Exam 3 Flashcards
How to solve for the concentration of a gas? Using partial pressure and total pressure
The fractional concentration of the gas = Partial pressure of the gas / total pressure of all gases
Example: Oxygen
149.0 / 713 = 0.21. <—— humidified gas! Taking humidity / displacement into account
159.0 / 760 = 0.21 <——- This is dry air!
FOR OUR CLASS:
149 / 760 = 0.196 <—— the 760 is what we will use for our class!
^713 would give us numbers that line up but for our class we use 760 as the total pressure
This is just rearranging: PIO2 = FIO2 (Pb - PH20)
Please watch lecture 3/6 13:10 for clarity
For our class, we are always going to use _____ mmHg for the total pressure when trying to find the concentration of a gas in the lungs!
760 mmHg!
How to figure out the concentration of nitrogen in lung air
569 / 760 =0.749 –> 74.9%
If we look at air in the lung right now, it should have a nitrogen concentration of about 75% if we take into account humidity being a portion of total air
Normal end tidal CO2
40 mmHg
For the Fowler’s test: On inspiration, air that’s in the anatomical dead space should have ____% nitrogen in it. Why?
0%
because there wasn’t any nitrogen in the inspired source.
The Fowler’s test is a cheap easy way to find out..
how much anatomical dead space someone has.
In the Nitrogen washout test, The greatest reduction in nitrogen concentration will be on the _____ breath. Why?
The greatest reduction in nitrogen concentration will be on the first breath because that is when there is the most nitrogen in the lungs to be displaced / diluted.
The Nitrogen Washout test is halted when the patient is expiring nitrogen at a concentration of _____
~2.5%
Typically, an abnormal Nitrogen Washout result is if it takes greater than __ minutes for nitrogen concentrations to get to ___%
-7 minutes
-2.5%
However, in a healthy person is should only take about 3.5 minutes!
Therefore, 7 minutes is abnormally abnormal because its really 2x what “normal” is in a healthy adult
The peak expiratory flow rate would be kind of the product of these two things:
-Elastic recoil pressure (being high)
-Pleural pressure (being positive to push air out)
The elastic recoil pressure in a healthy lung at total lung capacity, is about ___ cmH20
+30 cmH2O
The combination of the constriction of these two accessory muscles will give us a positive pleural pressure during forced expiration
-abdominal constriction
-internal intercostal constriction
The combined action of abdominal constriction and internal intercostal constriction should give us a pretty positive pleural pressure.
If you have a beaker of solution and it is surrounded by an environment of oxygen and you give it time to equilibrate, will the enviornmental or solution’s PO2 be higher?
They will be equal!
Oxygen is not very soluble, so we’re not going to have a great quantity of oxygen in solution→However, we should have about the same PO2 in the solution as what we have in the environment→Again, assuming we give the beaker of solution a long enough period of time to equilibrate with what’s in the environment.
The solubility of oxygen per dL in aqueous solution is ____
0.003 mL O2 / mmHg PO2
This means that for each mmHg I have, i can push 0.003 mL of oxygen into solution!
The solubility of oxygen per mL in aqueous solution is ____
0.00003 mL O2/ mmHg PO2
How much oxygen is dissolved in a solution with a PO2 of 100 mmHg?
How much = quantity of gas → will always be a volume!
100 x 0.003 =0.3 mL of O2 / dL of blood
How did we get those numbers?
The 100 mmHg is our PaO2
The 0.003 is our solubility of oxygen
Normal PvO2
40 mmHg
Normal PaO2
100 mmHg
How much oxygen is dissolved in a solution with a PO2 of 40 mmHg?
40 x 0.003 = 0.12 mL O2 / dL of blood
How did we get those numbers?
The 40 mmHg is our PvO2
The 0.003 is our solubility of oxygen
When you are trying to figure out how much oxygen is dissolved in solution, you have to know two things:
- PO2 of the solution
- The solubility coefficient
The solubility coefficient never changes!
If we have a solution and we want to figure out how much dissolved oxygen we have, we just multiply the ___ times the ______
PO2 x solubility coefficient
Each deciliter of blood has __ of O2 dissolved in it.
0.3 mLs
We need about ___ mLs of O2 each minute to stay alive
250