Anesthesia machine basics (asepsis)

What is the function of an anesthesia machine

delivers inhalation anesthesia and oxygen while removing gases

What are the 3 things an anesthesia machine must do

deliver oxygen at a controlled rate, vaporize liquids to gas, and removes exhaled gas

What is very important to insure proper function of an anesthesia machine

Maintenance

What are the components of an anesthesia machine

1. oxygen storage

2. pressure reducing valve

3. flowmeter

4. flush valve

5. vaporizer

6. inspiratory valve

7. negative pressure valve

8. corrugated breathing tube

9. expiratory tube

10. adjustable pressure relief valve

11. manometer

12. rebreathing bag

13. carbon dioxide absorber

14. scavenging system

What are the components of the oxygen source

Cylinder, two types of tanks E and H, color coated green, at 2200psi pressure, 100% o2, have a yoke and tank pressure gauge

What is the difference between an E and H oxygen tank

E is smaller and attached to the machine, H is larger and chained to a wall

What is the yoke part of a oxygen tank

a U-shaped metal clamp or connector that attaches a pressure regulator or flowmeter directly to the valve of a medical oxygen cylinder

What does the pressure reducing valve do

reduces pressure leaving the oxygen tank to 40-50 psi

What does the flowmeter do

reduces pressure to 15 psi, regulates o2 flow, (the floating ball tells you how much oxygen is given in L/min or ml/min)

What should you avoid with the flowmeter

Excess tightening

What is the flush valve

flushes valve, pure o2 only and vaporizer is bypassed

When should you not use the flush valve

Do not use with non-rebreather and do not push with pop off valve closed

What are the important function of the vaporizer

Temp, gas flow rate, back pressure

What are the parts of a vaporizer

inlet- o2 enters, outlet- o2 and anesthetic gas exits (circular system)

What are the vaporizers other functions

Holds liquid anesthetic, controlled delivery, is calibrated, precision v.s non-precision

what should be done with the vaporizer for good maintenance

serviced annually or per manufacturer recommendations and only use the liquid anesthetic the machine is calibrated for

What are the types of unidirectional valves

Inspiratory/expiratory, unidirectional, flutter valve (inhale/exhale)

what does an unidirectional valve do

insures one way direction of gas flow

What does the negative pressure relief valve do

Safety device that allows room air to enter the system

what is corrugated tubing/y piece

tubing comes together to form the y-piece

What is the weight range for a shorter/smaller diameter tubing

7-20kgs

What is the weight range for a longer/larger diameter tubing

>20kgs

What is the function of the Adjustable pressure relief valve (pop-off valve)

in the open postion it prevents pressure build up

What are the 3 flow rate techniques for the pop-off valve

wide, partial, and closed when bagging only

What is the most important thing to remember about the pop-off valve

The patient can not breath when the pop-off valve is closed

What are the functions of the manometer

pressure gauge and reads pressure in the system (cmH2O or mmHg units)

What is the normal resting pressure with the pop-off valve completely open

should be zero on the manometer

What pressure should you never exceed on the manometer when bagging a patient

20cmH2O

What are the function of the rebreathing/reservoir bag

patients re-breath exhaled gas and the bag deflates on inspiration and inflates on expiration

How do you find tidal volume

10ml/kg

What are 2 equations you can use to find the rebreathing bag/reservoir bag size

5x tidal volume or 30 x weight in pounds

what is the function of the carbon dioxide absorber

exhaled CO2 goes to the CO2 absorber or scavenger to track usage with ph indicator from a chemical reaction caused by the heat and water produced from the Co2 changing the color

What are the 2 types of CO2 absorbers

baralime (barium hydroxide lime) or sodalime (sodium hydroxide lime)

How much space does the carbon dioxide absorber leave

½ inch in air space at the top

what are the functions of the scavenging system

evacuates waste gas through active or passive systems

what is the difference between active and passive scavenging systems

Active is mechanical usually through a vacuum to the outside v.s passive that relies on gravity (f-air canister or hose to outside wall vent)

When should you leak test an anesthesia machine

before every procedure, after a hose or bag change, after changing the co2 absorber

How do you run a leak test

close the pop-off valve and occlude the breathing circuit then flush to 20-40mmHg making sure to observe the meter

why is leak testing important

reduces and eliminates gas leaks into the environment

what are the 2 types of Breathing circuits

rebreathing and nonrebreathing

rebreathing circuit

recirculation of expired gas, should be used in animals >7kg, universal f-circuit, corrugated hose

Non rebreathing circuit

no gas is rebreathed, should be used in animals <7kg, has low gas resistance and high oxygen flow, bypasses CO2 absorber and manometer, the patient can breath normally and receive fresh, new gas with minimal effort

Rebreathing oxygen flow rate

Induction: 50-100mL/kg/min

• Maintenance: 20-40mL/kg/min

• Recovery: 50-100mL/kg/min

Just need enough to match tidal

volume

Non rebreathing oxygen flow rate

200ml/kg/min for all phases

Precision vs. non-precision vaporizer

precision is temp controlled so the higher the temp the more gas is made

Flow of the anesthesia machine (Andrew)

O2 from tank goes to pressure release valve to flow meter to oxygen flush valve to vaporizer to unidirectional valve to inspiratory valve to expiatory valve to negative pressure relief valve, through corrugated tubing and y piece, to expartory tube, to adjustable pressure relief valve (pop off valve), nanometer, revisor bag, soda lime, scavenger system