3. Pulmonary Circulation

Study Guide

Blood flow through the right heart, pulmonary circulation, left heart, systemic circulation

vena cava - right atrium -tricuspid - right ventricle -pulmonary semilunar valves - pulmonary trunk - pulmonary arteries - lungs - pulmonary arterioles - pulmonary capillaries (exchange site picking up O2 dropping off CO2) - pulmonary venules - pulmonary veins - left atrium -mitral (bicuspid) valve - left ventricle - systemic circulation

What is the approximate CO of the right ventricle?

5 L /min

How does the pulmonary circulation compare to systemic circulation in terms of pressure and resistance?

Lower pressure and resistance than systemic circulation but blood flow stays the same

What is pulmonary wedge pressure and how is it measured?

Estimates left atrial pressure. measured through Swan-Ganz Catheter

directly proportional to the pressure gradient between the pulmonary artery and left atrium

How is pulmonary blood flow regulated?

regulated by intrapulmonary pressure and resistance

What is the difference in blood flow (in general, no numbers) between the three zones and why does this difference exist?

zone 1 lowest blood flow (PA>Pa>Pv)

zone 2 medium blood flow (Pa>PA>Pv)

zone 3 highest blood flow (Pa>Pv>PA)

(when upright due to gravity)

How does pulmonary blood flow change during exercise?

pulmonary blood flow increases due to the increase in CO, keeps the same low pressure even with increased flow, increases gas exchange efficiency

How does this compare with ventilation changes during exercise?

increase RR, increase TV, V/Q ratio stays near optimal

What does PVR measure?

pulmonary vascular resistance - the change in pressure from the pulmonary artery to the left atrium divided by the flow

What is the normal value?

1/10 the resistance of systemic circulation

Calculate PVR and determine if value is normal/abnormal

PVR = (pulmonary artery pressure (Ppa) - left atrium pressure (Pla)) / flow or cardiac output (Qt)

What is hypoxic vasoconstriction?

low oxygen levels in the alveoli cause the pulmonary arterioles to constrict

How is vasoconstriction different from what typically happens in other tissues during hypoxia?

in most other tissues, hypoxia causes vasodilation. In the lungs, vasoconstriction redirects blood away from poorly ventilated alveoli to optimize gas exchange

How is vasoconstriction beneficial to the pulmonary system

optimizes gas exchange

Is some shunting normal

yes a small amount

how does Tetralogy of Fallot cause tet spells or bluish coloring?

Triggered by crying, feeding, or exertion → ↑ oxygen demand

a hole between the ventricles (VSD) and narrowing of the pulmonary valve causes blood from the right ventricle (which is low in oxygen) to flow into the left side and go straight to the body without passing through the lungs. This causes low oxygen levels in the blood and leads to blue coloring

Left heart failure/mitral valve issues

If the left side of the heart is weak or the mitral valve is damaged, blood backs up into the lungs. This raises pressure in the pulmonary circulation, causing fluid to leak into the lungs — known as pulmonary edema. It makes breathing harder and can lead to shortness of breath and low oxygen levels.

what can these diseases cause to happen in the pulmonary circulation

• TOF: ↓ pulmonary blood flow → hypoxemia, cyanosis

• Left heart failure/mitral disease: ↑ pulmonary pressure → congestion, edema, possible pulmonary hypertension