Check Valves and Manufacturer-Check Valves and Manufacturer-Recommended Leak TestRecommended Leak Test

Low-Pressure Circuit Leak TestLow-Pressure Circuit Leak TestThe low-pressure leak test checks the integrity of the anesthesia machine from The low-pressure leak test checks the integrity of the anesthesia machine from the the flow control valves to the common gas outletflow control valves to the common gas outlet. .

It evaluates the portion of the machine that is It evaluates the portion of the machine that is downstream from all safety downstream from all safety devices except the oxygen analyzer. devices except the oxygen analyzer.

The components located within this area are The components located within this area are preciselyprecisely the ones most subject to the ones most subject to breakage and leaks. breakage and leaks. Leaks in the low-pressure circuit can cause hypoxia and/or Leaks in the low-pressure circuit can cause hypoxia and/or patient awareness.patient awareness.

Flow tubes, the most delicate pneumatic component of the machine, can crack Flow tubes, the most delicate pneumatic component of the machine, can crack or break.or break.

A typical three-gas anesthesia machine has 16 O-rings in the low-pressure A typical three-gas anesthesia machine has 16 O-rings in the low-pressure circuit. circuit.

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Leaks can occur at the interface between the glass flow tubes and the manifold Leaks can occur at the interface between the glass flow tubes and the manifold and at the O-ring junctions between the vaporizer and its manifold.and at the O-ring junctions between the vaporizer and its manifold.

Loose filler caps on vaporizers are a common source of leaks, and these leaks Loose filler caps on vaporizers are a common source of leaks, and these leaks can cause patient awareness under anesthesia.can cause patient awareness under anesthesia.

Several different methods have been used to check the low-pressure circuit for Several different methods have been used to check the low-pressure circuit for leaks, including the oxygen flush test, the common gas outlet occlusion test, leaks, including the oxygen flush test, the common gas outlet occlusion test, the traditional positive-pressure leak test.the traditional positive-pressure leak test.

The check valve is located downstream from the vaporizers and upstream from The check valve is located downstream from the vaporizers and upstream from the oxygen flush valve. the oxygen flush valve.

It is open in the absence of backpressure. Gas flow from the manifold moves It is open in the absence of backpressure. Gas flow from the manifold moves the rubber flapper valve off its seat and allows gas to proceed freely to the the rubber flapper valve off its seat and allows gas to proceed freely to the common outlet. common outlet.

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The valve closes when backpressure is exerted on it. The valve closes when backpressure is exerted on it.

Backpressure sufficient to close the check valve may occur with the following Backpressure sufficient to close the check valve may occur with the following conditions:conditions:

1) oxygen flushing, 1) oxygen flushing,

2) peak breathing circuit pressures generated during positive-pressure ventilation, 2) peak breathing circuit pressures generated during positive-pressure ventilation,

3)use of a positive-pressure leak test.3)use of a positive-pressure leak test.

Generally , the low-pressure circuit of anesthesia workstations without an outlet Generally , the low-pressure circuit of anesthesia workstations without an outlet check valve can be tested with a positive-pressure leak test, check valve can be tested with a positive-pressure leak test, and and machines with machines with check valves must be tested with a negative-pressure leak testcheck valves must be tested with a negative-pressure leak test..

Positive& Negative-Pressure Leak TestPositive& Negative-Pressure Leak Test

When performing a When performing a positive-pressure leak testpositive-pressure leak test, the operator generates positive , the operator generates positive pressure in the low-pressure circuit by using flow from the anesthesia machine pressure in the low-pressure circuit by using flow from the anesthesia machine or from a positive-pressure bulb to detect a leak.or from a positive-pressure bulb to detect a leak.

When performing a When performing a negative-pressure leak testnegative-pressure leak test, the operator creates negative , the operator creates negative pressure in the low-pressure circuit by using a suction bulb to detect leaks. pressure in the low-pressure circuit by using a suction bulb to detect leaks.

Inappropriate use of the oxygen flush valve to check the low-pressure circuit of an Ohmeda Inappropriate use of the oxygen flush valve to check the low-pressure circuit of an Ohmeda machine equipped with a check valve. The area within the machine equipped with a check valve. The area within the rectanglerectangle is not checked by is not checked by inappropriate use of the oxygen flush valve. The components located within this area are inappropriate use of the oxygen flush valve. The components located within this area are preciselyprecisely the ones most subject to breakage and leaks. Positive pressure within the patient the ones most subject to breakage and leaks. Positive pressure within the patient circuit closes the check valve, and the value on the airway pressure gauge does not decline circuit closes the check valve, and the value on the airway pressure gauge does not decline despite leaks in the low-pressure circuitdespite leaks in the low-pressure circuit

Positive-Pressure Leak Test Positive-Pressure Leak Test

250 Liters250 Liters

Pressure = 30 cmH2OPressure = 30 cmH2O

Negative-Pressure Leak Test Negative-Pressure Leak Test It is performed with a negative-pressure leak-testing device, which is a simple suction It is performed with a negative-pressure leak-testing device, which is a simple suction bulb. bulb.

