Question

Explain the mechanisms that influence hemodynamics

Answer 1

Study of blood flow is called as hemodynamics Heamodynamics. Blood hemodynamics can be influenced by :

1) Viscosity of plasma - Viscosity of plasma changes with temperature. As temperature increases plasma viscosity decreses, and hence flow Increases.

2) Plasma Osmolarity - Plasma Osmolarity is dependent upon the total solute particle in the plasma. Plasma proeteins are mainly responsible for change in osmotic pressure. It affects haemodynamics by altering the size and volume of RBC hence altering haematocirit.

3) RBC volume - Size and volume of RBC also affect the flow of blood. As RBC number or size increase it increases the viscosity hence decreses the flow of blood.

4) Hemodilution - After transfusion of colloid or crystalloid the RBC concentration decreses and hence blood flow Increases.

5) Cardiac Output - It is equal to Stroke volume x HR. As the cardiac output Increases flow of blood Increases and vice versa.

6) Tubulence of flow - It depends upon the smoothness of the inner surface of the blood vessel. Also depends upon the Reyonlds number. If the Reynolds number is more than 2000 it leads to turbulence in flow.

7) Velocity - Velocity of blood flow is inversely related to the cross section area.

8) Vascular Resistance - it is inversely proportional to the forth power of radius of blood vessel. Hence a small change in vessel diameter causes huge change in flow of blood.

9) Tension in vessel wall - this depends upon the thickness of the blood vessel wall. It is more in the arteries compared to the venous system. Hence blood flow is rapid in arterial system compared to venous sytem.

10) Blod pressure - It is the lateral pressure exerted by the blood on to th blood vessel. More the the blood pressure greater is the flow.

11) Capacitance of vessel - It is the capacity of blood vessel to accomodate the blood. It is inversely proportional to thickness of blood vessel. Venous system is having more capacitance than areterial system.