Without evidence of benefit, an intervention should not be presumed to be beneficial or safe.

- Rogue Medic

Correction to Why doesn’t CPR work for trauma

In looking at the diagram I made of tension pneumothorax for Why doesn’t CPR work for trauma, I realized that there is no easy way to fix the errors I made. I made a lot.

As Jon Levine explains in the comments –

Nice commentary on the futility of CPR in trauma (hypovolemic) but to be more accurate you should show the tension pnuewmothorax causes blockage/kinking of the preload not afterload to be be more accurate and repersentaive of the poor cardiac output ” Nothing into the pump nothing out.”

So, I had a lot of corrections to make.


Click on the images to make them larger and easier to read.

There is a difference between the thickness, and strength, of the walls of the blood vessels. The aorta is a thick muscular walled artery. The pulmonary veins are thinner walled and weaker. When pressure is applied, the pulmonary veins will kink first.

When the veins kink, the heart will still be beating. The heart will empty, but will not be able to fill up again. After two, or three, beats there should be essentially no blood left in the heart. Even empty, the heart continues to beat.

This condition is the same as with a patient who bled out, except that all of the blood may still be in the body – except the lack of blood is limited to the heart and the blood vessels from the obstruction to the heart and coming from the heart. The patient is just as dead with no blood in the heart as when there is no blood anywhere in the body.

CPR (CardioPulmonary Circulation) can correct the problem of a heart that is not bleeding, but if there is no blood to circulate or if there is an obstruction to circulation, CPR will not be effective.

Resuscitation of the exsanguinated patient is much more difficult (refilling the body with blood before the damage becomes irreversible) than correcting an obstruction. Tension pneumothorax can be corrected by releasing the pressure. The pressure is in the pleural space, so a hole to drain that pressure out of the body is the solution. That hole can be a needle, if it is long enough to reach the pleural space and does not itself become obstructed, a knife, or a chest tube (after using a knife).

The obstruction of cardiac tamponade can be similarly released, but it is not as easy to remove the pressure of the blood in the pericardial space as it is to release the pressure of the air in the pleural space.

I hope this clarifies tension pneumothorax.

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