VSAC 304 Anesthetic Equipment PDF

Anesthesia Equipment Barbara Ambros [email protected]  Learning Objectives To be able to describe the functions of an anesthesia machine and it’s individual components To be able to describe safety features  Anesthesia machine Delive...

Anesthesia Equipment Barbara Ambros [email protected]  Learning Objectives To be able to describe the functions of an anesthesia machine and it’s individual components To be able to describe safety features  Anesthesia machine Delivery of oxygen to patient (most veterinary machines utilize 100% oxygen) Delivery of anesthetic gas Assistance with ventilation Removal of exhaled carbon dioxide from the patient Mallard Large Animal Anesthesia Machine Anesthesia Machine: Basic Components  Anesthesia Machine: Basic Components Medical gas source (O2, air) Regulator Flowmeter Vaporizer Fresh (common) gas outlet Breathing system Can be divided into high and low pressure part  Anesthesia Machine: Basic Components Medical gas source (O2, air) Regulator Flowmeter Vaporizer Fresh (common) gas outlet Breathing system Can be divided into high and low pressure part  Anesthesia Machine: Basic Components Medical gas source (O2, air) Regulator Flowmeter Vaporizer Fresh (common) gas outlet Breathing system Can be divided into high and low pressure part  Medical Gas Source: Oxygen Compressed gas http://www.asevet.com/resources/cgs.htm - E-cylinder: attached to anesthesia machine 2200 psi, 700L Tank half full would register: 1100 psi and contain 350L - H-cylinder (7,000L) Liquid O2 Pipeline pressure: 50 - 60 psi Bank of Key to close O2 tank E-cylinder Liquid O2 H-cylinders https://www.wikihow.com/Fill-an-Oxygen-Tank  Medical Gas Source: Medical air Medical Air: Compressed medical air is formed by drawing ambient air into the compressor Considered “clean” (runs through series of filter driers and separators to remove water, oil, other impurities)  https://www.superavet.com/M6000%20Pureline Oxygen concentrator Filter and extract room air to produce oxygen for medical use Removes N2 and uses a compressor to store O2 in a pressure tank until required Requires an electricity supply Maximum of approximately 5 - 10 L/min Delivered at up to 92–95% oxygen Contains two zeolite molecular sieves in parallel https://www.caireinc.com/breathing-life-into-the-veterinary-medicine-market/ Zeolite retains nitrogen, some of the argon, other unwanted components of air  Identification and Safety System (gas specific) Color coding (O2: white or/and green), label Pin-index safety system (PISS) (E-cylinder) Connectors (H-cylinders): Diameter Index Safety System (DISS): body, nut and stem Miller’s Anesthesia Pin-index safety system Diameter Index Safety System Pin index safety system (PISS) uses a series of gas specific pin positions on the yolk that correspond to similarly positioned Pin receiver ports on the tank  Identification and Safety System (gas specific) Color coding (O2: white or/and green), label Pin-index safety system (PISS) (E-cylinder) Connectors (H-cylinders): Diameter Index Safety System (DISS): body, nut and stem Miller’s Anesthesia Pin-index safety system Diameter Index Safety System  Regulators (Pressure Reducing Valves) Convert variable high pressure to a constant working pressure (50-60 psi) E-tanks have one-stage regulator on anesthetic machine 2,200 psi down to 50-55 psi Pipeline supply: Regulator at O2source Set to 50-55 psi 2 stage regulators allow for variable output pressure Regulator with Gas Tank and Cylinder Pressure Gauges on top  Flowmeters Control rate of gas delivery to the low-pressure area Determine fresh gas flow (FGF) Specific for gas (density, viscosity) Color coded Liters/minute Operated by needle valve Precision instrument http://www.asevet.com/resources/flowmeter.htm  Vaporizer Vaporizes anesthetic agent and delivers at set concentration (% output on dial) Agent specific Temperature compensated volume percent. gas with fixed mass and volume is directly proportional When the vaporizer dial is in the “off ” position, the to the gas’s absolute temperature. Because of this, carrier gas only flows through the bypass chamber and measured‐flow