logging in or signing up AN APPROACH TO ANAESTHESIA WORKSTATION drshirisha Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: Embed: Flash iPad Copy Does not support media & animations WordPress Embed Customize Embed URL: Copy Thumbnail: Copy The presentation is successfully added In Your Favorites. Views: 1742 Category: Education License: All Rights Reserved Like it (2) Dislike it (0) Added: April 17, 2011 This Presentation is Public Favorites: 1 Presentation Description No description available. Comments Posting comment... By: dhineshprabhu (10 month(s) ago) very nice Saving..... Post Reply Close Saving..... Edit Comment Close Premium member Presentation Transcript AN APPROACH TO ANAESTHESIA WORKSTATION: AN APPROACH TO ANAESTHESIA WORKSTATION MODERATORS: DR.B.SOWBHAGYA LAKSHMI,MD PROFESSOR IN DEPT. OF ANAESTHESIOLOGY DR.KRISHNA PRASAD,MD ASSISTANT PROFESSOR PRESENTED BY DR.SIRISHA ANAPARTHI PG IN ANAESTHESIOLOGYSlide 2: NO EQUIPMENT IS MORE INTIMATELY ASSOCIATED WITH THE PRACTICE OF ANAESTHESIOLOGY THAN THE ANAESTHESIA MACHINESlide 3: The Anaesthesia Machine The anaesthesia machine is a device which delivers a precisely-known but variable gas mixture, including anaesthetizing and life-sustaining gases.HISTORY: HISTORY The original concept of Boyle's machine was invented by the British anaesthetist H.E.G. Boyle in 1917. Prior to this time, anaesthetists often carried all their equipment with them, but the development of heavy, bulky cylinder storage and increasingly elaborate airway equipment meant that this was no longer practical for most circumstances. The anaesthetic machine is usually mounted on anti-static wheels for convenient transportation.Slide 5: HISTORY : • 1917 – Boyle machine with a water sight feed type of flowmeter is introduced by Henry Edmund Gaskin Boyle. • 1920 – A vapourizing bottle is incorporated to the machine. • 1926 – A 2nd vaporizing bottle and by-pass controls are incorporated. • 1930 – A Plunger device is added to the vaporizing bottle. • 1933 – A dry-bobbin type of flowmeter is introduced. • 1937 – Rotameters displayed dry-bobbin type of flowmetersSlide 6: Anesthetic Machines Anesthetic machines began appearing at the end of the 19 th century Early anesthetic machines were utilized in dental anesthesia for administration of N 2 O and O 2 Initial machines were either: Continuous flow – continuous flow throughout inspiration and expiration ( eg . Heidbrink , Foregger , Boyle) Intermittent flow – flow of gas during inspiration only ( eg . McKesson) Machines evolved to incorporate reducing valves, flow meters, vaporizers and circuits with carbon dioxide absorptionSlide 7: Boyle Anesthesia Apparatus c. 1920 Modification of original machine developed by Dr. Henry Boyle in 1917 Coxeter dry flow meter allowed proportioning of O 2 , CO 2 & N 2 O Two glass vaporizing bottles Bottom illustrations: Case with accessories Machine stand with four cylinder yokes (2 each for N 2 O and O 2 ) + carrying handle 116a, 117Slide 8: Foregger Metric Gas Machine Montreal Model c. 1924 Modification of Richard von Foregger’s original metric gas machine for use with cyclopropane Eliminated reserve gas tanks, with exception of O 2 , because of the increased use of CO 2 absorbers “Wet flowmeters ” used water displacement to provide accurate measurement while introducing humidity to reduce the risks of interior static 23Slide 9: Water’s Cannisters (Waters “to and fro”) c. 1930 Ralph M Waters began experiments with CO 2 absorption in 1915 Developed “to and fro” system through which inspired and expired gases were directed Metal cylinder was packed with absorbent alkaline granules resulting in economy of gas use along with heat and moisture conservation 109 a-cSlide 10: McKesson Nargraf Machine (Model H) c. 1920 Modification of Dr. E I McKesson’s Model A machine of 1910 Reducing valves admit N 2 O and O 2 into two bags enclosed in metal drums at equal pressures Gases pass to percentage mixing chamber with proportion controlled by dial Intermittent flow is dependant upon patients inspiration 119Slide 11: Heidbrink Apparatus (mixing head only) c. 1930 Modification of Dentist Jay Heidbrink’s original