Translation Guide

By Adam Peterson,2014-01-20 04:32
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Translation Guide




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    Sem Lampotang, Dave Lizdas



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     FDA Anesthesia Apparatus Checkout Recommendations, 1993


    Emergency Ventilation Equipment



    High Pressure System


    Low Pressure System



    Scavenging System



    Breathing System



    Manual and Automatic Ventilation Systems






Final Position



    1. Verify Backup Ventilation Equipment is Available and Functioning.


     If the anesthesia machine fails, back-up ventilation equipment like a self-inflating manual resuscitator (SIMR) allows you to continue positive pressure ventilation. You should also check that the SIMR is functioning because a SIMR that is available but malfunctioning is of limited use in an emergency.



    2. Check O2 Cylinder Supply


     a. Open O2 cylinder and verify at least half full (about 1000 psi).

     If the central (pipeline) O2 supply fails, the O2 cylinder is the back-up O2 supply. You need to open the cylinder to read the cylinder pressure and infer the volume since O2 volume is directly proportional to O2 cylinder pressure. This is a necessary but not sufficient condition to obtain an accurate cylinder pressure reading - please view the VAM simulation to learn the procedure to read cylinder pressure correctly.


     b. Close cylinder.

     If you leave the O2 cylinder open and the central O2 supply fails, the anesthesia machine will be supplied with O2 from the O2 cylinder without a warning being raised about the loss of central O2 supply. When the O2 cylinder eventually runs out, a loss of O2 supply pressure alarm will occur but there will be no back-up O2 supply.

    If you close the O2 cylinder as instructed, an alarm will notify you that the central supply has failed. You then open the O2 cylinder and complete the case (if there is enough O2 in the reserve cylinder).




    3. Check Central Pipeline Supplies

     b. Attach Suction Bulb to common (fresh) gas outlet.

     In this step, you are setting the machine in the proper configuration for ensuing steps. The instructions do not state it but you obviously need to disconnect the fresh gas flow hose from the common gas outlet first before you will be able to connect the suction bulb.



     c. Squeeze bulb repeatedly until fully collapsed.

     When you squeeze the bulb repeatedly, you are evacuating the suction bulb and other plumbing to which it is connected and creating a vacuum that causes the bulb to collapse and remain collapsed.



     d. Verify bulb stays fully collapsed for at least 10 seconds.

     If there is a crack in the flowmeter tubes, atmospheric air will leak in through the crack and break the vacuum causing the suction bulb to re-inflate within 10 seconds.


     e. Open one vaporizer at a time and repeat ‘c’ and ‘d’ as above.

     With this step, you are checking one vaporizer at a time for leaks. You need to open the vaporizer to a non-zero setting on its concentration dial for the vaporizer to be in pneumatic connection with the suction bulb. The rationale for spending the time to check all vaporizers, one at a time, when generally, only one vaporizer is used in a case is unclear to this author.




f. Remove suction bulb, and reconnect fresh gas hose.

     In this step, you are setting the machine back to its usual configuration for ensuing steps.




    6. Turn on Machine Master Switch and all other necessary electrical equipment (not shown.)

     In this step, you are configuring the machine for ensuing steps. If you leave the master switch off, the flowmeters will not work.



    7. Test Flowmeters


     a. Adjust flow of all gases through their full range, checking for smooth operation of floats and undamaged flowtubes.

     You are checking for floats that get stuck in the flowmeter tube and provide erroneous flow readings.



     b. Attempt to create a hypoxic O2/N2O mixture and verify correct changes in flow and/or alarm.

     You are checking that the hypoxic guard mechanism prevents setting an FiO2 lower than 25% in machines that also deliver N2O.




    8. Adjust and Check Scavenging System


     a. Ensure proper connections between the scavenging system and both APL (pop-off)

valve and ventilator relief valve.

     A scavenging hose that is not properly connected to the scavenging system will release N2O and volatile anesthetics into ambient air. A scavenging hose exhausting gas to ambient air will generally not affect the operation of other sub-systems in the anesthesia machine but can be detected by visual inspection.



     b. Adjust waste gas vacuum (if possible).

     Too little suction from the waste gas vacuum will result in N2O and volatile anesthetics spilling into ambient air without any warning or alarm. Too much suction is wasteful and entrains air conditioned ambient air out of the OR.


     c. Fully open APL valve and occlude Y-piece.

     A fully open APL valve with the selector knob set to 'Bag' mode is the worst case configuration for excessive vacuum to enter the breathing circuit and collapse the patient's lungs. If the Y-piece is not occluded, ambient air can enter through the Y-piece (rendering test 8d meaningless) and excess O2 can flow out of the Y-piece (rendering test 8e meaningless).



     d. With minimum O2 flow, allow scavenger reservoir bag to collapse completely and verify that absorber pressure gauge reads about zero.

