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Topic: Cardiogenic Autotriggering |
mate222
New Member
Total Posts: 41
Joined: February 2002
From:
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Posted: November 13 2002 8:02 PM  
Hello:
Worked with a patient today in CMV a*sist with a rate of 15/min. The patient was paralyzed and sedated, but was still able to trigger extra breaths. We checked his level of neuromuscular blockade with a Train of Four and he was well paralyzed. Anyone with an explanation?
Susie.
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ChancesR
New Member
Total Posts: 7
Joined: February 2002
From:
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Posted: November 20 2002 7:49 AM
Hello Susie:
I suspect you already know the probable cause. Indeed, the most likely cause is 'cardiogenic triggering'. This phenomenon received some attention in a couple of journals a few years ago. As I understand it, with each contraction the beating heart transiently occupies less space in the thorax (mediastinum). As the heart contracts, the surrounding lung responds by expanding. This sets off a cascade of events whereby the pressure in the airways drop a little as the lung inflates. The ventilator senses the drop in airway pressure and interprets that as a drop in the PEEP. The vent response is to increase flow to maintain the PEEP. Every so often, the flow is enough to fool the vent into thinking the patient is triggering. Cool huh?
Anyhow, trigger criteria is met and the machine delivers a breath...even to the paralyzed patient. The term attributed to this is Cardiogenic Triggering.
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mate222
New Member
Total Posts: 41
Joined: February 2002
From:
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Posted: November 22 2002 7:44 AM
Hello Chances:
Yes, I had heard about this cardiogenic triggering, but was skeptical. Glad to know that at least one other acknowledges it. What do you do to reduce or negate cardiogenic triggering?
Susie.
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ChancesR
New Member
Total Posts: 7
Joined: February 2002
From:
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Posted: November 26 2002 7:31 AM
Susie:
The easiest act is to decrease your flow trigger sensitivity. Often by turning the trigger from 2L/min to 4L/min is enough. If you have a ventilator make that has a pressure trigger option, you may consider triggering with pressure instead of flow (less responsive). Finally, correction or resolution of the cardiac hyperdynamic state may also decrease the likelihood of cardiogenic autotriggering.
Hope that helps!
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n/a
New Member
Total Posts: 15
Joined: January 2002
From: Baltimore
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Posted: November 27 2002 8:07 AM
Hello Forum Members:
Great discussion. Thought you might be interested in these two references that further discuss cardiogenic triggering:
1. Imanaka H, Nishimura M, Takeuchi M, Kimball W, Yahagi N, Kumon K. Autotriggering caused by cardiac oscillation during flow-triggered mechanical ventilation. Critical Care Medicine 2000; 28: 402-407
2. Op?t T. Cardiogenic triggering observed in a patient with acute respiratory distress syndrome. Respiratory Care 2001; 46:1054-1055
Please let me know if I can be of further a*sistance.
P. Milo Frawley
ICON
Baltimore.
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bcc
New Member
Total Posts: 7
Joined: April 2002
From: Vancouver
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Posted: April 06 2008 12:45 PM
I read the posts regarding cardiogenic triggering. We recently had a patient that appeared to be exhibiting cardiogenic triggering, but the flow trigger was turned up to 10L/min! Can cardiogenic triggering still occur if the flow trigger is turned up that high? Clinically he did not appear to be making any spotaneous effort and the spontaneous MV was ~1L.
Thanks fo any input!
BCC
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Cowboy12
Member
Total Posts: 91
Joined: April 2002
From: Houston
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Posted: April 13 2008 1:42 PM
Based on my experiences with cardiogenic triggering it almost always seems to be in babies, probably due to their lung size in relation to their thorax. I also want to say that there is difference between auto cycling and cardiogenic rate picked up by the ventilator. I have seen babies with measured respiratory rates as high as their heart rate even in non triggered modes. Although a problem (high frequency alarm) not the potential for hyperventilation as in a triggered mode!
CB
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