Calculation of heart rate (HR) from ECG tracing:
How to say whether the heart is having regular rhythm or irregular rhythm from ECG:
RR interval between any two successive beats must be same in a long strip of ECG recording several heart beats in any one lead.
Calculation of velocity of blood flow(v):
Ohm’s law: Relation between pressure difference (ΔP), Flow rate (Q) and Resistance (R):
Relationship between mean arterial pressure (MAP), cardiac output (CO) and total peripheral resistance (TPR): (assuming right atrial pressure = zero)
MAP = CO x TPR
Poiseuille equation:
 Where, R = Resistance to blood flow;
 η = Viscosity of blood;
 l = Length of the blood vessel
 r = Radius of the blood vessel
When resistances are connected in series, the total resistance (R is calculated as:
When resistances are connected in parallel, the total resistance (R system is calculated as:
To calculate mean arterial pressure when systolic and diastolic pressure are given:

(a) First calculate pulse pressure (PP).
 PP = (Systolic pressure – Diastolic pressure)
 Mean Arterial Pressure = Diastolic pressure + 1/3 x Pulse pressure
 Mean Arterial Pressure = (2/3xDiastolic Pressure) + (1/3xSystolic Pressure)
 PP = (Systolic pressure – Diastolic pressure)
Law of LaPlace:
This law relates wall tension (T) with pressure (P) and radius (r) in a hollow organ such as blood vessel or ventricular chamber.
The relationship is: T α Pr or P α T/r
By keeping any one variable constant, the other two are related as in the above relationship. For example, when pressure remains constant, wall tension varies directly with radius. Similarly, when radius remains constant, wall tension varies directly with the pressure.
To calculate length (duration) of cardiac cycle:
Stroke volume (SV):
Stroke volume = (End diastolic volume – End systolic volume)
Calculation of ejection fraction (EF) when stroke volume (SV) and end diastolic volume (EDV) are known:
Calculation of cardiac output:
Calculation of forces that influence filtration and absorption at the capillary: