Exam 2 - Lecture 3 Flashcards
The top of the lung has what kind of blood flow?
Pulsatile
Zones 2 and 3 for entirely healthy people will have what kind of blood flow
continuous
How many west zones are there?
4
What is gravity dependence?
Gravity makes blood weigh more, which causes the vessels to open up and become distended.
When someone say an area of the lung is dependent, they’re referring to
the area closest to the planet
When alveoli pressure is 0 cmH2O, this means its relative to pressure ______
outside of the body
What holds the alveoli open?
Intrapleural space being -5cmH2O
Later lecture he said it’s more related to volume???? Lmao whatever
What are our alveoli made out of and what does this do?
elastic tissue, causes recoil pressure.
Recoil is ____ to intrapleural pressure.
opposite
e.g. If alveoli is 0, and intrapleural pressure is -5, then recoil pressure is +5.
If diaphragm contracts and causes intraplueral pressure to become -6cmH2O, what happens to alveolar pressure?
alveoli hasn’t expanded yet, so its pressure is now -1 because the elastic recoil pressure is still only +5.
Once alveoli expands from intrapleural pressure decreasing, the expansion of the tissue does what to recoil pressure?
Increases it.
e.g. intrapleural is now -6, but the recoil pressure has increased because the alveoli are stretched, so its now +6 and alveoli pressure is back to 0, but now filled with air.
When the diaphragm relaxes, and intrapleural pressure is now back to -5, what does this do to alveoli pressure?
Makes it +1, because the recoil pressure is still +6 while it has air in it.
What is the delta P that “empties the lung”?
The pressure in the alveoli vs the pressure outside the body.
What is the equation to figure out alveolar pressure?
PA = PIP + PER
e.g. 0 = -5 + 5
What’s another name for elastic recoil pressure?
Transpulmonary pressure
How can we solve for elastic recoil pressure?
PTP = PA - PIP
What is the force that gets the air into the lung?
Transpulmonary pressure
Sounds counterintuitive, but it’s the pressure that’s available to fill the lung, and this is true regardless of type of ventilation. Yes, even PPV.
If transpulmonary pressure goes up, then what happens to lung volume?
Goes up.
Inverse is true as well.
True/False: Pulmonary vascular resistance mostly stays the same
False
Constantly changing!!
What is the biggest influence on pulmonary resistance? What’s the other one mentioned?
Gravity
Also mentioned lung volume
The more air in the lungs, the higher or lower PVR?
Higher
What other structure can affect PVR? (not blood flow/heart)
Muscles
The lowest possible air we can have in the lungs is
RV
When is PVR the lowest during the respiratory cycle?
In between breaths, FRC.
Compare the increase in PVR between RV and TLC.
Both increase PVR, but RV has a greater increase on PVR than TLC if we exhale our ERV.
What’s the highest possible PVR?
Exhale until we only have RV.
What does the negative pressure do to the large vessels in the lungs?
Pulls them apart, decreases extraalveolar resistance
The diameter of the vessels in the lungs are reliant on
negative pleural pressure
more negative, more wide.
Large blood vessels in the lungs are
Extraalveolar
Alveolar vessels in the lungs are typically referred to as
capillaries
At low lung volumes, extraalveolar resistance is
really high
(less negative intrapleural pressure, not pulling them open as much)
How do we breathe out ERV?
Making pleural pressure much more positive
What happens to the alveoli capillaries during inhalation?
expanding alveoli causes the capillaries to lengthen and INCREASE resistance.
Alveolar vascular resistance during _____ lung volumes
High
Inverse to extraalveolar
Total PVR is ALWAYS the sum of
alveolar and extraalveolar vascular resistance.
If we have something that changes our _______, it will adjust PVR graph by a lot.
FRC
such as COPD or PPV
What happens to PVR when cardiac output increases?
Decreases
Why does PVR decrease with increased right heart output?
Vasculature is very compliant
What is distension?
As the blood vessels get more full because they’re so compliant, they become wider and larger.
Can happen from blood or air(?? he said this, doesn’t make sense)
When we put more blood through lungs, they _______ blood pathways. How does this aid in decreasing PVR?
Recruit
More routes for blood that can flow.
If right heart CO decreases, why can this become a vicious cycle?
PVR will increase, and if right heart CO decreases because it’s failing, then it now has to pump against a higher PVR on top of already struggling.