vaporizer settings on these older units does not enter the vaporizing chamber. A locking mech- had to be adjusted if there was any change in the tem- anism is frequently found on the dial control to ensure perature of the constituent gases. This was necessary to that the anesthetic chamber does not accidently get maintain a constant and predictable rate of delivery. turned on if the dial is bumped (Figure 5.3). Once this Additionally, as anesthetic agent vaporization occurred safety mechanism is disengaged, the dial is readily turned in these older systems, temperature decreased due to to any setting on the vaporizer. Once it is turned to “off ”, evaporation of liquid. Thereby, these vaporizers were 3 2 1 OFF Schematic of a variable-bypass vaporizer A Bypass channel Vaporizer outlet The carrier gas is split into two streams. Vaporizer inlet Gas mixture A entering the bypass chamber Carrier gas B B diverted over into the vaporization chamber Bi-metallic strip This splitting ratio varies, depending on the dial setting. The bi-metallic strip also adjusts this ratio, Wicks depending on location and temperature. In this example, the bimetallic strip is located at the entrance to the vaporization chamber. Bi-metallic strip Warm temperatures Vaporization chamber Cool temperatures Veterinary Figure 5.2 Schematic of a variable‐bypass vaporizer. The carrier gas is split into two streams, one entering Anesthetic the bypass chamberand Monitoring Equipment and one diverted over into the vaporization chamber. This splitting ratio varies, depending on the dial setting. KG TheCooley, bi‐metallic RA Johnson, 2018,this strip also adjusts p 57 ratio, depending on location and temperature. In this example, the bimetallic strip is located at the entrance to the vaporization chamber. DOI:10.1002/9781119277187 Vaporizer Safety Color coding Key-indexed filler systems Lock on dial Do not overfill Do not tip vaporizer Vaporizer Safety Color coding Key-indexed filler systems Lock on dial Do not overfill Do not tip vaporizer Vaporizer Safety Color coding Key-indexed filler systems Lock on dial Do not overfill Do not tip vaporizer Vaporizer Safety Color coding Key-indexed filler systems Lock on dial Do not overfill Do not tip vaporizer  Anesthetic Breathing Systems Deliver oxygen and anesthetic gases to patient Allow elimination of CO2 Allow ventilation of lungs Different types based on CO2 removal - Non-Rebreathing systems: Use high gas flow to flush out CO2 - Rebreathing systems: Use chemical reaction to remove CO2 with absorber  Breathing Bag and Breathing Tube Reservoir Bag Size: 6 - 10 times tidal volume (10mL/kg) Reservoir of gases during inspiration Allows monitoring of respiratory movements Ventilate lungs Breathing Tubes / Hoses Provides connection and reservoir for gases Apparatus Dead Space: Potential area for CO2collection  Rebreathing systems Allow rebreathing and conservation of exhaled gases Used on animals larger than 10 kg bodyweight (5-10kg pediatric circle system) CO2 removal depends on passage of gases through CO2 absorber (chemical reaction) Allow low/minimal flow anesthesia: Advantage: - Decreased use of volatile anesthetics (more economical) - Improved temperature and humidity control - Reduced environmental pollution Disadvantages - Difficult to rapidly adjust anesthetic depth  Rebreathing system - Components Inspiratory one-way valve Inspiratory breathing tube Y-Piece Expiratory breathing tube Expiratory one-way valve Reservoir bag CO2 absorber https://aneskey.com/circle-circuit/ Rebreathing system - Components F-circuit Breathing Tubes Flexible, low resistance conduits between Y-piece and one-way valves Corrugations reduce likelihood of obstruction if bent Add length volume to system, increase resistance F circuit: co-axial system (inspiratory inside expiratory) O2 flow rates for Circle system: 10-30mL/kg/min Low Flow (equals metabolic O2 demand) 4-10mL/kg/min Circle-circuit http://asevet.com/resources/circuits/circle.htm  Components of Circle System Y piece Unites ET-tube connector to inspiratory and expiratory breathing tubes Contributes to dead space Septum may be present to decrease dead space