Chapter 4
Anesthetic Machine and Equipment Check

No one likes surprises!

Richard M. Bednarski

Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, USA

1. Q. What anesthetic equipment should be checked prior to use?
   
2. A. Any anesthetic equipment used or anticipated to be used must be inspected and its proper function verified before use. Immediately after anesthetic induction you must be able to deliver oxygen and anesthetic gas, provide assisted ventilation, and have the capability of effectively using all of your monitors. A pre-anesthetic check of equipment prevents a potentially dangerous delay in providing oxygen and inhalant, as well as in monitoring vital signs. Typically the anesthetic machine, breathing system, airway device(s) including endotracheal tube or mask, and any monitoring equipment should be checked.
   

   There is no prescribed standard for verifying the correct function of anesthetic machines, breathing systems, airway devices, or anesthetic monitoring equipment. Because of the wide variety of anesthetic machines, vaporizers, and monitoring equipment available, the user must become familiar with the correct operation of their particular equipment. Although a sales representative should be able to provide a functional overview for the correct operation, there is no substitute for thoroughly reviewing the accompanying manufacturer’s owner’s manual.

   
   

   Leaks in the anesthetic machine, breathing system, endotracheal tube, and anesthetic ventilator can contribute to unnecessary exposure of personnel to anesthetic vapors. Although there are no federally mandated restrictions relative to anesthetic gas exposure, the Occupational Safety and Health Administration (OSHA) general duty clause requires that an employer provide a hazard-free working environment even in the absence of a relevant standard. A leak-free anesthetic gas delivery system is an important part of controlling waste anesthetic gas exposure.

   
   
3. Q. Who should perform the check?
   
4. A. Ideally the person responsible for anesthesia delivery and monitoring should verify proper equipment function. This person can be an appropriately trained technician or veterinarian. Most importantly, it must be a person familiar with proper use of all of the anesthetic and monitoring equipment.
   
5. Q. How often should the equipment be checked?
   
6. A. Many checks can be performed periodically, while others (e.g., monitoring equipment) should be performed daily prior to each day’s procedures. The oxygen source and associated supply line need to be checked only when problems are suspected, tanks are switched, or when new connections are made to the anesthetic machine. Items that are changed or removed and cleaned between cases, such as endotracheal tubes and breathing system components, should be checked prior to each use.
   
7. Q. Is there a good way to ensure the equipment is appropriately checked?
   
8. A. Although experienced users can rely on a mental checklist, a written checklist of tasks posted in the anesthetic induction area promotes consistency. Such a task list helps ensure that all anesthesia providers do not overlook anything and adhere to that facility’s standard of care (see Box 4.1). The checklist can be posted in the anesthetic induction area to verify that the appropriate anesthetic related supplies needed for each case are ready for use. A more detailed task list should be made available to verify proper anesthetic machine and monitoring equipment function (see Table 4.1). It is convenient to divide your pre-anesthetic equipment check into that associated with the: (i) gas supply; (ii) anesthetic machine; (iii) breathing system; (iv) ventilator; (v) airway supplies; (vi) monitoring equipment; and (vii) emergency equipment.

   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   

   Equipment	Notes
   Gas supply*	Open hospital supply oxygen cylinder valves or turn on oxygen concentrator. Ensure adequate tank pressure/volume for day’s use. Ensure pipeline pressure between 50–55 psi. Ensure portable E cylinder (backup) is connected to the anesthesia machine and contains a pressure at least 500 psi. Perform high pressure system leak check periodically (refer to text).
   Anesthesia machine*	Fill vaporizer(s) and close fill cap(s). Rotate vaporizer dial throughout its settings and shut off. Verify adequacy of CO2 absorbent material. Connect machine to oxygen source and verify correct flowmeter operation. Perform negative-pressure or positive-pressure low-pressure system leak check (refer to text).
   Waste gas scavenging system*	Switch on active waste gas scavenging system and confirm its connection to the scavenging interface. Ensure waste gas scavenging system interface is properly connected to pop-off valve via transfer hose. Test and if necessary adjust waste gas scavenging vacuum. If using activated charcoal passive scavenging check the weight of the activated charcoal canister and change if necessary.
   Breathing system	Connect appropriate breathing system and rebreathing bag to machine: Non-rebreathing <3 kg body weight Circle rebreathing >3 kg body weight Pressure check the breathing system: Begin with flowmeter off and pop-off valve open → — Non-rebreathing: Close pop-off valve. Occlude patient connection using hand or thumb. Activate oxygen flush valve to tightly distend rebreathing bag (30 cm H2O if pressure gauge present). System should retain pressure for minimum of 10 s. Fully open pop-off to confirm pressure release. — Circle rebreathing: Close pop-off valve. Occlude patient connection (Y piece or patient end of coaxial circuit) using hand or thumb. Activate oxygen flush valve to fully distend rebreathing bag (30 cm H2O). System should retain pressure for minimum of 10 s. Fully open pop-off to confirm pressure release.
   Mechanical Ventilator	Plug in electrical power cord and connect ventilator to compressed gas source. Connect ventilator transfer hose to rebreathing bag port of anesthesia machine. Insert pressure sensor (if present) between inspiratory valve and hose. Connect waste gas scavenging port of ventilator to waste gas scavenging system. Close pop-off valve. Turn flowmeters off. Occlude Y-piece. Activate oxygen flush valve to fully distend the ventilator bellows. Bellows should remain distended for at least 10 s.

   
   
9. Q. What are the components of a typical anesthesia machine?
   
10. A. See Figure 4.1. A hospital-wide oxygen source (high pressure cylinder(s), liquid oxygen storage tank, or oxygen concentrator and storage tank) is connected to a pressure regulator. Oxygen leaves the regulator at a pressure of 50–55 psi and enters the hospital supply line(s) to be directed to various locations within the facility. The anesthesia machine is connected to a hospital supply line. Alternatively or additionally a transport E cylinder of oxygen is attached directly to the anesthesia machine and pressure regulator. Oxygen from either source is routed to the oxygen flush valve and an oxygen flowmeter. Oxygen exits the flowmeter and is directed through an anesthetic vaporizer. A nitrous oxide E tank can be connected to a nitrous oxide-specific pressure regulator from which point it is routed to a nitrous oxide flowmeter. After leaving its flowmeter nitrous oxide joins the oxygen exiting from the oxygen flowmeter. Gas exits the vaporizer or the oxygen flush valve and is directed through a common gas outlet. In some machines a check valve preventing back-flow into the vaporizer and flowmeter(s) is located within the common gas outlet. Gas from the common gas outlet is directed into a non-rebreathing system or into a circle rebreathing system (Figures 4.2 and 4.3).