What is the significance of the mean arterial pressure?

What is the difference (physiological significance) between mean arterial pressure and pulse pressure?

• Answer:

  To start with basics. Systolic BP - Determined mostly by Cardiac output (so also Stroke volume output) Diastolic BP - Determined by peripheral resistance (arterial tree compliance / distensibility). Pulse Pressure : (1) PP = SBP - DBP (2) PP = Stroke Volume/Arterial compliance (approx) Both expressions are correct. Greater the stroke volume, greater amount of blood must be accomodated in arterial tree with each heartbeat, so there is greater pressure rise and fall during systole and diastole respectively and thus a greater pulse pressure Lesser the arterial tree compliance, greater is the rise in pressure at a particular stroke volume (Widkessel effect) So effectively pulse pressure determines - (a) pulse volume, (b) systolic hypertension or decrease in elasticity of blood vessels (as in Atherosclerosis) Mean Blood Pressure : It is the average of arterial pressures measured millisec by millisec in a period of time. It is not equal to average of SBP and DBP because in cardiac cycle greater fraction of time is spent in diastole rather than systole. Thats why MBP lies close to DBP value. So roughly MBP is 60% DBP and 40% SBP. Significance: (a) It is same for each organ and determines the regional blood flow (b) All cardiovascular reflexes reflect changes in MBP. At very high rates, systole time fraction increases, so MBP also gets raised towards SBP.