3/6 Lecture Flashcards
What is dead space?
Areas is the resp system where no gas exchange occurs
In healthy individuals, dead space is mainly is what areas?
Upper airways and conducting zone
When a normal, healthy adult takes in a breath of 500 mL, how many mL’s will end up in the conducting zone?
Does this area contribute to gas exchange?
150 mL
This air does not contribute to gas exchange.
In dead space ventilation, the first ____ mL of air will mix with the air in the _______ and the last ______ mL of air will be similar to the initial air in the ________ after it’s been humdified.
350 mL
lungs
150 mL
ballon
T/F: Dead space has hard boundaries
F
There’s typically a transitional zone where the air is a mix of both dead space and areas that participate in gas exchange.
What is the formula for the partial pressure of a gas?
PIO2 = FIO2 (PB - PH2O)
What is the partial pressure of oxygen in DRY (not humidified) air?
**about 160 mmHg
**
(0.21)(760) = 160 mmHg
What is the partial pressure of oxygen in WET, humidified air?
**about 150 mmHg
**
(0.21)(760 - 47) = 150 mmHg
If we want to solve for the fractional concentration of a gas in the lung, what two things are required?
- Partial pressure of the gas
- Total pressure of the system
What is the formula for the fractional concentration of a gas?
Concentration of the gas in Lung Air =
(Partial Press. of the gas in Alveolar Gas) /
(Total Press. of Gas)
What number do we use at the total pressure when solving for the concentration of a gas in Dr. Schmidt’s class?
760 mmHg
What are the standard alveolar gas concentrations at SBP? (4)
PAO2 = 104 mmHg
PACO2 = 40 mmHg
PAN2 = 569 mmHg
PAH2O = 47 mmHg
What are the standard inspired gas concentrations at SBP? (4)
PIO2 = 149 mmHg
PICO2 = 0.3 mmHg
PIN2 = 564 mmHg
PIH2O = 47 mmHg
What are the standard partial pressures and concentrations of dry atomspheric gas? (4)
N2 = 79% & 600.0 mmHg
O2 = 21% & 159 mmHg
CO2 = 0.04% & 0.3 mmHg
Total Dry Gas Mixture = ~100% & 760 mmHg
What is the concentration of Nitrogen in expired lung air?
75%
Why is using 760 mmHg is more accurate than using 713 mmHg?
760 mmHg accounts for the water vapor displacement in the lungs
Normal we aren’t concerned with nitrogen being absorbed by the patient unless they are ________?
Deep sea diving or some other crazy condition
What is the simplest pulmonary function test?
Fowler’s test
This pulmonary function test looks at how much nitrogen is expired from the patient.
Fowler’s
During Fowler’s test, the more nitrogen coming out of the patient, the ________ the reading on the nitrogen meter.
Higher
Fowler’s Test
If the patient is breathing normal room air at a normal depth and rate, we expect the nitrogen concentration in the expired air to be around ________.
What would Levitsky’s diagram show and why?
75%
Levitsky –> 80%, he factors in water vapor
If you grab a stranger off the street and make them blow into a nitrogen meter, what would the reading be if they are a normal, healthy adult?
75%
(569 mmHg) / (760 mmHg)
A ventilator with capnography function has a toggle button that can switch between what two features?
- Partial Pressure (in the alveoli) displayed in mmHg
- Concentration displayed as a %
What are the three things needed to perform the Fowler’s test?
- A nitrogen meter
- A patient
- a source fo 100% oxygen
What are the steps to Fowler’s test?
Fowler’s Test
- The patient is breathing RA.
- Hook the patient up to a source of 100% oxygen
- Instruct the patient to take a breath that is slightly deeper than usual (a VT of 1L instead of 0.5 L, patient does NOT need to inspire to TLC but a bigger breath than normal)
- The patient inhales 100% oxygen and eventually expired and this expired lung air is analyzing
Fowler’s Test
During inspiration, the oxygen gets ____ and the concentration of oxygen is ________ due to water vapor.
humidified
slightly reduced
Fowler’s Test
What is in the first portion of inspired air?
100% oxygen that will make it all the way to the lungs. No nitrogen.
Fowler’s Test
What is in the last portion of inspired air?
The last portion will stay in the anatomical dead space. This should have 0% nitrogen because there was no nitrogen in the inspired source (100% oxygen).
