230 likes | 465 Views
The Cardiac Cycle, Pump Function & Blood Pressure. Hemodynamics. Q = blood flow rate (mL/sec) P= pressure difference between ends of vessels R = resistance. P. = Q. R. P2. P1. Vessel diameter/radius is the most critical factor determining blood flow. D = 1, Q = 1 mL/sec.
E N D
Hemodynamics Q = blood flow rate (mL/sec) P= pressure difference between ends of vessels R = resistance P = Q R P2 P1
Vessel diameter/radius is the most critical factor determining blood flow D = 1, Q = 1 mL/sec D = 2, Q = 16 mL/sec D = 4, Q = 256 mL/sec
Poiseuille’s Equation πΔPr4 Q 8vl R =radius, v = blood viscosity, l = length increase radius, increase blood flow
Determinants of Systolic Pressure • Stroke Volume • Heart Rate • Distensibility of walls of aorta • Ejection velocity • peripheral “run off” • Blood volume remaining in aorta before next ejection
Determinants of Diastolic Pressure • Systolic Pressure • Aortic Distensibility • Rate of peripheral “run off” • Heart Rate (duration of diastole)
Effects of Posture on BP • Supine mean arterial BP=100 mmHg • Upright pressure varies with level above or below the heart • For every 1 cm above heart, pressure decreases by .77 mmHg. • For every 1 cm below heart, pressure increases by .77 mmHg.