General Question

augustlan's avatar

What happens when you put pressure on a wound?

Asked by augustlan (47376points) November 13th, 2012

I know it stops the bleeding, but how does it accomplish that? Obviously, it’s not like plugging a hole in a dike. In that case, when you remove the pressure, water just starts pouring out again. What exactly is the mechanism that keeps a wound from spurting forth fresh blood once the pressure is released? What is happening to the skin/nerves/whatever else underneath the pressure?

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16 Answers

Buttonstc's avatar

It’s sort of like pinching a straw so that liquid can’t get through or at least goes through very very slowly.

Except that the “straw” is located in your body and you’re compressing whatever blood vessel, vein or artery through which blood is trying to flow or spurt.

I’m sure a Doctor can explain it with correct medical terminology but that’s just my attempt at an analogy to get the idea across.

And there are situations where you can’t leave a tourniquet on too long without a break or serious complications can ensue. (At least that’s what they told us in first aid class.)

augustlan's avatar

Right, but why doesn’t it just start bleeding again once the pressure is removed? Is the vessel ‘glued’ shut, did it re-knit itself, or what?

livelaughlove21's avatar

I believe the pressure facilitates clotting by cutting off the flow of blood.

Buttonstc's avatar

No. That’s why you have to apply continuous pressure and get the person to an ER.

It’s a stop gap measure to prevent massive blood loss.

And if it’s a small enough issue like a cut finger then it clots after awhile.

However, if a kid splits their forehead open they bleed like it’s an artery and nothing does much good till it gets stitched as I discovered the hard way.

livelaughlove21's avatar

@Buttonstc Who said anything about a serious wound? You can get a minor cut that will stop bleeding after you apply pressure. And when you get blood taken, the nurse applies pressure to the area after removing the needle. Neither of these situations call for an ER visit.

Wounds bleed due to pressure pushing it out from the inside as our blood is constantly pushing through our bodies, and counter-pressure equalizes that. When the bleeding stops, it can clot, which explains why it does not start bleeding again when you release pressure – provided you applied it for a sufficient amount of time.

Buttonstc's avatar


Well to me, the word wound implies something more than a superficial cut. Since no specific detail was given, I did the best I could.

As I mentioned, I’m certain that a medical professional can give a far better answer.

I’m not a medical professional.

livelaughlove21's avatar

@Buttonstc Fair enough. But the word wound, by definition, is “An injury to living tissue caused by a cut, blow, or other impact, typically one in which the skin is cut or broken.”

So, technically, a paper cut could be considered a wound. I’m no medical professional either.

Buttonstc's avatar


Have it your way.

Brian1946's avatar

@Buttonstc @livelaughlove21 My level of medical amateurishness far exceeds either of yours! ;-p

dabbler's avatar

The question does refer to how does bleeding stop when it stops, so @livelaughlove21 is entirely correct that it’s clotting that stops the bleeding after pressure has been applied.

“What is happening to the skin/nerves/whatever else underneath the pressure?”
If the appropriate pressure (enough to stop bleeding, and not too much pressure) then those tissues are still getting circulation. If too much pressure is applied for too long then necrosis, tissue death can occur and gangrene could set in.

JLeslie's avatar

I think it is like leaving the faucet running the pipe won’t freeze. Slowing down the blood flow gives the wound a chance to clot up. If the blood is flowing a lot the blood is pushing through the clotting agents, or carrying them through and past the wound, and they don’t get a chance to adhere to the skin. A road rash type wound heals over without pressure because there is no force of blood, even though the wound is bloody. But, a puncture type of wound, or cut, the blood pressure has more force.

Cupcake's avatar

The medical term is hemostasis.

Holding pressure helps blood platelets adhere and aggregate at the site of injury, reducing and finally arresting bleeding when the small blood vessels are injured. more here

Rarebear's avatar

Sort of all of the above.
For superficial wounds, putting pressure over the blood pressure in the capillaries will stop flow. This allows platelets to aggregate as @Cupcake said. You can do the same with a venous laceration although it will often take longer and may take a suture to truly prevent further bleeding. For a laceration of a major artery, putting pressure just keeps you from bleeding to death until you can get to a hospital and get it repaired.

technomaster's avatar

It should stop bleeding if its a small enough cut. If it doesn’t work should go to er.

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lilmiss's avatar

It stops the bleeding

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