apparatus introduced in 1912 for administration of N 2 O and O 2 primarily for dental anaesthesia Proportioning device and valves reduced cylinder pressure of tank gases to working pressures 143Slide 12: Midget Kinet -O-Meter c. 1940 Modification of Dr. Heidbrink’s earlier apparatus to administer N 2 O / O 2 for dental anesthesia Flow meter panel calibrated for oxygen, nitrous oxide and cyclopropane along with four cylinder yokes (two each for O 2 and N 2 O) Mounted on a pole to which chart stand support is attached 118OUTLINE: OUTLINE The Machine Gas Supply Systems: Hospital pipeline Cylinder High Pressure System (exposed to cylinder pressure) Intermediate Pressure System (exposed to pipeline press) Low Pressure System (distal to flowmeter needle valve) Circle System CO2 Absorber System Unidirectional Valves Ventilator Scavenger SystemSlide 14: The Machine Ohmeda N.A.Drager (Narkomed)Slide 15: Anesthesia Machine: Jackson Memorial HospitalSlide 16: vaporizer bellow Corrugated tube Soda lime Flow meter ventilator APL valve Scavenging systemSlide 17: Basic SchematicsSlide 18: The Anesthesia Machine High Intermediate Low Pressure CircuitPNEUMATIC SYSTEM: PNEUMATIC SYSTEM 1. HIGH PRESSURE a. Hanger Yoke b. Power Failure Indicator c. Pressure Regulators 2. INTERMEDIATE PRESSURE SYSTEM a. Master Switch (Pneumatic component) b. Pipeline Inlet Connections c. Pipeline Pressure Indicators d. Piping e. Gas Power Outlet f. Oxygen Pressure Failure Devices g. Gas Selector Switch h. Second-Stage Pressure Regulator i . Oxygen Flush j. Flow Adjustment Control 3. LOW PRESSURE SYSTEM a. Flowmeters b. Hypoxia Prevention Safety Devices c. Unidirectional (Check) valve d. Pressure Relief Device e. Low-Pressure Piping f. Common (fresh) Gas Outlet 4.ALTERNATIVE OXYGEN CONTROLSlide 20: Gas Supply Systems Hospital PipelineSlide 21: Pipeline Trouble Pipeline sources are not trouble free : contamination (particles, bacteria, viral, moisture), inadequate pressure, excessive pressures, and accidental crossover (switch between oxygen and some other gas such as nitrous oxide or nitrogen) are all reported.Slide 22: DISS Pipeline inlets are connected with DISS (diameter index safety system) non-interchangeable connections. The check valve , located down stream from the pipeline inlet, prevents reverse flow of gases (from machine to pipeline, or to atmosphere), which allows use of the gas machine when pipeline gas sources are unavailable.Slide 23: PISS PISS (pin-index safety system) prevents misconnection of a cylinder to the wrong yoke. Keep cylinders closed except when checking machine, or while in use (if O2 from pipeline is unavailable)Slide 24: Diagram showing the index positions of a cylinder valve. Oxygen: 2 & 5 Nitrous oxide: 3 & 5 Air: 1 & 5 CO 2 : 1 & 6Slide 25: Color coding of medical gas cylinders and their pressure when full Name of the gas Body colour Shoulder colour Pressure ( kPa ) (At room temp) Oxygen Black White 13700 Nitrous Oxide Blue Blue 4400 Carbon dioxide Grey Grey 5000 Air Grey White/black quarters 13700 Entonox Blue White/blue quarters 13700 Oxygen/helium Black White/brown quarters 13700Slide 27: LAPSE IN MAINTENANCE Sudbury Ontario in the 1970s: 23 people died because the N 2 0 and O 2 pipelines were crossed over during repairsSlide 28: Gas Supply Systems Cylinder Pin Index Safety System: O2 2,5 N2O 3,5Slide 29: High Pressure System (parts which receive gas at cylinder pressure) hanger yoke (including filter and unidirectional valve) yoke block (with check valves) cylinder pressure gauge cylinder pressure regulatorsSlide 30: Bourdon GaugeSlide 31: Hanger Yoke & Check Valve Hanger Yoke orients cylinders provides unidirectional flow ensures gas-tight seal. Check Valve minimize trans-filling allows change of cylinders during use minimize leaks to atmosphere if a yoke is empty.Slide 32: Check valves The check valve , located down stream from the pipeline inlet, prevents reverse flow of gases (from machine to pipeline, or to atmosphere), which allows use of the gas from cylinder when pipeline gas sources are unavailable.Slide 33: Check ValveCYLINDERS: CYLINDERS The cylinder pressure regulator converts