6. Pulmonary blood flow and gas exchange 2+3: Haemoglobin +gas transport Flashcards
Why does the blood transport O2 from the lungs to the tissues?
to use O2 in energy production (and Co2 travels from tissues to lungs for removal)
How much O2 dissolves per litre plasma in ml?
3ml (solubility= 3/0.03ml/L/mm
Hg)
By how much does haemoglobin in RBCs increase O2 carrying capacity? (ml/L)
increases it to 200ml/L
How is a bulk of CO2 transported in the blood?
in solution in plasma (in various forms)
What is pulmonary circulation in terms of flow and pressure?
-high flow
-low pressure
system
What is the partial pressure gradient between alveoli and pulmonary arteries in mmHG for O2?
100mmHg (alveoli) to 40mmHg
What is the partial pressure of O2 in the air? (mmHg)
160mmHg
What is the partial pressure of O2 in tissues and veins? (mmHg)
40mmHg
Why isn’t the partial pressure of O2 in alveoli 160mmHg, and instead it’s 100mmHg?
when air enters the airways, it’s diluted down to 100mG by the time it travels down and reaches alveoli
What is the partial pressure gradient between pulmonary artery to alveoli in mmHG for CO2 (during removal)?
46mmHg to 40mmHg
Partial pressure gradient for O2 is 10 x greater than that for CO2, yet their rate of diffusion is quite similar- why?
because CO2 is much more soluble in water (which makes up for it)
What happens to pulmonary vessels if ventilation to an area of lung is compromised?(when O2 decreases and CO2 increases)
-local vasoconstriction in compromised region (pulmonary circulation only)
What does shunt refer to?
blood flowing through a poorly ventilated region without being oxygenated (it’s then redirected to better ventilated areas)
What does alveolar dead space refer to?
alveoli which are ventilated but not perfused
When can an alveolar dead space arise? (physiological)
when blood clot present blocking blood supply
Can ventilation in alveoli still occur when there is no blood perfusion?
yes
Why isn’t the partial pressure of O2 not the same as arterial content of O2?
because partial pressure only refers to O2 IN SOLUTION (the 3ml of O2 in plasma)
O2 in solution (how much O2 is dissolved in the plasma) is determined by what 2 factors?
- O2 solubility (which is fixed)
- partial pressure of O2 in gaseous phase (in alveoli)
both are driving O2 into solution
What is the general rule which drives the gas into solution?
value assigned to partial pressure of the gas in solution = partial pressure of gas in gaseous phase that is driving the gas into the solution
Describe the calculation that proves that partial pressure of O2 is 100mmHg (PP in alveoli)
- solubility of O2 in water is low; 0.03ml/L/mmHg
- we have 3ml/L of O2 in plasma so PP that is driving O2 into the liquid phase in plasma must be 100mmHg (3/0.03=100)
What is the general conclusion regarding PO2 in solution and gaseous phase.
the PO2 in solution= the PO2 in gaseous phase which results in that oxygen concentration in the liquid phase
What is another word for the PO2 (in arteries) which is at 100mmHg?- ie O2 arterial partial pressure
oxygen tension
Why do gases not travel in their gaseous phase in the plasma?
It would cause bubbles in the blood which could lead to fatal air embolisms
Why doesn’t the arterial PP of arteries not tell us anything about the oxygen levels?
because most of the oxygen is attached to haemoglobin in the plasma and not dissolved in the plasma (only 3ml)