Respiratory Sinus Arrhythmia
A new Respiratory Sinus Arrhythmia Section has been added to the ECG Analysis Module on www.richacls.com.
Below are some of the Key Learning Points (KLP)
Inspiratory Effects on the Sinus Node
- Inspiration causes slightly decreased blood pressure, which decreases vagal impulses to the heart, thereby increasing the heart rate.
Inspiratory Effects on the Sinus Node
- Expiration causes slightly increased blood pressure which increases vagal impulses to the heart thereby decreasing the heart rate.
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under the lesson in EKG: sinus arrythmia inspiration effects on sinus node: it states the following:During Inspiration:
1)The diaghram lowers
2)chest pressure decreases
3)venous return to heart decreases
4)blood pressure drops.
the third point is where I get confused,
It seems that as the chest pressure decreases the venous return increases as blood flow increases to the superior and inferior vena cava. the decrease in cardiac output and blood pressure is actually caused from pooling of blood in the lungs and resulting in less blood flow to the left side of the heart.
Sorry for the very late reply.
I appreciate your confusion and applaud your critical thinking. This curiosity of yours will be the engine that drives your education far beyond your peers. Keep it up.
Your question as I see it; On inspiration, with increased venous return to the superior and inferior vena cava, why does the cardiac output drop?
Answer: As the pressure drops in the chest with inspiration the pressure in the R/L atriums also drops thus decreasing ventricular filling resulting in decreased stroke volume (SV x HR=CO).
Best Regards
Rich Gilman RN