ANESTHESIA DELIVERY SYSTEMS – Flashcards
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Who regulates medical gas purity???....and who enforces the standards???
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Regulations regarding the purity of medical gases (O2, N2O, air) are written by the US Pharmacopeia/ National Formulary (USP/NF)....but it is the Food & Drug Administration (FDA) that enforces the purity standards. The FDA 'enforces' regulations of the Federal Food, Drug & Cosmetic Act....the FDA inspectors inspect medical gas & liquefication plants every other year. O2 cylinders and N2O tanks have been recalled for numerous reasons such as improper labeling, inappropriate testing, filling of cylinders with the wrong gases, and contamination of gases with ammonia, rusty water, bacteria, particulate matter, oil or residual sterilizing solutions such as chlorine. The most common contaminant of medical gas lines is water.
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Who controls such processes as the filling & manufacturing of gas cylinders???
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The US Dept of Transportation (DOT) The DOT has set requirements for the manufacturing, marking, labeling, filling, qualification, transportation, storage, handling, maintenance, requalification, and disposition of medical gas cylinders and containers. Tanks/cylinders should be 'inspected' at least every 5 years, or with special permit, up to every 10 years.
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What is the working pressure of the hosptial pipeline system??
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50 psig
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What is the Diameter Index Safety System (DISS), and what is its purpose???
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The pipeline inlet fittings are gas-specific DISS threaded body fittings....the DISS provides threaded non-interchangeable connections for medical gaslines, which minimizes the risk of misconnection.
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For which gases can the amount of remaining in the cylinder be determined by the reading on the pressure gauge??
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O2, air, Helium, and N2.....these gases are NOT in liquid form in high pressure cylinders. N2O and CO2 are 2 gases that are in the liquid form in pressurized cylinders, therefore the reading on the pressure gauge does not necessarily tell you how much gas is left in the cylinder.
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What is fusible plug??
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The Fusible Plug is a thermally operated, non-reclosing pressure-relief device with the plug held against the discharge channel.....it offers protection from excessive pressure caused by a high temperature but not from overfilling. The yeild temperature is the temperature at which the fusible material becomes sufficiently soft to extrude from its holder so that cylinder contents are discharged....the fusible plug has supplanted Wood's metal.
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What is the pressure in a "full" E cylinder of O2??....how many L of O2 can be released from a full E tank???....how long does it take to empty a full E tank of O2 if it is turned on at 5 L/min??
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A "full" E tank of O2 (2200 psi) will release 625-700 L (660L per M&M). It will take more than 2 hours to empty a full E tank of O2 at 5L/m (660L / 5 Lpm) = 132 minutes ~2000 psi = "full".......~660L ~1000 psi = "half-full".......~330L ~750 psi = "1/3 full"........~220L ~500 psi = "1/4 full".......~160L
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During the case, the wall O2 pressure fails. The E-cylinder registers 2000psig, but within a few breaths falls to 0 pressure....what should you do??
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Open the valve on the E-cylinder....the E-cylinder gauge may read 2000psig after the E-cylinder valve is turned off if the pressure in the line was not vented (bled)...such as during machine check. When the wall pressure of O2 falls, the O2 in the line from the closed E-cylinder "bleeds" quickly, and the pressure falls abruptly.
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How many Liters of N2O can be released from a "full" E tank?? A N2O tank pressure gauge reads 700 psi....what is the significance of this???
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1590 L of N2O is contained in a "full" E cylinder of N2O N2O pressure below 745 psig indicates that the cylinder contains no liquid and is < 1/4 full, and should be changed....the pressure gauge on the tank will fall rapidly where there is no more liquid in the tank....meaning there is only ~400L of N2O remaining.
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What is the purpose of cracking compressed gas (e.g. E or H) cylinders???
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The purpose of cracking a cylinder is to clear the cylinder of any dirt or dust before a fitting is placed. When the cylinder is turned on, gas enters the yoke and passes through a strainer nipple, which serves as a filter that removes dust particles that may be present on the cylinder valve or the contact surface of the yoke.
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What prevents 'back-flow' pressure in the gas cylinder??
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The "check valve" on the hanger yoke prevents back-flow pressure in a gas cylinder.
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What is the purpose of the Pin Index Safety System (PISS)??? Which sized gas cylinders have the PISS???
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The Pin Index Safety System (PISS) ensures that cylinders will NOT be interchangeable....for example, an O2 cylinder cannot be attached to a N2O yoke on the anesthesia machine. Gas cylinders with sizes A (small) through E have the Pin-Indexed Safety System (PISS).
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What are 4 components of the anesthesia gas machine that are exposed to "high pressures" (cylinder pressure)???
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4 components of the anesthesia machine that are exposed to high-pressure (cylinder pressure) include.... 1. Hanger yoke 2. Yoke block with check valves 3. Cylinder pressure gauge 4. Cylinder pressure regulators
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What are the 8 components of the anesthesia gas machine that are exposed to "intermediate" (pipeline pressure...50 psi) pressures??
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8 components of the anesthesia machine that are exposed to intermediate-pressure (e.g. pipeline pressure of ~50psi) include.... 1. Pipeline inlets 2. Check valves 3. Pressure gauges 4. Ventilator power inlet 5. O2 pressure-failure device 6. Flowmeter valve 7. O2 second-stage regulator 8. Flush valve
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What are the 4 components of the anesthesia machine that are exposed to "low" (i.e. dsital to flowmeter needle valve) pressures??
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4 components of the anesthesia machine that are exposed to low-pressure (e.g. distal to flowmeter needle valve) include.... 1. Flowmeter tubes 2. Vaporizers 3. Check valves 4. Common gas outlet
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What do pressure reducing devices ('regulators') do??
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They reduce high & variable pressure in a cylinder/tank to a lower pressure (40-48 psig)....therefore, gas flow is maintained constant without changing the supply pressure.
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Bourdon gauges is the type of high pressure 'regulator' found on cylinder/tanks. Does the Bourdon gauge found on cylinders, measure absolute or relative pressure??
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High cylinder/tank pressures are measured by the Bourdon gauge.....the gauge measures pressure 'relative' to the atmosphere. When the Bourdon gauge reads "0", then the pressure in the tank is 1 atmosphere (atm).
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What do 'second-stage' reducing devices ('regulators') do???
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Second-stage regulators receive gas from either the pipeline (wall) or the cylinder reducing regulator, and reduces the pressure further, down to 26 psig for N2O and down to 10-14 psig for O2.....thus eliminating fluctuations in pressure....maintaining gas flow, so flow remains constant. The in-coming O2 pressure from the cylinder is ~40-45 psig, and the "second-stage" regulator reduces it down to 10-14 psig....then the O2 is delivered to the flow control valve.
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What is a Thorpe Tube??....where is it located??
