QS Study

Cardiac Output is simply the amount of blood pumped by the heart per minute. It is the quantity of blood pumped into aorta each minute by the heart. (Guyton 10th) or, the amount of blood is pumped out by each ventricle into the circulation at each minute. Necessarily, the cardiac output is the product of the heart rate, which is the number of beats per minute, and the stroke volume, which is amount pumped per beat. It is an important measure of cardiovascular function.

The factors influencing the CO are-

(A) Physiological

  • Age: ↑Age →↓ CO.
  • Sex: 10-20% less in female due to less body wt. and surface area.
  • Surface area: More surface area → more CO
  • Posture: ↑ CO in sitting and lying posture than standing posture (20-30%). Because VR is less in standing position. [Cardiac Index = 3.21L/ min/ m2.]
  • Muscular exercise: May increase up to 700%.

Exercise (severe//Moderate) →↑ muscular activity →↑ CO.

  • Emotion, Excitement, Anxiety: If increases CO by 50-100%
  • Temperature: ↑ temp. →↑ H.R →↑ CO.
  • Pregnancy: It causes ↑ CO.
  • Erinephrine, Histamine: They cause ↑ CO.
  • Food: Metabolic activity →↑ CO (by 30%).

(B) Pathological