Maybe this is really a stupid question but maybe someone with the bio knowledge can clue this clueless guy in.
I understand that the embolism would cause a portion of the lung to no longer work. But can’t the lungs work with some level of impairment? Some people live with one lung removed, so how the hell does one clot bring the show to a close?
Does it take out the whole system?
Thanks.
It depends where the clot is. Like a heart attack, if the clot is near the end of the artery system of the heart, it can only stop blood flow to a small part of the heart. It hurts, and it sure is a heart attack, but you’ll likely survive that one.
Now imagine a clot that lodges right where the pulmonary artery enters a lung, occluding blood flow to the entire lung. That’s bad times.
here’s a link with some good info on pulmonary emboli
http://www.emedicine.com/EMERG/topic490.htm
Wow. I can’t believe how miserable the on-line info. (like kinoons link–no offense; it’s extremely reputable, but also rather opaque) on this topic is. Basic questions still not answered by eMedicine or any of its ilk:
what is the proximate cause of death in PE (i.e., BwanaBob’s question)–arterial blockage that restricts blood flow body-wide? rupture of pulmonary blood vessels leading to bleeding in the lungs (leading to rapid suffocation, gradual pneumonia, etc.)?
why are the lungs more susceptible to these blockages than other areas of the body? (also, why do clots here kill you, when those same clots–most of which broke off and migrated from a DVT in the legs–didn’t kill you when your leg veins were blocked?)
At least two reasons. It’s possible that the clot has blocked the blood flow into the lungs, from the right side of the heart, to such a degree that there’s inadequate blood making it through the lungs to maintain the blood pressure. In other words, there’s not enough flow of blood out lungs into the left heart. Secondly, the lungs themselves can be so damaged by the clot(s), that they can no longer get enough oxygen into the system
There is a direct path from the veins into the lungs. So, a clot coming from the legs (usually*) has no where to go but to the lungs. The presence of clots in the legs are not too serious for two reasons. One, the legs are not needed minute to minute for oxygen supply (unlike the lungs). Second, the clots in the legs usually don’t prevent blood from flowing in and out, whereas a big clot to the lungs is more than enough to completely block the flow.
Okay, here is another link with some more info
I’ll try to walk us through this one. I’m sure one of our doper MD’s will wander by and help us out here soon too.
Things that can kill you from a pulmonary embolism (PE)
Pulmonary hypertension – results from the heart trying to pump into the occluded arterial system of the lungs. Remember that about half of your circulating blood volume is in your lungs at any one time. Also, remember that the area between the air in your lungs and your blood stream, where gas exchange takes place, is only one cell thick. If hypertension is present in your lungs, blood can begin to migrate across this one cell thick membrane, ruining any gas exchange in that area of the lung
Should also be noted that a PE can result in a loss of surfactant. This too, leads to poor gas exchange at the alveolar level.
Right sided heart failure – It is possible for a PE to back up enough blood to cause heart failure. The right side of the heart is the side that supplies blood to the lungs. Again, at any time half of your circulating blood volume is in your lungs. Major PE’s can lead to the right side of the heart being overwhelmed. Blood will begin to backup into the great central veins. This also will decrease the amount of blood returning from the lungs to the left side of the heart. This decrease can lead to cardiogenic shock.
here’s info on shock, and specifically cardiogenic shock
http://www.merck.com/mrkshared/CVMHighLight?file=/mrkshared/mmanual/section16/chapter204/204a.jsp%3Fregion%3Dmerckcom&word=cardiogenic%20shock&domain=www.merck.com#hl_anchor
Cardiogenic shock – this occurs when the heart is unable to effectively circulate enough blood to meet the body’s needs. most commonly this occurs due to a major heart attack. Cardiogenic shock results in hypotension and poor perfusion of the entire body, most importantly, the brain, heart, and lungs. This poor perfusion can cause death of these tissues. Treatment focuses on attempting to make the heart beat more effectively.
Now, as to why it’s the PE that seems to get ya? When a DVT breaks off, it circulates through the venous system, back to the right side of the heart, and then goes to the lungs. In the lungs, the capillary system again narrows down to one cell wide, so the clot cannot fit through. The lungs just happen to be the most common narrow point a clot will meet first.
It is my understanding that a DVT usually does not cause enough restriction of circulation alone to cause any hemodynamic instability. They really become dangerous when they break loose and start floating around the body.
And I see that one of them did…thanks Karl!
Here is a Google Page of articles and definitions of Pulmonary Embolism.
It isn’t exactly like a clot somewhere else in the body.
The blood flow to the lungs is a spider’s web of capillaries that cover the alveolar portions of the lung. The capillaries are so small, only a single red blood cell can pass through at a time. The alveoli must have direct contact with the blood vessels to exchange oxygen for carbon dioxide. Each red cell is able to pick up O2 and carry it to where its needed. Alveoli are tiny grape-like structures in the farthest reaches of the lung. They look a little like grapes, but act more like tiny balloons. Balloons with glue inside. As long as they are inflated all is well, but if they collapse, its hard to open them up again.
Blood clots in the circulation are huge compared to the tiny capillaries, so the clot stops up stream in a larger vessel, blocking flow to large portions of the lung.
As the capillaries die, the alveoli collapse and the body is deprived of O2. As the alveoli collapse in a domino fashion, the larger air ways begin to collapse as well.
Soon the entire lung as collapsed. When that happens the unaffected lung migrates into the potential space created. When this happens, the structures in the good lung are compromised, causing further injury,
The clot can only rarely be removed because the patient has become so hypoxic they die before they can get to surgery.
The one thing that does work sometimes is putting a clot-busting drug, like TPA into the vessel. The problem is, even if you get blood flow back , The alveoli aren’t playing anymore.
Have I been clear enough?
Many thanks to all. My question has been answered.
Originally posted by picunurse
I have emphysema and was told the alveoli can never be opened up again.
Was I misinformed?
Different problem. With emphysema, the alveoli are damaged, the balloons have either burst, or been chronicly over inflated, losing their elasticity.
Whereas, the embolus is damage to the circulatory side, and the healthy alveloi collapse. These can be recruited back into action, but it takes time and therapy.