The Anesthesia Machine (Part 1) CVM 746 PDF

The Anesthesia Machine (Part 1) CVM 746 Dr. Lisa Ebner Lecture Objectives 1. Identify the parts of the anesthesia machine and describe their function. 2. Be able to trace the flow of oxygen from the source to the patient and describe what safety mechanisms are in place to prev...

The Anesthesia Machine (Part 1) CVM 746 Dr. Lisa Ebner Lecture Objectives 1. Identify the parts of the anesthesia machine and describe their function. 2. Be able to trace the flow of oxygen from the source to the patient and describe what safety mechanisms are in place to prevent use of the wrong medical gas. 3. Name at least 3 sources of oxygen that can be used in veterinary medicine. 4. Calculate the liters of oxygen remaining in an E tank given the available psi left and the amount of time that volume will last if given the current oxygen flow rate. 5. Know where to read the O2 flow setting on the floating indicators (i.e. ball vs. bobbin). 6. Explain the basic functioning parts of modern vaporizers. 7. Calculate a correct size reservoir bag for a given patient. 8. Indicate which components of the machine if used improperly could result in complications (e.g. death) in your patient. 9. Describe the steps necessary to perform a machine leak test (aka pressure check) on an anesthesia machine prior to use.  Exam Parts of the machine & (3) 1. High pressure system A. oxygen cylinder B. cylinder valve C. cylinder pressure gauge D. Regulator (or reduction valve) 2. Intermediate pressure system G. oxygen flush/bypass valve * 3. Low pressure system E. flow meter F. vaporizer H. common gas outlet I. common gas inlet J. one-way valves inspiratory expiratory K. pop-off valve Adapted from Figure 3.37 (page 43) in Lumb & Jones. 5th ed.  concentrator zr" ? type (less Oxygen sources Oxygen = - common Compressed gas in cylinders Cryogenic liquid supply E cylinder Large liquid oxygen containers installed G and H cylinders set up as a central supply at facilities that have a fairly constant system. demand. Usually 2 banks (each Liquid kept at -297◦F to prevent evaporation (i.e. Thermos bottle) then O2 drawn as containing 1 day’s supply) are required and passed through heater to connected to a common increase temp and raise pressure. manifold that converts them · larger facilities (g referral. hospitals) into one continuous supply. Pressure regulator ensures gas piped out at 50-55 psi Oxygen sources Image: http://www.ijaweb.org/article.asp?issn=0019- 5049;year=2013;volume=57;issue=5;spage=489;epage=499;aulast=Das Oxygen sources Oxygen concentrator http://www.superavet.com/pureline/ Increases O2 concentration by absorbing nitrogen onto a molecular sieve and allows O2 and trace gases to pass through  resulting in O2 concentration of 90-96% Compact, lightweight, reliable units that are easily transported Can save money compared to liquid or cylinder oxygen sources Maintenance required (i.e. cleaning or replacing filters) Takes a few minutes to reach max concentration of 96% Produces gas flows that would be acceptable for SA anesthesia patients for LA) · limited to St /not sufficient output capacity  Tapered screw neck threads, Oxygen cylinder attached to valve Can be made of steel, steel carbon fibers, or aluminum Cylinder filled and discharged through valve, the port is the base point of exit Protect port during transit Use sealing washer (gasket) over nipple prior to attaching cylinder to yoke Conical depression opposite side of port, receives retaining screw from yoke Handle or cylinder wrench used to open/close a cylinder valve - dry clean hands Open valve SLOWLY because rapid recompression of gas generates heat  adiabatic process + dust, grease = flash fire or explosion memorize Common cylinder size for O2 Capacity (liters) Pressure (psi) (completely full E 660 2200 H 6900 2200 & vollagertankgreaterare Oxygen cylinder safety Must be inspected and tested at least every 5 years Safety mechanisms to prevent connection of wrong gas Color coding: oxygen = green in USA, but white in the rest of the world. N2O = blue Pin Index Safety System (PISS) Diameter Index Safety System (DISS) Holes in cylinder valve positioned below manufacturer specific quick connector port, align with pins in yoke Imgage: http://www.e-lfh.org.uk Image: http://rcmedical.com  Regulator Cylinder pressure gauge Reduces the gas pressure from the Must be installed downstream of cylinder (or other source) to a each pressure regulator usable level of a constant 50 psi Calibrated in psi Specific for gas and tank size (E or H) Allows user to calculate Terminates in a gas specific male remaining liters in tank or DISS fitting pipeline pressure Using pressure to measure cylinder contents =P GV = CVz 2200 psi 1100 psi 660 L xL & Change cylinder when pressure < 500 psi! 2200x =1100(660) x = 726,000/2200 x = 330 L · round down if unsure  How many liters of oxygen are left in this E tank?  