limbiks_Exam 3 Lecture 1 Flashcards
What is a 100% O2 source?
Eliminates other gases from entering the patient
What is the purpose of most pulmonary function tests?
Analyze expired gas
What does expired gas indicate?
Status of the respiratory system
What percentage of oxygen is the person inspired from?
100%
Where should the first 350cc of the inspired air make it down in the lungs?
Deep parts for gas exchange
Where is the last 150cc of the inspired air found in the respiratory tree?
Conducting areas
Do conducting areas of the respiratory tree undergo gas exchange directly?
No
How much anatomical dead space does a normally sized average adult have?
150cc
Where in the respiratory tree is there no gas exchange happening?
Conducting zones
What is the first 150cc of air that a person exhales?
Anatomical dead space
What is the composition of the last 150cc of air expired by a patient?
100% oxygen with a little bit of water vapor
What is the purpose of a nitrogen meter in this apparatus?
Measures nitrogen in expired air
What would the nitrogen meter show in the first 100cc of expired air?
No nitrogen
Why is there no nitrogen in the first 100cc of expired air?
No nitrogen in inspired gas
Percentage of nitrogen in atmospheric air
80%
Percentage of nitrogen in alveolar air
75%
First 100 CC’s of volume expired
Nitrogen composition expected
What do we expect to see in the first 100cc of expired air?
No nitrogen
What happens to nitrogen levels in expired air after 100cc?
Nitrogen appears
What does nitrogen in expired air indicate?
Alveolar gas
Where is the Alveolar Plateau phase located?
100CC mark
What technique is used to determine anatomical dead space?
Adds 100CC of expired air with no nitrogen to transitional phase volume
What characterizes the transitional phase?
Rapidly increasing nitrogen
Halfway mark to plateau phase
Where nitrogen is coming off the patient
Anatomical Deadspace measurement
150 CC’s
Location of 100 CC’s with no nitrogen
Upper airways
PN2 of alveoli
75%
Where does alveolar gas mix with dead space gas in expired air?
First portion
Why is the nitrogen content low in the first portion of expired air?
Close to large airways
Importance of measuring anatomical dead space volume
To estimate volume of nitrogen-free area
Composition of anatomical dead space
Nitrogen-rich near beginning, nitrogen-poor closer to large airways
Definition of anatomical dead space
Area of gas exchange in airways
How do we calculate anatomical dead space?
Volume at midway point + 100 CCs
What is the total anatomical dead space in the example provided?
About 150 CCs
What does the fowler test measure?
Nitrogen deficiency in expired air
-24:30 Slide 2: What is Fowler’s test used for?
To determine anatomical dead space volume
-24:30 Slide 2: What is added to the volume of air expired to determine anatomical dead space?
Midway point at transitional area
What can expired gas help us visualize?
Inner workings of the lungs
What does expired gas measurement allow us to determine?
Anatomical dead space
What type of gas is typically used for the measurement?
100% Oxygen
Can we measure physiological dead space with this method?
Questioned if physio dead space can be measured
Can we measure alveolar dead space?
No
What is anatomical dead space?
Combination of Anatomical factors
What is alveolar dead space?
Wasted ventilation
What is the maximum rate of inspiration?
10 liters per second
What is the maximum expiratory flow rate for an average person?
10 liters per second
What is the point at which the lung is entirely filled up with air?
TLC
What is the start point for flow volume flow volumes?
RV
How fast can air go into the lungs during maximal effort?
10 Liters per second
What is the maximum flow rate?
10 liters per second
When does the maximum flow rate occur?
Early expiration
What is the relationship between expiration and flow rate?
Flow rate increases quickly at the start of expiration
What happens after the high point in lung volume?
Tapers off in a straight line
What are the start points on the horizontal axis in terms of lung volume?
Always RV
How is the horizontal axis represented in lung volume?
With numbers
What is the normal vital capacity?
4.5 liters
What units are pulmonary function lab results typically given in?
liters
Is there a standardized way to display numbers in pulmonary function labs?
No
What is the difference between the start point and another point mentioned?
Four and a half liters
Can the start point on the axis be arbitrary?
Yes
What could be a possible value for the start point on the graph?
Two or zero
What is important in determining volume on a graduated cylinder?
Distance between bars
Does the start or end point matter on a graduated cylinder?
No
Maximal effort inspiration and expiration flow rates
10 L/sec
During maximal effort, which curve represents the flow rate?
Smaller curves between top/bottom curves
How is the duration of inspiration/expiration indicated on the graph?
Airflow is in units of L/sec
What is the typical shape of the curve during inspiration?
Half circle
What is observed in the inspiratory curve?
Symmetry during inspiration
What occurs during expiration based on the curve?
Front-loaded and tapers off
What is the general shape of an expiratory flow curve?
