Anesthesia Machine 2024 PDF

The Anesthesia Machine Vicente Gonzalez, DNP, CRNA  Objectives: Gain a basic understanding of the anesthesia machine Learn the direction of gas flow through the machine Gain knowledge of Safety systems within the anesthesia machine Become able to troublesh...

The Anesthesia Machine Vicente Gonzalez, DNP, CRNA  Objectives: Gain a basic understanding of the anesthesia machine Learn the direction of gas flow through the machine Gain knowledge of Safety systems within the anesthesia machine Become able to troubleshoot basic errors and possible mishaps while using machine Learn FDA recommended anesthesia machine checkout  Components of Anesthesia Gas Delivery System 02 03 04 01 05 Anesthesi Vaporizers Breathing Ventilator Waste Gas a Machine System Scavenging System The primary Convert liquid Connects the Provides mechanical Collects and removes component of anesthetic anesthesia ventilation to the excess anesthetic the agents into machine to the patient. gases. anesthesia vapors. patient. gas delivery Can be set to deliver Prevents exposure of system. Allow precise Includes specific volumes and healthcare workers to control of breathing pressures. anesthetic gases. Delivers a anesthetic circuits, masks, mixture of concentration. and Essential for patients Ensures a safe gases to the endotracheal who cannot breathe working environment patient. Integrated into tubes. on their own. in the operating the anesthesia room. Includes machine. Ensures the flowmeters, delivery of pressure anesthetic gases gauges, and and removal of safety exhaled gases. features. 1 / Comprehensive Overview of Anesthesia Gas Delivery Systems Understanding Anesthesia Machine Functions 03 01 02 04 05 Safety Gas Mixture Pressure and Electrical System Backup Features for Creation Flow Control Integration Battery for Preventing and Delivery Power Regulates gas pressure Hypoxic Combines oxygen, nitrous Coordinates electronic Failure Provides Mixtures fail-safes Incorporates oxide, and anesthetic gases components emergency Maintains consistent flow Monitors oxygen levels power rates Ensures reliable operation Ensures precise delivery to continuously the patient Ensures continuous operation during outages 3 / Comprehensive Overview of Anesthesia Gas Delivery Systems Anesthesia Machine Safety Systems Oxygen Supply oxygen levels Provides power Pressure Failure during electrical Prevents delivery of Alarm outages dangerously low Alerts when oxygen oxygen Ensures continuous supply pressure concentrations operation of critical drops below safe systems levels Electronic Flow Control Valves Vaporizers for Ensures immediate Delivering corrective action to Controls flow of Anesthetic Agents prevent hypoxia oxygen, nitrous oxide, and air Precisely controls Fail-Safe System the concentration of Ensures precise to Prevent anesthetic agents delivery of gases to Hypoxic Gas the patient Ensures safe and Mixtures effective anesthesia Automatically Backup Battery delivery adjusts gas mixtures 6 / Comprehensive Overview of Anesthesia Gas Delivery Systems for Electrical to maintain safe Power Failure Pressure systems  Pressure Systems: High Pressure system: All parts receiving cylinder gas at high pressures (2000psi to ~45psi) Intermediate Pressure system: All parts receiving gas at pressures from ~45-50 psi; this includes cylinder gas down regulated by a first stage regulator. Begins at pipeline ends at flow valves Low Pressure system: All parts receiving gas from either a pipeline or cylinder source at ~15-30 psi; a second stage regulator drops pressures from intermediate to low pressures, and allows safe delivery of gases to patients. Begins at flowmeter ends at the common gas outlet. Gas Flow Through Anesthesia Machine 01 02 03 04 05 Gas Flow Gas Sources Gas Control Flow Flow Pathways Valves Measuremen Feedback High-pressure Compressed Electronic flow tDifferential systems oxygen control for pressure and Safety oxygen transducers Features Intermediate Nitrous oxide downstream of pressure systems Electronic flow Air control valves Maintaining control for nitrous Low-pressure oxide constant flow systems rates with Electronic flow changing control for air pressures No pressure sensor shut-off valves Proportional 5 / Comprehensive Overview of Anesthesia Gas Delivery Systems decrease in nitrous oxide flow on oxygen supply failure Importance of Pressure Regulators Importance of Pressure Regulators in Anesthesia Machines Pressure regulators are crucial components in anesthesia machines. They help control the flow of gases from high-pressure sources to ensure safe delivery to patients. Pressure