O2 transport Flashcards
How to calculate total pressure of gases?
P total = PH2O + ∑P consistent gases
How to calculate pp?
P gas = (Pb-PH2O) x ngas
PH2O : dry 0kPa / humidified 6kPa
Pb : atmospheric 100kPa
ngas : mole fraction, O2 at sea level 0.21
Define pp of gas dissolved in liquid?
amount of gas that would dissolve in the liquid (at eq) if the liquid was placed in contact w a gas phase of equivalent pp
What does the conc of gas dissolved in liquid depend on?
pp + solubility of gas
because conc=pp x solubility
Why can’t O2 transport alone?
low solubility = 0.2 mL/L/kPa
PA = 14 kPa can only dissolve 3mL of O2 per L
body needs 250 mL O2 per min at rest which would require CO= 80L
Role of Hb?
enables O2 to be conc within blood
binds 98% O2
What’s the total O2 carrying capacity?
3 mL/L (plasma) + 197 mL/L (Hb) = 200mL
Why’s O2 vs Hb dissociate curve sigmoidal?
- O2 affinity increased by more binding (cooperative binding )
- saturation + decreased free O2 binding sites
How’s O2 content in blood measured?
PaO2
CaO2 : total O2 content ml/L
O2 saturation : SaO2 (measured directly in arterial blood), SpO2 (estimated by pulse oximetry) %
Define PaO2
pp of O2 within gas phase (at a gas-liq interface) that would yield this much O2 in plasma at eq
Define CaO2
v of O2 carried by each L of blood (including plasma + bound O2)
Define O2 saturation
% of Hb binding sites occupied by O2
Why’s Hb effective?
- structure produces high O2 affinity so high saturation at low PO2
- conc of heme groups + Hb in 🔴
- O2 vs Hb curve shifts to unload O2 at tissues
- affinity changes on local environment so O2 delivery coupled to demand
When does saturation fall below 90% + effect?
when PaO2 falls below 8kPa
when PAO2 falls below 14kPa
O2 release from Hb increases as PO2 falls (tissues)
How is there a high carrying capacity?
4 O2 binding heme groups
5B 🔴/ml
270M Hb/🔴
Define Bohr effect
effect of CO2 + pH on affinity
Why left shift?
higher affinity ↓ CO2 ↓ 2,3-DPG ↓ temp ↑ pH
Why right shift?
lower affinity ↑ CO2 ↑ 2,3-DPG ↑ temp ↓ pH
How does increased 2,3-diphosphoglycerate affect affinity?
=intermediate of glycolysis, produced within🔴
during anaerobic metabolism alters Hb structure decreasing affinity as less O2 bind
Where’s the highest+lowest affinity Hb?
lungs
resting tissue
working tissue
Role of myoglobin?
O2 reservoir at muscle tissue only releases O2 at low PO2 STEEEEEEEEP + left
How is O2 transferred to baby?
foetal + maternal Hb in contact in placenta, O2 transferred to high affinity foetal Hb
What’s cyanosis?
purple discolouration of skin/tissue when excess deoxyhaemoglobin
What’s central cyanosis + eg?
blueish discolouration of core, mucous membranes, extremities
less oxygenation of blood
hyperventilation, V/Q mismatch
What’s peripheral cyanosis + eg?
blueish discolouration to extremities
less O2 supply to extremities
small vessel circulation issues
Diff ways hypoxia arise?
- less ventilation
- less perfusion
- less O2 carried in blood to meet demands
Cause of anemia?
iron deficiency
haemorrhage
How does CO poisoning happen?
-CO displaces O2 at Hb binding sites due to greater affinity >200x -less O2 binds + transported -CaO2 decrease -oxyhaemoglobin decrease
Why does hypoxia occur is absence of cyanosis?
carboxyhaemoglobin is cherry red
Anaemia readings?
↓total arterial O2 conc normal PaO2 normal SaO2 ↓Hb conc ↓oxyhaemoglobin
CO poisoning readings?
↓total arterial O2 conc normal PaO2 ↓SaO2 but NORMAL pulse oximetry normal Hb conc ↓oxyhaemoglobin
Why does curve shift left w CO poisoning?
CO inhibits glycolysis in 🔴 so ↓DPG –> left–> ↑ affinity
What’s Erythropoietin (EPO)
hormone secreted by kidney in response to hypoxia, induces production of 🔴within bone marrow
How to compensate for chronic hypoxia?
increase Hb conc-saturation will decrease due to reduced PaO2 but compensated by greater number of Hb
How + why does CO increase with hypoxia?
via increased heart rate to increase overall O2 transport - same number of Hb cycled from lungs to tissue rapidly, increasing total volume of oxygen
transported per unit time
Define polycythaemia
increase in 🔴 per unit of plasma
When does increased EPO secretion occur?
chronic hypoxic respiratory disease high altitude (due to chronic hypoxia involved)
How do athletes use EPO?
altitude training
illegal doping
