Exam 3 - Lecture 1 Flashcards
What is the partial pressure of nitrogen after gas exchange?
Around 569mmHg
How do we find the % of nitrogen in expired lung air?
569 divided by 760 = ~75%
What is % of oxygen in the atmosphere?
79-80%
Why is nitrogen % lower in lungs?
Due to the dilution of water vapor, that’s why 75% is more accurate for expired lung air.
What are the units for nitrogen (or any gas) concentration?
No units, just 75%.
The units cancel each other out in the division.
Does 75% nitrogen reflect alveolar gas or fresh inspired gas?
Alveolar
The transition between dead space and alveolar gas isn’t a hard boundary, there’s a _____. This is especially true for _____ test.
Gradual mix zone; Fowlers test
For a fowlers test, its reading what gas?
EXPIRED gas of nitrogen with nitrogen meter
What are the unit the capnograph in fowlers test measures?
Either mmHg or just %.
What are the sources needed for fowlers test?
Patient, nitrogen meter, 100% O2
How much do you tell patient to breathe in during fowlers test?
1L instead of 500mL
The nitrogen detected during the fowlers test comes ONLY from
the lungs
During fowlers test, on the last portion of inspired breath, is the air that ends up in ______, and it should have how much nitrogen in it?
Anatomical dead space; ZERO nitrogen
The first portion of expiration of breath during fowlers test should have _____ nitrogen
zero
during fowlers test, as you continue to expire more, the air from the deeper portions will begin to have ____
nitrogen
How does fowlers test assess for anatomical deadspace?
During a fowlers test, you inspire 100% O2. Any nitrogen that comes during expiration, will had to have come from lungs, after you expire anatomical deadspace (which should have zero nitrogen).
Therefore, the amount of volume you expire before nitrogen is detected, is your anatomical deadspace.
What’s the specific spot on graph of fowlers test we should focus on to determine amount of anatomical deadspace?
midpoint of transitional phase, should be 150mL
What is it called when nitrogen begins to level out on graph of fowlers test?
Alveolar plateau
What is a cheap and easy way to determine anatomical dead space?
Fowler’s test
What is alveolar plateau dependent upon?
How deep the inspiratory breath was.
What is the nitrogen washout test?
Hook the patient up to 100% O2 and a nitrogen meter.
Assess how many breaths it takes them to breathe out all of their nitrogen. The results can determine pathophysiology depending upon how many breaths it took.
During nitrogen washout test, what is the percentage of nitrogen in the first breath?
80%
What should the % of nitrogen be on the 8th breath during nitrogen washout test?
~15%
When is the greatest reduction in nitrogen concentration during nitrogen washout test?
after the first breath
What % do they halt the nitrogen washout test?
once it reaches ~2.5%
In a healthy 20 year old patient, the nitrogen washout test should take ______
way under 7 minutes
Then said a healthy person should take half the amount of time… 3.5 minutes?
A normal healthy patient should get to 2.5% by ____ breaths.
30
Per the “unhealthy” patient chart, how many breaths did it take them to get to 2.5%?
What else is noted about the chart?
60.
It’s inconsistent and scattered due to air being directed into different places with each breath.
What are the 2 main reasons it takes a person with COPD longer to complete nitrogen washout test?
So much more air in their lungs already + difficult to expire = longer to dilute
What size are the breaths on flow volume loops according to Schmidt?
“Very large breaths” lol (VC)
What is the measured flow rate (units) in flow-volume loops?
L/s on the Y-axis
What is the x-axis on flow-volume loop?
lung volume
What is the flow volume loop displaying?
How fast you breathe in and out at certain lung capacities throughout the between TLC and RV
What’s the max flow rate of air on the flow-volume loop?
10L/s
What part of inspiration has the fastest flow rate?
halfway point of inspiration
What part of expiration has the fastest flow rate?
faster at the beginning, then tapers off
