L16: Carriage Of Oxygen Flashcards
What does diffusion depend on
Partial pressure gradient
What are the 2 ways oxygen is carried
1) physically dissolved in plasma
2) chemically bound to haemoglobin in RBC
What does the oxygen dissolved in plasma exert
Partial pressure
What is the chemical combination of oxygen with haemoglobin determined by
Partial pressure hence the oxygen in the plasma
What is Henry’s law about
How much gas is dissolved in the liquid (plasma)
Why do we need the chemical combination of oxygen with haemoglobin if oxygen can be dissolved physically in plasma
The dissolved oxygen in plasma is not enough for the body
Inside the haem group which iron allows oxygen to bind
Iron (Fe2+)
What is co-operative binding
Binding of oxygen to iron in haemoglobin makes the binding and unwinding of other oxygen binding to other haem easier and
What does oxygen content mean
The amount of oxygen in:
dissolved in plasma AND bound to haemoglobin
What does oxygen capacity mean
The maximum amount of oxygen that combines with haemoglobin in blood
Does the oxygen capacity involve the oxygen in dissolved plasma
No
What is oxygen capacity only dependent on
Concentration of haemoglobin
At what pao2 is the haemglobin 100% saturated
Normal pao2 of 13kpa
What does a flat association curve indicate
Despite the change of Po2 from 8-13kpa most of oxygen is still bound to haem
What is 2,3-DPG
Side reaction of glycolysis
What does the flat association curve indicate
Despite the changes from 13 to 8kpa the haemoglobin is still 90% saturated (enough for a persons oxygen delivery)
What does the steep dislocation curve indicate
Despite the changes from 8 to 3kpa the haemoglobin concentration is desaturated by 60%
What does the steep dissociation curve ensure
Delivery of oxygen for tissue
How can the oxygen binding affinity to haemoglobin be shifted to the right
Increase pco2 in arterial blood
Decrease ph
Increase temperature
Increase 2,3DPG concentration
What are the factors that affect the haemoglobin concentration
Diet
Reduced RBC (anaemia)
Carbon monoxide poisoning
What is the Bohr effect
Increasing pco2
Decreasing ph
When do we get an increase in pco2, increase in H+ (decreasing ph) and increase in temperature
At a high metabolism
What does a right shift in the hb dissociation allow
Allow a further amount of oxygen delivery to the tissue
What is the auto regulated delivery in tissues
Amount of oxygen delivered is depends on how fat the curve is shifted to the right and how the metabolism has changed
Does pao2 have any affect on the hb dissociation curve
No
Is the ability to deliver oxygen in anaemia affected
No
Where does carbon monoxide bind
Same site as oxygen in haemoglobin
Why is carbon monoxide more fatal than anaemia
Oxygen is not released from the haemoglobin until tissue po2 is 1kpa
And at 1kpa the tissues are dying
What are the variants of haemoglobin in RBC
Adult haemoglobin Fetal haemoglobin Haemoglobin S Metheoglobineaemia Mygoblobin
What is the affinity for oxygen for fetal haemoglobin compared to adult haemoglobin
Higher affinity
Why does fetal haemoglobin have a higher affinity for oxygen
To pick up oxygen in maternal blood
When do we get haemoglobin s
In sickle cell anaemia
Which direction does sickle cell anaemia shift the hb dissociation curve
Right
What is myoglobin
Oxygen store in muscle with one haem group
What is hypoxia
Low oxygen in the blood for delivery or consumption for tissues to maintain normal function
What are the types of hypoxia
Hypoxic hypoxia
Anaemic hypoxia
Stagnant hypoxia
Histotoxic hypoxia
Wha is hypoxic hypoxia
Low arterial oxygen and low saturation of oxygen
What are the clinical conditions that cause hypoxic hypoxia
Hypoventialtion
Diffusion limitation
V/Q mismatch
Shunt
What is anaemic hypoxia
Normal pao2 and normal staturation of oxygen but low oxygen conten
What are the clinical conditions of anaemic hypoxia
Blood loss
Carbon monoxide poisoning
What is stagnant hypoxia
Low blood flow in a small tissue or large tissue
What are the clinical conditions that give stagnant hypoxia
Cardiac failure
What is histotoxic hypoxia
High venous oxygen and high saturation of venous oxygen due to inability to utilise oxygen
What are the clinical conditions that result in histotoxic hypoxia
Cyanide poisoning
