Ohm's Law: I=V/R I = current (electrical flow)

V= voltage (electrical potential energy)

R = resistance to flow

For fluid dynamics: Q=P/R Q = blood flow

P = pressure (potential energy)

R = resistance to flow

P1

Q

R

P2

Arterial (Pa)

Venous (Pv)

Alveolar (PA)

Zone 1

PA>Pa>Pv

Zone 2

Pa>PA>Pv

Zone 3

Pa>Pv>PA Blood FlowD

ista

nce

Pulmonary Circulation

1

2

3

Assumes PA=0 mmHg

Pulmonary Artery

Pulmonary Capillaries

Pulmonary Vein

LeftAtrium

0

10

20

30

40

50

60

mm

Hg

Pulmonary ArterialCatheter Tracing

Left Atrial Pressure Tracing

Pulmonary Circulation

0 1 2 31

10

100

Distalcomponent

Proximalcomponent

PCWP

Bi-exponential decay ofpulmonary arterial pressure

Pre

ssu

re (

mm

Hg)

Time (seconds)

Arteriole Venule

37 mmHg

17 mmHg

InterstitialHydrostatic P=1

Oncotic P=25

Pnet=(Pi-Po)+(o-i)

Arterial (Pa)

Venous (Pv)

Alveolar (PA)

Zone 1

PA>Pa>Pv

Zone 2

Pa>PA>Pv

Zone 3

Pa>Pv>PA

Pulmonary Circulation