Lecture 18: O2 and CO2 Exchange Flashcards
What is the respiratory minute volume?
The amount of air we breath in and out per unit time, the rate of air inhaled and exhaled
What is the equation for respiratory minute volume?
What are the units for respiratory minute volume?
VE = VT x f
L/min
What does VT stand for?
What does this mean?
What are the units?
tidal volume
the amount of air inhaled per breath (ie. breathing strength)
L/breath
What does f stand for?
What does this mean?
What are the units?
respiratory rate
breathing speed
breaths/min
What is dead space?
the volume of inhaled air that remains in the bronchial tree that does not reach the alveoli
What is the alveolar ventilation?
What are the units?
the amount of air that reaches the alveoli
L/min
What is the equation for alveolar ventilation?
VA = (VT - VD) x f
Which is lower, respiratory minute volume or alveolar ventilation?
alveolar ventilation
What is Dalton’s Law?
The pressure of a mixed gases is the sum total of the pressure of each individual gas
Describe the composition of the dry inhaled air in order
Majority is nitrogen
Oxygen
water vapor
CO2
How has the composition of air changed between the dry inhaled air and the saturated air in the alveolar sac?
The nitrogen has dropped slightly
The oxygen has dropped slightly
The carbon dioxide has increased a lot but still less than O2
The water vapour has increased a lot but still less that O2
Why does the O2 level drop in the alveolar air?
Because it is lost to the bloodstream
Why does the CO2 level increase in the alveolar air?
Because it enters from the bloodstream
How has the composition of air changed between the saturated air in the alveolar sac and the saturated exhaled air?
The nitrogen has dropped slightly
The O2 has increased
The CO2 has decreased
The water vapour has remained the same
Why does the O2 level increase in the exhaled air compared to the alveolar air and how does this compare to the inhaled air?
- because it mixes with the oxygen that remains in the dead space that never made it to the alveoli
- it is decreased compared to the inhaled air
What three factors determine the rate of diffusion across the blood barrier?
- surface area of the membrane
- thickness of the membranes
- pressure difference between the two sides
How does the surface area affect the rate of diffusion?
increased surface area increases the rate of diffusion
What is a condition that shows that surface area affects the rate of diffusion? How does it affect the rate of diffusion and why?
emphysema is a disease which causes dilation of the alveolar spaces and alveolar walls
there is a reduction in the surface area which means there is less contact between the air and the capillaries, so O2 exchange is greatly reduced
How does the thickness of the membrane affect the rate of diffusion?
Why?
thicker membrane decreases the rate of diffusion because there is a greater distance to travel
What is a condition that shows that membrane thickness the rate of diffusion? How does it affect the rate of diffusion?
pulmonary fibrosis which thickens and scars the alveolar membranes
this decreases the rate of diffusion
What three things determines the pressure difference between the capillaries and alveolar sacs?
- atmospheric oxygen
- alveolar ventilation
- blood oxygen
How does atmospheric oxygen affect the pressure difference?
Increased atmospheric O2 increases the alveolar oxygen
What affects the alveolar ventilation (which then affects the pressure difference)?
tidal volume and respiratory rate (if these increased, alveolar ventilation increases as VD stays pretty much constant)
What factor affects the O2 in the blood (which then affects the pressure difference)?
The exercise level
Describe the O2 level in the blood when at rest and how this affects the amount in the alveoli
there is reduced O2 consumption so there is increased O2 in the venous return so there is less of a need to transfer O2 to the blood from the alveoli
Describe the O2 level in the blood when exercising and how this affects the amount in the alveoli
there is increased O2 consumption so there is less O2 in the venous blood and therefore more O2 is pulled from the alveoli into the blood
The process of diffusion and determining factors also work for CO2
TRUE OR FLASE?
true
exchange stop when the _________ is the same
pressure
Which is lower, alveolar ventilation or respiratory minute volume and why?
alveolar ventilation is lower due to dead space