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The Thorpe tube is the tapered (variable orifice) tube with an indicator bobbin ("Rotameters") that is part of the constant-pressure 'variable-orifice' flowmeter found in anesthesia machines. The Thorpe tube ("varible-orifice" tube) is located in the manifold area of the anesthesia machine & is tapered, with the smallest diameter at the bottom of the tube, and the largest at the top....the Thorpe tube ("variable-orifice") uses a 'rotating indicator', known as "rotameters".
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The flowmeter arrangement on modern gas machines must account for BOTH LOW & HIGH Flow Rates....a machine with 2 flowmeter tubes in series---one for low flow rates & one for high flow rates---allows a single flowmeter to indicate both high and low flow rates. A machine with a single flowmeter tube actually has "dual tapers" in the tube---one to accurately reflect low flow rates & the other for high flow rates. In the arrangement of flow meters, where is the O2 flowmeter best located???
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To ensure against accidental decreases in delivered O2 concentration, the O2 flowmeter should be the last in the sequence of flowmeters (farthest right on the machine in the US). [NOTE: Single taper-->Dual tubes......or Dual taper-->Single tube. The Thorpe tube is a "tapered tube.]
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The Auxiliary flowmeters are useful for attaching supplemental O2 delivery devices, such as a nasal cannula, to the gas machine. What is an advantage and a disadvantage of the auxiliary flowmeter???
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An advantage....the breathing circuit and gas delivery hose remain intact while supplemental O2 is delivered to a spontaneously ventilating patient....also, an O2 source is readily available for the Ambu bag if the patient needs to be ventilated manually for any reason during the case. A disadvantage....if pipline supply has lost pressure or has been contaminated, the auxiliary flowmeter becomes unavailable....also, the fraction of FiO2 cannot be varied with the auxiliary flowmeter.
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What physical property of gases is applied to calibration of flowmeters.....density or viscosity???
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Flowmeters are calibrated for specific gases based upon the gas VISCOSITY at LOW FLOWS.....and the gas DENSITY at HIGH FLOWS. Recall that with low flow rates, laminar flow is typically favored and the fluid viscosity is a key determinant of laminar flow. At high flow rates, turbulent flow is more likely, and the fluid density effects the flow.
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What anesthetic gases are delivered from "Variable-Bypass" vaporizers???....and what are 3 characteristics of modern day variable-bypass vaporizers??? Where should the Variable-bypass vaporizers located...and why???
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The PIAs (volatile agents) that are delivered from Variable-Bypass vaporizers are ISO, ENFL, HALO, & SEVO. Modern day variable-bypass vaporizers are.... 1. Agent specific 2. Temperature-compensated 3. "Flow Over" (carrier gas flows over the anesthetic liquid in the vaporizing chamber) The gas delivered to the Variable-Bypass vaporizer is divided into carrier gas (flows over liquid anesthetic in the vaporizing chamber), and Non-Carrier gas, which leaves the vaporizer unchanged.....so b/c the gas flowing into the modern day vaporizer is divided into 2 streams, it is also known as a "Variable-Bypass" vaporizer. The variable-bypass vaporizers should be located 'outside the circle system', between the flowmeters & the common gas outlet....this placement lessens the likelihood of concentration surges during use of the O2 flush valve.
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What is the transport ("T") dial setting on a Drager Vapor 20.n. gas machine???....what is the equivalent of this on other gas machines???
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The Drager Vapor 20.n gas machine has a transport ("T") dial setting that helps prevent "tipping-related" problems....this function is provided by the vaporizer cassette systems of other modern gas machines.
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What system prevents filling a vaporizer with the incorrect agent??
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The "Keyed Filling Port" system on modern vaporizers prevents filling with the incorrect agent.
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Most contemporary anesthesia gas machines have variable-bypass vaporizers....but which modern gas machine does NOT have a variable-bypass vaporizer???
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The TEC 6 Desflurane Vaporizer is NOT a Variable-bypass vaporizer.....it is known as a "DUAL--GAS BLENDER" Vaporizer. The TEC 6 vaporizer is an electrically heated, thermostatically controlled, constant-temperature, pressurized, electromechanically coupled "Dual Circuit, Gas-Vapor Blender". The pressure in the Vapor circuit is "electronically regulated" to equal the pressure in the Fresh Gas circuit....at a constant FGF rate, the operator regulates vapor flow using a conventional concentration control dial. When the FGF rate decreases, the working pressure increases proportionally. For a given concentration setting, even when varying the FGF rate, the vaporizer output is constant b/c the amount of flow through each circuit remains proportional
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What are 2 reasons why DES needs a specifically-designed vaporizer??
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DES is delivered from a heated (39*C) & pressurized (1300mmHg...2x the vapor pressure) vaporizer. The DES vaporizer is NOT a flow-over vaporizer as is used with SEVO or ISO. 1. DES vapor pressure of 669mmHg is near 1 atm, so it almost boils at sea level 2. DES is only 1/5 as potent as the other PIAs, so a relatively large volume of vapor must be delivered to the patient. B/c the TEC 6 vaporizer is a "dual-gas blender", it will maintain a 'constant concentration of vapor output" (% v/v), NOT a constant partial pressure, regardless of ambient pressure.....this means that at high altitudes, the partial pressure of DES will be 'decreased' in proportion to the atmsopheric pressure. The TEC 6 requires 'manual adjustment' of the concentration control dial at altitudes other than at sea level to maintain a constant partial pressure of DES.
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DES is heated to 39*C in the TEC 6 vaporizer (a dual-gas blender)....what is the heat source and what is the saturated vapor pressure (SVP) of DES at this temperature???
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In the TEC 6 vaporizer, DES is 'electrically' heated in a sump that is "upstream" of both the common outlet and shut-off valve. Heating DES to 39*C creates a saturated vapor pressure of 2 atmospheres (~1300mmHg), which drives the agent towards the FGF. ***In contrast to other vaporizers, NO FGF goes through the DES sump (i.e. FGF never comes in contract with the liquid DES)
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The TEC 6 vaporizer does NOT automatically compensate for changes in elevation. The concentration of DES is unaffected by elevation, but the partial pressure decreases. At high elevations, the anesthetist must increase the concentration on the control dial to raise the partial pressure to the desired level. Since the partial pressure of agent delivered to the patient is what counts, you would need to increase the concentration setting when you are in the mountains so as to deliver an equivalent partial pressure of DES to the patient. Calculate the partial pressure of DES delivered from the TEC 6 vaporizer at sea level (1 atm = 760mmHg), and also in the mountains where the atmospheric pressure is 600mmHg. Do your calculations explain why delivering 5% in the mountains results in lighter anesthesia??
