Flashcards in 13. Pulmonary circulation Deck (25):
pulmonary circulation vs systemic circulation according PO2
in pulmonary circulation, a decreasing in PAO2 causes a HYPOXIC VASOCONSTRICTION
decreased PAO2 associated vasoconstriction in pulmonary circulation - purpose
it shifts blood away from poorly ventialted regions of lung to well - ventilated regions of lun
a consequence of pulmonary hypertension is
copulmonale and subsequent right ventricular failure ( jugular venous distention, edema , hepatomegaly)
pulmonary circulation - perfusion limited ( definition )
Gas equilibrates early along the length of the capillary
pulmonary circulation - perfusion limited --> pincreasing erfusion can be increased ....
only by blood flow
pulmonary circulation - perfusion limited - example gases
1. O2 ( normal health)
pulmonary circulation - diffusion limited (definition
gas does not equilibrate by the tie blood reaches the end of the capillary
pulmonary circulation - diffusion vs perfusion limited in exercise
normally gas Equilibrates but at the end of the caopillary
Vgas = (A/T) xDK (P1-P2)
T:alveolar wall thickness
DK (P1-P2) is the difference in partial pressures
pulmonary circulation - diffusion is decreased in ( and why)
1.emphysema (increased alveolar wall thickness)
2. pulmonary fibrosis ( decreased area)
Vgas = ( area / alveolar wall thickness ) x DK (P1-P2) - situation of decreased A
Vgas = ( area / alveolar wall thickness ) x DK (P1-P2) - situation of increased T
• Normally, pulmonary circulation is a ____ (high/low) resistance, ____ (high/low) compliance system.
Within the lungs, a decrease in PAO2 causes what process to occur within the vasculature in the area?
• Within the lungs, hypoxic vasoconstriction serves what physiologic function?
It shifts blood away from the poorly ventilated areas of the lung to those that are well ventilated
Name the perfusion-limited gases.
Oxygen (normal health), carbon dioxide, nitrous oxide
Under perfusion-limited conditions, where along the length of the pulmonary capillary do the partial pressures of a gas equilibrate?
Early (gas exchange is not limited by its ability to cross the membrane, only by the supply of blood)
A patient becomes hypoxic from a massive hemorrhage. Under these perfusion-limited conditions, how can pulmonary gas exchange be increased?
By increasing blood flow
• Name the diffusion-limited gases.
Oxygen (emphysema, fibrosis), carbon monoxide
• Under what two conditions is oxygen a diffusion-limited gas?
Emphysema and fibrosis
• Under diffusion-limited conditions, where along the length of the pulmonary capillary does the gas equilibrate?
It does not equilibrate (the characteristics of the gas cause it to diffuse slowly across the alveolar membrane
• A patient with untreated pulmonary hypertension presents with jugular venous distention, edema, and hepatomegaly. What caused this?
The patient is showing signs of cor pulmonale (right heart failure), a complication of pulmonary hypertension
• What is the equation for diffusion of a gas across a membrane?
Vgas = A/T × Dk(P1 - P2), where A = area, T = thickness, DkP1 - P2) = difference in partial pressures
• A patient has emphysema. Which variable is affected by his disease in the equation for gas diffusion, and how? (See image.)
The area of membranes available for gas transfer (A) is decreased in emphysema, causing a decrease in diffusion