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Anesthesia Information and Emergency Medicine


Aestiva Gas Machine Operation Checklist

ITEMWho performs?Frequency to CheckHow to Check?Notes/RationaleFDA #
System Switch to STANDBY position.Provider AND TechDailyStandby position allows cessation of minimum oxygen flow so that static leaks in the ventilator may be checked.
Vaporizer filling.ProviderEach case.Fill any depleted vaporizers. Make sure fill port is closed tightly.Loose connections or depleted volatile agent might cause awareness under anesthesia.7
Low pressure leak testTechDailyCheck for level seating of vaporizers and tight locking knobs. Open each FGF knob 1.5 turns. Pump negative pressure bulb at the opened CGO repeatedly for each opened vaporizer. Check for no bulb inflation in <30 sec. Close FGF knobs.A low pressure leak would cause the influx of room air, causing the bulb to reinflate.  Each vaporizer must be opened to depress the back-bar valves, which then tests the integrity of the back-bar port O-rings.8
Vaporizer interlock.TechDailyInterlock: while testing each vaporizer for leaks, attempt to turn on each of the other vaporizers.Vaporizers are designed not to deliver two agents at once.
Check auxiliary oxygen flowmeterTechDailyTurn on while watching indicator, then turn off.Auxiliary oxygen, when available, is a basic requirement during monitored care, and a critical safety backup.
Look for exhaustion of carbon dioxide absorbentProvider AND TechEach case.As absorbent is exhausted, it will turn purple from top down.  Desiccation may be indicated by purple at the bottom, or by discovery of fresh gas flow ON at the start of the day.Exhaustion is indicated by a majority of the agent turning purple.  Clinical evidence for exhaustion is the rebreathing of inspired carbon dioxide detected by capnometry.  Purple color may revert back to white in some absorbents, or the coloration may be hidden internally (channeling).11
Replace CO2 absorbent when necessary.Provider AND TechWhen necessary and Monday MORNING.When using cartidges, make certain that the wrapper is completely removed and gasket/housing rims are wiped clean of dust.We use a “conventional” GE Medisorb absorbent. Change whenever exhausted, or desiccated, or exposed to prolonged FGF, or not used for a prolonged period. Desiccated absorbent may produce toxic substances.11
Gas sampling line and water trap.TechEach case.Ensure firm, straight connections of tubing and empty the water trap if liquid is present. Analyzer must be OFF for subsequent leak testing.The gas sampling line is an integral part of the breathing system and is included in the leak testing, but must not be turned on.
Static ventilator leak checkTechDailySwitch to Vent mode. Occlude Y-piece. Press flush to fill bellows and release. Wait to assure that bellows does not collapse.This test checks for leaks in the ventilator relief valve or bellows (or breathing circuit), when no pressure is applied to the system. It can only be done when the machine is off, so that the ventilator will not activate.12
Ventilator scavenger circuit and oxygen flush.TechDailyFollowing above test, press O2 flush and ascertain that breathing circuit pressure is <10cm. Check that scavenger reservoir bag (if present) is not distended under pressure. If so, increase scavenger suction to green zone indicator.The oxygen flush valve should not stick.  The Aestiva/5 scavenges patient fresh gas AND ventilator drive gas and therefore requires high suction; otherwise, undesired PEEP may develop.9
Suction for patient.Provider AND TechEach case.Ensure adequate patient suction.An essential element for patient care.2
Backup ventilation devices.Provider AND TechEach case.Ensure self-inflating non-rebreathing bag operates properly by squeezing with and without thumb occlusion. Test and/or locate jet ventilator, LMA, Cook® transtracheal catheter.The clinician must be prepared to ventilate and oxygenate the patient in the event of machine failure or patient difficulty.1
Medical gas supplyProvider AND TechDailyCheck for approximately 50psi on all line pressures and check for adequate oxygen cylinder supply by opening and then closing the oxygen cylinder.Backup oxygen must be ensured, both by checking the pressure, and by closing the valve after checking.5,6
Battery backup powerTechDailyOpen the circuit breaker behind the machine, reach around to turn machine on, and look for battery backup indicator on the orange screen.  Then close the circuit breaker, observing the illumination of the green LED “mains indicator” on the panel.Although the machine can operate for at least 30 minutes on battery, it should always be operated on wall supply. With loss of all power, note that none is required to deliver fresh gas, vapor, and manual ventilation.3
System Switch to ON
Minimum oxygen flow,  alarm, calibration, and moisture drain.TechDailyCheck min. O2 flow of 25-75 ml/min. Remove O2 sensor and wait. Note audible low FiO2 alarm. Press the 21% calibration wheel when reading is stable. Replace sensor tightly, checking O-ring. Press drain button. Open/close absorber drain cock.The oxygen flow control knob is mechancally set to remain slightly open, allowing minimum oxygen flow. The sensor may also be calibrated to 100%. Water normally accumulates in this trap and must be drained away from the flow sensors.10
Flow sensor calibration and vent settings.TechEach case.Remove flow sensor module and wait for “No Insp/Exp Flow Sensor”. Reinsert flow sensor.For optimal volume measurement, compensation, and ventilator function, the flow sensors must be calibrated for each case, or if the temp changes >5°C.15
