Understanding Air Embolus and Blood Circulation

In summary: Why would you have cohesive forces in air?Surface tension requires a surface, that means phase boundary between liquid and gas in this case, it has nothing to do with forces in the bulk of the bubble.
  • #1
Charles123
132
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I have never really thought why an air embolus can restrict the passage of blood, until now, and I don't really understand. Why can't the circulation pressure just push the air embolus forward until it is eventually expelled in the lungs? Or why can't it dissolve the embolus? In a plant is easier the see why it is a problem, there is not a push, but a pull, due to transpiration, the presence of an embolus will interfere with the cohesion attraction that makes possible the transpiration pull. But in blood circulation I am not seeing why is a problem.
Thank you
Regards
João
 
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  • #2
I would guess too low a pressure to push the bubble when it blocks the vessel.
 
  • #3
I agree, for a venous air embolus the pressures are unlikely to be great enough to push the air through. For arterial emboli I thought that at the capilllary level the air gets 'trapped' and a secondary response occurred as a direct result of the exposure of the endothelium to air, causing a complement cascade and microinfarcts. I suppose a big enough embolus ending up in the heart would empty it and drop cardiac output.
 
  • #4
Thank you both for your answers.
"I agree, for a venous air embolus the pressures are unlikely to be great enough to push the air through." But what makes air more difficult to push?
"For arterial emboli I thought that at the capilllary level the air gets 'trapped' and a secondary response occurred as a direct result of the exposure of the endothelium to air, causing a complement cascade and microinfarcts." Why does it get trapped? How does that secondary response works?
"I suppose a big enough embolus ending up in the heart would empty it and drop cardiac output." I have read about this, but I don’t understand why it is not just a brief transient situation.
Regards
 
  • #5
Charles123 said:
"For arterial emboli I thought that at the capilllary level the air gets 'trapped' and a secondary response occurred as a direct result of the exposure of the endothelium to air, causing a complement cascade and microinfarcts." Why does it get trapped? How does that secondary response works?

I may well be wrong here but I have a feeling it is something to do with hyperoxygenation causing an inflammatory response, and this response causes endothelial damage. I am not sure why the air gets trapped though. Is the pressure at the capillary bed only a fraction of the arterial pressure? I wonder if an increase in resistance due to the presence of an air obstruction would cause incoming blood to be diverted through other vessels, preventing the bubble to be washed through, perhaps? Interesting question.

Charles123 said:
"I suppose a big enough embolus ending up in the heart would empty it and drop cardiac output." I have read about this, but I don’t understand why it is not just a brief transient situation.
Regards

For the heart full of air, I think purely the contraction of the heart when not filled with blood means the air gets compressed without a significant outgoing pressure, so arterial pressure plummets.
 
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  • #6
"For the heart full of air, I think purely the contraction of the heart when not filled with blood means the air gets compressed without a significant outgoing pressure, so arterial pressure plummets."

You mean the hear is only able to compress the air, which then expands again, its compressed again, but it never gets expelled from the heart?
 
  • #7
Yes I think so. I'm not sure how transient it is though, as you were saying. Out of curiosity what does happen in a plant? Would it stop the flow completely?
 
  • #8
I think so... There would be no more cohesion
 
  • #9
Guess again - we need additional pressure to fight the surface tension.
 
  • #10
Borek, how so?
What about what happens in arteries/veins, no more insights?
Regards
 
  • #11
To squeeze the bubble into a thinner vessel requires changing curvature of the bubble surface. Just like water doesn't drop from a capillary because it is held by the surface tension - it is the same process, only reversed.
 
  • #12
Water not falling from a capillary is more capillarity than surface tension, inst it?
And surface tension in the air? Why would you have cohesive forces in air?
 
  • #13
Surface tension requires a surface, that means phase boundary between liquid and gas in this case, it has nothing to do with forces in the bulk of the bubble.

Perhaps water in a capillary is not the best example, as it wets the glass. Have you ever seen mercury in the capillary? There is (almost) no wetting, but because of strong surface tension mercury doesn't drop, you need some extra pressure to force it out of the tube.
 
  • #14
I know it requires an interface between 2 different constituents, but it is as wikipedia puts it - "This property is caused by cohesion of similar molecules, and is responsible for many of the behaviors of liquids.". The boundary causes the difference in attraction that does not exist in the bulk of the liquid as you put it.
 
  • #15
How does an air embolus restrict the passage of blood?

I understand that air bubbles clog smaller arteries, surface tension with insufficient time/surface area through which to dissolve, air bubbles maintain themselves, but they are pushed trough, aren`t they? So why don’t they just eventually get dissolved and/or then ultimately expelled by the lungs? Is it a matter of blood clothing in contact with oxygen? How does that work?
Thank you
Regards
 
  • #16


Any one who's interested (OP posted this elsewhere and got an answer.)

http://en.allexperts.com/q/Physics-1358/2012/9/air-embolism.htm [Broken]
 
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  • #17
He already got an answer here.
 
  • #18
And this is a follow-up: http://en.allexperts.com/q/Physics-1358/2012/9/decompression-sickness.htm [Broken]

Also, does anyone know how the air-coagulation relation work?

Regards
 
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  • #19
Charles123 said:
And this is a follow-up: http://en.allexperts.com/q/Physics-1358/2012/9/decompression-sickness.htm [Broken]

Also, does anyone know how the air-coagulation relation work?

Regards
I think the other poster summed it up when they told you
This is the last time I answer a follow-up on this question and beat this dead horse
 
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1. What is an air embolus?

An air embolus is a condition where air bubbles enter the bloodstream and block the flow of blood. It can be caused by medical procedures, such as injections or surgery, or by injuries that create an opening in the blood vessels.

2. How does air embolus affect blood circulation?

Air embolus can disrupt the normal flow of blood through the body and cause various health problems, such as organ damage, stroke, heart attack, or even death. The air bubbles can also create clots and blockages in the blood vessels, which can lead to tissue damage and other complications.

3. What are the symptoms of air embolus?

The symptoms of air embolus can vary depending on the location and severity of the blockage. Common symptoms include difficulty breathing, chest pain, confusion, dizziness, weakness, and loss of consciousness. In severe cases, it can also cause seizures, coma, or paralysis.

4. How is air embolus diagnosed?

Doctors may use various methods to diagnose air embolus, such as physical examination, medical history review, imaging tests (X-ray, MRI, CT scan), or blood tests. They may also look for signs of decreased blood flow or oxygen levels in the affected area.

5. What is the treatment for air embolus?

The treatment for air embolus depends on the severity and location of the blockage. In some cases, the air bubbles may dissipate on their own and no treatment may be needed. However, in more serious cases, doctors may need to remove the air bubbles through a procedure called "decompression" or administer medication to break up the clots. Oxygen therapy may also be used to increase the oxygen levels in the blood.

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