L16 - respiratory physiology - transport and exchange of gasses Flashcards
what is daltons law
the individual pressure of a gas in a mixture is its partial pressure
sum of partial pressures = total pressure
what is henrys law
gasses diffuse from high partial pressure to low partial pressure
how much o2 is consumed by tissues per min
250ml
how much CO2 is produced by tissues per min
200ml
what is the respiratory quotient
o2 consumed
CO at rest
5L/min
Va at rest
total air
oxygen only
4.2L/min
882
what is PO2 at the alveoli
13.3
what is PO2 in tissues
5.3
what factors affect rate of diffusion
Partial pressure difference
diffusion barrier thickness & permeability
solubility of gas in water
what is PCO2 in tissues
6.1
what is PCO2 in alveoli
5.3
what is systemic PO2
12.5
what is systemic CO2
5.3
why doesnt systemic PO2 = Alveolar PO2
- anatomical right to left shunt
2. partial draining of coronary venous blood into LV
explain anatomical right to left shunt
deoxygenated bronchial vein blood mixes with oxygenated pulmonary vein blood
define % saturation
%of O2 binding sites on Hb , bound to O2
define O2 content
sum of gas present in blood (bound to HB and dissolved in plasma)
define max O2 carrying capacity
amount of O2 blood is capable of carrying when Hb is 100% saturated
why do we need haemoglobin
for dissolved oxygen alone CO would have to be 83L/min to supply tissues with sufficient O2
what factors affect binding of O2 to Hb
PO2 & co - operativity
PCO2 (pH)
temperature
2, 3 diphosphoglycerate
what is the normal shape of the o2 Hb dissociation curve
sigmoidal
explain cooperativity of Hb
binding of each successive O2 increases affinity of remaining binding sites
release of O2 causes release of O2 from the other binding sites
what is 2,3 diphosphoglycerate
product of glycolysis that accumulates when o2 supply isn’t sufficient
what effect does increased PCO2 temp [2,3 DPG] and decreased pH have on the O2 Hb dissociation curve
causes a right shift - decreased affinity of oxygen so oxygen dissociates
define oxygenation
the binding of oxygen to Hb binding sites
what effect does decreased PCO2 [2,3 DPG] temp and increased pH have on the O2 Hb dissociation curve
shift to right, higher affinity for oxygen so it wont dissociate in tissues
explain the effects of anaemia on oxygen transport
- reduced no. of rbc
reduced Hb - reduced O2 carrying capacity
- mild tissue hypoxia
effects of anaemia on O2 Hb dissociation curve
flatter version of normal - not as high
explain the effects of CO poisoning on oxygen transport
- CO binds to Hb at higher affinity than O2
- fewer O2 binding sites available
disrupts cooperativity (O2 that binds doesn’t
dissociate) - severe hypoxia
effects of CO poisoning on O2 Hb dissociation curve
no longer sigmoidal
lower and flatter
how is CO2 transported in blood
HCO3
carbamino compounds (on Hb)
dissolved in plasma
what enzyme speeds up the CO2 - HCO3 reaction
carbonic anhydrase
what is the haldane effect
deoxy Hb promotes the uptake of CO2 by RBCs better than oxygenated Hb due to
haldane effect A
haldane effect B
what mechanisms favour the forward reaction of CO2 - HCO3
H+ binds to deoxy Hb (removing H+)
HCO3 leaves via chloride shift
what is the haldane effect A
H+ binds to deoxy Hb (removing H+)
favouring the forward reaction of CO2 - HCO3
what is the haldane effect B
deoxy Hb more readily forms carbamino compounds with CO2 than oxy Hb does
what is hypocapnia
drop in PaCO2
increased pH
respiratory alkalosis
what is hypercapnia
increase in PaCO2
decrease in pH
respiratory acidosis