Upside-down ice cream cone
Where does the expiratory flow curve show higher flow?
Left side
How does the expiratory flow change as air continues to come out of the lung?
Starts fast then tapers off
What is usually the focus when conducting pulmonary function tests?
Expiratory side
Why do we have a high peak expiratory flow rate at the beginning of the maneuver?
Big airways at total lung capacity
What happens as we get towards lower and lower lung volumes?
Effort independence
What is the period when expiratory flow rate becomes effort independence?
Towards lower lung volumes
At what lung volume does max expiratory flow rate become independent of effort?
Around FRC
What contributes to small airway collapse?
Pressure generated
Where are small airways more likely to collapse?
Bottom part of the lung
When does expiratory flow rate become effort independent?
37:30-42:30 Slide 8
What happens to alveoli at the top and bottom as lung volume decreases?
Top alveoli are full, bottom alveoli empty first
Why do the alveoli at the bottom empty out first as lung volume decreases?
Reduced traction and airway diameter
What happens to airway diameter as we reach lower lung volumes?
Airway diameter reduces
Why does applying pressure at lower lung volumes shut the airway?
Airway diameter is reduced
What factors influence the shape of the normal curve?
Airway width, elastic recoil, traction
Why does airway collapse become more likely with reduced traction or elastic recoil?
Higher probability of airway collapse
How are the curves typically plotted?
Expiratory part only
What does the blue curve on the right in an expiratory flow volume loop indicate?
Restrictive lung disease
What does the blue curve on the left in an expiratory flow volume loop indicate?
Obstructive disease
What is the typical expiratory and inspiratory flow rate a typical person can generate under maximal effort?
About 10 liters per minute
Typical expiratory flow rate for an average 34 year old person
10 L/min
Max expiratory flow rate for a large football player
Faster than 10 L/min
Why do restrictive lung diseases lead to a reduction in max expiratory flow rate?
Airways are more narrow and more likely to collapse
What effect does having less full alveoli have on the airways in restrictive lung disease?
Makes airways more narrow
Why are the airways in restrictive lung diseases more likely to collapse?
Because they are narrower than in a normal lung
What happens to the peak expiratory flow rate in obstructive lung disease?
Reduced
Why does the expiratory flow rate taper off in obstructive lung disease?
Loss of traction springs
What happens to airways with reduced alveolar support during exhalation?
Airways collapse, limiting end expiratory flow rate.
What would we expect to see with both obstructive and restrictive lung diseases?
Reduction in peak flow rate for different reasons
What might we see as obstructive lung disease worsens?
Crazy patterns
What is the average vital capacity?
1.5 liters
How is vital capacity measured?
Helium dilution technique
What is FRC?
Functional residual capacity
Where is FRC located?
Around the vital capacity
What does the drawing on the left indicate?
Passive expiration
What does the drawing on the right represent?
Forced expiration
What happens during passive expiration?
Diaphragm drops, pleural pressure drops, generates negative alveolar pressure
How did pleural pressure change?
-8
What was the recoil pressure of the alveolus?
10
What is alveolar pressure when pleural pressure is -8 and recoil pressure is +10?
2
What is the reference pressure at the entrance to the respiratory system?
Zero atmospheric pressure
What delta p is required to move volume out of the lungs?
Two centimeters of water
What happens to the alveolus during exhalation?
It gets smaller
What happens to the recoil pressure to the alveolus during exhalation?
It is being reduced
What alveolar pressure allows air to be in balance again?
Positive eight
How does air move during passive expiration?
Air moves out of the lungs.
What do we know about pressure gradients?
Not static
Where is the pressure highest in relation to the source (alveolar elastic recoil)?
Closest
What would we expect to see at a point between alveolar and mouth pressure?
Lower pressure gradient
What changes in the pressure gradient might be observed in different parts of the system?
Illustrated changes
Where is the beginning of the small airway located?
Next to the alveolus
Why is the pressure in the small airway lower than in the alveolus?
Not as close to the source
How does the pressure change as you move farther away from the alveolus in the small airway?
Pressure decreases
Why is there no risk for airway collapse as we move down the respiratory tree?
Higher internal Airway Pressure than pleural pressure
What is the relationship between pleural pressure and internal pressure in the airway?
Negative pleural pressure, positive internal pressure
What provides support at the very beginning of the small airway?
Traction springs
What keeps the airway open when internal pressure is higher than the surrounding pressure?
Pressure difference
What do conducting bronchioles typically have for structural reinforcement?
Cartilage
What provides structural reinforcement to resist collapse in the conducting branches of the respiratory tree?
Cartilage
Why do the walls of airways become thicker as we move further up the respiratory tree?
To resist collapse
What helps keep the airway open in the presence of positive external pressure?