regulators play a key role in maintaining appropriate pressures for gas mixtures. Proper functioning of pressure regulators 11 / Comprehensive Overview of Anesthesia Gas Delivery Systems is essential for the safe operation of anesthesia machines. High Pressure System Gas from cylinders System includes cylinders, hanger yoke, cylinder pressure gauge, and pressure regulator (first- stage)  Cylinder Hanger Yoke PISS Nipple Check Valve Washer Retaining Screw Checking Oxygen Tanks and Pressure Gauges 01 02 Checking Oxygen Tanks Oxygen Pathways within and Pressure Gauges Intermediate-Pressure System Ensure the oxygen cylinder Components pressurized by is securely closed after oxygen: fresh gas pressure check flowmeter, pressure sensor shut-off valves, oxygen Risks of leaving backup supply failure alarm switch, oxygen cylinder open oxygen-powered ventilator, during pipeline use auxiliary oxygen flowmeter, auxiliary oxygen power outlet 8 / Comprehensive Overview of Anesthesia Gas Delivery Systems Inserting a cylinder in the machine Cylinder Gauges High pressure cylinder gauge is a Bourdon type gauge which measures the pressure within a given cylinder. Cylinder Gauges Digital Display Bourdon Gauge Consists of a closed coiled tube connected to the cylinder in which pressure is to be sensed. As the pressure increases the tube will uncoil, while a reduced pressure will allow the tube to coil more tightly. This motion is transferred through a link to a gear connected to an indicating needle. High Pressure Regulator Works to control the highly variable pressure inside a cylinder It can otherwise be difficult to control this pressure and deliver it safely to the anesthesia machine and the patient Reduces the high pressure in a cylinder to about 45 psi Sometimes a two-stage pressure regulator (two in series) are used Gas from the N2O compressed gas cylinder enters the anesthesia machine through a pressure regulator that decreases the pressure to A 10 psi B 15 psi C 30 psi D 45 psi E 60 psi Gas from the N2O compressed gas cylinder enters the anesthesia machine through a pressure regulator that decreases the pressure to A 10 psi B 15 psi C 30 psi D 45 psi E 60 psi Intermediate Pressure System All parts of the machine which receive gases at reduced pressure from cylinders (35-45 psi) Starts at the first stage regulator when cylinder gases used Includes pipeline gas inlets and pressure gauges which deliver gases at about 50 psi Oxygen failure safety valve and oxygen supply failure alarm (pressure) Flow valves Oxygen flush valve Hookup of oxygen source to anesthesia machine results in 5 immediate functions (5 Task of Oxygen) 1. Power outlet accessory Driving gas for ventilator 2. O2 flush valve Located at machine outlet to circuit O2 flush of 35-75 L/min 3. Low Pressure sensor shut-off valve When O2 supplied at ~50 psi it holds open this valve which allows N2O to flow to the flowmeter. Remains open as long as psi remains >25, if it falls below 25 psi N2o flow is shutoff. 4. Supply failure alarm system (high priority alarm) Activated when O2 falls below 28 psi Alarms sounds before 25 psi, the point at which N2O flow will cease 5. Second stage pressure regulator (Flowmeter) Gas pressure is decreased to a constant pressure of 16 psi as flow from wall varies at times between 40-50psi After passing 2nd stage pressure regulator, sits in “stand by” at flow control valve  5 1 4 3 2 2 Intermediate pressure system Components Safety 1. Flush Valve 1. O2 flush during the delivers 02 straight from the pipeline or cylinder regulator at inspiratory phase may cause 45-50 psi. barotrauma (recessed into 2. First stage regulator machine) Pipeline gas ranges f/ 40 - 60 psi depending on overall gas usage 2. To maintain constant flow with changing 3. Fail-Safe System supply pressures (50–60 psi) 1. Each gas line supplying 3. shuts off the N2O supply if there is a loss each flowmeter has a of O2 supply pressure. Because of the fail- “failsafe” valve (20 psi ). safe device, a decrease in N2O flow (with 2. It senses only pressure the N2O flowmeter bobbins dropping to and does not check whether zero) may actually be the first sign of loss the supplied gas is actually oxygen. of oxygen supply pressure (ie 02 pipeline hose disconnect). Oxygen Failure Oxygen failure safety valve shuts off the flow of all other gases when oxygen pressure drops below a set limit (20-25 psi) If there is decreased flow of oxygen, will activate On some machines, air audible and visual alarms can be delivered even in the presence of low oxygen supply pressure Does not prevent delivery of a hypoxic mixture Datex-Ohmeda and