phy 4 Flashcards
“Effect of Partial
Pressure on Gas Solubility?”
increasing partial pressure in gas phase, proportionally increases the concentration of the gas in the liquid phase
partial pressure of a gas in solution
partial pressure in the gas mixture with which it is in equilibrium
henrys law
At a constant temperature, the amount of a given gas dissolved in a given type and volume of liquid (e.g. blood) is directly proportional to the partial pressure of that gas in equilibrium with that liquid
resting O2 consumption of body cells
250ml/min
in which forms is oxygen found in the blood and what percentage of O2 do these forms carry, respectively
“oxygen bound to haemoglobin - 98.5%
oxygen carried in its dissolved form - 1.5%”
normal arterial O2 concentration
200ml per litre
normal arterial PO2
13.3kPa
normal haemoglobin(Hb) concentration
150 grams per litre
“how many oxygen molecules can one haemoglobin molecule bind to?
what structures on the haemoglobin molecule allow oxygen binding?”
“1 Hb can bind to 4 oxygen molecules
oxygen binding is facilitated by the 4 haem groups present in a haemoglobin molecule. each haem group can reversibly bind to oxygen”
when is haemoglobin considered to be fully saturated
When all the Hb present is carrying its maximum O2 load
which factor primarily determines the percent saturation of haemoglobin with O2
PO2
normal PO2
95% or above
what is the composition of haemoglobin
“2 Beta Chains
2 Alpha Chains
4 Haem Groups”
what shape is an oxygen haemoglobin saturation curve
sigmoid
what is oxygen delivery to tissues a function of
“oxygen content of arterial blood
cardiac output”
oxygen delivery index equation
“DO2I = CaO2 x CI
where
DO2I = Oxygen Delivery Index (ml/min/metre2)
CaO2 = Oxygen content of arterial blood (ml/L)
CI = Cardiac index (L/min/metre2)
“
cardiac index
cardiac output with regard to the body surface area(i.e. size of the individual)
O2 content of arterial blood is determined by
“haemoglobin concentration[Hb] (gram/L)
saturation of Hb with O2, SaO2”
CaO2 equation
“CaO2 = 1.34 x [Hb] x SaO2
“
what is the SaO2 determined by
PO2
“Oxygen Delivery to the Tissues can be impaired by
“
“respiratory disease
decreased partial pressure of inspired oxygen - they can decrease arterial PO2 and hence decrease Hb saturation with O2 and O2 content of the blood
heart failure - decreases cardiac output
anaemia - this decreases Hb concentration and hence decreases O2 content of the blood
asthma”
Partial pressure of inspired oxygen depends on
“total pressure (e.g. atmospheric pressure)
proportion of oxygen in gas mixture (about 21% in atmosphere)”
what happens to the partial pressure of inspired oxygen when the altitude increases
decreases because increasing altitude decreases atmospheric pressure thus decreasing the pressure gradient between the atmosphere and the intraalveolar pressure
water vapour pressure in the lungs
47mmHg
how do respiratory disease and a decreased partial pressure of inspired oxygen affect oxygen delivery to the tissues
they can decrease arterial PO2 and hence decrease Hb saturation with O2 and O2 content of the blood
cooperativity
binding and unbinding of one oxygen to haemoglobin increases and decreases the affinity of Hb for O2, respectively
components of foetal haemoglobin
2 alpha and 2 gamma subunits, whilst HbA has 2 alpha and 2 beta subunits
why does HbF have a higher affinity for O2 than HbA
HbF interacts less with 2,3- Biphosphoglycerate in red blood cells than HbA
whats the structural significance of HbF
it allows O2 to transfer from mother to foetus even if the PO2 is low
presence of myoglobin in the blood indicates
muscle damage