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If you set the dial on the TEC 6 at 5% and you are at sea level, the partial pressure of DES going to the patient is 0.05 x 760mmHg = 38mmHg (Dalton's law of partial pressures)....but if you go up into the mountains where the total atmospheric pressure is 600mmHg, then the partial pressure of DES delivered to the patient when the TEC 6 dial is set at 5% is...0.05 x 600mmHg = 30mmHg. These calculations explain why setting the dial at 5% results in lighter anesthesia in the mountains than it does at sea level....the partial pressure going to the patient for a given dial setting is lower in the mountains.
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Early vaporizer designs were susceptible to a "Pumping Effect"....what is this pumping effect???...what was the result of this effect in terms of anesthetic delivery?? How is it prevented in modern machines??
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Early vaporizer designs were susceptible to a "Pumping Effect"....intermittently fluctuating pressure in the breathing system, such as that generated by PPV or by intermittent pressing and releasing of the O2 flush valve, which caused fluctuating back pressure to be transmitted into the low-pressure system. The "pumping effect" is more pronounced at Low Flow rates. The result of this pumping effect was an increased concentration of anesthetic delivered. New anesthetic vaporizers incorporate mechanisms that decrease the size of the vaporizing chamber relative to the bypass channel & increase the volume of the inflow channel. Vapor-saturated gas cannot make its way back into the bypass channel, & thus, the pumping effect is prevented.
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What are 6 examples of how a vaporizer can be hazardous??
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1. Vaporizer filled with incorrect agent 2. Bypass chamber contaminated with liquid anesthetic if the vaporizer is tipped & spills (then when turned on, delivers a very high concentration of agent) 3. Simultaneous administration of 2 agents if the interlock mechanism is not operative 4. Development of leaks 5. Contaminated liquid anesthetic placed into the vaporizer 6. overfilling of the vaporizer
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What are 3 functions of the Interlock System on the anesthesia machine???
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Contemporary machines are secured to the anesthesia machine in manifolds that hold 2-3 units....the Interlock System, a.k.a. the Vaporizer Exclusion system...."prevents more than one vaporizer from being turned on at a time".....the operator is prevented from delivering more than any one agent simultaneously....it also ensures that all vaporizers are locked in such that leaks are decreased, and trace vapor output is minimal when the vaporizer is off.
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Generally, the Ohmeda anesthesia machines have machine outlet check valves. What is the main function of the check valve(s) in a gas machine??
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Check valves (a.k.a. UNI-Directional...or ONE-WAY Vavles) prevent retrograde flow (back flow) during PPV, therefore, minimizing the effects of downstream intermittent presure fluctuations on inhaled anesthetic concentration. Check valves (one-way valves) function to.... 1. Prevent "back-flow" from high-pressure to low-pressure sides (prevents "pumping effect" of gases) 2. Allows for an empty cylinder to be exchanged for a full one with minimal loss of gas 3. Minimizes leakage from an open cylinder to the atmosphere
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Where is the machine outlet check valve located???....when is it open and closed???
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The Machine Outlet Check Valve is located downstream from the vaporizers & upstream from the O2 flush valve. It is open in the absence of back pressure.....gas flows freely to the common outlet.....the valve closes when back pressure is exerted back on it....back pressure is created by intermittent positive pressure and O2 flushing.
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The check valve found between cylinders that are "double yoked" has what purpose???
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In the case of cylinders that are "double-yoked", the check valve prevents transfer of gas from the cylinder with higher pressure to the cylinder with lower pressure....also one of the double-yoked cylinders can be changed while the other cylinder is in use.
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What is the purpose of the Pressure Relief Valves???
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Negative & Positive pressure relief valves protect the patient from the negative pressure of the vacuum system (scavenging) or positive pressure from an obstruction in the disposal tubing.
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What is the purpose of the Fail-Safe Valve on the anesthesia machine??? At what pressure does the fail-safe valve shut off the flow of N2O or other gases??
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The Fail-Safe Valve prevents the delivery of hypoxic gas mixtures from the machine in the event of failure of the O2 supply....O2 is the only anesthetic gas that does not have a Fail-safe valve. The Fail-Safe Valve....is a.k.a. "O2-Failure Safety Valve/ Device".... "Low-Pressure Guardian System"...... "O2-Failure Protection Device"..... "Pressure Sensor Shut-off System/Valve"..... "Pressure Sensory System"...... "Nitrous Oxide Shut-off Valve". Line pressures of <30 psi will usually close the flow of all gases, except O2, to the common gas outlet.
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During an anesthetic, the fail-safe valve shuts down all non-oxygen gas flow. What has happened???
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The O2 pressure fell below 25-30 psi....when O2 pressure falls below 25-30 psi (~50% of normal), a fail-safe valve automatically closes the N2O and other gas lines to prevent accidental delivery of a hypoxic gas mixture to the patient. A gas 'whistle' or electric alarm sounds to alert the anesthetist to this occurrence.
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What do you do when the O2 low-pressure alarm sounds??
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When the O2 Low-pressure alarm sounds (indicating profound loss of O2 pipline pressure), fully open the E cylinder, disconnect the pipeline, and consider use of low FGF to conserve tank....call for back-up tank if possible.
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The scavenging system needs to be checked daily, as outlined by the FDA guidelines in 1993. 5 components of the scavenging system include the gas-collecting system, the transfer tubing, scavenging interface, the gas disposal tubing, and an active or passive gas disposal assembly. Where is the valve of the scavenging system located??....and to what is the outlet of the scavenging system connected???
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Waste gas scavengers dispose of gases that have been vented from the breathing circuit by a pressure release valve located in the breathing circuit or the ventilator. Either of these valves is connected to hoses leading to the scavenger system. The outlet of the scavenging system can be a direct line to the outside (passive scavenging) or a connection to the hospital's vaccum system (active scavenging).
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What are indications that the scavenging system is malfunctioning??? Why does the scavenging system have 2 pressure relief valves??
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When a scavenging system malfunctions or is misused, positive or negative pressure can be transmitted to the breathing system....this is more likely to occur with closed interfaces. The scavenger system has 2 pressure relief valves....one relief valve is for negative pressure, and the other is for positive pressure. The positive pressure relief valve opens if flow of waste gases into the vacuum source is insufficient and the reservoir bag distends, thus allowing some of the exhaled gases to vent into the room. The negative pressure relief valve opens if the flow of waste gases into the vacuum system is too high and the bag collapses, thus letting room air in.
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The vacuum control valve should be adjusted to allow the evacuation of what volume of waste gas per minute???......what would happen if there was too much suction was applied to the scavenging system???....or too little suction??
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The vacuum control valve should be adjusted to allow evacuation of 10-15 L/min of waste gas. Excessive suction manifests as collapse of the gas reservoir bag....and too little suction allows excessive pressure in the breathing system, leading to barotrauma.
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What is the proportioning system on the anesthesia workstation???
