Pulmonary and Systemic Oedema

Question 1

describe interstital fluid

Answer 1

acts as the go-between blood and body cells

extra cellular fluid (from body water) is interstitial e.g. bathing the body of cells - acting as the go-between blood and body cells

Question 2

explain starling forces governing movement across the capillary wall

Answer 2

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

Question 3

describe odema

Answer 3

accumulation of fluid in interstitial space

Question 4

describe the special adaptions by the pulmonary circulation

Answer 4

hydrostatic pressure is low

Question 5

describe pathophysiology of pulmonary oedema

Answer 5

diffusion distance increases - gas exchange compromised in pulmonary oedema

Question 6

causes of oedema

Answer 6

raised capillary pressure
reduced plasma osmotic pressure
lymphatic insufficiency
changes in capillary permeability

Question 7

describe capillaries

Answer 7

one cell thick
rapid exchange of gases, water and solutes with interstitial fluid
removes metabolites from cells
terminal arterioles regulate blood flow to capillary bed - blood flow is very slow to allow adequate time for exchange

Question 8

describe transport across capillary wall

Answer 8

exchangeable proteins are moved across by vesicular transport
plasma proteins (large molecules) generally cannot cross capillary wall
lipid-soluble substances pass through the endothelial cells
water soluble substances go through the water-filled pores 

fluid movement follows pressure gradient
movement of gases and solutes follow Fick’s Law of diffusion (downhill)

Question 9

describe transcapillary fluid flow

Answer 9

driven by pressure gradients across capillary wall

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

Question 10

describe raised capillary pressure

Answer 10

arteriolar dilatation
raised venous pressure;
left ventricular failure - pulmonary oedema
right ventricular failure - peripheral/pitting oedema (ankle, sacral)
prolonged standing - swollen ankles

Question 11

heart failure and frank-starling curve

Answer 11

shifts to right

Question 12

describe reduced plasma osmotic pressure

Answer 12

normal [plasma protein] = 65-80 g/l
oedema < ~30 g/l;
malnutrition
protein malabsorption
excessive renal excretion of protein
hepatic failure

Question 13

describe lymphatic insufficiency

Answer 13

lymph node damage

filariasis - elephantiasis

Question 14

describe changes in capillary permeability

Answer 14

inflammation

histamine increases leakage of protein

Question 15

describe left ventricular failure - pulmonary oedema

Answer 15

pulmonary oedema is accumulation of fluid in the interstitial and intra-alveolar lung spaces
it is manifested clinically by varying degrees of shortness of breath
clinically there may be crepitations in auscultation of lung bases
CXR shows haziness in perihilar region