Respiratory Physiology 5 - O2 and CO2 Exchange Flashcards
This is the amount of air you can breathe per minute.
Respiratory minute volume
This describes the inhaled air that never gets to the alveoli and so cannot undergo gas exchange.
Dead space
Dead space is approximately how many mL of air?
about 150 mL (it usually just fills the upper airways and of no use to gas exchange)
This describes the amount of air that can get to the alveoli.
Alveolar ventilation
What determines the alveolar ventilation?
Tidal volume - dead space * respiratory rate
Essentially breathing strength and breathing speed
What is the equation for respiratory volume per minute?
Respiratory volume = tidal volume * respiratory rate
Gas diffusion depends on what?
Partial pressures
Dalton’s law states that the pressure of a mixtures of gases is?
Equal to the pressures of each individual gas.
When a gas can exert its own individual pressure in a gas mixture, this pressure is known as?
Partial pressure
True or false. Alveolar ventilation is affected by the amount of dead space in the respiratory system.
True. Because remember, alveolar ventilation takes into account the amount of dead space in the resp. system.
AV = TV - DS * Resp. Rate
True or false. Alveolar ventilation is measured as a volume of air per unit time.
True
The blood air barrier is made of what kinds of epithelia?
Type 1 pneumocytes => simple squamous epithelium (provides great SA for gases to diffuse across membrane
Capillary endothelium
Alveolar endothelium
What law describes the movement of gases across membranes between the alveoli and the capillaries?
Fick’s Law of Diffusion
According to Fick’s Law of diffusion, what are the 3 factors that determine the rate of diffusion?
1) surface area of the membranes
2) thickness of the membrane
3) pressure difference between 2 sides because remember, gases move down their pressure gradient
Diffusion constant depends on what 2 things?
Solubility and molecular weight
- when something has a low solubility, it doesn’t have the ability to diffuse into the bloodstream or circulation (like Nitrogen)
- when remembering what determines diffusion constant, just think about what PROPERTY of gases are important in enabling this process.
True or false. The low density of the capillaries creates lots of surface area for gas exchange.
False; capillaries are in higher density because it creates lots of available areas for gas exchange to occur.
More capillaries present = more gas exchange can occur
This is a disease characterised by dilation of the alveolar spaces and destruction of the alveolar walls. It is an example of chronic obstructive lung disease.
Emphysema.
Reduction in surface area means?
Less contact between air and capillaries so oxygen exchange would be greatly reduced
or less interaction between air and capillaries so less amount of oxygen can be exchanged.
This structure is very important in separating two things together; it is mostly comprised of the alveolar and capillary walls.
Blood Air Barier
Thickness of the membrane and rate of diffusion are inversely related to each other.
This means that as the thickness increases, the rate of diffusion?
Decreases. Because there’s more space in between the alveolar air and blood - so more distance for oxygen to travel through.
Thickening and scarring of the alveolar walls can arise from?
Chronic inflammation or exposure to industrial chemicals.
The main factor that affects the rate of diffusion is:
Pressure gradient
How would O2 be moved from the alveoli into the pulmonary capillaries? (what would the pressure gradient look like?)
Remember: gases move down their concentration gradient. So in order for gas from the alveoli to move into the pulmonary capillaries,
The pressure inside the pulmonary capillaries must be lower than the pressure outside in the alveoli.
How would CO2 move from the pulmonary capillaries and into the alveoli? (what would the pressure gradient between the two look like?)
The pressure must be higher in the pulmonary capillaries (so the pressure in the alveoli would be lower) so the air can move from the capillary out to the alveoli.
Alveolar partial pressure of Oxygen depends on what 3 things?
Partial pressure of oxygen in the air
Alveolar ventilation (amount of air inhaled per minute)
Oxygen consumption - blood oxygen
*mainly oxygen consumption and alveolar ventilation
Why doesn’t the atmospheric PO2 affect the alveolar partial pressure as much?
Because the atmospheric PO2 is usually constant.
What happens to the oxygen consumption and levels of O2 in the venous blood when we’re exercising?
Oxygen consumption increases
Low oxygen levels in venous blood because exercise depletes level of oxygen
What does the alveolar partial pressure of CO2 depend on?
Alveolar ventilation and CO2 production.
*atmospheric CO2 is negligible
If the pressure between the alveolar walls and pulmonary capillaries are the same, what does this mean?
There will be no movement because gas can only move down once there is a pressure gradient/pressure difference between both sides.
