Respiratory Phys - Pulmonary circulation

Question 1

Hypoxic vasoconstriction

Answer 1

Shifts blood away from poorly ventilated regions of the lung to well-ventilated regions of lung Caused by decreased P_AO2

Question 2

Decreased P_AO2 causes what change in lung perfusion?

Answer 2

Causes hypoxic vasoconstriction

Question 3

Perfusion limited gas exchange

Answer 3

Normal health O₂, CO₂, N₂O Gas equilibrates early along the length of the capillary Diffusion can be increased only if blood flow increases

Question 4

Diffusion limited gas exchange

Answer 4

Pathology (Emphysema, Fibrosis) O₂, CO Gas does not equlibrate by the time blood reaches the end of the capillary

Question 5

Consequences of pulmonary hypertension:

Answer 5

Cor pulmonale

Right ventricular failure (JVD, edema, hepatomegaly)

Question 6

What is the equation for diffusion?

Answer 6

V_gas = A/T x D_k(P1 - P2)

A = area

T = thickness

D_k(P1 - P2) = difference in partial pressures

Question 7

In the diffusion equation, Area decreases in what condition?

Answer 7

Emphysema

Question 8

In the diffusion equation, Thickness increases in what condition?

Answer 8

Pulmonary fibrosis

Question 9

Pulmonary vascular resistance (PVR) equation

Answer 9

=( P_{pulm artery} - P_{L atrium}) / CO

P_{pulm artery} = pressure in pulmonary artery

P_{L atrium} = pulmonary wedge pressure

ΔP = Q x R, so R = ΔP / Q (Q = flow)

Question 10

Resistance =

Answer 10

R = 8nl / πr^4

n = viscosity of blood

l = vessel length

r = vessel radius

Question 11

Alveolar Gas Equation

Answer 11

P_AO2 = P_IO2 - (P_aCO2 / R)

~150 - (P_aCO2 / 0.8)

R = respiratory quotient = CO₂ produced / O₂ consumed

Question 12

A-a gradient equation

Answer 12

= P_AO2 - P_aO2 = 10-15 mmHg

Question 13

Increased A-a gradient occurs in what conditions?

Answer 13

Hypoxemia: shunting, V/Q mismatch, fibrosis (impairs diffusion), increased F_iO2, increased age

High A-a gradient usually not good