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A Proportioning System on the anesthesia workstation is a hypoxia prevention safety device.....manufacturers equip the machine with a proportioning system in an attempt to "prevent creation & delivery of a hypoxic mixture". N2O and O2 are mechanically and/or pneumatically linked so that the minimum O2 concentration at the common gas outlet is between 23-25%, depending upon the manufacturer. EX: "Link-25 Proportioning" system
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How does the "Link-25 Proportioning" System work???
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The Link-25 proportional system is found on conventional Datex-Ohmeda machines, and the heart of the system is the "mechanical integration of the N2O and O2 fow control valves"....it allows independent adjustment of either valve, yet automatically intercedes to maintain a minimum of 25% O2 concentration with a maximum N2O:O2 flow ratio of 3:1. This system automatically increases O2 flow to prevent delivery of a hypoxic mixture. A 14-tooth sprocket is attached to the N2O flow control valve, and a 28-tooth sprocket is attached to the O2 flow control valve...which are both linked physically by a chain. When the N2O flow control valve is turned through 2 revolutions, (28-teeth) the O2 flow control valve will revolve once b/c of the 2:1 gear ratio....the final 3:1 flow ratio results b/c the N2O flow control valve is supplied by ~26psig, whereas the O2 flow control valve is supplied by 14 psig....thus the combination of the "mechanical & pneumatic" aspects of the system yields the final O2 concentration. The 25-Link system can be thought as a system that increases O2 flow when necessary to prevent delivery of a FGF mixture with O2 concentration <25%.
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What are 5 conditions that "fool" the Proportion-Limiting System??
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The following 5 situations can lead to a delivery of hypoxic gas mixtures on workstations equipped with proportioning systems.... 1. Wrong supply gas 2. Defective pneumatics or mechanics 3. Leaks downstream 4. Inert gas administration (Helium, N2, CO2) 5. Dilution of inspired O2 concentration (FiO2) by PIAs [NOTE: An inert, 3rd gas (e.g. Helium, N2, CO2), can cause delivery of a hypoxic mixture b/c contemporary proportioning systems link only N2O and O2....use of an O2 analyzer is mandatory (or preferentially a multi-gas analyzer, when available) if the operator uses a 3rd gas]
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What is a "Double-Circuit" Ventilator???
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"Double-Circuit" ventilators ('bellows in a box, bag in a bottle) in which 1 circuit contains patient gas and the other contains drive gas....are used most commonly on modern machines. The bellows is housed in a pressure chamber, and the inside of the bellows is connected to the breathing system. The double-circuit separates breathing system gas from driving gas.....conventional ventilators are pneumatically driven.
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The mechanism of operation of high-frequency jet ventilation involves a "bias flow" of fresh gas at the level of the oscillator that provides the source of respiratory gas and washes out CO2. Injection of high velocity pulse of gas into the airway through a narrow cannula entrains fresh gas....operation of the jet ventilator, therefore, is based upon the "Venturi" effect and "Bernoulli's Principle". What O2 sources and delivery pressures are acceptable for transtracheal jet ventilation????....what sources and pressures are NOT adequate for jet ventilation??
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If a high-pressure system is available (ex: a metered & adjustable O2 source with a hand-controlled valve and a Leur-lock connector), then 15-30 psi of O2 can be delivered directly through the catheter, with insufflations of 1-1.5 seconds at a rate of 12 insufflations per minute. If a 16g catheter has been placed, this system will deliver a TV 400-700mL. At a delivery pressure of 50 psi, a 16g catheter delivers 500mL/second....in most instances, 25 psi is sufficient inspiratory pressure. Low-pressure systems cannot provide enough flow to expand the chest adquately for oxygenation and ventilation (e.g. Ambu bag 6psi, Common gas outlet 20psi, etc).
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Consider a ventilator in "pressure control" mode....what parameter fluctuates with each cycle?...what patient parameters determine this fluctuation???
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In pressure control mode, the ventilator is set so that the inspiratory pressure is greater than the PEEP....in this mode, the TIDAL VOLUME fluctuates (varies) with alterations in patient pulmonary compliance, pulmonary resistance, and with patient-ventilator asynchrony. Pressure ventilators terminate the inspiratory phase when a pre-selected pressure is achieved in the ventilator circuit...when this pressure is reached, the ventilator cycles.
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Intermittent Mandatory Ventilation (IMV) is intermittent mechanical inflation of the lung during periods of spontaneous ventilation &is used during weaning from the ventilator.....weaning using IMV is initiated by gradually decreasing the number of mechanical breaths delivered each minute. How does IMV differ from "Assist Controlled" ventilation???
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The Assist Control (AC) ventilator is set for a 'fixed rate', but patient effort of sufficient magnitude will trigger a set TV. IMV (intermittent manditory ventilation) allows spontaneous respirations while the patient is on the ventilator....a selected number of mechanical breaths (with set TV) is selected to supplement spontaneous breathing.
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How should the ventilator be set for intra-op ventilation for a patient with COPD???....why???
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Set the ventilator to deliver LARGE TV (10-15mL/kg) at a SLOW RATE (6-10 bpm)....the slow rate allows time for complete exhalation to occur, which minimizes air trapping. A large TV (10-15ml/kg) combined with a slow inspiratory flow rate minimizes the likelihood of turbulent flow through the airways and optimizes ventilation-perfusion matching. A slow rate (6-8 breaths/minute) provides sufficient time for exhalation to occur.
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What are 3 beneficial effects of Continuous Positive Airway Pressure (CPAP) administered to the critically ill patient?? When is CPAP useful in anesthesia???
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CPAP.... 1. Increases lung compliance (which decreases the WOB) 2. Diminishes ventilation:perfusion (V:Q) mismatching 3. Increases TV above the closing volume Examples of usefulness in anesthesia.... 1. CPAP 5-10 cmH2O is commonly applied when patients are intubated but breathing spontaneously...it helps maintain FRC and may prevent atelectasis since the normal mechanism for maintaining airway & alveolar patency (mild resistance to airflow by the epiglottis and upper airway structures) is bypassed by the ETT. 2. CPAP is used to maintain FRC in the post-op period 3. CPAP to the non-dependent lung may be useful during OLV to reduce shunt.
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What is the goal of PEEP ventilation (positive end-expiratory pressure)...and by what mechanism does PEEP achieve this goal?? What are 2 effects of PEEP on the respiratory system during spontaneous respirations??
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The goal of optimal PEEP ventilation is to achieve optimal arterial oxygenation with an FiO2 </= 50% with the least decrement in CO and tissue perfusion. The 2 universal pumonary effects of PEEP are.... redistribution of extravascular water.....& increased FRC through maximal alveolar recruitment....as FRC increases, oxygenation increases. (recall that FRC is a oxygen reservoir/reserve). PEEP expands collapsed (but perfused) alveoli...thus PEEP increases FRC and reduces right-to-left intra-pulmonary shunting. 1. PEEP increases lung volume at end-expiration (increases FRC) 2. PEEP prevents airway & alveolar closure at end-expiration.
