface 4. The gas disposal tubing 5. an active or passive gas disposal assembly |
| What are the indications that the scavenging system is malfunctioning? | Increased positive pressure can be transferred to the breathing system resulting in decreased bellows movement from the vent, increased ventilation pressures, desaturation due to decreased fresh gas flows and CO2 buildup |
| When the O2 flush button is pushed, what is the liter flow rate? | 35-75 L/min |
| In the arrangement of flow meters, where is the O2 flowmeter best located? | To ensure against accidental decreases in delivered O2 concentration, the O2 flow meter should be last in the sequence of flowmeters. Right hand location of the O2 flowmeter is the standard in the U.S. |
| *****Why do some modern gas machines have 2 flowmeter tubes whereas others have one flowmeter tube? | Flowmeter arrangement on modern machines must account for both ↑ and ↓ flow rates. A machine with 2 meters in series-1 for ↓ & 1 for ↑. Machine with 1 meter has dual tapers in tube- 1 for ↓ % one for ↑ (Single taper=Dual Tubes, Double taper=Single Tube) |
| What is the fail-safe system designed to do? The fail-safe system operates on the basis of pressure or Flow? when does the fail safe system shut off flow of all gases | The fail-safe system is designed to prevent delvivery of hypoxic mix. the fail-safe system is activated by ↓ pressure. It shuts off or proportionately decreses flow of all gases when the pressure in the O2 delivery line decreases to <20-30 psi |
| At what pressure does the fail-safe valve shut off the flow of N2O or other gases? | Line pressures of 15-30 psi will usually close the flow of all gases, except O2, to the common gas outlet |
| Which anesthetic gas has no fail-safe? | Oxygen |
| During an anesthetic the fail-safe valve shuts down all non-O2 gas flow. What happened? | the O2 pressure fell below 25-30 psi. When O2 pressure falls below 20-30 psi (roughly 50% of normal), a fail-safe valve automatically closes other lines to prevent delivery of hypoxic mixtures to patient. An alarm sounds to alert the CRNA of this |
| *****What are your actions when the O2 low pressure alarm sounds? | When the O2 low-pressure alarm sounds - indicating profound loss of O2 pipeline pressure, fully open the E cylinder, disconnect the pipeline, and consider use of low FGF |
| What typer of flowmeter uses rotameters? | Variable orifice flow meters use rotameters |
| *****What is a Thrope tube? | the Thorpe tube is the tapered (variable orifice) tube with an indecator bobbin that is part of the constant-pressure variable-orifice flowmeter found in anesthesia machines |
| *****The Thorpe tube of the variable-orifice flowmeter is tapered, as you know. Describe the tapering of the Thorpe tube and the Thorpe tube's location in the anesthesia machine. | Thorpe tube is located in the manifold area of the anesthesia machine and is tapered, with the smallest diameter at the bottom and largest at the top |
| What is the purpose of a proportioning system? | They have been placed on newer anesthesia machines to prevent delivery of a hypoxic gas mixture. The delivery of N2O and O2 are linked in such a way that the minimum concentration of O2 at common gas outlet is 25% |
| how does the proportioning system work? | N2O and O2 are interfaced either mechanically or pnematically so that the minimum O2 concentration deliverd is 25%. The proportioning system lower the delivery of gases other than O2 to keep the O2 concentration above 25% |
| Does the proportioning system have an alarm? When does it go off? | Yes. It is located between N2O and O2 flowmeters. It is an actual chain linkage between the O2 and N2O flowmeters. Increasing the flow through the N2O flowmeter automatically ↑ O2 flow and maintains O2 of 25%. Alarm sounds when N2O/O2 mix falls below 25% |
| how often should a complete test of all anesthesia apparatus be performed? | At least each day before the first case |
| Give 6 examples of how a vaporizer can become hazerdous | 1. Filled with wrong anesthetic 2. bypass chamber contaminated with liquid anesthtic if vaporizer is tipped 3. simultaneous admin of 2 anesthetics if the interlock mech is broken 4 Leaks 5 contaminiateed liquid anesthetic placed in vap 6 overfil of vap |
| For a vaporizer that is calibrated at sea level, will the amount of agent delivered at high altitude be greater than, the same as, or less than the dialed setting? | Increased (Look up rationale) |
| The vaporizer calibrated in Denver is set to deliver 1.5% Forane in O2. Will the patient in Denver be anesthetized to the same depth with setting as the patient who is anesthetized at sea level with a vap calibrated at sea level and the dial set to 1.5% | Denver will not be as deep as sealevel. ATM in Denver is 670, PP of Florane going to the pt in Denver will be 10.5 at Sea level pp of florane is 11.4 |