Drager have proprietary versions of this system O2 Pressure-Sensor Shutoff Datex-Ohmeda O2 Failure Protection Device Drager Oxygen Flush Valve Provides oxygen at 35-55 L/min directly to the common gas outlet, bypassing flowmeters and vaporizers Oxygen may reach a connected patient at a pressure of 45-50 psi Potential barotrauma Used to rapidly refill or flush the breathing circuit Must have a built-in rim to prevent inadvertent activation and spring to prevent prolonged activation Oxygen Flush Valve Do Not Press Low Pressure System Begins at the second stage regulator where all gas pressure is dropped from the intermediate pressure system to about 16 psi Includes flowmeters vaporizers Common gas outlet Flow Valves Touch and color-coded to prevent use of the wrong gas Oxygen knob is fluted, larger than the others, and protrudes further Oxygen located furthest to the right Oxygen Proportioning Device Used to ensure that nitrous oxide can only be delivered in the presence of oxygen Prevents delivery of low oxygen content nitrous oxide to the patient When nitrous oxide is used it adds a minimum of 21-25% oxygen to the mixture. Maintains a minimum O2/N20 Ratio- 1:3 *O2/NO2 Proportioning Device-Automatically mixes O2 and NO2 to setting selected on dial Proportioning Device Proportioning Device Datex-Ohmeda Link-25 Proportioning Device Drager’s ORMC/S-ORC Flowmeters Constant-pressure variable-orifice flowmeters use an indicator ball or bobbin which displays the flow of gas through a Thorpe tube Utilize a ball, bobbin or float as marker The tube is narrow at the bottom and low flow raises the marker; as the flows increase and the marker rises in the widened tube, greater flows pass around it and reach the common gas outlet May be single or double tube design Flowmeters Flowmeters Specifically designed and calibrated for each gas The flow rate of a gas through a constriction depends on the gas’s viscosity at low laminar flows, and its density at high turbulent flow. (Hagen-Poiseuille) Floats should rotate freely, inside of tubes is coated to prevent static electricity May malfunction due to dirt inside, misalignment, sticking markers Leaks may occur and could cause hypoxic gas mixture to be delivered Flowmeters Flow into the meters moves from left to right, exiting the common manifold to the right of the oxygen flowmeter. If there is a leak in either of the first two flowmeters, oxygen continues uninterrupted out to the patient. A leak in the oxygen flowmeter, or somewhere beyond it can cause delivery of a hypoxic mixture. Oxygen is furthest on the right, so that in event of leak the chances of hypoxic mixture are lessened To ensure that oxygen is always delivered, there is a minimum setting of 50-150ml/min constant flow even when the oxygen flowmeter is in the full-off position Flowmeters (aka Thorpe tubes) Are constant pressure, variable orifices with a low pressure of 16 psi Tube is tapered with the largest diameter on top, it is hand calibrated & no 2 tubes are alike They are gas specific 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 float Read ball at the middle, & arrow float at the top Flowmeter Leaks Off Off Off Off Power Failure Battery supply for 30 minutes Added Backup systems Pneumatic Vs Electrical Alternative Oxygen Separate axillary flowmeter Can be used to control Oxygen in power failure Common Gas Outlet Also known as the fresh gas outlet Only one outlet on the anesthesia machine, compared to multiple gas inlets Must have an anti-disconnect device to prevent accidental disconnection from the breathing circuit Oxygen from the flush valve goes directly from the intermediate pressure system to this outlet, directly to the patient APL Valve (AKA Pop-off valve) Usually fully open during spontaneous ventilation, but must be partially closed during manual or assisted bag ventilation If open too wide, too much volume is allowed to escape and not enough delivered to the patient If closed too tightly, not enough volume escapes, and larger volumes and possibly high airway pressures are created Requires very fine tuning APL Valve Unidirectional Valves Maintain the flow of anesthetic gas in the direction intended. In the inspiratory limb it allows the forward flow of gas towards the patient, in the expiratory limb it moves gas away from the patient towards the bag/ventilator and scavenger system May occasionally malfunction causing difficulties in ventilating the patient Rebreathing of carbon dioxide may occur if either valve malfunctions The expiratory valve is also exposed to moisture from the patient’s airway upon exhalation, and could stick, increasing