high, variable cylinder pressure to a constant pressure of approximately 45 psi downstream of the regulator. This is intentionally slightly less than pipeline pressure, to prevent silent depletion of cylinder contents if a cylinder is inadvertently left open after checking its pressure. Cylinder pressure gauge indicates pressure in the higher-pressure cylinder only (if two are opened simultaneously).Slide 36: Anesthesia Components Anesthesia Machine Frame Regulator Placed on O 2 tanks to decrease pressure from tank 2 types of tanks “E” Tanks 650L @ 1800PSI “H” Tanks 7100L @ 2200PSI Output pressure adjusted with knobSlide 37: E cylinder Characteristics Gas US (International) PSI Capacity (L) PISS O2 Green (white) 1900 660 2-5 N2O Blue (blue) 745 1590 3-5 Air Yellow (B & W) 1900 625 1-5 **** We’ll use 2000psi for O2 instead of 1900psi****Slide 38: HOW LONG BEFORE O2 TANK IS EXHAUSTED??? -The time to exhaustion is calculated by dividing the remaining O2 volume in the cylinder by the rate of consumption of O2. -Remaining volume in liters (L) in an E-cylinder is calculated by dividing the cylinder pressure in psig by 2000 psig and multiplying by 660 L.Slide 39: EXAMPLE If cylinder gauge reads 1,000 psig, this represents (1000/2000) X 660 = 330 L left in that tank. The rate of consumption of O2 during mechanical ventilation is the sum of the O2 flow meter setting and the patient’s minute ventilation (VT in L x RR in breaths/min). If FGF is 0.5 L/min O2 and 1.0 L/min N2O and VT is 0.7 L and RR is 10 bpm, then the minute ventilation is 7 L/min (0.7L x 10 bpm) * The total O2 consumption is 7.5 L/min . The expected time to exhaustion is thus approximately 330 L divided by 7.5 L/min = 44 min (ignoring the gas sampled by the gas analyzer and leaks )Slide 40: Intermediate Pressure System Machine piping “guts” Gauges-pipeline (intermediate press. ) Hospital Pipeline Outlets Hospital Pipeline InletsSlide 41: Intermediate Pressure System ( receives gases at low, relatively constant pressures (37-55 psi, = pipeline pressure) (*For consistency we’ll use 50 psi) pipeline inlets and pressure gauges ventilator power inlet Oxygen pressure-failure device (fail-safe) and alarm flowmeter valves oxygen second-stage regulator oxygen flush valveSlide 42: Oxygen Pressure Failure Devices A Fail-Safe valve is present in the gas line supplying each of the flowmeters except O 2 . This valve is controlled by the O 2 supply pressure and shuts off or proportionately decreases the supply pressure of all other gasses as the O 2 supply pressure decreases Historically there are 2 kinds of fail-safe valves Pressure sensor shut-off valve ( Ohmeda ) Oxygen failure protection device ( Drager )Slide 43: Oxygen Pressure Failure Devices Machine standard requires that an anaesthesia machine be designed so that whenever the oxygen supply pressure is reduced below normal, the oxygen concentration at the common gas outlet does not fall below 19%Slide 44: Pressure Sensor Shut-Off Valve Oxygen supply pressure opens the valve as long as it is above a pre-set minimum value (e.g. 20 psig). If the oxygen supply pressure falls below the threshold value the valve closes and the gas in that limb (e.g. N 2 O) does not advance to its flow-control valve.Slide 45: Pressure Sensor Shut-Off ValveSlide 46: Oxygen Failure Protection Device (OFPD) Based on a proportioning principle rather than a shut-off principle It shuts off or proportionately decreases & ultimately interrupts supply of N 2 O if O 2 supply pressure decreases The pressure of all gases controlled by the OFPD will decrease proportionately with oxygen pressure.Slide 47: Oxygen Failure Protection Device (OFPD)Slide 48: Oxygen Supply Failure Alarm The machine standard specifies that whenever the oxygen supply pressure falls below a manufacturer-specified threshold (usually 30 psig), a medium priority alarm shall blow within 5 seconds.Slide 49: Limitations of Fail-Safe Devices/Alarms Fail-safe valves do not prevent administration of a hypoxic mixture because they depend on pressure and not flow. These devices do not prevent hypoxia from accidents such as pipeline crossovers or a cylinder containing the