| A flow-compensated vaporizer compensates for what? | Temperature. A flow-compensated vaporizer is equipped with an automatic temp compensating device that helps maintain a constant vaporizer output (flow) over a wide range of temps |
| What volitile agents are delivered from variable-bypass vaporizers? | The volitile agents that are delivered from variable-bypass vaporizers are isoflurane, enflurane, halothane, and sevoflurane |
| What are 3 characteristics of modern day variable bypass vaporizers? | 1. Agent specific 2. Temp-compensated 3. flow over |
| Describe flow over in a variable bypass vaporizer | (carrier gas flows over anesthetic liquid in the vaporizing chamber). The gas delivered to the variable-bypass vaporizer is divided into carrier gas, which flow over liquid in vaporizing chamber, and non-carrier gs, which leaves the vap unchanged. |
| Where should variable-bypass vaporizers be located? why? | Variable bypass vaporizers should be located outside the circle system between flow meters and the CGO. This placement lessens the likelihood of concentration surges during the use of O2 flush valve |
| ****What risk is associated with a dysfunctional flush valve? | A damaged or defective flush valve can stick in the fully open position, causing barotrauma |
| What is the temperature and pressure in the desflurane vaporizer? Is the desflurane vaporizer a flow over-vaporizer? | Desflurane is delivered from a heated (39 degrees C) and pressurized (1500mmHg) vaporizer. The desflurane vaporizer is not a flow-over vaporizer |
| *****Most contemporary anesthesia gas machines have variable bypass vaporizers. Which moder gas machine does NOT have a variable bypass vaporize? What is the appropriat description of this vaporizer's operation? | Unlike most contemporary vaporizers, the Tec 6 vapoizer is NO a variable bypass vaporizer. The Tec 6 vaporizer is best called a dual-gas blender vaporizer |
| *****The Tec 6 desflurane vaporizer is a dual gas blender, as you know. What are the implications of this type of vaporizer when a change in altitude is encountered? | The Tec 6 will maintain a constant concentration of vapor output, not a constant partial pressure, regardless of ambient press. This means that at ↑ altitudes, the partial press of Des will be ↓ in proportion to the atm press. requires manual adjustmemt |
| *****Des is heated to 39C in the Tec 6 vaporizer. What is the source of heat and what is the sat vapor pressure of des at this temp? | In the Tec 6 vap, des is electrially heated. The Saturated VP of Des is 2 atm, which drives the agen towards the FGF |
| Describe the loaction of the heated des reservoir in relation to the common outlet and shut-off valve | It is heated upstream of both the common outlet and shut-off valve |
| State 2 reasons why des needs a specially-designed vaporizer | 1. Des's VP of 669 is near atm pressurre, so it almost boils at sea level 2. Des is only 1/5 as potent as other volitile agents, so a relatively large volume of vapor must be delivered to the patient |
| Des cannot be used in contemporary flow-over (variable-bypass) vaporizers for what reason? #1 | 1. The cooling effect associated with vaporization of large quntities of des is great; a variable bypass vaporizer couldn't maintain constant tem if des were delivered from one of them. |
| Des cannot be used in contemporary flow-over (variable-bypass) vaporizers for what reason? #2 | 2. because des vaporizes so extensively, a tremendously high FGF would be needed to dilute the des to appropriate concentrations. The tec 6 vaporizer is heated and overcomes these (previous card) |
| Does the Tec 6 Des vaporizer automatically compensate for changes in elevation? What are the implication of this fot eh CRNA? | It doesn't automatically compensate for changes. The concentraton of des is unaffected by elevation, but the pp decreases. At high altitude, the CRNA must increase the concentration on the dial to raise the pp to desired level |
| Calculate the pp of des delivered form the Tec 6 vaporizer at sea level and also in the mountains (600mmHg) Delivering 5% Des | Do Math using Dalton's Law of pp. answers are 38 sea level and 30 mountains |
| What would happen to Des if it were used in a flow-over vaporizer at high altitude | Because Des has high VP (669) at 20 C, it would boil at room temp at high altitude, if it were not used in a specially constructed heated and pressurized vaporizer |
| *****You are scheduled to provide anesthesia to a patient with a known susceptibility to MH. How will you perpare the gas machine in anticipation of this case? | 1. Thoroughly flush gas machine with 1005 O2 for 10 min to remove residual traces of volitle agents form rubber and plastic components of machine. 2. Breathing circuits and CO2 canister should be changed. 3. Vaps should be drained, inactivate or removed |
Created by:
SRNA84