resistance Unidirectional Valves Unidirectional valves Carbon Dioxide Absorbent Allows for rebreathing of alveolar gas which conserves heat and moisture Decreases the need for higher flow of gases, since they can be recirculated The absorber removes carbon dioxide which has been exhaled by the patient Gases and anesthetic agents can be recirculated in an economical fashion This is the component that allows the circle system to exist Carbon Dioxide Absorbent Soda Lime, Baralyme or CaH lime (amsorb) Both undergo complex chemical reactions with carbon dioxide, the end products of which are heat, water, and calcium carbonate Soda lime is most commonly used and 100g of absorbent can absorb 26 L of CO2 4-mesh or 8-mesh size of granules; too small can lead to restriction to flow Carbon Dioxide Absorbent Contains an indicator dye which will change color with increasing hydrogen ion concentration When 50-70% of the absorber granules have turned purple, the canister should be replaced When exposed to fresh air, regeneration of granules may occur, but the absorption capabilities have been exhausted The carbon dioxide absorber is the canister and assembly which houses the absorbent Carbon Dioxide Absorbent pH of 13.5 Exhausted when hydroxides have become carbonates Ethyl violet is the dye used turns purple CO2 Absorber Oxygen Sensor Required at all times when the anesthesia machine is in use May be polarographic (Clark electrode), or galvanic (fuel cell); these require calibration and have slightly slow response times May also be paramagnetic which are more costly but are self-calibrating and have no consumable parts; they also have a fast response time and can detect inspired and expired concentrations of oxygen All analyzers must have low-level alarms which are active while the machine is on  Spirometers Also known as respirometers, are used to measure the patient’s exhaled tidal volume Most commonly, a rotating vane is present in the expiratory limb (Wright respirometer); the flow of gas across the vanes causes them to rotate and the number of rotations/time is measured Humidifiers May be active or passive Passive humidifiers, also known as heat and moisture exchangers (HME) or artificial noses are most commonly used They provide an economical way of adding moisture to inhaled gases by trapping the moisture contained in exhaled gases, they conserve heat by the same means Active humidifiers may transmit nosocomial infections, cause thermal lung injury and increase airway resistance from excessive condensation  Color LCD Display Inspired Gas Tanks Pipeline Expired Gas  LCD Display Out Blank Screen Emergency Activation Adjust Flow Only Secondary O2  Preanesthesia Self-Check Procedures Oxygen Cylinders suction is adequate system function for airway clearance Verify availability Ensure carbon and functionality of dioxide absorbent is Monitors and oxygen cylinders not exhausted and Alarms spare absorbent is Verify pressure on Confirm availability available backup oxygen of required monitors cylinder mounted on and check alarm anesthesia machine settings Ventilation Anesthesia Devices Machine Check manual Check vaporizers for ventilation devices adequate fill and for proper function tight closure of filler ports Patient Suction 33 / Comprehensive Overview of Anesthesia Gas Delivery Systems Test scavenging Ensure patient  Missed Steps in Preanesthesia Setup Verify Auxiliary Ensure a low inhaled Oxygen and oxygen Manual concentration alarm Ventilation is set. Check the Backup Oxygen availability and Cylinder functionality of the auxiliary oxygen Confirm pressure on cylinder. anesthesia machine's backup Ensure the self- oxygen cylinder. inflating manual ventilation device is operational. Test Vaporizers Ensure vaporizers Ensure Adequate are adequately Patient Suction filled. Verify suction is Check for tight adequate for airway closure and the clearance. absence of leaks. Monitor and Alarm Settings 49 / Comprehensive Overview of Anesthesia Gas Delivery Systems Check monitors and alarm settings. Summary The anesthesia machine is only as safe as the person controlling it. You must learn all the functions of any equipment you may be utilizing in the clinical setting. You must know how to troubleshoot any problems that might arise. When in doubt, start by looking at your patient, then everything else. Read, read, read. You must know more than just what is in this lecture! References: Anesthesia equipment 3rd edition Miller’s Anesthesia chapter 22 Some images, for illustration purposes only, come from other sources which are not meant to be part of the reading material. Questions??