Gas Transport 3 Flashcards
Compared the components of inspired (fresh) air vs expired (stale)
Where does gas exchange occur in the lungs
Between the capillaries and alveoli
How does gas exchange take place in the lungs
Through passive diffusion moving from high to low partial pressures
What is partial pressure
Pressure which any gas exerts whether alone or mixed with other gases
Gas partial pressure is proportional to
fractional concentration (aka # of molecules
When is there greater or less pressure, with more or less molecules
Less molecules = less pressure
More molecules = more pressure (more collisions
What is total (dry gas) pressure (aka Daltons Law)
What components make up the ambient pressure of our atmospheric air
Explain atmospheric pressure vs altitude
Pressure is higher at sea level than at increased altitude
What is the pressure at sea level
760mm hg (1 atmosphere) at 0 degrees celsius
Name 6 characteristics of barometric (air pressure)
**Note not less oxygen at higher altitudes (still 21% no matter the level). There is just less pressure at higher altitudes.
How to calculate partial pressure of gas
What is the partial pressure of O2 at the top of Mt Everest where barometric pressure is 253mmHG
= 0.21 x 253mmHg = 52mmHG
Water vapor is
Water in its gas phase (means it has a partial pressure)
Partial pressure of water vapor varies with
Temperature alone and does not depend on barometric pressure. Pressure increases with increasing temperatures. (at body temp it is 47mmHg
What are the gas pressures inside the body
**Note 713 x 0.21 = partial dry gas (150mmHg) in slide
Gas diffusion
What layers do oxygen and carbon dioxide diffuse through between alveoli and red blood cell
What are the 3 pulmonary diffusion phases
What is Fick’s Law
Flow of gas (V) is proportional to alveolar surface area multiplied by the diffusion constant multiplied by driving pressure all divided by tissue barrier thickness (a = proprotional)
Gas diffusion is proportional to
Is gaseous diffusion greater in oxygen or carbon dioxide
Oxygen because it has a smaller MW
What impairments affect gas phase diffusion
- Emphysema increases alveolar diffusion distance
- Airflow obstruction causes collateral channel to be used prolonging gas transit time (see slide)
Does CO2 or O2 have greater membrane diffusion
CO2 because it has greater solubility = changes to liquid fastes
Explain this image
Oxygen and carbon dioxide exchange until their partial pressures are equalized. PPO2 when it comes in is 40mmHg and when it leaves its 100mmHg. In a healthy lung it takes 0.25 seconds for carbon dioxide and equilibrium to equalize both at rest and during exercise. Therefore, when there is a respiratory disease, rate of diffusion is slow and equilibrium may not be achieved during exercise, but at rest they may be fine because they have so much buffer time (0.75s) for oxygen to get into red blood cells even if diffusion is slowed down. During exercise, there is no buffer time because they take 0.5s to have their oxygen equalize when in actuality they need to be at a rate of 0.25s (like a healthy lung). As a result not all of their red blood cells are becoming oxygenated and that is where we will first start seeing impacts with respiratory disorders is in exercise.
