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What is the best way to increase Alveolar Ventilation?
Increase the tidal volume
How much CO2 do we produce per min?
what percent of Alveolar ventilation is this?
What is the partial pressure of CO2 in the Alveolis?
The partial pressure in the alveoli is equal to the sum of?
- how can we increase alveolar O2 PP?
- all the partial pressure of the gases.
- - increase the Alveolar pressure and the proportion.
T/F water vapor pressure does not change PAO2 concentations largely?
It does NOT change bc it is basically a constant
A change in what Alveolar gases Changes the proportion of Alveolar O2?
What are Four factors that result in a change in PAO2?
- Alveolar Pressure
What is the Respiratory quotient?
Normal Respiratory Quotient ration?
- Ratio of Amt of CO2 produced/O2 consumed during metabolism.
What gas equation answers the question of how much PAO2 alveolar conc?
Alveolar gas equation PAO2 = PIO2 - 1.2(PaCO2)
Explain alveolar equation?
Takes the Inspired air concentration and subtracts the amount of O2 being absorbed, which is 1.2 times the amount of CO2 being produced. thats why you x by 1.2 to give you the amount of o2 being absorbed. subtract that amount and and you will know what the alveolar PAO2 pp is.
Why is Alveolar Air equation important?
Alveolar PO2 and CO2 conc. are directly or inversely proportional?
- Tells us PAO2 pp
- Tells us if lungs are transferring O2 into blood
- Tells us estimate about what PaO2 should be
- - If difference bt the 2 incleases = lung blocking diffusion
When using the alveolar PAO2 equation, what respiratory quotient should be used for FI02 > 60%?
- 1.0 instead of 1.2
- - dt nitrogen washout, PaO2 and PAO2 ratio is slightly off.
doubling alveolar ventilation will do what to PACO2 and what will it do to Oxygen?
- Decrease by half
- Increase, but not by double bc Atm O2 pp is fixed at concentration at 150mmHg (subtracted vapor pressure)
What is a quick way to approximate PAO2 concentration?
FiO2 x 6
What are the assumptions that the alveolar O2 calculation does not factor?
- PB changes throughout the day
- FIO2 often not a precise measurement
- PAO2 does not always equal PaO2
- Resp Quotient is not always 0.8
- Water Vapor Pressure changes with body temp
What does the AaDO2 gradient tell us?
What is another name for it?
Why is the PAO2 equation important when figuring out the Aa gradient
- Tells us the adequacy of O2 transfer from the atmosphere into the blood.
- Alveoli-Arterial Oxygen Difference
- Calculating PAO2 is necessary bc you cant measure PAO2 with a machine. So with this PAO2 calculation, you can now have the advantage of knowing the gradient. You can get the PaO2 from the blood gas, but PAO2 must be calculated
How do you calculate A-a Gradient? What is a normal A-a gradient?
What is the primary deteriminate of increased A-a gradient?
T/F PAO2 must AlWAYS be Higher than PaO2
- PAO2 - PaO2
- 5-15 mmHg
- V/Q mismatch
Normal A-a gradient will be less than 10-15mmHg difference. If breathing 1oo% fio2, it can be higher? T/F
A-a gradient is age dependent?
However, is Alveolar O2 conc. age dependent?
What is the cause of increase Aa gradient then?
- True - 10-110mmHg
- True - 1mmHg increase per decade of life
- NO - Depends on FiO2, PB, and PaCO2, Rquo.
- V/Q mismatch
What is a way to calculate PaO2 based on age?
PaO2 ~ = 100 - (Age x 0.4)
what is a way to calculate A-a gradient
A-a ~ = (Age/4) + 4
Besides the A-a gradient, what is another way to calculate V/Q mismatch?
- PaO2/FiO2 ration
- normal =480
- Deficit = <300
- ARDS = <200
What are alveoli characteristics in the base of the lungs?
smaller transpulmonary pressure, more compliant, less volume, Higher blood pressure, less resistance,
Gravity affects Ventilation and perfusion equally?
False. Thats why you see a greater V/Q increase compared to the mismatch at the base of the lung. 3.5apex to 0.6base, 1.0 close to hilus
What does a V/Q mismatch of 0 cause?
What is the cause?
- Right to left shunt bc there is no gas exchange. Blood moves by alveoli and no gradient is equilibrated. Alveolar conc = Blood tension
- - No Ventilation
Ventilation with no perfusion = increased or decreased mismatch?
Alveolar PP = ?? in this state.
Increased mismatch = alveolar dead space?
What does decreased mismatch cause?
- increased to infinity
- PA = Atmospheric PP
T/F - Hypoxia may occur with normo, hypo, or hypercapnia?
What is normal PACO2 to PaCO2 gradient?
If both CO2 and O2 gradient is normal, then it is a ventilation problem.
If either gradient is abnormally high, it is a V/Q mismatch.
What does HPV hypoxic Pulmonary vasoconstriction protect from?
Right to left shunt
What is the first line of defense against hypoxia?
Collateral ventilation - easier to redistribute air vs blood.
What are factors that inhibit HPV?
- Volatile agents
- increase PVR