Breathing circuit leaks and alarms.TechEach case.Set O2 flow to 250ml.  Occlude Y, flush to > Plimit, then stop. Note high Paw alarm, then “Contg. Press. Alarm”. There must be NO drop in pressure.  Leaks <250ml/min are generally acceptable. Proper function of airway pressure alarms is important for patient safety.12
APL calibration, scavenger, and high O2 calibration.TechDailyBleed APL to 30 by dial, check calibration with circuit pressure gauge. Open APL fully and press O2 flush, noting pressure <10cmH2O. Release and check for NO negative press. O2 monitor should read >90%.This tests the approximate calibration of the APL valve, and its ability to scavenge high flow of gas without obstruction or pressure buildup. The elevation in oxygen concentration to 100% confirms that oxygen gas is the source.9,10
Manual ventilation, uni-directional flow, tidal volume and apnea alarm.Provider AND TechEach case.Second bag at the Y. Flush, actuate bi-directional manual ventilation. Check uni-directional valves, tidal volume measurement and lack of resistance or obstructions. Listen for “reverse flow” alarm. Pause and wait for apnea alarm after 30 sec.This checks the ability to ventilate the patient in the manual vent mode. Incompetent uni-directional valves will cause reverse flow and activate the alarm. Testing the apnea alarms is critical.13
Mechanical ventilation, leaks, and pressure limiter.TechDailyWith FGF still OFF, activate and adjust mechanical vent settings. Observe for any loss of gas. Press O2 flush and note inspiratory cut-off when Pmax is attained. Increase O2 and N2O each to 10 l/min.Proper function of mechanical ventilation, with limitation of unsafe airway pressures, is critically important.  Inadequate scavenger function may cause pressure buildup at high FGF.12
ProportionatorTechDailyLower O2 until it drags down the N2O, then increase the N2O to see if it drags up the O2. Check that FiO2 does not decrease to <21%. Turn off N2O and leave O2 at 6 l/min. Check for PEEP <3cm.  Remove the test lung and turn vent selector to bag.This checks the minimum oxygen ratio controller and scavenger exhaust.
Vaporizer back pressure testTechDailyWith oxygen at 6 l/min, turn on one vaporizer at a time to 1%. Check that oxygen flow remains >5 l/min.If there was abnormal resistance in the vaporizer, then the oxygen flow would drop more.
“Exit Room” to silence alarmsProvider AND TechEach case.Press “exit room” button and confirm.Alarms must be reset for the subsequent patient and silenced when leaving the room.4
Checking during the case.ProviderEach case.Some functions are most easily, effectively, and safely checked when the patient is initially pre-oxygenated and then attached to the machine.
Verify availability and proper function of required monitors and alarms.ProviderEach case.Is the capnogram present?  The function of numerous monitors is verified as they are connected to the patient.  Default alarm limits must be checked for appropriateness while “auto-set” limits are convenient once the patient is connected and has stable, desired vital signs.Audible and visual alarms help to alert the clinician to potentially dangerous situations.4
Verify adequacy of absorbent and competence of uni-directional valves.ProviderEach case.The clinician should verify the absence of inspired carbon dioxide.Either exhausted absorbent or incompetent uni-directional valves could cause inspired carbon dioxide.13
Verify proper vaporizer outputProviderEach case.The clinician should ascertain that expected levels of volatile agents are shown on the anesthetic gas analyzer.Accurate output of the vaporizer is expected, although it is not appropriately or accurately measured at the endotracheal tube. Vaporizer calibrations are checked by biomedical PM.7
Document completion of checkout procedure per department policyProvider AND TechEach case.Document the checkout on the anesthetic record and Tech Check log.The clinician is ultimately responsible for basic operation of the machine, and responsible for proper response to an intraoperative machine failure. To promote backup safety measures, the anesthesia technician will perform the indicated tests.14
TIME OUT! ProviderEach case.Do I have all of the following: Oxygen? Agent? Pressure? Absorbent? Suction? Monitoring? Backup vent?The clinician should follow customary JCAHO recommendations for “TIME OUT” to overcome potential errors or omissions from distractions.15
Do the following between cases:The machine must be prepared adequately for subsequent cases.
All gas flows OFF between cases.Provider AND TechEach case.Turn fresh gas flow knobs to the off position whenever the machine is not in use.Leaving flows on is wasteful and may desiccate the absorbent.
Breathing circuit drain and flow sensor humidity.TechEach case.Press the drain button >10 sec. Check for humidity on the flow sensors and replace if wet.Moisture droplets around the flow sensors will cause them to fail. Replace with a dry unit and allow existing unit to dry out.
Change the circuit and suction apparatusTechEach case.Check for tight connections and damage to the circuit.Both systems are contaminated. Hoses may have cuts or kinks.
Review and perform all “each case” items in this list.TechEach case.Follow the same sequence.Changing a circuit, filling a vaporizer, or opening the absorbent canister may create a leak.
Alarm resetsTechEach case.Press “exit room” button and confirm.Alarms must be reset for the subsequent patient.
End of day
Machine off to STANDBYProvider AND TechDailyAt the conclusion of the day’s list, power down the machine. On-call machines should be left ON, following the above step, and re-booted in the morning for checkout procedures.STANDBY mode allows trickle charge of battery and stops all gas flow to prevent dessication of the absorbent. ON mode allows immediate use of machine and continuous flushing with minimum O2 flow.
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