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Cardiac Physiology II, Cardiac Physiology II-a Microcirculation 3 processes for trans-endoth exchange, Cardiac Physiology II-a Systemic Circulation LaPlace eqn: P=T/r, T=rP (dynes/cm) wall pressure, tension, tube rad. sphere-> P=2T/r (b/c r1=r2) thick walls: σ=rP/W (wall thickness) (dynes/cm^2) heart->sphere-enlarged heart inc. rad ->need more wall T to maintain P aneurysm->increased T, prone to rupture, <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow> <mtext> Total Fluid Energy (bernoulli's) 1/2ρV^2+P+ρgh=constant (kinetic+pressure from heart+hydrostatic) -for frictionless fluid, blood not constant -energy dissipated thru friction, viscosity -linear V greater->KE greater (A1V1=A2V2) -lateral pressure less w/ higher V -thus total energy is constant -if supine, hydrostatic term same throughout -standing-> </mtext> </mrow> </math> Aortic Stenosis A smaller, so V larger -reduced pressure, flow to cor. aa., Vent. systole->stroke volume -some forward to caps -most stored in elastic aa. -aorta-walls stretched, P rises -larger SV, larger P increase Pulse P=SV/compliance Vent. diastole->elastic recoil -maintains cap flow thru cycle -Windkessel effect reflected waves->bigger pulse P -secondary wave small -dicrotic notch b/w 2 waves Pathology Arteriosclerosis-fast P rise&fall (less compliant) aortic insuff-valve defect, backflow raises SV fast P rise, fast fall Aortic Stenosis-mean pulse P down HTN-raises mean P and pulse P, 3 processes for trans-endoth exchange Pinocytosis Minor pathway for exchange -for large water-sol molecs -memb. receptors in caveolae -pinch off to form vesicle -holds plasma, proteins -transcytosis, Cardiac Physiology II-a Microcirculation II Interstitium -space b/w cells -coll, PG fibers -fluid like plasma-gel add'l fluid into gel, then free -pitting edema low compliance at neg. fluid P high comp. at pos. free fluid P, Interstitium -space b/w cells -coll, PG fibers -fluid like plasma-gel add'l fluid into gel, then free -pitting edema low compliance at neg. fluid P high comp. at pos. free fluid P Safety Factor 3 Mechs that prevent edema 1. Plasma filters thru cells, to interstitium ->wash proteins into lymph 2. little add'l vol. needed to zero the neg P ->less force to get fluid out of caps 3. rate of lymph flow can increase -total safety factor=17mmHg, Cross-sectional area Aorta<caps>venae cavae Area of v.larger than paired a. BUT P drop over vv. is larger ->b/c collapsed at many pts Total CO through each segment -equal flow, so diff Vs aorta-33cm/sec caps-0.3mm/sec Vent. systole->stroke volume -some forward to caps -most stored in elastic aa. -aorta-walls stretched, P rises -larger SV, larger P increase Pulse P=SV/compliance Vent. diastole->elastic recoil -maintains cap flow thru cycle -Windkessel effect reflected waves->bigger pulse P -secondary wave small -dicrotic notch b/w 2 waves, Most nutrient exchange in cap bed -some lipid-solubles thru a'oles, v'ules -CO2, O2 Aa. pressures pulsatile -20% blood volume -pulse P increases toward periph. -mean P drops gradually to veins RESISTANCE side -arterioles-site of most vasc. resistance Small vessels-no pulse b/c high resistance -pressure head drops Vv. shallow P head in major vv. -hold 75% systemic blood vol. can alter capacity CAPACITANCE side-'discharges' when needed ???? Cross-sectional area Aorta<caps>venae cavae Area of v.larger than paired a. BUT P drop over vv. is larger ->b/c collapsed at many pts Total CO through each segment -equal flow, so diff Vs aorta-33cm/sec caps-0.3mm/sec, Measure BP Arterial P -listen to Korotkov sounds -turbulent flow in deformed brachial a. -no sound when occluded or open -record BP when sounds heard then not Venous P -directly in cardiac cath lab -or during physical- distance above sternal angle->cmH20 -should be zero at 45deg supine Cap Wedge P-reflects pulm cap pressure -correlates w/ L. atrial P (filling P of Lvent) -Swan-Ganz catheter- vena cava->R atrium-> ->R. vent->pulm. a.->wedged here -stops blood flow -pressure opposite to wedge~L.atrium P meanmmHg, shows venous a, c, v waves -elevated wedge P->L. vent failure Mean Mean BP=area under wave/duration -electronically when catheter used -estimated as (2*dias+1*sys)/3 -okay estimate for normal wave -varies greatly if abnormal wave