     If the 'negative' pressure relief valve in the scavenging system is defective and allows excessive vacuum in the scavenging system to enter the breathing circuit, the absorber pressure gauge will indicate this fault by displaying a sub-ambient pressure (pressure less than 0 cm H2O).



     e. With the O2 flush activated, allow the scavenger reservoir bag to distend fully, and then verify that absorber pressure gauge reads less than 10 cm H2O.

     If the positive pressure relief valve in the scavenging system is defective and allows excessive pressure in the scavenging system to enter the breathing circuit, the absorber pressure gauge will indicate this fault by displaying a pressure greater than 10 cm H2O. This is a step that is often incorrectly performed.




    9. Calibrate O2 Monitor


     a. Ensure monitor reads 21% in room air.

     Accuracy of the O2 monitor at 21% O2 is more important than at 100% O2 because an error of 10% O2 is more serious at 21% O2 than at 100% O2. That is, the O2 monitor displaying 21% O2 when the actual O2 is 11% has more dire consequences than a monitor displaying 100% O2 when the actual O2 is 90%. Therefore, we calibrate with room air, a calibration gas of constant composition (21% O2) that is always available and free.



     b. Verify low O2 alarm is enabled and functioning.

     A hypoxic gas mixture can cause brain damage and death. A low O2 alarm will warn of such an occurrence when the O2 concentration falls below the low O2 alarm threshold.



     c. Reinstall sensor in circuit and flush breathing system with O2.

     You are attempting to expose the sensor to 100% O2 by pressing and holding the O2 flush.



     d. Verify that monitor now reads greater than 90%.

     During an O2 flush, the wash-in of O2 in the breathing circuit is initially very fast with the measured O2% rising quickly. It takes much longer for the O2% to rise from 90% to 100%. Because of time and practical considerations, 90% O2 is good enough.




    10. Check Initial Status of Breathing System


     a. Set selector switch to ‘Bag’ mode.

     In this step, you are configuring the machine for ensuing steps.



     b. Check that breathing circuit is complete, undamaged and unobstructed.

     During unpacking, a box cutter may accidentally cut the breathing circuit causing a leak. Visual and tactile (by running one's hand over the circuit) inspection can help detect a damaged, incomplete or obstructed breathing circuit. On the assumption that a new disposable breathing circuit is used for each case, this step is repeated before every case unlike steps 1 - 9 because a new circuit can introduce a new fault.


     c. Verify that CO2 absorbent is adequate.

     Absent or exhausted CO2 absorbent will result in unintended CO2 rebreathing, especially at low fresh gas flows. Exhausted CO2 absorbent is indicated by a change in color to purple.



     d. Install breathing circuit accessory equipment (eg, humidifier, PEEP valve) to be used during the case.

     This step has to precede step 11 where a breathing system leak check is performed so that leaks in the breathing circuit accessory equipment are also detected. If breathing circuit accessory equipment are added AFTER step 11 and have leaks, they will introduce breathing system leaks that are not detected during the pre-use check but during the case.




    11. Perform Leak Check of the Breathing System


     a. Set all gas flows to zero (or minimum).

     A high gas flow will mask (feed) a leak, preventing its detection.



     b. Close APL (pop-off) valve and occlude Y-piece.

     An open or partially open APL valve can act as a leak. An unoccluded Y-piece acts as a large leak and will give a false positive indication of a breathing system leak.


     c. Pressurize breathing system to about 30cmH2O with O2 flush.

     An O2 flush is a quick way to build up pressure in the breathing circuit. A high pressure in the breathing circuit will cause gas in the breathing circuit to exit to atmosphere through a leak.



     d. Ensure that pressure remains fixed for at least 10 seconds.

     A breathing system leak will allow gas in the breathing circuit to escape to atmosphere and cause the pressure to drop below 30 cm H2O within 10 seconds.


     e. Open APL (pop-off) valve and ensure that pressure decreases.

     You are verifying that the APL valve is functioning properly by relieving pressure through the APL valve. This is a step that is often incorrectly performed.



    12. Test Ventilation Systems and Unidirectional Valves


     a. Place a second breathing bag on Y-piece.

     The second breathing bag will be used to simulate a patient's lungs.



     b. Set appropriate ventilator parameters for next patient.

     You want to test the ventilator at the settings that will be used with the next patient.


     c. Switch to automatic ventilation (Ventilator) mode.

     You want to test the ventilator at the settings that will be used with the next patient.

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