Fowler’s Test
Expiration:
The first portion of expiration should have _% of nitrogen.
0%
This is air from anatomical dead space (no gas exchange)
Fowler’s Test
What is the concentration of nitrogen in the last portion of expiration?
0%
This should have 0% nitrogen because there was no nitrogen in the inspired source (100% oxygen).
Fowler’s Test
Midpoint of Expiration:
As more air is exhaled, this air starts to resemble ____________ and ________ starts showing up in the exhaled air?
lung air; nitrogen
Fowler’s Test
What part of expiration phase does nitrogen start to appear in expired air?
Midpoint of expiration
Fowler’s Test
What part of expiration does nitrogen concentration start to level out?
What does this represent?
Alveolar plateau
It represents air from the deeper parts of the lung where gas exchange occurs
Fowler’s Test
The ________ is used to measure anatomical dead space.
midpoint of the transitional phase
How much dead space should a healthy, average-sized 20 yo adult have?
What if they are taller?
150 mL
Taller = they will have more anatomical dead space
If you are ventilating someone with more anatomical dead space, what vent setting would you need to adjust to ensure proper gas exchange?
They would need larger tidal volumes
Fowler’s Test
What is the Fowler’s test best used for?
Figuring out the anatomical dead space of a patient
Fowler’s Test
What does A describe?
Volume in the dead space
Fowler’s Test
What does B describe?
When expiration begins
Fowler’s Test
What does C describe?
midpoint of the transitional phase
Fowler’s Test
What letter is used to measure anatomical dead space?
C
midpoint of the transitional phase
Fowler’s Test
What does D describe?
Alveolar plateau
Fowler’s Test
What the alveolar plateau would be depends on what?
how large the inspired breath was
Fowler’s Test
What does E describe?
Gas in the anatomical dead space being expired. 0% nitrogen!
Fowler’s Test
What does F describe?
the volume of the anatomical dead space
Fowler’s Test
How can you determine the anatomical dead space from this test?
Plot where expiration begins and where the midpoint of the transtional phase are to determine the anatomical dead space
Nitrogen Washout Test
What is the purpose of the Nitrogen Washout Test?
To analyze how even ventilation is within the lungs
Nitrogen Washout Test
If a patient is hooked up to the nitrogen metere and simply exhales, we would expect the nitrogen meter to read around _______
569 mmHg ,75% (per Schmidt), or 80% (per Levitsky) nitrogen in the air
Nitrogen Washout Test
What is the procedure for the Nitrogen Washout Test?
- Pt is hooked up to a source of 100% oxygen and a nitrogen meter
- The patient starts breathing in 100% nitrogen at normal tidal volumes and normal rates
- Each breath dilutes the nitrogen inthe lungs because the inspired gas mixture (100% oxygen) has no nitrogen in it. The nitrogen concentration in the lungs will be a little lower than it was initialy as it gets diluted.
- The test is typically halted when the nitrogen concentration in the expired air reaches around 2.5%
Nitrogen Washout Test
When does the greatest reduction in nitrogen concentration occur?
After the first breath because that’s when there’s the most nitrogen in the lungs to dilute
Nitrogen Washout Test
When is the NWT typically hatled?
How long should this take for a healthy 20 yo patient?
When the nitrogen concentration in the expired air reaches around 2.5%
Way less than 7 minutes, about half of 7 minutes which would be around 3.5 minutes
Nitrogen Washout Test
A NWT that lasts > 7 minutes indicates what?
Abnormal result indicating that there may be an issue with the lungs
> 7 minutes is twice what the normal value would take in a healthy 20 yo patient
Nitrogen Washout Test
How can the dilution process be calculated?
By considering factors like starting lung volume and breath depth
Nitrogen Washout Test
Which graph is normal? Which is abnormal?
Normal = Graph A
Abnormal = Graph B
Nitrogen Wash Out Test
Graph A appears ____ because the scale is not linear.
Exponential
The scale for the y-axis exponentially increases but shows a fairly straight line when you observe the plotted data points.
Nitrogen Washout Test
What do the blue dots represent?
Each expired breath
Nitrogen Washout Test
Which graph is abnormal and why?
Graph B
The blue dots are more scattered, creating a curve. This indicates that the air is being directed to different places in the lungs on each breath so the wash-out of the nitrogen will not be uniform.
