Define Airway Resistance
(T/F) the airway resistance equation Flow = Change in P/R only holds true for laminar flow
How do Bronchoconstrictors affect airway resistance
Causes contraction of smooth muscle
Parasympathetic Nervous System - Ach
Histamine - Overly strong response to irritants - causes constriction
How does Bronchodilators affect Airway Resistance
Causes relaction of smooth muscle
SNS - Epi/NE ßAdrenergic Receptors
SNS - fight/flight - want bronchodilation to have increased airflow to bring in more oxygen and expire more CO2
How does Mucous effect air way resistance
Main problem is that there is a production of to much mucus, causing an effective decrease in the radius of the airway.
How does increased lung volume effect airway resistance
Increased Lung Volume = Decreased Resistance
State of the lung is more inflated
Patients with obstructive disease combat
by breathing at a higher lung
volume to open airways
What is Dynamic Airway Collapse?
Situation where airway complete collapses = Resistance goes to infinity - No flow
Will the airway be open or closed if the Pressure of the Airway is greater than the pressure of the Intrapleural space?
It will be open
Will the airway be open or closed if the Pressure of the Airway is less than the pressure of the Intrapleural space?
It will be closed
Why is there no airway collapse in a healthy person during quiet breathing?
No airway collapse.
Strong tendency for the lung to deflate towards intrinsic producing a force on IP space. Tendency for chest wall to inflate, creating opposing forces and a negative Pressure.
Negative PIP causes a vacuum for it to pull airways open
How does a healthy person under forced expiration effect airway collapse:
Collapses the airway
This causes a PIP to be positive
People start using expiratory muscles for forced expiration
Causes the chest wall to deflate in a dramatic Fashion.
How does a patient with emphysema during quiet expiration affect airway collapse?
Positive PIP causes airway collapse. Reduced pressure gradient for outward air flow. Collapse of airway during expiration while trying to compensate for pressure gradient. Overall reduction in integrity of the wall of the airways.
Lungs don’t tend to recoil as well. In terms of the forces the lungs can apply, there is much less force that can be applied as compared to a healthy situation.
Other problem with emphysema: as a result of reduced tendency to deflate, will start using muscles during quiet breathing causing chest wall to exert forces on IP space.
What is anatomical Dead space?
Volume of the lung that does not undergo gas exchange
What is alveolar dead space?
Alveolar dead space refers to the alveoli that do not engage in gas exchange:
Can arise if there is a complete occlusion - NO Blood flow
Functionally no different than anatomical dead space
Seen in pulmonary edema
How does a snorkel affect anatomical dead space
Air has to go through snorkel causing a larger anatomical dead space
Have to breathe more deliberately and slowly in order to get air the site of gas exchange. Must take in more air to account for the area that is wasted ventilation
Define Total Lung Capacity
how large the lung is when in maximal inspiration - 7L in avg person
Define Residual Volume
Residual Volume - The size of the lung after engaging in maximal expiration
Define Vital Capacity
Difference between Total Lung Capacity and Residual Volume. Change in volume that lung undergoes. Volume of air that flows into and out of the lung
Define Functional Residual Capacity
Volume of the lung after you have performed a quiet expiration. Minimal volume the lung obtains
Define Tidal Volume
Volume of air that flows when breathing quietly
How does Destructive disease affect the dynamic of airflow
Obstructive disease - increased airway resistance
Decreased air flow, and ratio will decrease
What is FEV1.0
FEV1.0 - Forced expired volume - amount of air flowing out of lung in the first second of this task
What is FVC?
FVC: Functional vital capacity - Vital capacity - volume of air that flow into and out of lung
What does FEV1.0/FVC Represent
Reflects the rate of airflow during expiration
Typical value = .8
1.0 = reaching residual volume in that first second.
What is the flow volume curve?
Maximal inspiration and forced expiration. Patient is asked to use different amount of effort during this test. Look at the behavior of airflow during these different tasks
Curve for A getting more flow for part of the time - Maximal Effort
As you continue and lung starts to get closer to residual volume terms come together
Even though you are engaging in greater effort not getting more flow because airway collapse