wrong gasSlide 50: Contd. These devices prevent hypoxia from some problems occurring upstream in the machine circuit (disconnected oxygen hose, low oxygen pressure in the pipeline and depletion of the oxygen cylinder) Equipment problems that occur downstream (for example leaks or partial closure of the oxygen flow control valve) are not prevented by these devices.Slide 51: Oxygen Flush Valve (O2+) Receives O2 from pipeline inlet or cylinder reducing device and directs high, unmetered flow directly to the common gas outlet (downstream of the vaporizer) Machine standard requires that the flow be between 35 and 75 L/min The ability to provide jet ventilation Hazards May cause barotrauma Dilution of inhaled anestheticSlide 52: Second-Stage Reducing Device Located just upstream of the flow control valves Receives gas from the pipeline inlet or the cylinder reducing device and reduces it further to 26 psig for N2O and 14 psig for O2 Purpose is to eliminate fluctuations in pressure supplied to the flow indicators caused by fluctuations in pipeline pressureSlide 54: Low Pressure System Extends from the flow control valves to the common gas outlet Consists of: Flow meters Vaporizer mounting device Check valve Common gas outletSlide 55: Flowmeters -Thorpe tube is an older term for flowmeters. -Components : needle valve, indicator float, knobs, valve stops. -Flow increases when the knob is turned counterclockwise (same as vaporizers). - At low flows, the annular-shaped orifice around the float is (relatively) tubular so (according to Poiseuille's Law) flow is governed by viscosity . (laminar flow) - At high flows (indicated on the wider top part of the float tube), the annular opening is more like an orifice, and density governs flows. (turbulent flow)Slide 56: Low Pressure System Distal to Flowmeter Needdle Valve Flow Meters - measures and indicates the rate of gas flowing through it. Variable orifice/Thorpe tube-constant press. flow meters. Rate of flow r/t: 1) pressure drop across the constriction 2) size of annular opening 3) Physical properties of the gas (viscosity and density) Indicator, float or bobbin- 1) rotometers 2) non-rotating floats 3) ball floats Sequence of flowmeters tubes is very important to decrease chance of hypoxic mixture., Gas flow is from left to right, O2 on right side. Any leak in flowmeters will vent other gas out or entrain air before O2 is added to gas mixture decreasing chance that O2 will be lost or diluted. FLOWSlide 57: Flowmeter assembly When the flow control valve is opened the gas enters at the bottom and flows up the tube elevating the indicator The indicator floats freely at a point where the downward force on it (gravity) equals the upward force caused by gas molecules hitting the bottom of the floatSlide 59: Arrangement of the Flow-Indicator Tubes In the presence of a flowmeter leak (either at the “O” ring or the glass of the flow tube) a hypoxic mixture is less likely to occur if the O2 flowmeter is downstream of all other flowmeters In A and B a hypoxic mixture can result because a substantial portion of oxygen flow passes through the leak, and all nitrous oxide is directed to the common gas outlet * Note that a leak in the oxygen flowmeter tube can cause a hypoxic mixture, even when oxygen is located in the downstream positionCONTD………………………….: CONTD…………………………. Needle valve can be damaged if it is closed with force Flowtube (Thorpe tube) is tapered (narrower at bottom) and gas-specific If gas has 2 tubes, they are connected in series with a single control valveCONTD……………………………: CONTD…………………………… Care of flowmeters includes ensuring that: floats spin freely qualified service personnel regularly maintain gas machines an O2 analyzer used always (of course, the readings are erroneous during use of nasal cannula ) one never adjusts a flowmeter without looking at it one includes flowmeters in visual monitoring sweeps one turns flowmeters off before opening cylinders, connecting pipelines, or turning machine "on".Slide 62: Proportioning Systems Mechanical integration of the N2O and O2 flow-control valves Automatically intercedes to maintain a minimum 25% concentration of