The machine's master switch, flow control valves, and vaporizers are turned off.The machine's master switch, flow control valves, and vaporizers are turned off.

The suction bulb is attached to the common fresh gas outlet and squeezed repeatedly The suction bulb is attached to the common fresh gas outlet and squeezed repeatedly until it is fully collapsed.until it is fully collapsed.

This action creates a vacuum in the low-pressure circuitry. This action creates a vacuum in the low-pressure circuitry.

The machine is free of leaks if the hand bulb remains collapsed for The machine is free of leaks if the hand bulb remains collapsed for at least 10 at least 10 seconds. seconds.

A leak is present if the bulb reinflates during this period. A leak is present if the bulb reinflates during this period.

The test is repeated with each vaporizer individually turned to the “on” position The test is repeated with each vaporizer individually turned to the “on” position because internal vaporizer leaks can be detected only with the vaporizer turned on.because internal vaporizer leaks can be detected only with the vaporizer turned on.

Negative-Pressure Leak TestNegative-Pressure Leak Test

Food and Drug Administration negative-pressure leak test. Left, A negative-pressure leak-Food and Drug Administration negative-pressure leak test. Left, A negative-pressure leak-testing device is attached directly to the machine outlet. Squeezing the bulb creates a vacuum testing device is attached directly to the machine outlet. Squeezing the bulb creates a vacuum in the low-pressure circuit and opens the check valve. Right, When a leak is present in the low-in the low-pressure circuit and opens the check valve. Right, When a leak is present in the low-pressure circuit, room air is entrained through the leak and the suction bulb inflates.  pressure circuit, room air is entrained through the leak and the suction bulb inflates.  

Negative-Pressure Leak TestNegative-Pressure Leak Test

If the bulb reinflates in less than 10 seconds, a leak is present somewhere in the If the bulb reinflates in less than 10 seconds, a leak is present somewhere in the low-pressure circuit. low-pressure circuit.

Therefore, it differentiates between breathing circuit leaks and leaks in the low-Therefore, it differentiates between breathing circuit leaks and leaks in the low-pressure circuit. pressure circuit.

The The “universal” negative-pressure leak test “universal” negative-pressure leak test is the most sensitive of all is the most sensitive of all contemporary leak tests because it is not dependent on volume. contemporary leak tests because it is not dependent on volume.

That is, it does not involve the use of a breathing bag or corrugated hoses whose That is, it does not involve the use of a breathing bag or corrugated hoses whose compliance could mask a significant leak.compliance could mask a significant leak.

It can detect leaks as small as 30 mL/min.It can detect leaks as small as 30 mL/min.

Finally, the operator does not need detailed or in-depth knowledge of proprietary Finally, the operator does not need detailed or in-depth knowledge of proprietary design differences. If the operator performs the universal test correctly, the leak will design differences. If the operator performs the universal test correctly, the leak will be detectedbe detected

Circle System TestsCircle System Tests

The circle system tests evaluate the integrity of the circle breathing system, The circle system tests evaluate the integrity of the circle breathing system, which spans from the common gas outlet to the Y-piece .which spans from the common gas outlet to the Y-piece .

It has two parts—the It has two parts—the leak testleak test and the and the flow testflow test. .

To thoroughly check the circle system for leaks, valve integrity, and To thoroughly check the circle system for leaks, valve integrity, and obstruction, both tests must be performed preoperatively.obstruction, both tests must be performed preoperatively.

The The leak testleak test is performed by closing the pop-off valve, occluding the Y-piece, is performed by closing the pop-off valve, occluding the Y-piece, and pressurizing the circuit to and pressurizing the circuit to 30 cm H30 cm H22OO with the with the oxygen flush valveoxygen flush valve. .

The value on the pressure gauge will not decline if the circle system is leak The value on the pressure gauge will not decline if the circle system is leak free, but this does not ensure valve integrity. free, but this does not ensure valve integrity.

The value on the gauge will read 30 cm HThe value on the gauge will read 30 cm H22O even if the unidirectional valves are O even if the unidirectional valves are

stuck shut or the valves are incompetent.stuck shut or the valves are incompetent.

