Pulmonary and Systemic Oedema Flashcards
what does interstitial fluid do?
acts as the go-between blood and body cells
what is the role of capillaries?
allows rapid exchange of gases, water and solutes with interstitial fluid
- delivery of nutrients and O2 to the cells
- removal of metabolites from cells
what does blood flow in the capillaries depend on?
the contractile state of the arterioles
what regulates regional blood flow to the capillary bed in most tissues?
terminal arterioles
what are precapillary sphincters?
they regulate flow in a few tissues
describe blood flow through the capillary bed
very slow to allow adequate time for exchange
describe fluid movement across the capillary wall
it follows pressure gradient (bulk flow)
follows fick’s law of diffusion
how do lipid soluble substances pass across the capillary wall?
through the endothelial cells
how do water soluble substances pass across the capillary wall?
through water-filled pores
what does ultrafiltration of transcapillary fluid flow mean?
exchange across the capillary wall is essentially protein-free plasma
what is net filtration pressure?
forces favouring filtration-forces opposing filtration
what are the starling forces?
forces involved in transcapillary fluid flow
what are the forces favouring filtration?
Pc- capillary hydrostatic pressure
pieI- interstitial fluid osmotic pressure
what are the forces opposing filtration?
pieC- capillary osmotic pressure
Pi- interstitial fluid hydrostatic pressure
which end are the forces favouring filtration ?
arteriolar
which end are the forces favouring reabsorption?
venular
what is the equation for NFP?
(PC + pieI) - (pieC+PI)
where does excess fluid of systemic capillaries go?
it is returned to the circulation via the lymphatics as lymph
how is accumulation of interstitial fluid prevented?
efficient lymphatic drainage removes any filtered fluid
what is oedema?
accumulation of fluid in interstitial space
diffusion distance increase- gas exchange compromised in pulmonary oedema
what are the 4 causes of oedema?
raised capillary pressure
reduced plasma osmotic pressure
lymphatic insufficiency
changes in capillary permeability
what happens during raised capillary pressure?
arteriolar dilatation
raised venous pressure
what does left ventricular failure cause?
pulmonary oedema
what does right ventricular failure cause?
peripheral oedema
what does HF do to the frank-stirling curve?
shifts it to the right
what happens in reduced plasma osmotic pressure?
lower plasma protein concentration (<30g/L results in oedema) malnutrition protein malabsorption excessive renal excretion of protein hepatic failure
what causes lymphatic insufficiency?
lymph node damage
filariasis- elephantiasis
what happens if there is changes in capillary permeability?
inflammation
histamine increases leakage of protein
what is pulmonary oedema?
accumulation of fluid in the interstitial and intraalveolar lung spaces
what are the clinical signs of pulmonary oedema?
SoB
crepitations in lung bases
chest x ray shows haziness in perihilar region
where can pitting oedema be found?
ankles
sacrum