How does viscosity affect PVR?
Increases it
What’s the relationship with sympathetic stimulation and PVR?
Increased stim will increase PVR. Also, the lungs act as a reservoir for blood, so the increased PVR will help push some of that extra blood out for the body to use.
What is special about histamine in lungs?
It acts as a vasoCONSTRICTOR in the lungs, inverse to what happens systemically.
At sea level, gas pressure is how many mmHg and torr?
760
What is 760 torr/mmHg equal to in ATM?
1 ATM
What is atmospheric pressure? how does it compare between sea level and high altitudes?
Product of gravity and everything above us in the atmosphere.
That’s why pressure is higher at sea level and lower at high altitudes.
You need two things to get gas into the body
GAS (obviously, fucking dipshit) and pressure
Nitrogen (N2) has a concentration fraction/percentage of ___ and this indicates what?
79
79% of our atmosphere is nitrogen.
Other than oxygen (21%) filling the rest of the atmosphere, there are small/negligible amounts of ?
CO2(0.4%, or .004), methane, etc.
How would Oxygen concentration in the atmosphere be denoted by fractional?
F [O2] = 21/100
What is a partial pressure?
individual pressure from one of the gases
e.g. Nitrogen is 79% of 760 mmHg, so its partial pressure is ~600mmHg
How is partial pressure denoted for nitrogen?
PN2 = 600mmHg
How does the partial pressure change with altitude changes? Give me an example with Nitrogen at 700mmHg atmospheric pressure.
the PERCENTAGE never changes!!!!
The partial pressure number does.
e.g. N2 is 79%, and pp 600mmHg at standard total atmospheric pressure of 760mmHg
If altitude changes and total atmospheric pressure is now only 700, then N2 is still only 79% of that, but now 553mmHg.
What’s the partial pressure of Oxygen at .79 ATM?
First, convert atm to torr/mmHg
760 x .79 = 600.4
Torr/mmHg = 600.4
600.4 x .21 (O2) = 126.084 mmHg
The partial pressure of oxygen in this situation is 126.084
How does adding water vapor affect gasses?
Gasses are displaced by water vapor and it dilutes it.
What is the main gas that gets displaced by water vapor?
Nitrogen, since it’s the most dominating presence
Partial pressure for water vapor is ____. What is special about it?
47mmHg
it is not affected by altitude!! it is ALWAYS 47mmHg!!!!
How do you figure out the PIO2 in the presence of water vapor? What is PIO2?
Pressure of inspired oxygen
PIO2= FIO2 (PB - PIH2O)
comes out to PIO2 = .21 (760 - 47) = 149mmHg at sea level
So if someone is at an atmospheric pressure of, say, 473mmHg, just use 473 instead of 760. 47 never changes!!! EVER!!!!
What is the pressure of O2 inspired during the beginning of the breath? CO2?
149 and 0 (technically more than 0, but its negligible, won’t count it)
Fresh gas combines with gas in lungs. What’s the gas pressures in the lungs from venous blood?
O2 = 40mmHg
CO2 = 45mmHg
What’s the PO2 and PCO2 of venous blood?
40 and 45mmHg
How many mL of fresh inspired gas actually gets combined with the existing air in the lungs? (and how much existing air?)
if 500mL is inspired, we only get about 350mL to get mixed, with 150mL being dead space.
350mL combines with 3000mL of pre-existing gas that has a different concentration of gases.
What’s the gas pressures of O2 and CO2 once gas exchange happens? These are our normal levels for what?
104mmHg and 40mmHg
Normal Alveolar gasses of PAO2 and PACO2
What happens to alveolar nitrogen during exchange?
Same as normal because we don’t actually really exchange it, its still 569mmHg (he said 600mmHg earlier???)
How much CO2 per O2 is unloaded during gas exchange?
The same rate.
If CO2 and O2 are exchanged in equal amounts in the lungs, why does O2 change so much (40 -> 104) but CO2 hardly changes (45 -> 40)?
O2 binds to hemoglobin which allows a large amount to be carried within a small volume.
CO2 is highly soluble, and exists in multiple forms, spreading out its concentration, therefore creates a lower partial pressure.
What’s the total pressure of PAO2 and PACO2?
144mmHg
(104mmHg + 40mmHg)
How is PAO2 written out?
Alveolar PO2