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The The flow testflow test checks the integrity of the unidirectional valves, and it detects checks the integrity of the unidirectional valves, and it detects obstruction in the circle system. obstruction in the circle system.

It can be performed by removing the Y-piece from the circle system and It can be performed by removing the Y-piece from the circle system and breathing through the two corrugated hoses individually.breathing through the two corrugated hoses individually.

The valves should be present, and they should move appropriately. The valves should be present, and they should move appropriately.

The operator should be able to inhale but not exhale through the inspiratory The operator should be able to inhale but not exhale through the inspiratory limb and able to exhale but not inhale through the expiratory limblimb and able to exhale but not inhale through the expiratory limb..

The flow test can also be performed by using the ventilator and a breathing The flow test can also be performed by using the ventilator and a breathing bag attached to the “Y”-piece.bag attached to the “Y”-piece.

Workstation Self-TestsWorkstation Self-TestsAs mentioned previously, many new anesthesia workstations now incorporate technology that As mentioned previously, many new anesthesia workstations now incorporate technology that allows the machine to either automatically or manually walk the user through a series of self-tests to allows the machine to either automatically or manually walk the user through a series of self-tests to check for functionality of the electronic, mechanical, and pneumatic components.check for functionality of the electronic, mechanical, and pneumatic components.

Tested components commonly include the gas supply system, flow control valves, circle system, Tested components commonly include the gas supply system, flow control valves, circle system, ventilator, and, in the case of the Datex-Ohmeda Anesthesia Delivery Unit (ADU), even the Aladin ventilator, and, in the case of the Datex-Ohmeda Anesthesia Delivery Unit (ADU), even the Aladin cassette vaporizer. cassette vaporizer.

One particularly important point of caution with self-tests should be noted on systems with One particularly important point of caution with self-tests should be noted on systems with manifold-mounted vaporizers such as the Dräger Medical Fabius GS and the Narkomed 6000 series.manifold-mounted vaporizers such as the Dräger Medical Fabius GS and the Narkomed 6000 series.

A manifold-mounted vaporizer does not become part of an anesthesia workstation's gas flow A manifold-mounted vaporizer does not become part of an anesthesia workstation's gas flow stream until its concentration control dial is turned to the “on” position. stream until its concentration control dial is turned to the “on” position.

Therefore, to detect internal vaporizer leaks on this type of system, the “leak test” portion of the self-Therefore, to detect internal vaporizer leaks on this type of system, the “leak test” portion of the self-diagnostic must be repeated separately with each individual vaporizer turned to the “on” position.diagnostic must be repeated separately with each individual vaporizer turned to the “on” position.

If this precaution is not taken, large leaks that could potentially result in patient awareness, such as If this precaution is not taken, large leaks that could potentially result in patient awareness, such as from a loose filler cap or cracked fill indicator, could go undetected.from a loose filler cap or cracked fill indicator, could go undetected.

Low-Pressure SystemLow-Pressure SystemCheck Initial Status of Low-Pressure System:Check Initial Status of Low-Pressure System:

      a.    Close the flow control valves and turn the vaporizers off.  a.    Close the flow control valves and turn the vaporizers off.  

    b.    Check the fill level and tighten the vaporizers’ filler caps.   b.    Check the fill level and tighten the vaporizers’ filler caps.   

Perform Leak Check of Machine Low-Pressure System:Perform Leak Check of Machine Low-Pressure System:

      a.    Verify that the machine master switch and flow control valves are OFF. a.    Verify that the machine master switch and flow control valves are OFF.

      b.    Attach a “suction bulb” to the common (fresh) gas outlet.   b.    Attach a “suction bulb” to the common (fresh) gas outlet.   

c.    Squeeze the bulb repeatedly until it is fully collapsed.    c.    Squeeze the bulb repeatedly until it is fully collapsed.   

d.    Verify that the bulb stays d.    Verify that the bulb stays fullyfully collapsed for at least 10 seconds.   collapsed for at least 10 seconds.  

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

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

Turn on Machine Master Switch and All Other Necessary Electrical Equipment.   Turn on Machine Master Switch and All Other Necessary Electrical Equipment.   

Test Flow Meter : Test Flow Meter : 

    a.    Adjust the flow of all gases through their full range while checking for smooth a.    Adjust the flow of all gases through their full range while checking for smooth operation of the floats and undamaged flow tubes.  operation of the floats and undamaged flow tubes.  

    b.    Attempt to create a hypoxic Ob.    Attempt to create a hypoxic O22/N/N22O mixture and verify correct changes in flow O mixture and verify correct changes in flow

and/or alarm.and/or alarm.

