Breathing but no pulse?

September 7, 2006 4:18 PM

Why can your heart carry on beating when you've stopped breathing but not the other way round?
posted by denishowe to Science & Nature (10 answers total)

Because if your heart stopped beating you'd be dead.
posted by cholly at 4:23 PM on September 7, 2006

Voila. Your blood pools, your cells quickly become anaerobic, fill with waste products, can't make energy, and die.
posted by gramcracker at 4:29 PM on September 7, 2006

When you stop breathing, there is still oxygen in your body to sustain yourself.
posted by mphuie at 4:38 PM on September 7, 2006

Why can your heart carry on beating when you've stopped breathing but not the other way round?

It can't. Or, conversely, it can, but only for a very short time, just like you can carry on breathing while your heart has stopped beating for a very short time.
posted by kindall at 4:41 PM on September 7, 2006

Response by poster: Well, duh, of course you'd die eventually, either way round. However, you don't die the instant your heart stops but, I'm told, you do stop breathing. Is this true? Instantly? Why?
posted by denishowe at 4:45 PM on September 7, 2006

Best answer: As long as your heart is beating, it's got access to practically the entire volume of blood in your circ. system for oxygen and fuel even if your lungs aren't adding any more, it's quite a bit, and the autonomic nervous system will make sure that things like your brain aren't getting a lot of access to it.

If your heart stops, your diaphragm only has access to the volume of blood in its capillaries, and rapidly runs out of oxygen and fuel.
posted by oats at 4:49 PM on September 7, 2006

Because your respiratory drive centers are in your brainstem, and if you're dead (brain dead) your body doesn't have any input to make it breathe.
posted by gramcracker at 4:50 PM on September 7, 2006

I am currently undergoing plenty of testing to figure out why I have heart palpitations. When my heart starts "sputtering" (which is what it feels like), I feel the urge to take a deep breath. I'm told this is because the blood isn't getting pumped out, and so my body thinks I'm not getting oxygen and instinctually makes me take a deep breath. If my heart sputters badly enough for 3-4 seconds, everything begins to go black. (It's happened to me twice.) I have not actually blacked out - both times my heartbeat corrected in time to prevent it.
posted by IndigoRain at 4:54 PM on September 7, 2006

This is why CPR has you do 15 heart compressions, followed by only two quick breaths. All the breathing in the world won't help the person if that oxygen isn't getting carried to the places it needs to be (vital organs, including the heart itself).
posted by chrisamiller at 5:32 PM on September 7, 2006

CPR compressions to ventilation has been changed to 30 to 2 as of '05 (pdf AHA).

Cardiac muscle cells are autorhythmic - they contract on their own and react with each other. Other parts of the body are made up of other muscle cells that rely on the nervous or hormonal stimulation to move.
posted by dog food sugar at 8:15 PM on September 7, 2006