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When the patient is receiving PEEP, is the inspiratory force necessary to open the PEEP valve increased by the level of expiratory pressure employed???
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YES.....if a patient receiving 10cmH2O PEEP and a 1cm H2O effort is required to normally open the valve, a total spontaneous inspiratory force of 11cmH2O is necessary to open the PEEP valve. The patient's WOB is directly increased by the opening pressure of the valves and the PEEP level. PEEP valves are uni-directional (one-direction) and will cause obstruction if aligned backward in the circuit....therefore, they must be put onto the expiratory arm (NOT the inspiratory arm).
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How does PEEP affect the SV, CO, Systemic arterial BP, and CVP??
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PEEP compresses alveolar capillaries, therefore, it decreases return of blood to the LV (decreases LV preload), and hence, the SV, CO, and systemic arterial BP are all decreased....thus hypotension may occur. However, the CVP may increase.
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What are 3 disadvantages to PEEP r/t the pulmonary system??
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1. Barotrauma 2. Increased extravascular lung water 3. Redistribution of pulmonary blood flow (decreases VR to LV, decreasing preload)
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Describe the difference between "prophylactic" and "conventional" PEEP?? What is "best" PEEP????
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Prophylactic PEEP....1-5 cmH2O is used to increase FRC in order to prevent atelectasis and decrease shunting. Conventional PEEP....5-20 cmH2O is applied if PaO2 50%.....the "best" PEEP is defined as the level of PEEP with the highest O2 transport, which is the product of CO and O2 content.....this PEEP correlates with the highest total respiratory compliance, the highest mixed venous O2 tension, and the lowest VD/VT. The "Best" PEEP is the level of PEEP that produces maximal arterial blood oxygenation without overdistention of alveoli, as reflected by static lung complicance....PEEP is added incremetally by 2.5-5 cmH2O while breathing <50% FiO2...the goal is to deliver the amount of PEEP that maximally improves the PaO2 without substantially decreasing the CO or increasing the risk of barotrauma.
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What is high PEEP??
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High PEEP is the level of PEEP with the lowest intra-pulmonary shunt & without compromising CO....and is >25 cmH2O.
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Some instances in which PPV with 25cmH2O would not be sufficient to ventilate a patient includes... 1. Upper airway obstruction 2. The patient has sufficient muscle tone to prevent chest expansion 3. The patient has decreased pulmonary compliance 4. The individual has increased pulmonary resistance What effect does IPPV (intermittent positive pressure ventilation) have on the pulmonary circulation, CO, HR, BP, and VR??
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IPPV causes compression of pulmonary capillaries with a shift of blood from capillaries to pulmonary veins and arteries. IPPV decreases VR to the LV, thus decreases CO and arterial BP...it may cause a reflex increase in HR.
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The patient has been on mechanical ventilation support for 2 days & you now desire to withdraw support. What 7 objective criteria supporting the feasibility of discontinuing mechanical ventilation???
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7 objective criteria supporting withdrawal from ventilation include.... 1. VC > 10-15mL/kg 2. A-aDO2 60mmHg while breathing 50% FiO2 4. Maximal negative inspiratory pressures > 20cmH2O 5. Normal pH maintained 6. Spontaneous Respiratory Rate < 20 breaths/min. 7. VD/VT ratio <0.6
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What is suggested protocol to wean a patient from SIMV (synchronized intermittent mandatroy ventilation)???
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To wean from SIMV, progressively decrease the frequency (rate) of breaths by 1-2 breaths/minute, and as long as the arterial CO2 tension (PaCO2) and the respiratory rate remains acceptable....generally a PaCO2< 45-50mmHg and a RR < 30 breaths/min.
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After weaning and removal from mechanical ventilation, you are ready to extubate the trachea.....what 2 criteria indicate awake tracheal extubation is appropriate???
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Extubation is reasonable if patients.... 1. Tolerate 2 hours of spontaneous breathing during T-tube weaning (trial)...or.... 2. When an SIMV rate of 1-2 breaths/minute is tolerated without deterioration of ABGs, mental status, or cardiac function.
question
Why are soda lime granules of a certain size??? What is the recommended mesh size for granules???
answer
The size provides an appropriate balance between absorptive efficiency (surface area) and resistance to airflow (channeling). Optimal size of 4-8 mesh represents a compromise between absorptive capacity and resistance to airflow through the canister. The advantage of small granules is increased absorptive capacity d/t increased surface area....but the disadvantage is that smaller granules also lead to increased resistance to gas flow d/t smaller interspaces.
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What is channeling???...and what causes it??? What problem could arise if channeling occurs??
answer
Channeling is the preferential passage of gases through the soda lime canister through low resistance pathways...most frequently caused by loose packing of absorbent granules. If channeling is present, then "rebreathing CO2" would occur.
question
When the soda lime becomes exhausted, it changes from white to violet....what should be done to compensate for exhausted CO2 absorbent if this occurs in the middle of surgery and it would be impossible to change at this time???
answer
Increase the FGF rate....high FGF rate is used to blow CO2 out of the system, then change the cannister after the case.
question
What are 3 indicators of exhausted soda lime???....and what are 4 initial s/sx exhibited by the patient when the soda lime becomes exhausted??
answer
1. The soda lime turns from white to violet 2. Inspired CO2 concentration increases (b/c of re-breathing) 3. The patient shows s/sx of CO2 retention The s/sx exhibited by the patient with exhausted soda lime (hypercapnia....CO2 retention) include.... 1. Increased BP (HTN) 2. Increased HR (Tachycardia) 3. Dry, flushed skin 4. Cardiac dysrhythmias
question
When filled, what % of the space in the soda lime cannister is air???
answer
~50%....the air space occupies 48-55% of the volume of the cannister.
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How many liters of CO2 can be absorbed for each 100g of soda lime???
answer
The maximum volume of CO2 that can be absorbed is about 26L of CO2 per 100g of commonly used absorbants.
