Interesting Case- High pressure airway alarm

[Aether2000]

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Case today using a GE Avance S5 Carestation Anesthesia Machine. First case of the day, L3-S1 TLIF, elderly female with severe kyphosis in the prone position. The max airway pressure alarm set for 40 cm. When switched to Vc ventilation, TV 450ml, RR 10, no PEEP added. Peak airway pressures 25cm but the high pressure alarm is activated continuously. There was also a message box noting high PEEP of 12cm with a question of tube obstruction. Switching to manual ventilation, the high pressure alarm disappeared as did the measured PEEP. What is going on?

 

[Arantius]

Assuming the situation is that she has restrictive lung disease from the kypho. The vent is trying to deliver a set tidal volume in a short amount of time, which, given her low pulmonary compliance, requires high pressures to deliver this volume over a set time which is not variable. vent goals in this pt should be to recruit alveoli, maximize FRC, minimize barotrauma. When you are manually ventilating the patient, you are adjusting your grip to the perceived compliance of the lung and delivering the volume over a longer period of time with a lower or more gradual increase in pressure, thus the alarms are not triggered. You could flip to pressure control mode but would have to be careful about monitoring tidal volumes with position changes, surgeons leaning on the patient, etc. You could also try to increase compliance by paralyzing the patient (likely not to help but worth a shot if no neuromonitoring), or if not tolerated and hypoxic or unable to ventilate would need to flip supine and reconsider necessity of an elective surgery for chronic pain in the setting of her severe lung disease.

 

[Aether2000]

Neuromonitoring was being used limiting the inhalation anesthesia MAC, a remifentanil infusion was used, and no neuromuscular blockade. SpO2 varied from 98-100% throughout the case. Varying the I:E ratio from 1:5 to 1:1 made no difference in the peak pressure of 22-25cm, but the peak pressure alarm was set at 40cm. So why the peak pressure alarm, when the peak pressure was well under the peak pressure alarm setting?

 

[narcusprince]

Was your scavenger connected? Was their any tampering with the scavenger?

 

[narcusprince]

Was your scavenger connected? Was their any tampering with the scavenger?

With a open pop off valve open and manual ventilation you likely will see the pressure drop. But switched back to the vent you the pressure rises back to the maximum displacement of the scavenger bag and then you start releasing gas into the room. Once you have ruled out patient specific etiology and not obstructed tube. Likely with most spine cases you move the machine around in the room perhaps that is where the disconnection happened.

 

[Aether2000]

There was indeed tampering with the scavenger system on all machines on one side of the OR. The scavenger valves controls had all been rotated to the max position. Once this was discovered, the PEEP being delivered using the ventilator disappeared and the pressure alarms were no longer active. We suspect the night cleaning staff playing with all the anesthesia machines. No idea why.

 

[Arantius]

There was indeed tampering with the scavenger system on all machines on one side of the OR. The scavenger valves controls had all been rotated to the max position. Once this was discovered. The PEEP being delivered using the ventilator disappeared and the pressure alarms were no longer active. We suspect the night cleaning staff playing with all the anesthesia machines. No idea why.

Why on earth would someone tamper with this??? what?

 

[urge]

With a open pop off valve open and manual ventilation you likely will see the pressure drop. But switched back to the vent you the pressure rises back to the maximum displacement of the scavenger bag and then you start releasing gas into the room. Once you have ruled out patient specific etiology and not obstructed tube. Likely with most spine cases you move the machine around in the room perhaps that is where the disconnection happened.

There was indeed tampering with the scavenger system on all machines on one side of the OR. The scavenger valves controls had all been rotated to the max position. Once this was discovered, the PEEP being delivered using the ventilator disappeared and the pressure alarms were no longer active. We suspect the night cleaning staff playing with all the anesthesia machines. No idea why.

I don't get it. One person is suggesting the scavenger was closed, but the OP says the scavenger was fully open. And somehow closing it halfway fixed the problem. Not convinced.

 

[urge]

With a open pop off valve open and manual ventilation you likely will see the pressure drop. But switched back to the vent you the pressure rises back to the maximum displacement of the scavenger bag and then you start releasing gas into the room. Once you have ruled out patient specific etiology and not obstructed tube. Likely with most spine cases you move the machine around in the room perhaps that is where the disconnection happened.

Don't follow you. Both bag and vent are hooked to the scavenger. A closed scavenger would create same continuous PEEP issues whether on bag or vent, once both are full. Momentarily, yes, if the bag is empty the pressure will drop to zero. But the problem is still there.

 

[urge]

Case today using a GE Avance S5 Carestation Anesthesia Machine. First case of the day, L3-S1 TLIF, elderly female with severe kyphosis in the prone position. The max airway pressure alarm set for 40 cm. When switched to Vc ventilation, TV 450ml, RR 10, no PEEP added. Peak airway pressures 25cm but the high pressure alarm is activated continuously. There was also a message box noting high PEEP of 12cm with a question of tube obstruction. Switching to manual ventilation, the high pressure alarm disappeared as did the measured PEEP. What is going on?

Did your machine pass the self checkup in the morning? Was it even done? Smells fishy.

 

[narcusprince]

Did your machine pass the self checkup in the morning? Was it even done? Smells fishy.

The machine will still pass a self check especially if the flow rate is low and the scavenger bag is large.

 

[Aether2000]

The scavenger valve was completely closed causing the scavenger bag to be fully inflated. Yes a machine check was performed but not any of the 16 full machine checks that almost no one does routinely (in fact how many of you watch the oxygen cylinder pressure for a full minute recording the pressures or do a routine vaporizer gasket check with a manometer or do a low P test?). The scavenger was not checked prior to the case but the valves were functional and checked. I find it curious the high airway pressure alarm was activated with a normal airway pressure no matter what the scavenger was doing. This is a new machine to me and clearly has some idiosyncrasies of which I was unaware.

 

[urge]

The machine will still pass a self check especially if the flow rate is low and the scavenger bag is large.

I have a hard time processing that but since I have not experienced it I'll give you the benefit of doubt.

However, we do not set flows for the test. It is all automated at whatever flow it was programmed, which I don't know.

Anyway, good catch on the closed scavenger.

 

[deleted87051]

The scavenger valve was completely closed causing the scavenger bag to be fully inflated. Yes a machine check was performed but not any of the 16 full machine checks that almost no one does routinely (in fact how many of you watch the oxygen cylinder pressure for a full minute recording the pressures or do a routine vaporizer gasket check with a manometer or do a low P test?). The scavenger was not checked prior to the case but the valves were functional and checked. I find it curious the high airway pressure alarm was activated with a normal airway pressure no matter what the scavenger was doing. This is a new machine to me and clearly has some idiosyncrasies of which I was unaware.

I've seen the exact same thing in the aisys. If the scavenging is completely shut off the patient circuit eventually becomes pressurized during expiration and the high peep alarm goes off.

 

[Mman]

There was indeed tampering with the scavenger system on all machines on one side of the OR. The scavenger valves controls had all been rotated to the max position. Once this was discovered, the PEEP being delivered using the ventilator disappeared and the pressure alarms were no longer active. We suspect the night cleaning staff playing with all the anesthesia machines. No idea why.

That is by far the most common reason I see PEEP on the vent that shouldn't be there. Doesn't happen often, but often enough that I routinely check it if we are having problems. And no, I have no idea why it happens. As one of my attendings in residency told me, if you saw the people that wander through ORs at night you'd question it less.