Scavenging SystemScavenging System

Adjust and Check Scavenging System: Adjust and Check Scavenging System:

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

    b.    Adjust the waste gas vacuum (if possible).   b.    Adjust the waste gas vacuum (if possible).   

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

d.    With minimum Od.    With minimum O22 flow, allow the scavenger reservoir bag to collapse completely and flow, allow the scavenger reservoir bag to collapse completely and

verify that the absorber pressure gauge reads about zero.  verify that the absorber pressure gauge reads about zero.  

    e.    With the Oe.    With the O22 flush activated, allow the scavenger reservoir bag to distend fully and flush activated, allow the scavenger reservoir bag to distend fully and

then verify that absorber pressure gauge reads less than 10 cm Hthen verify that absorber pressure gauge reads less than 10 cm H22O.O.

Breathing SystemBreathing SystemCalibrate OCalibrate O22 Monitor:   Monitor:  

    a.    Ensure that the monitor reads 21% in room air.   a.    Ensure that the monitor reads 21% in room air.   

b.    Verify that the low-Ob.    Verify that the low-O22 alarm is enabled and functioning. alarm is enabled and functioning.

      c.    Reinstall the sensor in the circuit and flush the breathing system with Oc.    Reinstall the sensor in the circuit and flush the breathing system with O 22.  .  

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

.  Check Initial Status of Breathing System:   .  Check Initial Status of Breathing System:   

a.    Set the selector switch to “Bag” mode.   a.    Set the selector switch to “Bag” mode.   

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

    c.    Verify that COc.    Verify that CO22 absorbent is adequate. absorbent is adequate.

      d.    Install the breathing circuit accessory equipment (e.g., humidifier, positive end-expiratory d.    Install the breathing circuit accessory equipment (e.g., humidifier, positive end-expiratory pressure [PEEP] valve) to be used during the procedure. pressure [PEEP] valve) to be used during the procedure.

.  Perform Leak Check of Breathing System:.  Perform Leak Check of Breathing System:

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

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

    c.    Pressurize the breathing system to about 30 cm Hc.    Pressurize the breathing system to about 30 cm H22O with an OO with an O22 flush. flush.

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

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

Manual and Automatic Ventilation SystemsManual and Automatic Ventilation Systems

Test Ventilation Systems and Unidirectional Valves:  Test Ventilation Systems and Unidirectional Valves:  

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

b.    Set the appropriate ventilator parameters for the next patient. b.    Set the appropriate ventilator parameters for the next patient.

      c.    Switch to automatic ventilation (Ventilator) mode.  c.    Switch to automatic ventilation (Ventilator) mode.  

    d.    Turn the ventilator ON and fill the bellows and breathing bag with an Od.    Turn the ventilator ON and fill the bellows and breathing bag with an O22 flush. flush.

      e.    Set Oe.    Set O22 flow to minimum and other gas flows to zero. flow to minimum and other gas flows to zero.

      f.     Verify that during inspiration the bellows delivers appropriate tidal volume and that f.     Verify that during inspiration the bellows delivers appropriate tidal volume and that during expiration the bellows fills completely.   during expiration the bellows fills completely.   

g.    Set the fresh gas flow to about 5 L/min.  g.    Set the fresh gas flow to about 5 L/min.  

    h.    Verify that the ventilator bellows and simulated lungs fill h.    Verify that the ventilator bellows and simulated lungs fill and emptyand empty appropriately appropriately without sustained pressure at end expiration. without sustained pressure at end expiration.

      i.     Check for proper action of the unidirectional valves.   i.     Check for proper action of the unidirectional valves.   

j.     Check the breathing circuit accessories to ensure proper function. j.     Check the breathing circuit accessories to ensure proper function.

      k.    Turn the ventilator OFF and switch to manual ventilation (Bag/APL) mode.  k.    Turn the ventilator OFF and switch to manual ventilation (Bag/APL) mode.  

    l.     Ventilate manually and ensure inflation and deflation of the artificial lungs and l.     Ventilate manually and ensure inflation and deflation of the artificial lungs and appropriate feel of system resistance and compliance.  appropriate feel of system resistance and compliance.  

    m.    Remove the second breathing bag from the Y-piece.m.    Remove the second breathing bag from the Y-piece.