oxygen with a maximum N2O:O2 ratio of 3:1Slide 63: Low Pressure System Safety Devices -Purpose is to decrease risk of hypoxic mixture * Mandatory Minimum O2 Flow- factory preset minimum O2 flow that always flows when machine is on. * Minimum O2/N2O Ratio– 1:3 Device or proportioning system : Flow valves linked mechanically or pneumatically so O2 cannot be set below 25%. Alarm will signal if O2/NO2 ratio falls below preset value * O2/NO2 Proportioning Device- Automatically mixes O2 and NO2 to setting selected on dialSlide 66: Hypoxic breathing is POSSIBLE hypoxic guard systems CAN permit hypoxic breathing mixtures IF : wrong supply gas in oxygen pipeline or cylinder, defective pneumatic or mechanical components, leaks exist downstream of flow control valves, or if third inert gas (such as helium) is used.Slide 67: SAFETY MECHANISMS IN LOW PRESSURE SYSTEM Oxygen must enter the common manifold downstream to other gases It prevents hypoxia in event of proximal gas leak Oxygen concentration monitor and alarm prevent administration of hypoxic gas mixtures in event of a low-pressure system leak, thus precisely regulating oxygen concentrationSlide 68: Safety in flowmeter subassembly Each flowmeter is housed in an independent, colour coded pin specific module Oxygen flowmeter is placed downstream Backpressure check valve Link device Backlight displaySlide 69: Flow control valve assembly Oxygen flow control valve is physically distinguishable from other gas knobs It projects beyond control knob of other gases Its diameter is larger Placement of knobs at a distance All are colour codedSlide 70: Hypoxia prevention safety devices Mechanical integration of the N 2 O and O 2 flow-control valves Automatically intercedes to maintain a minimum 25% concentration of oxygen with a maximum N 2 O:O 2 ratio of 3:1Slide 71: Limitations of the system Machines equipped with proportioning systems can still deliver a hypoxic mixture under the following conditions: Wrong supply gas Defective pneumatics or mechanics (e.g. the Link-25 depends on a properly functioning second stage regulator) Leak downstream (e.g. broken oxygen flow tube) Inert gas administration: Proportioning systems generally link only N 2 O and O 2Slide 72: Low Pressure System Vaporizers - Classification: A. Method of regulating output concentration 1. Concentration calibrated 2. Measured flow B. Method of vaporization 1. Flow over 2. Bubble Through 3. Injection C. Temperature compensation 1. Thermocompensation 2. Supplied heat D. Specificity 1. Agent specific 2. Multiple agent E. Resistance 1. Plenum 2. Low resistanceSlide 73: VAPORIZERS Vapor Pressure (VP) Molecules escape from a volatile liquid to the vapor phase, creating a “saturated vapor pressure” at equilibrium VP is independent of Atmospheric Press VP increases with Temperature VP depends ONLY on the Physical Characteristics of the Liquid & on its TemperatureSlide 74: CLASSIFICATION Variable bypass Fresh gas flow from the flowmeters enters the inlet of any vaporizer which is on. The concentration control dial setting splits this stream into bypass gas (which does not enter the vaporizing chamber), and carrier gas (also called chamber flow, which flows over the liquid agent)Slide 75: CLASSIFICATION Flow over Carrier gas flows over the surface of the liquid volatile agent in the vaporizing chamber (as opposed to bubbling up through it (as in the copper kettle and Vernitrol)Slide 76: CLASSIFICATION Temperature compensated Equipped with automatic devices that ensure steady vaporizer output over a wide range of ambient temperatures Agent-specific Only calibrated for a single gas, usually with keyed fillers that decrease the likelihood of filling the vaporizer with the wrong agent Out of circuit As opposed to (much) older models such as the Ohio #8 (Boyle's bottle) which were inserted within the circle system.Slide 77: Vaporizer Interlock Mechanism Safety mechanism that allows ONLY one vaporizer at a time to be openedSlide 78: Vaporizers – safety mechanisms Arrangement of vaporizers on back bar Colour coded, agent specific key filling system Interlock device Select-a-tec system Firmly securedSlide 79: Vaporizer Interlock Mechanism Safety mechanism that allows ONLY one vaporizer at a time to be openedSlide 80: Circle System Circle System - CO2 absorber housing and absorber , unidirectional valves , inspiratory and expiratory ports , fresh gas inlet, APL valve, pressure gauge, breathing tubes, Y-piece, reservoir bag, bag/vent switch selector, respiratory gas monitor sensor.Slide 81: The Circuit: Circle System Arrangement is variable, but to prevent re-breathing of CO2, the following rules must be followed: Unidirectional valves between the patient and the reservoir bag Fresh-gas-flow cannot enter the circuit between the expiratory valve and the patient Adjustable pressure-limiting valve (APL) cannot be located between the patient and the inspiratory valveSlide 82: Circle System CO2 Absorber System : Housing (canister support), Absorbent, baffles, side tube Unidirectional Valves -aka Flutter valves, one way valves, check valves, directional valves, dome valves Canister - Air space 50%, void space 42%, pore space 8% Soda Lime : 4% Sodium Hydroxide, 1% potassium hydroxide, 14-19% H2O, and calcium hydroxide to make 100%, Silica and kielselguhr for hardness Indicator for color change with exhaustion of CO2 absorption capabilities CO2+H2O H2CO3 2NaOH+2H2CO3+Ca(OH) 2 CaCO3+NaCO3+4H2O heat released 13,700 cal./mole CO2 absorbed Barium Hydroxide Lime : 20% Barium hydroxide, 80% calcium hydroxide, and +/- potassium hydroxide, Indicator for color change with exhaustion of CO2 absorption capabilities Ba (OH) 2 . 8H2O+CO2BaCO3+9H2O 9H2O+9CO2 9H2CO3 9H2CO3+9Ca(OH) 2 9CaCO3+18H2O 2KOH+H2CO3 K2CO3+2H2O Ca(OH) 2 +K2CO3 CaCO3+2KOH Regeneration (color change loss) with rest can occur. Appears new but is exhausted Granule size 4-8 mesh- 4 mesh equals strainer with 4 openings/inchSlide 83: Circle system CO2 Absorber System canisters unlocked Removing both canisters & soda lime canister locking lever Removing canister & soda lime Exhausted soda lime Replacing fresh soda limeSlide 84: Circle System Advantages: Relative stability of inspired concentration Conservation of respiratory moisture and heat Prevention of operating room pollution PaCO2 depends only on ventilation, not fresh gas flow Low fresh gas flows can be used Disadvantages: Complex design = potential for malfunction High resistance (multiple one-way valves) = higher work of breathingSlide 85: Unidirectional or check valve Located between vaporizer and common gas outlet reduces the pressure increase due to back pressure caused by IPPVSlide 86: Circle system Unidirectional Valves Unidirectional valves- aka flutter valves, one way valves, check valves, directional valves, dome valves. Found on Inspiratory and Expiratory flow ports Narkomed Machine Ohmeda MachineSlide 87: Ventilator Ventilator Components: Driving gas supply, injector, controls, alarms, safety-release valve, bellows assembly, exhaust valve, spill valve, connection for ventilator hose Bellows assembly Ventilator controlsCONTD…………….: CONTD……………. Driving gas supply or power gas supply-O2 pneumatically drives (compresses) ventilator bellows Injector or Venturi mechanism-Increases the flow of driving gas by using the BERNOULLI Principle- As a gas flow meets a restriction, its lateral pressure drops. Any opening in the tube at this constriction will entrain air (suck air in) Controls-Adjusts Flow, Volume, Timing, and Pressure of the driving gas that compresses the bellows Pneumatic -Uses pressure changes to initiate changes in respiratory cycle Fluidic or fluid logic -Uses gas streams through channels in solid material. Allow forcompact ventilator Electronic -Electronic control of many addition ventilation parameters powered by a driving gas on newer machines. Must have both power and pnuematics . Alarms-ASTM standards group alarms into three levels: High, Medium, Low Priority correlates to;operator immediate action, prompt action,or awareness. Loss of main power is the only required alarm with a required duration of at least 2 minutes Safety relief valve-aka pressure limiting valve, drving gas pressure relief valve. Vents driving gas if factory pre-set pressure is reached (65-80 cm H2O) or adjustable