Uneven ventilation = uneven dilution of nitrogen which leads to more scattered data points and this will take much longer to reach the 2.5% nitrogen concentration (> 7 minutes)
Nitrogen Washout Test
____ is the hallmark of a sick lung
uneven ventilation
Nitrogen Washout Test
____ might also delay nitrogen washout because there’s more nitrogen in the lungs.
Larger lungs (such as with people with COPD)
Nitrogen Washout Test
T/F: In COPD patients, the tidal volume is normal, but the lungs are large, so it will take longer to dilute the nitrogen.
T
Flow Volume Loops
What are FVL’s used to assess?
Airflow rates during deep breathes, specifically maximal effort vital capacity breaths.
It helps assess the speed of air explusion and gives insight into lung function
Label all the parts of the graph
A. TLC
B. RV
C. Effort Dependence
D. Effort Independence
E. Maximal curve/peak expiratory flow
F. Vital Capacity
G. Expiration Curve
H. Inspiration Curve
Flow Volume Loops
T/F: The peak expiratory flow curve represents the highest level of effort in expelling air.
True
Flow Volume Loops
The airflow rate during expiration is ____ at higher lung volumes.
effort-dependent (left side of the graph, letter E)
Meaning the harder the patient pushes to force air out, the faster the airflow
Flow Volume Loops
In this graph, airflow initially starts at zero and then rapidly increases to a peak around ________ L/s.
10 L/s
Airflow can go higher in completely healthy inividuals than this as well but this diaphragm goes as high at 10 L/s
Flow Volume Loops
After peak expiratory flow, the airflow rate ________ as lung volume decreases
slows down
Flow Volume Loops
What does the peak expiratory flow curve represent?
The maximum effort a patient gives to push out (expire) air
Flow Volume Loops
At lower lung volumes, the airflow rate is ________. Meaning that the rate at which air exits is capped, no matter how hard you push, the airflow won’t increase past a certain point.
Effort-indepedent (Letter D)
Flow Volume Loops
On the inspiratory side of the loop, the fastest rate of inspiration occurs around the ________ of the maximal curve of inspiratory cycle
midpoint
This is when the largest amount of effort is being applied during inspiration
Flow Volume Loops
T/F: As effort decreases, the rate of inspiration increases.
F.
the rate of inspiration decreases
less effort = slower air intake
Flow Volume Loops
T/F: Unhealthy lungs (ex: COPD) can cause faster expiratory flow rates and a quicker expiration time.
False:
Unhealthy lungs can cause slower expiratory flow rates and a more prolonged expiration time
Flow Volume Loops
The more unhealthy you are, the ____ you’re going to be able to get out air.
slower
This is an indicator that something is wrong with the patient’s lungs
Flow Volume Loops
____________ is typically more important in pulmonary function tests because it provides information about airway resistance, lung compliance, and overall lung function.
Expiratory flow (top part of the graph)
Flow Volume Loops
T/F: Inspiratory flow (bottom part of the graph) is less commonly measures but it still provides valuable information in specific tests.
T
Flow Volume Loops
________ is critical for measuring flow rate in this test.
Maximal effort
Flow Volume Loops
What curve are we primarily focused on for FVLs?
maximal effort curve
Flow Volume Loops
We mostly focus on ____, as it is the primary indicator of lung health.
Expiratory flow
Flow Volume Loops
The expiratory side of the FLW is skewed to what side?
The left side
Flow Volume Loops
Where are the really fast flow rates before they taper off?
Effort dependent expiratory curve
Flow Volume Loops
What shape does the inspiratory side of the FVL look like?
an oval
Flow Volume Loops
What shape does the expiratory side of the FVL look like?
skewed to the left
Flow Volume Loops
The expiratory flow rate is a product of what?
- Elastic recoil pressure
- How much recoil pressure can be gnereted in someone with terribale elastic recoil
Flow Volume Loops
If we stretch our lungs to TLC, a lot of ______ is built up
Elastic recoil pressure
(PER)
We must have a PTP of ____ to fill a normal, healthy lung to TLC
30 cmH2O
What is the difference between PTP and PER?
PTP = pressure needed to get air in the lungs
PER = helps get air out of the lungs quickly
PIP should be ____ if you have maximal effort and are trying to squeuze air out of the lungs as fast as possible.
positive
What muscles are involved in forced expiratory maneuvers to create a positive PIP?