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The most abundant constituent of both soda lime & Baralyme is Calcium hydroxide [Ca(OH)2]....soda lime has 62% and Baralyme has 80%. The CO2 absorber works via the chemical reaction of "neutralization", where an acid is neutralized by a base. What are the 5 final products when CO2 reacts with soda lime??? What are the 4 final products when CO2 reacts with Baralyme???
answer
Final products of Soda Lime... Calcium carbonate (a precipitate), Sodium hydroxide, Potassium hydroxide, Water & Heat Final products of Baralyme.... Calcium carbonate (a precipitate), Barium hydroxide, Water, & Heat
question
The American Society for Testing and Materials (ASTM) standards for the reservoir bags require that when a bag distends to 4 times its normal capacity, the pressure will not exceed 50cmH2O. What are the 11 components required on an anesthesia machine??
answer
1. Gas inlets 2. Pressure regulators 3. O2-pressure Failure devices 4. Flow-control valves & flowmeters 5. Vaporizers 6. Fresh Gas outlets 7. Spirometers 8. Breathing circuit pressure gauges 9. Ventilators 10. Waste-gas scavengers 11. O2 analyzers
question
Along with the standard 11 components required on the anesthesia machine, the CIRCLE System also includes 5 components.... 1. gas reservoir bag 2. 2 corrugated tubes 3. 2 uni-directional valves 4. canister containing a CO2 absorbent 5. overflow valve to permit escape of excess gases ....of these components, the 2 uni-directional valves generate the greatest resistance to breathing during spontaneous ventilation....the inspiratory effort required to open most uni-directional valves is from 0.5 to 1.0 cmH2O pressure. What are 5 characteristics of the CIRCLE system??
answer
The CIRCLE system is.... 1. The most used semi-closed anesthetic breathing system 2. A true breathing circuit 3. Anesthetic gases & O2 circulate in 1 direction entirely within the confines of the components of this system 4. Inspired concentrations change slowly unless the fresh gas inflow is increased 5. The inspired O2 concentration cannot be predicted when using low flows (FGF < 1.2L/min).
question
What are 5 advantages & 5 disadvantages of the CIRCLE system???
answer
5 Advantages of the CIRCLE System.... 1. Conservation of gases 2. Conservation of body heat 3. Conservation of Moisture (H2O) 4. Minimal operating room pollution 5. Relative constancy of inspired gas concentrations [***NOTE: the major advantage of using a Pediatric Circle absorber system is conservation of heat & moisture.] 5 Disadvantages of the CIRCLE system.... 1. Possibility of tubing disconnection 2. Possibility of leaks 3. Exhaustion of soda lime in CO2 absorber 4. Failure of uni-directional valves (thus rebreathing of exhaled gases occurs) 5. Not easily moveable
question
What is the most common site for breathing circuit disconnection???
answer
Although disconnection can occur anywhere in the breathing system....most commonly, disconnection occurs between the breathing system and the tracheal tube connector or the heat-moisture exchanger (HME) filter.
question
Where does the FGF enter the breathing circuit in the Circle system??? In a Circle system, where is the Dead Space located??
answer
FGF enters the circuit between the CO2 absorber and the inspiratory valve. Dead space is located between the Y-piece and the patient.
question
When does a "Semi-closed", or "Semi-open", system exist??? Why is "re-breathing" not an option in a "semi-open" system?? What are the 2 main features of both a "semi-open" and "semi-closed" systems??
answer
A "semi-closed" or "semi-open" system exists when High FGF are used in a circle system....therefore, b/c a "semi-open" system requires high FGF, rebreathing does not occur. The 2 main features of the "Semi-open" breathing system are.... 1. Gas reservoir bag 2. Utilization of a uni-directional valve and/or high FGF rates to prevent rebreathing of exhaled gases. The 2 main features of the "Semi-closed" breathing system are.... 1. Gas reservoir bag 2. Provides for partial rebreathing of exhaled gases
question
What are 4 advantages of the "Semi-open" breathing system ???
answer
The "semi-open" systems are... 1. Lightweight 2. Portable 3. Easy to clean 4. Offer low resistance to gas flow
question
Why is the APL (adjustable pressure limiting) valve important in the "Semi-closed" system???
answer
The APL valve automatically relieves pressure within the "semi-closed' system.....the APL adjusts the limit of positive pressure attained within the patient circuit & alters the amount of gas contained within the rebreathing bag. When the desired pressure in the circuit is exceeded, gas flows out of the APL valve and is vented into the scavenging system.
question
When does a "closed" system exist??? What is the main feature of a "closed" system???
answer
When the FGF to the circle system provides O2 equal to that being consumed by the patient (~150-500mL/min of O2).....therefore, when using a "closed" system, the FGF should be approximately 150-500mL/min, to satisfy the patient's oxygen requirements during anesthesia. Therefore, for a 70kg male, the minimum O2 gas flow breathing via a "closed" system is 150 ml/min. The main feature of the "closed" system.....the FGF into a circle system is decreased sufficiently to permit closure of the overflow (APL) valve, and all the exhaled CO2 is neutralized in the CO2 absorber.
question
What are the 4 advantages of the "closed" breathing system??? What is the main disadvantage of the "closed" system??
answer
Advantages of the "closed" system: 1. Maximum humidification 2. Efficiency of Gas usage 3. Less pollution of gases to the atmosphere 4. Economy The major disadvantage of the "closed" system is.... the inability to rapidly change the delivered concentration of anesthetic gases and O2. Closed systems have the slowest induction times.
question
What 2 things should be appreciated when switching from a "closed" to a "semi-open" system???
answer
1. The low flow rate of the "closed" system needs to be changed to a high FGF rate 2. There will no longer be re-breathing of exhaled gases or chemical neutralization of CO2.
question
What are the 2 main features of an "open" breathing system???....and what are the 2 main disadvantages of the "open" breathing system??
answer
The 2 main features of the "open" system include.... 1. There is NO gas reservoir bag 2. There is NO rebreathing of exhaled gases .....therefore, the 'greatest heat loss' occurs with "open" or 'non-rebreathing' systems. The 2 main disadvantages of the "open" system include... 1. The absence of a physical connection of this anesthetic breathing system to the patient results in spillage of anesthetic gases into the atmosphere 2. Inability to assist or control ventilation of the lungs
question
Which breathing systems are valveless??
answer
Open insufflation systems, open--open drop systems
question
What is the major advantages of the Ayre's T-piece?? ....what flows are required with the Ayre's T-piece to prevent rebreathing or air entrapment??
answer
The Ayre's T-piece can supply varying concentrations of inspired O2 without positive pressure with the patient breathing spontaneously.....CO2 accumulation is minimized and resistance to ventilation is minimal since there are no reservoir bag or valves. A FGF rate equal to 2-3 times the patient's minute ventilation avoids rebreathing.
question
What is the modification of the Mapleson D system also called??.....what is the advantage of this circuit compared to other pediatric circuits??
answer
The BAIN circuit....the Bain circuit helps maintain body temperature (conserves heat) b/c inspired gas is surrounded by exhaled gas....the exhaled gas transfers heat to the inspired gas.
question
The Jackson--Reese (a.k.a. Mapleson F) system is a modification of the Mapleson E system. What are 3 characteristics of the Jackson--Reese system???
answer
The Jackson-Reese system has.... 1. Minimal dead space and low resistance to breathing 2. Can be used with mask or an ETT 3. The scavenging system can be adapted to this system so as to reduce pollution of the atmosphere with anesthetic gases.
question
What flow rate is required with the Jackson--Reese system....why???