set pressure is reached.Slide 89: Bernoulli’s Principle At constriction: Flow is higher Pressure is lowerSlide 90: Ventilator Bellows Assembly: Housing- Usually made of hard rigid clear plastic Bellows; ASCENDING -standing, upright. Compressed downward during inspiration. ASCEND DURING EXPIRATION Pressure is always positive. PEEP 2-4 cm H2O. DESCENDING -hanging, inverted. Compressed upward during inspiration. DESCEND DURING EXPIRATION . Weight of bellows results in negative airway pressure during exhalation until bellow refilled. IMPORTANT difference between ascending and descending is that when there is a major leak or disconnect, the ascending bellows will collapse (unless prevented by scavenging system). When a disconnection occurs with a descending bellows system, the ventilator will continue it’s upward movement anddownward movements, drawing in room air and driving gas during it’s descent and discharging it during the upward movement. Gas flow during upward movement may generate enough pressure such that the low pressure alarm is not activated. Remember that the type is described by how the bellows move during EXPIRATION What type is shown?Slide 91: Scavenger System Scavenger System consists of: 1 ) gas collecting assembly, 2) a transfer means, 3) the interface, 4) gas disposal tubing, 5) gas disposal assembly. (some or all components may be combined). ASTM standard fitting size for scavenger hoses 19 mm ( international standard 30mm) to prevent incorrect connection to breathing hoses (22mm). 1 3 2 1 4&5 4&5Slide 92: Scavenging Systems Protects the breathing circuit or ventilator from excessive positive or negative pressure .Slide 93: Scavenging SystemsSlide 95: Miscellaneous safety mechanisms Antistatic wheels and locking of wheels Backup battery Pressure relief valve Common gas outlet with retaining device to prevent disconnection Provide temporary electrical power (> 30 min) to monitors and alarms in event of power failureSlide 96: ESSENTIAL FEATURES PURPOSE Non-interchangeable gas specific connections to pipeline inlets (DISS) with pressure gauges, filter and check valve Prevent incorrect pipeline attachments; detect failure, depletion, or fluctuation Pin Index Safety system for cylinders with pressure gauges, and at least one oxygen cylinder Prevent incorrect cylinder attachments; provide backup gas supply; detect depletion Low oxygen pressure alarm Detect oxygen supply failure at the common gas inlet Minimum oxygen/nitrous oxide ratio controller device (hypoxic guard) Prevent delivery of less than 21% oxygen Oxygen failur e safety device (shut-off or proportioning device) Prevent administration of nitrous oxide or other gases when the oxygen supply fails Oxygen must enter the common manifold downstream to other gases Prevent hypoxia in event of proximal gas leak IN A NUTSHELL…Slide 97: CONTD. Essential features Purpose Oxygen concentration monitor and alarm Prevent administration of hypoxic gas mixtures in event of a low-pressure system leak; precisely regulate oxygen concentration Automatically enabled essential alarms and monitors (e.g. oxygen concentration) Prevent use of the machine without essential monitors Vaporizer interlock device Prevent simultaneous administration of more than one volatile agent Capnography and anaesthetic gas measurement Guide ventilation; prevent anaesthetic overdose; help reduce awareness Oxygen flush mechanism that does not pass through vaporizers Rapidly refill or flush the breathing circuitSlide 98: Danger Unpleasant SurprisesSlide 99: Checking Anesthesia Machines 8 Categories of check: Emergency ventilation equipment High-Pressure system Low-Pressure system Scavenging system Breathing system Manual and automatic ventilation system Monitors Final PositionSlide 100: Anesthesia Machine Checkout Steps 1-3: Emergency Ventilation Equipment *1. Verify Backup Ventilation Equipment is Available & Functioning High Pressure System *2. Check Oxygen Cylinder Supply a. Open 02 cylinder and verify at least half full (about 1000 psi). b. Close cylinder. *3. Check Central Pipeline Supplies a. Check that hoses are connected and pipeline gauges read about 50 psi.Slide 