13. Pulmonary circulation Flashcards Preview

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Flashcards in 13. Pulmonary circulation Deck (25):
1

pulmonary circulation vs systemic circulation according PO2

in pulmonary circulation, a decreasing in PAO2 causes a HYPOXIC VASOCONSTRICTION

2

decreased PAO2 associated vasoconstriction in pulmonary circulation - purpose

it shifts blood away from poorly ventialted regions of lung to well - ventilated regions of lun

3

a consequence of pulmonary hypertension is

copulmonale and subsequent right ventricular failure ( jugular venous distention, edema , hepatomegaly)

4

pulmonary circulation - perfusion limited ( definition )

Gas equilibrates early along the length of the capillary

5

pulmonary circulation - perfusion limited --> pincreasing erfusion can be increased ....

only by blood flow

6

pulmonary circulation - perfusion limited - example gases

1. O2 ( normal health)
2. CO2
3. N2O

7

pulmonary circulation - diffusion limited (definition

gas does not equilibrate by the tie blood reaches the end of the capillary

8

pulmonary circulation - diffusion vs perfusion limited in exercise

normally gas Equilibrates but at the end of the caopillary

9

diffusion equation

Vgas = (A/T) xDK (P1-P2)
A;area
T:alveolar wall thickness
DK (P1-P2) is the difference in partial pressures

10

pulmonary circulation - diffusion is decreased in ( and why)

1.emphysema (increased alveolar wall thickness)
2. pulmonary fibrosis ( decreased area)

11

Vgas = ( area / alveolar wall thickness ) x DK (P1-P2) - situation of decreased A

emphysema

12

Vgas = ( area / alveolar wall thickness ) x DK (P1-P2) - situation of increased T

pulmonary fibrosis

13

• Normally, pulmonary circulation is a ____ (high/low) resistance, ____ (high/low) compliance system.

Low, high

14

Within the lungs, a decrease in PAO2 causes what process to occur within the vasculature in the area?

Hypoxic vasoconstriction

15

• 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

16

Name the perfusion-limited gases.

Oxygen (normal health), carbon dioxide, nitrous oxide

17

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)

18

A patient becomes hypoxic from a massive hemorrhage. Under these perfusion-limited conditions, how can pulmonary gas exchange be increased?

By increasing blood flow

19

• Name the diffusion-limited gases.



Oxygen (emphysema, fibrosis), carbon monoxide

20

• Under what two conditions is oxygen a diffusion-limited gas?

Emphysema and fibrosis

21

• 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

22

• 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

23

• 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

24

• 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

25

In the equation for gas diffusion, which variable is affected by pulmonary fibrosis, and how?

Thickness of the alveolar membrane is increased in pulmonary fibrosis, causing a decrease in diffusion