Oxygen flush valve Receives O2 from the pipeline inlet or cylinder pressure regulator and directs a high unmetered flow directly to the common gas outlet 35 to 75 L/min when activated  possible barotrauma, so NEVER use ⑤ when connected to a non-rebreathing system Image: http://asevet.com/resources/quickflush.htm Flow meter Indicates rate of flow of gas passing through them Turn control knob counterclockwise to increase flow and clockwise to decrease flow (do not over tighten!) Gas specific calibration Reliable vaporizer output when flowmeter set ⑪ between 500-2000 mL/min  so don’t set flowmeter lower than 0.5 L/min with a rebreathing system! Image: www.hubpages.com  (?) Tube Thorpe Variable orifice flow indicator – tube is internally tapered Flow meter (smallest diameter at bottom), so as height increases = more gas flow  ensure correct units - W How many L/min of oxygen is being delivered with this flow meter setting? 1 5 min. don't want below 0 5. 4min ↳ Unidirectional valves Only present on a rebreathing system – allows gases to only travel in one direction Inspiratory valve Expiratory valve stuck -valves Can get Disadvantage: increases resistance to breathing; if one or both valves are leaky  patient will rebreathe CO2 Vaporizer A device that changes a liquid anesthetic agent into its vapor and adds a controlled amount of that vapor to the fresh gas flow going into the patient breathing system. Modern vaporizers share the following designs: Gas specific Concentration calibrated Variable bypass Flow-over vaporization method Temperature compensation Vaporizer ! agent-specia Concentration calibrated vaporizers are located between the flowmeter and common gas outlet Vaporizer output is controlled by a dial/knob that image: http://www.pharmacology2000.com/physics/Chemistry_Physics/physics17.htm is calibrated in volumes percent Dilutes the saturated vapor pressure by splitting the gas flow that passes through the vaporizer: bypass to the vaporizer outlet vaporizing chamber Stream of gas passes over the surface of the liquid. Increasing surface area (i.e. wicks, spiral tracks) of gas-liquid interface enhances efficiency of vaporization. Image: www.asevet.com Temperature compensation Bimetallic strip or valves adjusts flow through vaporizing chamber when temp varies Images:http://asevet.com/resources/vaporizer/precisionvap.htm  Vaporizer hazards Two vaporizers on machine turned on at same time Interlock systems will prevent this If the vaporizer is tipped, overfilled or filled with the wrong agent  Image: http://www.anesplus.com consult the manufacturer for the best recommendations. - walk backwards machine towards pulling yourself Generally, if vaporizer is tipped it should be flushed with a high O2 flow rate for the max time recommended by manufacturer. Ideally, vaporizer should be emptied prior to transport, left in upright position, and dial set to “0” position. Overfilled vaporizer may deliver lethal concentrations or cause vaporizer failure with zero output If filled with wrong agent, vaporizer must be completely drained and all liquid discarded. O2 should be run through until no agent detected Isoflurane Bottles of liquid anesthetic are color-coded: Purple = Isoflurane sevoflurane Yellow = Sevoflurane Agent-specific keyed filling systems also available (v. Well Elling Image: http://www.supplierlist.com/product_view/readeagle/145878/ 101104/Anesthesia_Vaporizer_Adaptor.htm Common/Fresh gas inlet and outlet Receives all gases and vapors from the machine and delivers the mixture to the breathing system. Common/Fresh gas inlet The hose that connects to the breathing system can be different on every machine, but make sure the connection