Section 5 - Lecture 6 Flashcards
What must be subtracted from total barometric pressure when calculating the pressure of gas in alveolus and trachea?
Water vapor pressure
True or False? All gas is fully saturated.
T
Factors affecting diffusion and transport of gas:
surface area, partial pressure differences, advantageous diffusion properties
Graham’s Law:
the rate of effusion of a gas is inversely proportional to the square root of the mass of its particles
how much faster does CO2 diffuse across the membranes than O2?
20 times faster than O2
Conductance is affected by:
surface area, diffusion constant, and pressure difference
True or False? O2 and Co2 exchange in the lungs is perfusion limited.
T
Is cardiac output diffusion limited?
yes
Do gases bound to hemoglobin exert a pressure?
no
CO2 in capillary blood remains at zero but is
high in the blood, low solubility gas moves from the alveolus to the blood without restriction
Normal PaO2:
100
When will it take longer for the alveoli to reach its full volume?
increase resistance or decrease compliance
Partial pressure of any gas, either in the alveoli or in the blood =
the fractional concentration of the gas (F) times the total barometric pressure (PB)
What is barometric pressure?
760 mm Hg
What is FO2 for inspired air?
0.21 (fractional concentration)
What is the partial pressure of inspired O2?
160 mm Hg
Pressure of oxygen in trachea:
150 mm Hg
Pressure of N2 in trachea:
563 mm Hg
Do gases that are soluble or insoluble in blood diffuse faster?
insoluble (check)
Are insoluble gases in the blood perfusion limited?
yes
List insoluble gases:
anesthetic gases, NO
Are gases with low solubility in alveolar-capillary membrane, but high in solubility in the blood because of affinity to hemoglobin diffusion limited?
yes, i.e. O2 and Co2
Duration for equilibrium of O2 and CO2 to be reached:
0.25 seconds, even in high blood flow
Is there a greater uptake of O2 in ml/min or elimination force Co2 in ml/min in respiration?
uptake (25% more)
Normal respiratory exchanges ratio:
0.8
Do we inspire more N2 or O2?
N2
Pressure of H20 at 37 degree C in the lungs:
47 mm Hg
How much of a pressure drop in CO2 is there when passing through the lungs from pulmonary artery to pulmonary vein?
6 mm Hemoglobin (46 -40 mm Hg)
How much of a pressure increase in O2 is there when passing through the lungs from pulmonary artery to pulmonary vein?
60 mm Hg
How much pressure of CO2 is added via metabolism?
6 mm Hg
What is the alveolar time constant related to?
How fast blood moves through capillaries
Time constant =
airways resistance X compliance
Do alveolar units with long time constant fill and empty quickly or slowly?
slowly
Will an alveolar unit with increased compliance fill and empty at a slower or faster rate?
slower (take longer)
Why does an increase in compliance lead to longer filling and emptying time in the alveolar units?
more gas goes to upper alveoli, more time for gas to equilibrate bw upper and lower parts of the lungs, takes longer to expire the same amount of air
Normal inspiratory and expiratory times:
in: 2 seconds, out: 3 seconds
How much time is require for the alveoli to fill almost completely?
2 seconds
Is carbon monoxide diffusion limited?
yes
2 factors that will decreases perfusion across lungs
decreases surface area or increases thickness,
Will exercises decrease or increase transit time?
decrease