101: Anesthesia Machine Checkout Steps 4-7: Low Pressure Systems *4. Check Initial Status of Low Pressure System a. Close flow control valves and turn vaporizers off. b. Check fill level and tighten vaporizers' filler caps. *5. Perform Leak Check of Machine Low Pressure System a. Verify that the machine master switch and flow control valves are OFF. b. Attach "Suction Bulb" to common Fresh gas outlet. c. Squeeze bulb repeatedly until fully collapsed. d. Verify bulb stays fully collapsed for at least 10 seconds. e. Open one vaporizer at a time and repeat 'c' and 'd' as above. f. Remove suction bulb, and reconnect fresh gas hose. *6. Turn On Machine Master Switch and all other necessary electrical equipment. *7. Test Flowmeters a. Adjust flow of all gases through their full range, checking for smooth operation of floats and undamaged flowtubes . b. Attempt to create a hypoxic 02/N20 mixture and verify correct changes in flow and/or alarm.Slide 102: Anesthesia Machine Checkout Scavenging System *8. Adjust and Check Scavenging System a. Ensure proper connections between the scavenging system and both APL (pop-off) valve and ventilator relief valve. b. Adjust waste gas vacuum (if possible). c. Fully open APL valve and occlude Y-piece. d. With minimum 02 flow, allow scavenger reservoir bag to collapse completely and verify that absorber pressure gauge reads about zero. e. With the 02 flush activated allow the scavenger reservoir bag to distend fully, and then verify that absorber pressure gauge reads <10 cm H20.Slide 103: Anesthesia Machine Checkout Breathing System *9. Calibrate 02 Monitor a. Ensure monitor reads 21% in room air. b. Verify low 02 alarm is enabled and functioning. c. Reinstall sensor in circuit and flush breathing system with 02. d. Verify that monitor now reads greater than 90%. 10. Check Initial Status of Breathing System a. Set selector switch to "Bag" mode. b. Check that breathing circuit is complete, undamaged and unobstructed. c. Verify that C02 absorbent is adequate. d. Install breathing circuit accessory equipment (e.g. humidifier, PEEP valve) to be used during the case. 11. Perform Leak Check of the Breathing System a. Set all gas flows to zero (or minimum). b. Close APL (pop-off) valve and occlude Y-piece. c. Pressurize breathing system to about 30 cm H20 with 02 flush. d. Ensure that pressure remains fixed for at least 10 seconds. e. Open APL (Pop-off) valve and ensure that pressure decreases.Slide 104: Anesthesia Machine Checkout Manual and Automatic Ventilation Systems 12. Test Ventilation Systems and Unidirectional Valves a. Place a second breathing bag on Y-piece. b. Set appropriate ventilator parameters for next patient. c. Switch to automatic ventilation (Ventilator) mode. d. Fill bellows and breathing bag with 02 flush and then turn ventilator ON. e. Set 02 flow to minimum, other gas flows to zero. f. Verify that during inspiration bellows delivers appropriate tidal volume and that during expiration bellows fills completely. g. Set fresh gas flow to about 5 L/min. h. Verify that the ventilator bellows and simulated lungs fill and empty appropriately without sustained pressure at end expiration. i. Check for proper action of unidirectional valves. j. Exercise breathing circuit accessories to ensure proper function. k. Turn ventilator OFF and switch to manual ventilation (Bag/APL) mode. l. Ventilate manually and assure inflation and deflation of artificial lungs and appropriate feel of system resistance and compliance. m. Remove second breathing bag from Y-piece.Slide 105: Anesthesia Machine Checkout Monitors 13. Check, Calibrate and/or Set Alarm Limits of all Monitors Capnometer, Pulse Oximeter, Oxygen Analyzer, Respiratory Volume Monitor (Spirometer), Pressure Monitor with High and Low Airway Alarms Final Position 14. Check Final Status of Machine a. Vaporizers off b. AFL valve open c. Selector switch to "Bag" d. All flowmeters to zero e. Patient suction level adequate f. Breathing system ready to useSlide 106: THANK USlide 107: The essence of intelligence is skill in extracting meaning from everyday experience You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.