MonitorsMonitors

Check, Calibrate, and/or Set Alarm Limits of All Monitors:Check, Calibrate, and/or Set Alarm Limits of All Monitors:

      a.    Capnometer   a.    Capnometer   

b.    Oxygen analyzer  b.    Oxygen analyzer  

    c.    Pressure monitor with high– and low–airway pressure alarms   c.    Pressure monitor with high– and low–airway pressure alarms   

d.    Pulse oximeter  d.    Pulse oximeter  

    e.    Respiratory volume monitor (spirometer)e.    Respiratory volume monitor (spirometer)

Final PositionFinal Position

Check Final Status of Machine:  Check Final Status of Machine:  

    a.    Vaporizers off  a.    Vaporizers off  

    b.    APL valve open    b.    APL valve open   

c.    Selector switch to “Bag”  c.    Selector switch to “Bag”  

    d.    All flowmeters to zero (or minimum)  d.    All flowmeters to zero (or minimum)  

    e.    Patient suction level adequate  e.    Patient suction level adequate  

    f.     Breathing system ready to usef.     Breathing system ready to use

Summary of Checkout RecommendationsSummary of Checkout RecommendationsItem 1: Verify that the auxiliary oxygen cylinder and self-inflating manual ventilation device Item 1: Verify that the auxiliary oxygen cylinder and self-inflating manual ventilation device are available and functioningare available and functioning

Item 2: Verify that patient suction is adequate to clear the airwayItem 2: Verify that patient suction is adequate to clear the airway

Item 3: Turn on the anesthesia delivery system and confirm that AC power is available Item 3: Turn on the anesthesia delivery system and confirm that AC power is available

Item 4: Verify the availability of required monitors, including alarmsItem 4: Verify the availability of required monitors, including alarms

Item 5: Verify that pressure is adequate on the spare oxygen cylinder mounted on the Item 5: Verify that pressure is adequate on the spare oxygen cylinder mounted on the anesthesia machineanesthesia machine

Item 6: Verify that piped gas pressures are ≥50 psigItem 6: Verify that piped gas pressures are ≥50 psig

Item 7: Verify that vaporizers are adequately filled and, if applicable, that filler ports are Item 7: Verify that vaporizers are adequately filled and, if applicable, that filler ports are tightly closedtightly closed

Item 8: Verify that there are no leaks in the gas supply lines between the flow meters and Item 8: Verify that there are no leaks in the gas supply lines between the flow meters and the common gas outletthe common gas outlet

Item 9: Test scavenging system functionItem 9: Test scavenging system function

Item 10: Calibrate or verify calibration of the oxygen monitor and check the low-oxygen Item 10: Calibrate or verify calibration of the oxygen monitor and check the low-oxygen alarmalarm

Item 11: Verify that the carbon dioxide absorbent is not exhaustedItem 11: Verify that the carbon dioxide absorbent is not exhausted

Item 12: Check for proper breathing system pressure and leaksItem 12: Check for proper breathing system pressure and leaks

Item 13: Verify that gas flows properly through the breathing circuit during both Item 13: Verify that gas flows properly through the breathing circuit during both inspiration and exhalationinspiration and exhalation

Item 14: Document completion of checkout proceduresItem 14: Document completion of checkout procedures

Item 15: Confirm ventilator settings and evaluate readiness to deliver anesthesia care Item 15: Confirm ventilator settings and evaluate readiness to deliver anesthesia care (ANESTHESIA TIME-OUT)(ANESTHESIA TIME-OUT)

Completed before Each ProcedureCompleted before Each Procedure

Item 2: Verify that patient suction is adequate to clear the airwayItem 2: Verify that patient suction is adequate to clear the airway

Item 4: Verify the availability of required monitors, including alarmsItem 4: Verify the availability of required monitors, including alarms

Item 7: Verify that vaporizers are adequately filled and, if applicable, that filler ports are Item 7: Verify that vaporizers are adequately filled and, if applicable, that filler ports are tightly closedtightly closed

Item 11: Verify that the carbon dioxide absorbent is not exhaustedItem 11: Verify that the carbon dioxide absorbent is not exhausted

Item 12: Check for proper breathing system pressure and leaksItem 12: Check for proper breathing system pressure and leaks

Item 13: Verify that gas flows properly through the breathing circuit during both Item 13: Verify that gas flows properly through the breathing circuit during both inspiration and exhalationinspiration and exhalation

Item 14: Document completion of checkout proceduresItem 14: Document completion of checkout procedures

Item 15: Confirm ventilator settings and evaluate readiness to deliver anesthesia care Item 15: Confirm ventilator settings and evaluate readiness to deliver anesthesia care (ANESTHESIA TIME-OUT)(ANESTHESIA TIME-OUT)