Heart rythm

[souzoutekiokami]

Is the human heart rate supposed to vary between the inspiration and expiration?
My heartbeat accelerates and decelerates when I breathe, and I thought it was normal, but I heard is isn't.
So, is it?

[itdood]

Hi Jerry, it's very noticeable the younger we are.  Very prominent in kids.  I can still feel mine vary if I check my pulse.  I can still see on it on heart rate monitor too.  It will vary by about 5 bpm for me.  Pulse gets lower when we exhale and higher when we inhale.

The full term for it is respiratory sinus arrhythmia (RSA).  RSA increases the efficiency of gas exchange.  The theory is that extra beats are unnecessary during exhale.

Think about it, it does make sense.  When you inhale, you're at the peak of exchanging gases, the heart pumps more blood to further enhance the process.  When you exhale, gas exchange slows down so the extra pumping would be of no benefit so it slows down too.

This is mediated by vagal tone.  This is why meditation and controlled breathing can slow down a heart.  It really demonstrates just how much influence the vagus nerve plays in HR.

[Jerry_NJ]

Thanks, I stand corrected.  

If it happens to me the difference is too small for my ear to detect.  I have used a stethoscope many time to check my AFib, even when in NSR, to assure me I was in NSR.  I can easily detect the irregular rhythm caused by my active AFib, that would mask, I'd guess, any difference in the rate driven by breathing.  

I'd think to detect it would require the ability to detect as little as a 100 milliseconds difference in the time between pulses... just a guess again.  This is a easy job on an EKG.

[grendslori]

It is most certainly normal. In some people, on EKG, it is more noticable than others, but it is definately normal in all people. And as itdood said, it is called a Sinus Arrhythmia.

[itdood]

Hi, yep it's normal.  It's called sinus arrhythymia.  Don't let the term arrhythmia throw you, in this case it's perfectly normal.  Sinus arrhythymia with respiration makes oxygenating your blood more efficient.  It naturally evolved.

[Jerry_NJ]

I can't visualize your conditions from the little you tell us.

If you are talking about breathing normally when at rest I'd guess the breathing in and out are about 2 seconds each, perhaps a little more.

So, if my mean resting HR is 60 there would be only two beats on either in or out breathing.  That being in the "ball park" then for me to even notice any difference one would have to be more like 3 beats and the other remains at 2, or perhaps moves toward 1 or less.  Just using my numbers I'd say anything like 3 beats against 1 beat is not normal.  It is surely foreign to me and my heart beat, to which I have listened and timed carefully, but not to detect a difference between breathing in and out... I do not recall ever noticing a difference.