http://asevet.com/resources/circuits/circle.htm  Universal F Breathing System Co-axial (hose inside a hose), inner hose carries fresh gas flow Less bulk, dead space https://intriquip.com/veterinary-anesthesia-circuits-explained/  Rebreathing System: Denitrogenization Required for all rebreathing systems Air is 21% O2 and 79% N2 (CO2 amount low) Body and anesthetic machine are equilibrated with air Once connected to breathing system and 100% O2 flows: N2 moves down partial pressure gradient from body into breathing system This process takes about 20 minutes High FGFs are used (30 mL/kg/min) for first 20 minutes to flush out N2 and to reduce risk of inhaling hypoxic mixtures  Rebreathing system - Components One-way (unidirectional) valves Prevent the rebreathing of exhaled gas Gases enter a unidirectional valve from below and raise disc Allow gas to pass in one direction only, add resistance to breathing One-way valves  Rebreathing system - Components CO2 absorber Contains chemical absorbent for removing CO2 from exhaled gases Exothermic reaction, produces water, pH increases (pH sensitive indicator leads to color change) Granules turn from white to purple as they become exhausted http://asevet.com/resources/circuits/circle.htm  Non-Rebreathing System CO2 removal is dependent on fresh gas flow during expiratory pause: Use high gas flows of 150 –300 mL/kg/min https://intriquip.com/veterinary-anesthesia-circuits-explained/  Non-Rebreathing System Advantages Less resistance to breathing Less mechanical dead space Rapid manipulation of anesthetic depth Disadvantages Significantly higher waste of both carrier gas High flow of dry cool gas (heat and humidity loss)  Failure to remove CO2 Non-rebreathing systems Inadequate fresh gas flow in non-rebreathing systems Kinked inner tube Bain Hidden tears or disconnections in coaxial systems Rebreathing systems Stuck 1-way valves Exhausted CO2 absorber in rebreathing system  Circuit Pressure Gage (Manometer) Corresponds with pressure generated in the patient breathing circuit Guide for positive pressure ventilation of lungs and system leak test Not greater than 10 –25 cmH2O pressure for lung ventilation Highest number corresponds to the peak inspiratory pressure reached (PIP) But also watch chest expansion of animal: give a normal breath  Scavenging System Conducts waste anesthetic gases away from workspace Passive (e.g. Charcol canisters) Active (negative pressure system) Pink coloured hoses for safety http://asevet.com/resources/circuits/nrb.htm  Adjustable pressure limiting (APL) valve Pop-off valve/Exhaust valve/Scavenging valve Allow excess gas within the breathing system to be vented into a waste-gas scavenging system Always leave open during spontaneous breathing Only closed during lung ventilation and leak test Temporarily closed during manual ventilation Closed using mechanical ventilators, have their own valve Attach scavenging hose to exhaust valve shroud  O2 Flush Allows oxygen to bypass flowmeters and vaporizers O2 delivered at high flow and pressure (40-70 L/min) Only be use with circle system Used to flush out circle system of anesthetic in emergency Can be used for leak test Never use when a non-rebreathing (Bain) circuit is connected to patient Anesthesia ventilators  Ventilators Used to provide intermittent positive pressure ventilation (IPPV) A dedicated person can also provide IPPV A ventilator allows person to attend to other jobs May require driving gas (O2, air) and electricity The ventilator bellows replaces the rebreathing bag Indications: Open thorax (diaphragmatic hernia repair, thoracotomy,..) Neuromuscular blockade (skeletal muscle paralysis) https://www.superstarmedicals.com/c/veterinary-anesthesia-machine/  Ventilator settings Tidal volume (TV): 10-15mL/kg Respiratory rate (RR): 6-20 bpm Inspiratory time: 1-1.5 seconds I-E RATIO: 1:2 - 1:4 Peak Inspiratory Pressure (PIP): 10-20cmH2O Pressure-limiting adjustment = Maximum working pressure For health patients limit to 30 cmH2O (or less) Watch the chest wall rise and fall normally with ventilation (closed chest) Guide ventilation settings with a capnograph Do not need to know for exam!