Cartilage
What is the airway structure in the small airways?
Soft tissue, no cartilage.
What happens during forced expiration?
Strong abdominal contraction, high pleural pressure, high alveolar pressure
How is a high alveolar pressure achieved during forced expiration?
Positive pleural pressure combined with positive recoil pressure
What is the significance of an alveolar pressure of positive 35?
Pushes air out quickly
What contributes to the quick air expulsion at positive 35 pressure?
Pleural pressure and elastic recoil
What pressure is present at the mouthpiece in the given scenario?
Zero
What is the alveolar pressure?
Positive 35
What is the pressure in the small airway?
Positive 30
What is the internal pressure at the edge where cartilage starts?
Positive 25
Why shouldn’t the airway collapse in this scenario?
Pressures are the same
What makes an airway prone to collapse?
Higher pleural pressure
What happens when internal airway pressure is equal to surrounding tissue pressure?
No collapse
What happens to pressures as we go up in the drawing?
Numbers get smaller
What is the alveolar pressure in this scenario?
33
What is the pressure in the airway when moving farther from the alveolus?
28
Approximately, what is the next pressure point labeled on the graph?
23
What is the pressure a little bit further away from the alveolus?
23
What is the pressure before entering the reinforced cartilaginous airways?
23
What happens if the pleural pressure is +25 but the internal airway pressure is +23?
Small airway collapse
What results from high pleural pressure causing small airway collapse?
Limitation in the rate at which air can leave the lungs
Why does the lung’s elastic recoil pressure decrease?
As the lung empties (reduction in lung volume)
What is the consequence of decreased recoil pressure in the lungs?
Lower alveolar pressure, affecting small airway support
What happens when there is a reduction in lung volume?
Decrease in elastic recoil and force expiration rate
How does a decrease in lung volume affect tissue springiness?
Decrease in tissue springiness and recoil pressure
What is prone to dynamic compression?
Small airway
When does dynamic compression occur?
Forced expiration
What conditions increase the likelihood of dynamic compression?
Lack of springs or traction, already narrow airway
What do pulmonary function tests measure?
Air flow speed
What do healthy lungs show in a pulmonary function test?
Fast air exit
What does slow air exit in a pulmonary function test indicate?
Obstructive lung disease
Common obstructive lung diseases seen clinically are?
Asthma, emphysema
What happens to the resistance in a parallel circuit as more pathways are added?
The resistance decreases.
What are the two basic setups for electrical resistances in circuits?
Parallel and series circuits.
How does current flow in a parallel circuit?
Through one of two or more pathways.
What are the two pathways that could lead to lower overall resistance?
R1 and R2
What is the impact of setting up resistances in a series?
More difficult to get through
What is the formula for total resistance in a series setup?
R1 + R2 = total resistance
What is the total resistance of a series circuit with two resistors of 2 ohms each?
4 ohms
What formula is used to calculate the total resistance of resistors in parallel?
1/R_total = 1/R1 + 1/R2
How do we express the formula for resistors in parallel?
1/R_total = 1/R1 + 1/R2
What does conductance describe?
How easy it is to get current through a setup
What would happen if resistance was replaced by conductance in a mathematical formula?
Math would have to be flipped
How do you calculate the total conductance of a system with parallel conductances?
Conductance 1 + Conductance 2 = Conductance total
What is the relationship between conductance and resistance?
Conductance is the inverse of resistance.
How do you calculate total system resistance for resistances in series?
Sum of individual resistances
What happens if two items are arranged in a series back to back?
Harder to get current through
How is the total system conductance calculated for items in series?
Using a specific expression
What formula is used for individual resistances in a parallel pathway?
Reciprocal formula
What is the relationship between conductance in a series?
Overall conductance lower
How to calculate conductance of a system with two conductors in series?
1/Conductance total = 1/Conductor 1 + 1/Conductor 2
What is the function of the lungs?
Get air into the lungs
What force must be overcome to get air into the lungs?
Elastic recoil
What can become an impediment to filling the lung with air?
Chest wall
What is an obstacle when chest wall BMI is high?
Filling lung with air
What are the two impediments to filling the lungs?
Chest wall and elastic recoil of the lung
What is compliance a measure of?
How easy it is to get air into the system
What does lung compliance refer to?
Ease of putting air into the lungs
Why would the compliance of a system with two impediments be lower than each part individually?
Arranged in series
What are the two components that contribute to the compliance of the overall respiratory system?
Chest wall compliance and lung compliance
How is the total system compliance calculated?
1 over the total system compliance equals the sum of 1 over the compliance of the lung plus 1 over the compliance of the chest wall.
What is the compliance of the lung and chest wall individually?
0.2
What is the total compliance when considering both the lung and chest wall?
10
