Fluid shift across the wall: Pulmonary and Systemic Oedema

Question 1

what proportion of our bodies is extracellular fluid?

Answer 1

1/3 rd roughly

Question 2

what percentage of ECV is interstitial i.e bathing the body cells

Answer 2

about 75%

Question 3

where does the exchange of nutrients occur?

Answer 3

at the capillaries

Question 4

what does the thin capillary wall allow for?

Answer 4

rapid exchange of gases, water and solutes with interstitial

Question 5

what are the other functions of the capillaries ? 2 things

Answer 5

• removal of metabolites from cells

- delivery of nutrients and oxygen to the cells

Question 6

what does the blood flow in the capillaries depend on?

Answer 6

the contractile state of the terminal arterioles

Question 7

In some tissues (e.g. mesentry) there is another component involved in the regulation of flow, wha is this?

Answer 7

the precapilary sphincters

Question 8

what is the rate of blood flow like in the capillary beds?

Answer 8

very slow to allow adequate time for exchange

Question 9

which molecules can cross the capillary wall? 3 things - generally

Answer 9

1. lipid soluble sustances
2. small, water soluble substances
3. exchangeable proteins

Question 10

how are lipid soluble substances moved from the capillaries to the interstitium?

Answer 10

they pass through the endothelial cells

Question 11

how are small water soluble substances moved from the capillaries to the interstitium?

Answer 11

through the water filled pores between endothelial cells

Question 12

how are exchangeable proteins moved from the capillaries to the interstitium?

Answer 12

they are moved across by vesicular transport

Question 13

which molecules cannot generally cross the capillary wall?

Answer 13

plasma proteins

Question 14

give some examples of the small water-soluble substances that can pass through the pores?

Answer 14

Na, K, Glucose and amino acids

Question 15

give some examples of the lipid soluble substances that can pass through the endothelial cells ?

Answer 15

O2 and CO2

Question 16

Fluid movement follows _____

Gradient (bulk flow)

Answer 16

Fluid movement follows Pressure Gradient (bulk flow)

Question 17

which law does the movement of gases and solutes follow?

Answer 17

flick’s law of diffusion

Question 18

Transcapillary fluid flow is _____ driven by _____ gradients across the capillary wall

It is called ___ i.e. exchange across the capillary wall of essentially protein-free ___

Answer 18

Transcapillary fluid flow is passively driven by pressure gradients across the capillary wall

It is ultra-filtration i.e. exchange across the capillary wall of essentially protein-free plasma

Question 19

what is the NPP =

Answer 19

forces favouring filtration (ie movement of fluid from the capillary to the interstitium) - forces opposing filtration

Question 20

what is the other factor that effects net fluid filtration?

Answer 20

filtration coefficient (kf). Pressure is more important though

Question 21

what are the two forces favouring filtration just after the arterioles

Answer 21

Pc - capillary hydrostatic pressure

(pi)i interstitial osmotic pressure

Question 22

what are the two forces opposing filtration just before the venules

Answer 22

(pi)c - capillary osmotic pressure
Pi - interstitial hydrostatic pressure

the main one is the capillary osmotic pressure

Question 23

NFP = (P_ + π_) - (π_ + P_)

Answer 23

(PC + πi) - (πC + Pi)

Question 24

Starling forces favour ___ at arteriolar end, ______ at venular end

Answer 24

Starling forces favour filtration at arteriolar end, reabsorption at venular end

Question 25

what are the major forces involve din systemic transcapillary flow?

Answer 25

Pc and (pi) c

Question 26

During a day filtration exceeds reabsorption by 2- 4 litres. How is the excess fluid returned to the circulation?

Answer 26

via the lymphatics as lymph

Question 27

what are the mechanisms to protect the lungs against pulmonary oedema? 4 things

Answer 27

Pulmonary resistance is only ~10% of that of the systemic circulation

Pulmonary capillary hydrostatic pressure is low (~ 8-11 mmHg)

Capillary osmotic pressure at 25 mmHg

Efficient lymphatic drainage remove any filtered fluid thus preventing accumulation of interstitial fluid

Question 28

what is oedema?

Answer 28

accumulation of fluid in interstitial space

Diffusion

Question 29

what does pulmonary oedema affect in the lungs? two things

Answer 29

gas exchange and compliance

Question 30

what are the 4 causes of oedema?

Answer 30

1. raised capillary pressure
2. reduced plasma osmotic pressure
3. lymphatic insufficiency
4. changes in capillary permeability

Question 31

what are the two main causes of raised capillary pressure

Answer 31

• arteriolar dilatation

- raised venous pressure

Question 32

what three things may cause raised venous pressure?

Answer 32

1. LV failure
2. Right ventricular failure
3. prolonged standing

Question 33

where is the oedema in LVF?

Answer 33

lungs

Question 34

where is the oedema in RVF?

Answer 34

peripheral oedema )ankles, sacral)

Question 35

what is the normal plasma osmotic pressure?

Answer 35

65-80 g/l

Question 36

what plasma osmotic pressure is required for oedema?

Question 37

what can cause a low plasma osmotic pressure?

Answer 37

malnutrition

protein malabsorption

excessive renal excretion of protein

hepatic failure

Question 38

what can cause lymphatic insufficiency?

Answer 38

• lymph node damage

- filariasis - elephantiasis

Question 39

what kind of oedema is present in lymphatic insufficiency and why?

Answer 39

if someone has a lymphatic obstruction you get non-pitting oedema because you cannot push the fluid back into the lymphatics

Question 40

what causes changes in the capillary permeability?

Answer 40

inflammation

- histamine increases leakage of protein

Question 41

what is the symptom from pulmonary oedema?

Answer 41

breathless

Question 42

wat are the signs of pulmonary oedema?

Answer 42

creps at the lung bases

Question 43

what does a cxr show in pulmonary oedema?

Answer 43

haziness in perihilar region