answer
About 5 L/min total flow is required to eliminate rebreathing and keep the reservoir bag inflated. The FGF requirements should be 2.5-3 times a child's minute ventilation to prevent rebreathing during spontaneous ventilation. A 500mL reservoir bag is used for pediatrics up to 2.5-3 years of age....then a larger a bag may be used for older pediatrics.
question
What are 3 disadvantages of the "Non-Rebreathing" Jackson--Reese Pediatric circuit, which are all d/t the required high flow rates in the non-rebreathing circuit??
answer
1. Increased heat loss from the patient....b/c the Jackson-Reese 'non-rebreathing' circuit promotes a decrease in body temperature. 2. Decreased humidity of gases, thus the high flow of dry gases can cause the patient to develop mucosal drying and hypothermia. 3. The need to deliver a FGF more than 2.5-3 times the patient's minute ventilation, which wastes large volumes of anesthetic agents.
question
What are 2 advantages of the "non-rebreathing" Jackson--Reese pediatric circuit??
answer
1. It minimizes the WOB b/c this circuit has no valves to be opened by the patients respiratory effort. 2. It minimizes dead space The net result is a 'more rapid induction' of anesthesia, but there is a greater risk of anesthetic overdose.
question
What are 3 advantages of the pediatric circuits....e.g. Mapleson D, Mapleson F??
answer
1. Decreased WOB b/c in the absence of valves, resistance to flow is low 2. Decreased dead space, which permits more rapid induction and allows respiratory efforts to be observed by watching movement of the anesthesia bag 3. No need for a CO2 absorber
question
Rank the relative efficiency of the Mapleson systems with respect to prevention of rebreathing "during Spontaneous Ventilation". Then rank them with respect to prevention of rebreathing "during Controlled Ventilation".
answer
During SV, the relative efficiency of Mapleson circuits to prevent rebreathing is.... A > DFE > CB. During Controlled Ventilation (PCV or VCV), the relative efficiency of Mapleson circuits to prevent rebreathing is.... DFE > BC > A
question
What is the most commonly used system for delivery of anesthetic gases to both pediatrics and adults???
answer
The "Semi--Closed" breathing circuit.
question
Where should the O2 sensor be placed???
answer
The O2 sensor should be placed in the INSPIRATORY LIMB of a Circle system.....if it was placed at the common gas outlet, it does not detect rebreathing or disconnect distal to the common gas outlet, and does not measure the respiratory concentration of O2.
question
The components of the Low Pressure system of the anesthesia machine include.... 1. Flow indicators 2. Vaporizers 3. Vaporizer circuit control valves 4. Vack pressure safety devices 5. Low-Pressure safety devices 6. Common gas outlet What 4 actions should be done to check the Low Pressure system???
answer
1. Close the APL valve & occlude system at the patient end. 2. Fill system via the O2 flush valve until the reservoir bag is full, while keeping pressure in system negligible...then set the O2 flow to 5L/min. 3. Slowly decrease the O2 flow until pressure no longer rises above 20cmH2O...this approximates total leak rate, which should be no greater than several hundred mL/min (or even less for closed circuit techniques). [CAUTION: Check valves in some machines make it imperative to measure flow (in step 3) when pressure just stops rising.] 4. Squeeze the reservoir bag to pressure of about 50 cmH2O and verify that system is tight.
question
What are the 9 parameters that the anesthesia machine must monitor in order to comply with the ASTM F1850-00???
answer
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 BP 9. Continuous ECG
question
What type of anesthesia machines should be tested with a Negative Pressure Leak Test?? How is this test performed??
answer
Anesthesia machines with CHECK VALVES should be tested with a Negative Pressure Leak Test....in 1993, the FDA implemented a universal Negative-pressure Leak Test that can be used on all contemporary anesthesia machines, regardless of the presence or absence of check valves. [NOTE: To perform a Negative Pressure Leak Test....a suction bulb is attached to the Common Fresh Gas Outlet & squeezed repeatedly until the bulb is fully collapsed....the anesthesia machine is "leak free" if the bulb remains collapsed for at least 10 seconds.]
question
When the O2 flush button is pushed, what is the Liter flow rate??? .....and what risk is associated with a dysfunctional flush valve??
answer
35-75 L/min. A damaged or defective flush valve can stick in the fully open position, causing barotrauma.
question
You are scheduled to provide anesthesia to a patient with a known susceptibility to MH...how will you prepare the gas machine in anticipation of this case???
answer
The concern in this situation is that there are trace amounts of PIAs in the rubber and plastic components of the machine and in the ventilator & CO2 absorber. The following 3 actions should be taken to prepare the machine for this patient.... 1. The machine should be thoroughly flushed with 100% O2 for at least 10 minutes to remove residual traces of PIAs from rubber and plastic components in the machine (60minutes for the Drager) 2. The breathing circuits and CO2 absorber canister should be replaced 3. Vaporizers should be drained, inactivated, or removed.
question
Does the descending bellows descend during inspiration or exhalation???....and what is the potential disadvantage of the descending bellows??? What about the ascending bellows makes it more advantageous???
answer
The Descending bellows ("hanging" bellows) descends during Expiratory phase.....if a disconnect happens, the descending bellows will continue its upward & downward movement....the drive gas pushes the bellows upward during inspiratory phase. During the expiratory phase, room air is entrained into the breathing system at the site of disconnect b/c gravity acts on the weighted bellows. This is why the Ascending Bellows is safer....b/c ascending bellows will NOT rise if disconnection occurs....also the ascending bellows permits easier detection or circuit leaks or disconnects, and less chance of high airway pressures from gas entering the breathing circuit through bellow leaks.
question
Why does looking at the volume returned on an ascending bellows 'not' reflect true tidal volume???
answer
The respirometer measures exhaled gases....TV settings of the ascending bellows, as indicated on the outside of the plastic canister, differ from respirometer readings....this is d/t compression of gases, expansion of the breathing circuitry hoses during the mechanically ventilated inspiration, and the addition of humidifiers. Decreased lung compliance will also force gases that were not used by the patient through the respirometer.
question
The gas enters that bellows during expiration, is composed of what??? What gas is present outside of the bellows....and what gases are present within the bellows???
answer
During the expiration phase of the ventilatory cycle, 'exhaled gases from the patient & fresh anesthetic gases' flow into the bellows. Pressurized O2 from the ventilator power outlet is found between the inside wall of the enclosure and the outside wall of the bellows (i.e. outside of the bellows). The inside of the bellows, which is an extension of the anesthesia breathing circuit, is filled with anesthetic gases.
question
What is the goal of humdifying the inspired gases??
answer
The goal is to improve mobilization of secretions by increasing water content (reducing airway drying) and decreasing viscosity. However, large amounts of condensed water vapor in an ETT can obstruct the breathing circuit.
question
When is a NPA preferable to an OPA??
