The VAM team has been funded by the Anesthesia Patient Safety Foundation (APSF) to develop and evaluate a simulation of the anesthesia machine pre-use check.
The last version (circa 1993) of the FDA anesthesia machine pre-use checklist is now more than 11 years old and is valid only for an anesthesia system that is equipped with an ascending bellows ventilator. Significant developments during that time include the introduction of anesthesia ventilators without bellows (e.g., piston ventilators) and anesthesia workstations that include semi-automated pre-use checks.
As each step of the 1993 FDA pre-use check is simulated, a hyperlink
will be placed in the list below.
The steps shaded in gray need not be repeated or can be abbreviated
after the initial checkout, if an anesthesia provider uses the same
anesthesia machine in successive cases.
The potential malfunctions that can be detected with each part of the checklist will also be simulated.
For convenience, a disposable 1993 FDA checklist is formatted to print as a FlashPaper or Word document on one page which, when folded in four, should fit in a medical scrub pocket. Print as many copies as you need.Emergency Ventilation Equipment
1. Verify backup ventilation equipment is available and functioning (e.g. Ambu bag).
High Pressure System2. Check oxygen cylinder supply:
a. Verify that at least one backup cylinder is available and check to see that it is at least half full (about 1000 psi) by opening the cylinder valve and verifying that the cylinder pressure gauge goes up. No other cylinders need to be checked.
b. Close the oxygen cylinder valve after checking.
3. Check central pipeline supplies:
Low-pressure SystemCheck that hoses are connected and that the pipeline pressure gauges read about 50 psi.
4. Check initial status of low pressure system.
a. Close the flow control valves and turn the vaporizers off.
b. Check the vaporizer fill levels and tighten the vaporizer filler caps, test interlock system.
5. Perform leak check of low pressure system.
a. Verify that the machine master switch and flow control valves are off.
b. Attach a suction bulb to the common gas outlet.
c. Squeeze the bulb repeatedly until it is fully collapsed.
d. Verify that it stays collapsed for at least 10 seconds (a vacuum cannot be created if there is a significant leak).
e. Open one vaporizer at a time and repeat step c & d (the bulb will initially re-inflate due to the gas that was in the vaporizing chamber).
f. Remove the suction bulb and reconnect the fresh gas flow hose to the common gas outlet.
6. Turn on the machine master switch and all other
necessary equipment.
The low pressure alarm should be heard because of the sudden increase
of gas pressure in the oxygen pipeline.
7. Test flowmeters.
a. Adjust flow of all gases through their full range, checking for smooth operation of floats and undamaged flowtubes. The minimum flowrate of oxygen should be 200 ml/min in Ohmeda Modulus I and II machines.
b. Attempt to create a hypoxic O2/N2O mixture by adjusting flowmeters and make sure the hypoxic safeguard mechanism prevents this from happening.
Scavenging System
8. Adjust and check scavenging system.
a. Ensure proper connections between the scavenging system and both the APL valve and ventilator relief valve.
b. Adjust waste gas vacuum.
c. Fully open APL valve and occlude the Y-piece.
d. With minimum O2 flow, allow the scavenger reservoir bag to collapse completely and verify that the absorber pressure reads about zero (this tests the negative pressure relief valve - room air is drawn into the scavenging system).
e. With the O2 flush activated allow the scavenger reservoir bag to distend fully, and then verify that the absorber pressure gauge reads < 10 cm H2O (this tests the positive pressure relief valve - the high flow of the O2 flush will overcome the scavenging system and excess gas will vent through the valve).
Breathing Circle System
9. Calibrate the oxygen monitor.
Two different oxygen analyzers are actually used in our operating room.
One type is an electrochemical (slow) sensor that measures FiO2 in the inspiratory limb of the circuit. The FiO2 will be displayed in the same display as the ventilator settings.
The other type is a paramagnetic sensor (fast) that is inside the gas-analyzing unit that also does infrared absorption spectrometry of the anesthetic gases and shows the capnogram.a. Ensure the oxygen monitor reads 21% in room air.
b. Verify that the low O2 alarm is enabled and functioning.
c. Reinstall the sensor in the circuit and flush breathing system with O2.
d. Verify that the monitor now reads greater than 90%.
10. Check initial status breathing system.
a. Set the selector switch to Bag mode.
b. Check that the breathing circuit is complete, undamaged and unobstructed.
c. Verify that CO2 absorbent is adequate and not exhausted.
d. Install breathing circuit accessory equipment (e.g. PEEP valve) that is to be used during the case.
11. Perform (positive pressure) leak check of the breathing system.
a. Set all gas flows to minimum.
b. Close APL valve and occlude the Y-piece.
c. Pressurize the breathing system to about 30 cm H2O with O2 flush (check the inspiratory pressure gauge).
d. Ensure that the pressure does not decrease for at least 10 seconds.
e. Open the APL valve and ensure that the pressure decreases.
Ventilation Systems
12. Test ventilation systems and unidirectional valves.
a. Place a second breathing bag on the Y-piece.
b. Set appropriate ventilator parameters for next patient.
c. Set the selector switch to Ventilator mode.
d. Turn the ventilator on and fill bellows and breathing bag with O2 flush.
e. Set O2 flow to minimum and other gas flows to zero.
f. Verify that during inspiration bellows delivers appropriate tidal volume and that during expiration bellows fills completely.
g. Set fresh gas flow to about 5 L/min.
h. Verify that the ventilator bellows and simulated lungs fill and empty appropriately without sustained pressure at end expiration.
i. Check for proper action of the unidirectional valves.
j. Exercise breathing circuit accessories to ensure proper function.
k. If everything works satisfactorily, turn the ventilator off and switch the selector switch to Bag mode.
l. Ventilate manually and feel if there is an appropriate amount of system resistance and compliance during inflation and deflation of the "artificial lungs".
m. Remove the second breathing bag from the Y-piece.
Monitors
13. Check, calibrate and/or set alarm limits of all monitors.
Final Position
14. Check final status of machine.
a. Vaporizers off
b. APL valve open
c. Selector switch to Bag mode
d. All flowmeters to zero or minimum (oxygen)
e. Patient suction level adequate
f. Breathing system ready to use