Respiration 3 Flashcards
What is movement of gas proportional to
Pressure gradient
Solubility of gas in liquid
Temp
What is Dalton’s law of pressure
Pressure from a mix of gases = sum of the partial pressure from 1 gas
What is partial pressure of gas dependent on
It’s abundance in the atmosphere
If 78% of atmosphere is nitrogen what is the pp N
78%
What needs to be taken into account with alveolar air when measuring partial pressures of o2, co2 and nitrogen
The water vapour / h20
Need to measure dry gases only
What is solubility in liquid dependent on
Temp and partial pressure
In a partial pressure gradient , what happens to o2
It will move to liquid and only some will dissolve
It isn’t as soluble as co2
Why does o2 need carriers in blood
It’s lack of solubility in liquid
Why would oxygen move to the blood because of partial pressure and co2 out into alveoli
Pp o2 is lower in the blood than alveoli so moves into blood
Ppco2 higher in blood so moves into alveoli
Why can co2 easily move into alveoli
It is more soluble in liquid
Why doesn’t temp impact diffusion
It’s always at body temp
Why is large perfusion/ blood flow to the lungs better for diffusion
They run parallel to the bronchioles and close capillary to alveoli type 1 cells = reduces diffusion pathway
What is ficks law of diffusion
Flux = permeability x Conc gradient / distance
Which ficks diffusion variable can change
Concentration gradient (permeability and distance doesn’t change in blood and alveoli)
Explain the pressures which allow o2 to diffuse from alveoli into tissues
100 mmhg at alveoli vs 40 mmhg at the capillaries
O2 moves in
Capillaries now have 100mmhg compared to tissues with 40mmhg = diffusion into tissues
Explain how co2 gets from tissues due to partial pressures
46 mmhg at tissues vs 40 in blood system = diffusion into blood
46 now in blood = diffusion into alveoli due to it being 40mmhg
What is the effect of pp02 and co2 and ventilation
Hypoventilation = increased PPc02 and low ppo2 in the alveoli
Hyperventilation = high ppo2 in the alveoli and low ppco2 (more removed)
What is the therapy called used to treat low ppo2 in the lungs eg due to anemia or blood loss
Hyperbaric oxygen therapy
What does hyperbaric oxygen therapy allow
More exchange of o2 to the tissues
How does emphysema cause lack of exchange due to lack of diffusion
Depletion of alveoli, not many alveoli decreases SA for gas exchange
Which 2 ways does restrictive fibrosis decrease diffusion
Reduces alveoli permeability by increasing its thickness (affect in ficks law)
Also lack of elastic on lungs causes lack of lung compliance and ventilation
How does edema increase diffusion distance
Produces fluid in the interstitial space
This means there’s a lack of o2 gradient because it’s not as soluble in liquid as co2
How does asthma affect gas exchange / diffusion
Obstruction to ventilation decreases ppo2 in the system
Low FEV1
Explain the levels of perfusion vs ventilation at the base and top of lungs
At base of lungs there is more blood flow than ventilation
At top of lungs too much ventilation and not enough perfusion
What does lack of ventilation at base of lungs cause
Lack of oxygenation to match the large blood flow
What does high ventilation and low perfusion st top of lungs cause
Dead space (air removed before exchange)
What would affect ventilation at the top of lungs
Posture and rate of ventilation
Upright causes high in top of lungs
Ventilation perfusion matching allows levels to be at ….
0.9-1
How is lack of ventilation at base meaning lack of oxygenation of blood overcome
Hypoxic pulmonary vasoconstriction
What does hypoxic pulmonary vasoconstriction do
If low po2 is sensed eg in base of lungs then vasoconstriction allows redirection of blood to other areas of high p02
What happens when po2 is increased in alveoli
Vasodilation of vessels / arterioles
What do bronchioles respond to in hypoxic pulmonary vasoconstriction
Pco2 levels in the blood
What happens when there is low pco2 in blood
Bronchioles will constrict as exchange doesn’t need to happen
When do bronchioles vasodilate
When pco2 is too high in the blood ie 46 mmhg
Needs exchanging out of body
What is Henry’s law
At constant temp, the amount of gas dissolved in liquid is dependant on the solubility and the partial pressure of the gas