answer
An NPA (nasal trumpet) is better tolerated than an OPA if the patient has intact airway reflexes...also preferred if the patient's teeth are loose or in poor condition, if there is trauma or pathology of the oral cavity, and can be used when the mouth cannot be opened. [NOTE: The length of the nasal passage is estimated as the distance from the nares to the meatus (opening) of the ear....the length should be 2-4 cm longer than a corresponding OPA.]
question
What are 4 contraindications to using a NPA??
answer
Contraindications for using an NPA (nasal trumpet) include.... 1. Anticoagulation 2. Basilar skull fracture 3. Pathology, sepsis, or deformity of the nasal cavity or nasopharynx 4. Hx/o nosebleeds requiring medical treatment
question
An OPA (oral airway) creates an artificial, patent passage to the hypopharynx....and can be used to prevent the patient from biting the ETT or tongue, facilitate oropharyngeal suctioning, obtain a better mask fit (better ventilation), and provide a pathway for inserting devices into the esophagus or pharynx (i.e. FOB, OGT, etc). What are indications and contraindications for an OPA??
answer
An OPA is indicated for an obstructed upper airway in an UNCONSCIOUS patient & when there is need for a bite block in an unconscious patient. An OPA is Contraindicated in the AWAKE or LIGHTLY Anesthetized patient....b/c the patient may cough or develop laryngospasm during insertion if reflexes are intact.
question
What is the purpose of the Laryngoscope Flange??
answer
The flange projects off the left side of the laryngoscope and serves to sweep the tongue out of the way and to guide instrumentations along the blade.
question
A lighted intubation stylet (lightwand) uses transillumination of the soft tissues in the anterior neck to guide the tip of the tracheal tube into the trachea or to determine the position of the tracheal tube or other airway device. When is a Lightwand useful??
answer
During DL, the lightwand can be used to improve the view of the hypopharynx....it is especially useful in situations where a fiberscope is unavailable or endoscopy is difficult to perform (e.g. when an airway obscured by blood or secretions or when a patient's head cannot be flexed or extended). [NOTE: For oral intubation, a "J" or "hockey stick" bend of ~75 to 120 degrees just proximal to the cuff is recommended.....be careful NOT to bend the stylet at the point at which the bulb meets the shaft, b/c it may loosen or break off while placing it into the patient's airway and dislodge into the patient's airway].
question
Potential uses of the airway exchange catheter include....tracheal tube or supraglottic (LMA) device exchange, Replacing or existing tube, changing an ETT from oral to nasal, intubation, extubation, To provide ventilation during microlaryngeal surgery (if it has a hole in it), to provide a useful guide to the trachea during flexible endoscopy or to Facilitate passage of a ETT over a fiberscope. What are features are advantageous for an airway exchange catheter???
answer
Airway exchange catheters have a central lumen, & rounded, atraumatic ends.....the catheters are graduated from the distal end.....and the proximal end is fitted with either a 15mm or a Luer-lock Rapi-Fit adapter, which can be quickly removed and replaced for ETT removal or exchange. With these adaptors an O2 source can be used to provide insufflated or jet-ventilated O2 if the patient fails extubation and/or if re-intubation over the catheter fails.
question
What is an Eschmann introducer??
answer
A 60cm, 'stylet-like' device that has a 5mm external diameter and a 35-degree bend 2.5cm from the end that is inserted into the trachea.....its structure is designed to provide a combination of stiffness and flexibility and is extremely useful when DL view is poor or the ETT cannot be otherwise guided into the glottis. It is also useful in limiting the degree of necessary neck movement during intubation with potential C-spine injuries and to lessen the risk of dental damage. Once it has entered the trachea, a distinctive "clicking" feel is sensed as the tip passes over the cartilge rings of the trachea.
question
Inspiratory pressure should be limited to what value when providing PPV by a manual resuscitator (ex: bag-valve mask)??
answer
When providing PPV with a manual resuscitator (such as a BVM), it is 'imperative' to limit the positive pressure to 25cmH2O to avoid inflating the stomach, which increases the risk of regurgitation.
question
What are 3 characteristics of high-frequency jet ventilation???
answer
1. Small TV (< than dead space) 2. High ventilation rate (60-3,000 breaths per minute) 3. Low airway pressure
question
Transtracheal ventilation is performed by inserting a large catheter through the cricothyroid membrane and connecting it to a source of O2 under pressure. What 2 criteria must be met when providing O2/gas source for transtracheal jet ventilation (TTJV)???....and what 3 gas sources meet these criteria??
answer
In order to provide adequate ventilation through the non-compliant tube used in TTJV, a "high-pressure O2 source" and a "regulating valve" are required. High pressure O2 is delivered reliably through... 1. Central wall outlets 2. High flow (50-100 psi) tank regulators 3. The flush valve on the anesthesia machine Central line or tank gas is used to power a jet injector (blow gun) connected to the transtracheal catheter. [Low pressure systems, such as a self-inflating resuscitation bag or an anesthesia breathing system, CANNOT provide enough flow to expand the chest adequately. However a low pressure device may be used temporarily until a more definitive airway is secured.]
question
What 3 systems reliably work & can be easily (& inexpensively) used for transtracheal jet ventilation??
answer
1. Jet injector (blow gun) is powered by regulated or unregulated pipeline O2 pressure 2. Jet injector is powered by an O2 cylinder regulator 3. The anesthesia machine flush valve is used. The fresh gas outlet of the machine is connected to noncompliant tubing by standard 15mm tracheal tube connector...the other end is connected to the transtracheal catheter.
question
What are 5 complications of 'high-frequency' jet ventilation???
answer
Complications of 'high-frequency' jet ventilation include... 1. Gas trapping 2. Bronchoconstriction 3. Failure to adequately ventilate the patient 4. Inaccurate delivery of anesthetic gases 5. Damage to tracheal mucosa and thickened secretions d/t inadequate humidification of inspired gases (**most common complication)
question
What are 5 complications of high-frequency 'translaryngeal' jet ventilation??
answer
Complications of high frequency 'translaryngeal' jet ventilation..... 1. Barotrauma (pneumothorax or mediastinal air) 2. Gastric dilation 3. inadequate ventilation during inhalation or exhalation 4. Vocal cord motion (unless transtracheal jet ventilation is used) 5. Blowing tumors, blood or debris into the depths of the lungs
question
What are 7 complications of 'transtracheal' jet ventilation??
answer
Complications of 'transtracheal' jet ventilation include... 1. Barotrauma with resultant pneumothorax 2. Subcutaneous emphysema (air) 3. Mediastinal emphysema (air) 4. Exhalation difficulty 5. Arterial perforation 6. Esophageal puncture with bleeding, hematoma, and hemoptysis 7. Damage to tracheal mucosa if non-humidified gas is delivered [RLN injury is NOT a common complication]
question
What is the hallmark s/sx of laryngotracheal damage??
answer
STRIDOR
