Gas Exchange In The Lungs Flashcards
What is ficks first law of diffusion?
Flux of molecules across a barrier depends on the permeability of the barrier to these molecules
What are some of the features of the solubaility of respiratory gases?
CO2 is much more soluable than O2, and diffuses into liquid much faster than CO2
What are the layers between gas and the blood?
5 cell membranes, 3 lars of cytoplasm , 2 layers of tissue fluid.
What is the distance between the gas and blood?
Is approx 0.6 um, however, the distance decreases during ventiliation as the lung distends
What changes in the gas concentrations as gases move towards the alveoli?
Proportionally the concentration of gases drop, as the gases are diluted as we move towards the alveoli
How does the concentration of O2 in the alveoli compaed to the external environment?
It is lower, due to the continious diffusion of oxygen across the alveoli, and the diluting affect of CO2 entering the alveoli, as it travels the opposite direction to O2
Ywhat are the factors affecting the rate of gas diffusion through the respiratory membrane?
Thickness of the membrane, surface area of the membrane, diffusion coefficient in the substance of the gas, pressure difference of the gas between the two sides
When is the thickness of the membrane increased?
Increase as a result of the oedema fluid in thee intersitial space.
What could reduce the surface area of the lung?
Decreased by the removal of an entire lung, and emoysema results in the alveloi combining
How does fibrotic lung disease impair gas exchange?
Thickened alvelor membrane slows the gas exchange,
How des pulmonary oedema cause a diffusion impairment?
Fluid in the intersispital space increases the diffusion distance
What is the dead soace?
The last air that stays in the airways and is first aiout and therefore never reaches the alevoli
What is the serial dead space (anatomical)
The volume of the airways where no gas exchange takes place
What is the distrubitiveq space?
Some parts ot he lungs are not airways and do not support gas exchange, due to dead or damaged alveoli or with poor perfusion, adn therefore add to the serial dead space and the total is the physiological dead space
How do you calculate the rate of alveolar ventilation rate?
Dead space must be completely filled with air at each breath, and therefore the dead space ventilitation rate is the dead space vol x resp rate, normally 14-16 breaths/ minute and you subtract this from the pulmonary ventilation to get AVR