is secure when setting up your machine for a patient. Attaches closer to the patient on a non-rebreathing system, so never activate the oxygen flush valve when using this type of system. Reservoir bag Inspiratory reservoir of oxygen (+/- anesthetic gases) for the patient to be able to take 5-6 breaths from (tidal volumes) Used to monitor frequency of respiratory rate and compliance of patient’s pulmonary system during assisted ventilation Manual ventilation by anesthetist from squeezing bag up to 20 cmH2O while occluding APL valve momentarily or replaced by ventilator hose (pop-off) during mechanical ventilation. To determine what size to use for a patient: ① Body weight (kg) x tidal volume (mL/kg) x 5 Ex: 25 kg dog x 10 mL/kg x 5 = 1250 mL…so round up to 2 L bag What size reservoir bag would you select for a 35 lb dog? 35 = 795 5. A. 0.5 L B. 1L C. 2L D. 3L Adjustable pressure- limiting (“Pop-off”) valve User adjustable valve that releases gases to a scavenging system Used to control pressure in the breathing system Transiently close APL to deliver manual ventilation to patient ⑪ Otherwise, must be kept open at all times - will rupture alveoli  Safety concerns & Top 3 “Killers” (know these &Why they're Bad Improper cylinder storage Tipping over vaporizer Closed pop-off valve Wrong inhalant in vaporizer Overfilling vaporizer Opening a cylinder too quickly and & Too little O2 having dust or grease around valve Using oxygen flush valve when Too high vaporizer setting attached to a small patient O2 and N2O are flammable Taking a steel cylinder into a MRI room  Cylinder storage Cylinder valve, pressure regulator, or gauges should never come in contact with oils, greases, organic lubricants, rubber or combustible substances Valve kept closed at all times unless cylinder is in use, ideally use a protection cap when stored. “Bleed” all pressure from system. Store between 20 to 130◦F, away from heat duct Properly stored at all times (i.e. cart or attached to yoke) Never drop, drag, slide or roll a cylinder! http://www.bing.com/videos/search?q=mythbusters+%2b+o xygen+tank&view=detail&mid=7125AB2CF287E142A3F77125 AB2CF287E142A3F7&FORM=VIRE1 Costs Purchase a new vs. refurbished machine Service and maintenance costs Trained and certified technician Routine maintenance usually 1-2 times/year http://bluepearlvet.com/locations/kentucky/kentucky- Keep accurate records veterinary-community/kentucky-newsletters/2015-winter/ Safety feature upgrades Key-fill adapters Pop-off occlusion valve Pressure relief valve – watch a video of how it works here: https://www.essentialmedicaldevices.com/ Image: http://www.jdmedical.com/veterinary- products/anesthesia-accessories/pop-off-occlusion-valve/  How to perform a machine leak test (aka “machine pressure check”) 1 2 3 4 5 6 7 30 colo for 30 seconds W ~ Make sure O2 Close the APL Occlude the Press the O2 flush Observe the Release the Remove button to pressurize flow meter is (pop-off) patient end of the system to 30 pressure gauge APL valve occlusion from OFF valve the Y-piece cmH2O for approximately Y-piece with a hand, non-rebreathing 30 seconds. finger, or systems just use flowmeter to fill See instructions syringe plunger system below. Continuation of Step 5: If no leak observed, proceed to step 6 If leak observed, slowly titrate the O2 flow meter up to maximum of 300 mL/min If this stops the leak, the machine and breathing system is acceptable to use If it takes >300 mL/min of O2 to stop the leak, the machine and breathing system should not be used until the source of the leak is identified Your homework… Draw your own diagram of an anesthesia machine, using an anesthesia machine from surgery lab. Be sure to label all parts. Keep practicing psi calculations Read corresponding Chapter in the Handbook of Veterinary Anesthesia (chapter 12)  Cylinder label Pressure gauge Cylinder valve regulator Hanger yoke: orients and supports cylinder, provides gas-tight seal  Nipple Index pins Retaining screw Reservoir bag or ventilator Conical hose goes here Port depression to receive yoke PISS retaining screw holes Resources Handbook of Veterinary Anesthesia. 5th ed. Chapter 12. Dorsch and Dorsch. Understanding Anesthesia Equipment. 5th ed. Chapters 1-6. Lumb & Jones. Veterinary Anesthesia and Analgesia. 5th ed. Chapter 3.