Respiratory Mechanics and Compliance: Lecture 5 Flashcards
True or False
To generate flow into the lungs we need to decrease the alveolar pressure
true
Flow is measured by what?
Liters per second
Why is there positive and negative flow?
- breath out is a positive flow
- breath in is a negative flow
Is it possible to have 0 flow? if so when would that occur?
yes, between inspiration and expiration
What happens to volume, flow, alveolar and pleural pressure during INSPIRATION?
Volume = increases
Flow = negative
Alveolar pressure = negative
Pleural pressure = negative increases negatively
What happens to volume, flow, and alveolar and pleural pressure during EXPIRATION?
Volume = decreases
Flow = positive
Alveolar pressure = positive
Pleural pressure = increase, less negative
What causes us to get winded?
- when we get hit in the gut that can temporality paralyze our phrenic nerve
- the phrenic nerve is the one that send the signals to our diaphragm to keep our breathing
- which is why we find it hard to breath
During inspiration what does the diaphragm do?
it flattens and pulls everything down to allow the lungs space to expand
What is pneumothorax?
fully uninflated lung collapsed lung
What is the pleural pressure at the end of an expiration before an inspiration?
-4
True or False
As we expand the lung in inspiration the recoil pressure will increase due to the elastic force
true
What is the definition of the pneumothorax?
abnormal condition of air entering the pleural space
What will happen if the pleural pressure somehow equals the alveolar pressure and the atmospheric pressure?
- the pressure gradient will no longer exist across either the lung wall or the chest wall
- with no opposing negative pressure the lung will collapse to its unstretched size
How could we un-stretch our lungs “right now?”
breathing everything out, where the pleural pressure may become positive
Is it possible for us to fully deflate your lungs?
naurrr
What are the 2 common types of pneumothorax?
(a) Traumatic pneumothorax
- puncture wound in the chest wall
- complete puncture
ie. car accident
(b) Spontaneous pneumothorax
- a hole in the lung
ie. genetic
If one of our lungs collapses will we die?
no
True or False
Both types of pneumothorax can lead to a collapsed lung
true
Airflow is dependent on what?
pressure gradients
True or False
During inspiration, negative intrapleural and alveolar pressure is needed to move air into the lungs
True
Inspiratory muscles generate the force required to change what?
volume to generate airflow
During expiration which pressures will move air out of the lung once the inspiratory muscles relax?
recoil pressure
The expiratory muscles are required to increase which pressures to empty the lungs?
intrapleural and alveolar pressures
What is respiratory compliance?
How much air do we move for a given level of respiratory effort or pressure change?
What does it mean if we have a highly compliant lung?
we do not need much effort to move lots of air
What does it mean if we have a poorly compliant lung?
we need a lot of effort to move a little air
True or False
Compliance refers to how much effort is required to stretch or change the size of the lungs
True
What happens to the compliance of the lungs when you have COPD?
- alveoli become stretchy
What is COPD?
Chronic obstructive pulmonary disease
- high lung compliance
What is the equation for compliance?
change in lung volume/change (Palv - Pip) = change in volume/change Ptp
recoil pressure is the same as what?
Transpulmonary pressure
Why would we breathe at the linear area of the normal compliance curve? (sigmoid)
there is a specific level of inflation where it is the most efficient and easiest to breath
What is fibrosis? (case of decreased compliance)
where the lung is stiff and scared
True or False
If we have a stiff lung we need to create large amounts of pressure to move little volume
True
Increased compliance is equal to what kind of stiffness?
decreased stiffness
Decreased compliance is equal to what kind of stiffness?
Increased stiffness
True or False
In highly compliant lung, for little changes in pressure they get large amounts of volume
True
Why wouldn’t everyone want highly compliant lungs?
because it would make breathing out harder, and we lose the elasticity and recoil pressure
Why do we not need expiratory muscles to expire air?
because of the recoil pressure, aka transpulmonary pressure
True or False
For highly compliant lungs (emphysema) they need to recruit expiratory muscles to breath out
True
The normal compliance of a lung in cmH20 is what?
2.0L
Why do we breath where we breath?
it optimizes the work that we do
What are the 2 factors affecting a lung’s elastic recoil for lung and total respiratory compliance? (aka factors of compliance)
- Highly elastic connective tissue in the lungs
- any diseases that we mentioned will affect the connective tissue (stiff or floppy) - Surface tension of the alveoli
- ability to balance out the alveolar pressure from each alveolus throughout the lung
(premature babies do not secret surfactant so they cannot regulate the tension and pressure in the alveoli)
What is pulmonary surfactant?
- complex mixture of lipids and proteins
- made by type 2 alveolar cells
- spreads out between water molecules in the fluid lining of the alveoli and lowers alveolar surface tension
What are the 2 benefits of the pulmonary surfactant?
- Reduces work of the lungs
- Reduces recoil pressure of smaller alveoli more than larger alveoli (helps have a healthy compliance level)
What is the law of Laplace?
Pressure = 2(tension)/radius
Why would we want to breath at the lines “part” of the compliance curve?
About the graph
there is less amount of pressure required to move air
What is an example of a disease that causes highly compliant lungs?
Emphysema
What is an example of a disease that causes poorly compliant lungs?
lung fibrosis
True or False
Compliance is the change in volume divided by the change in pressure
True
True or False
highly compliant lungs will have problems breathing out and poorly compliant lungs will have problems breathing it
True
What helps regulate surface tension in the lung?
- surfactant
What does surfactant do?
reduces surface tension in the alveoli and makes it easier to inflate
What do Type 1 Alveolar cells do?
flat for gas exchange
What do Type 2 Alveolar cells do?
secretes surfactant
Without surfactant what would occur within two different sizes of alveoli?
- T1=T2
- Pressure would be higher in the smaller alveoli
- Pressure would follow its gradient going from the smaller alveoli to the larger one causing the smaller one to collapse
With surfactant what would occur within two different sizes of alveoli?
- Surface tension is proportional to radius
- pressures will remain the same (P1=P2)
