Pulmonary Circulation And Perfusion

Question 1

Pulmonary vasculature

Answer 1

Low resistance, highly distensible
Recruitment: increasing number of blood vessels
Distension: increasing radius of pulmonary vessels

Constriction ability of pulmonary arterioles less than systemic

Question 2

Effect of lung vol on vascular resistance

Answer 2

As lungs fill with air, dec in pulmonary vascular resistance due to radial traction
As cont to fill with air, increase in pulmonary vascular resistance as alveolar vessels compressed
Lowest total pulmonary vascular resistance exists at FRC
As RV -> TLC, inc pressure in alveolar vessels

Question 3

Perfusion of blood flow

Answer 3

Affected by gravity
Most blood found in base of lungs
Z1: PA > Pa > Pv, on ventilator or hemorrhage
Z2: Pa > PA > Pv, resistance dec by recruitment
Z3: Pa > Pv > PA, resistance dec by recruitment and distension
Normal quiet breathing, zone 2 and 3
Lying down, zone 2 because no gravity

Question 4

Effects of gravity on lung ventilation and perfusion

Answer 4

Base
Ventilation: intrapleural pressure greater, smaller transmural pressure gradient, alveoli smaller and more compliant, more ventilation
Perfusion: greater intravascular pressure, more recruitment and distension, lower resistance, more blood flow