- Diaphragm
- Internal intercostal muscles
- Abdominal muscles
DIA
What respiratory muscles are located inbetween the ribs and inside the rid cage?
Internal intercostal muscles
What does intercoastal mean?
Inbetween and inside the rib cage/thorax
When these respirtory muscles contract it pulls all the ribs close together which reduces chest volume and increases PIP (more positive)
Internal intercostal muscles
When these respirtory muscles contract it pushes the abdominal content upward and toward the diaphragm
Abdominal muscles
The combined action of the internal intercostal muscles and the abdominal muscles contracting makings PIP more _________.
Positive
In COPD, elastic recoil pressure is ______.
weak, they all all their “springs”
If elastic recoil is weak, what is needed to push air our of the lungs? Where do we run into problems with this?
forced expiration
At some point, all that forced expiration will cause the small airways will collapse. This limits the rate that air can be squeezed out of the lungs so it is problmamtic if there is’t a normal amount of lung recoil.
Paralyzed patient’s rely entirely on _________
lung recoil
If recoil pressure is low, expiration takes _______.
longer
T/F: Unhealthy lungs require more time for expiration on the ventilator.
True
Flow Volume Loops
If analyzing FVL for a pulmonary function test, what side of the graph are you focused on?
the expiratory side
Flow Volume Loop
What is this representing?
This is the maximal curve on the expiratory side of a FVL
Flow Volume Loops
The maximum expiratory flow rate for an obstructive lung disease is significantly ________ than in a normal, healthy lung.
Why is this?
lower
Elastic recoil is missing!
No elastic recoil will lead to __________.
small airway collapse
Flow Volume Loops
What does the slope of the obstructive disease curve represent? (pink line)
It’s slightly curved (concave), representing an abnormal effort-independent phase
The shape of the maximum expiratory curve tells us what?
tissue behavior during forced expiration
T/F: There is no reason for concern if the maximum expiratory curve is lower than what is should be normally.
F.
You should be concerned for serious pathology
In this type of lung disease, there is more scar tisse or more “strings.”
Restrictive lung disease
In this type of lung disease, it is difficult to fill the lung up with air because too much extra tissue
restrictive lung disease
In restrictive lung diseases, tissue recoil is ________ than normal but the amount of air (lung volume) that can get into the lung is much _________.
higher; less
The problem in restrictive lung disease is ______________.
Lung volume
Lung volume is the problem NOT elastic recoil!
Why is the maximal curve on the expiratory side of a FVL for a restrictive disease lower than normal?
Because these lungs has too much springy tissue in the lungs which makes the lungs difficult to fill with air.
Less air in the lungs = lower max expiratory flow rate
This is why the max expiratory flow curve is lower than normal but higher than the obstructive disease
T/F: Restrictive lung disease is more of a “fullness” issue rather than a recoil issue
T
What is FVC?
Forced vital capacity, almost always referes to the expiratory portion of the FVL.
What are the RVs for each of these curves?
Restrictive = ~1L (lowest RV)
Normal = 1.5 L
Obstructive = ~5.25L (largest RV)
How would you determine the vital capacity from this graph?
Subtract the two end points of the curve from each other
VC = TLC - RV
Example: Normal lung TLC is 6 L and RV is 1.5 L
6 L- 1.5 L = 4.5 L
The lower the air flow rate or the smaller the vital capacity _________.
The worse the disease
What is the atmospheric pressure based on this picuture?
What is the alveolar pressure based on this picuture?
What is deltaP?
Atmospheric pressure = 0 mmHg
Alveolar pressure = +35 mmHg
deltaP = 35 - 0 = +35 mmHg
The further up the respiratory tree you go, the _____.
pressure decreases (becomes less positive)
The upper airways are supported by what and what is it’s fuction other than support?
Cartilage
Prevents airway collapse during FVC
Where is the vulnerable point in the respiratory system?
The point just before cartilage shows up
At the vulnerable point in the respiratory system, if the alveolar pressure is high but the pleural pressure is low, will the airway stay open or collapse?
Stay open
1.
At the vulnerable point in the respiratory system, if the alveolar pressure is low but the pleural pressure is high, will the airway stay open or collapse?
Small airways will collapse
This is because the internal airway pressure is not sustainable to maintain opening of the airway
