PULMONARY 02: LUNG MECHANICS 1 Flashcards
What is the law that describes how air will flow in and out through airways?
Boyle’s law, and it dictates air will flow according to pressure gradients
Inspiration is __(active/passive)__ ; expiration is __(active/passive)
Active; passive
What is the most important muscle of respiration?
Diaphragm
Aside from the diaphragm, what is the other major set of muscles that aids in inspiration?
External intercostals
What are the accessory muscles of expiration?
Internal intercostals
Abdominal muscles
Other accessory muscles to inspiration?
Sternocleidomastoid; scalenus (lift of wall of chest)
At the end of inspiration and expiration, what is the pressure across the entire system? Why?
Pressure difference across the system is zero, because there is no air flow. Inward recoil of the lung and outward recoil of the chest wall are balanced.
Pressures in alveoli relative to outside in inspiration
Alveolar pressure is below atmospheric pressure, leading air to flow in
Pressures in alveoli relative to outside during expiration
Alveolar pressure is above atmospheric pressure, therefore air will flow out (along gradient)
Boyle’s law
At a fixe temperature, the volume of a gas is inversely proportional to the pressure exerted by the gas
come on, make your gen chem teachers proud by remebering this one
If you double the volume of a system, what will happen to the pressure?
The pressure will drop (1/2 original value)
If you halve the volume of a system, what will happen to the pressure (at a given number of gas molecules)?
Pressure will double
How is the shift in pressures required to change alveolar pressure relative to the outside accomplished?
Muscles changing the volume of the chest cavity
The thoracic and abdominal cavities are separated by the ____(muscle)____
diaphragm
The lungs are in what body cavity
Thoracic
How do the major muscles of inspiration aid in increasing the volume of the chest cavity?
The diaphragm pulls down and enlarges the thoracic cavity in a vertical direction
The external intercostals pull the ribs up and out
In deep, forceful inspiration, how do the accessory muscles help?
The scalenus and sternocleidomastoid raise the sternum and elevate the first two ribs, enlarging the portion of the thorax
Nasal muscles are also activated and this provides some MINOR addition of volume
Tidal breathing is ____mL air going in/out of lungs
500mL
Expiration is mostly a (active/passive) process, and therefore muscles aid in this by:
Passive process:
Diaphragm relaxes, allowing muscle to resume dome shape and reducing volume of chest cavity. Additionally, intercostal muscles relax, and the ribs fall due to gravity. This increase in pressure leads to the lungs deflating and thorax compressing due to natural recoil
In forceful expiration, the ___ muscles engaged help in expiration by:
Abdominal muscles help by incresing abdominal pressure, pushing chest cavity up more.
Internal intercostals contract, and flatten the rib cage bby pulling ribs down and out
Why do the internal and external intercostals have opposing effects?
They are placed differently on the ribs themselves when compared to the spine
The External intercostals have the most superior rib being the point that has the attachment closest to the ribs. This means that when contracting, the second rib will be ulled up and toward the stable point diagonally. The internal intercostals have the opposite arrangement, with the inferior rib having the stable spinal-adjacent position. This means contraction pulls down diagonally toward the inferior rib
Attached is a picture of the external intercostals.
The pleural space is filled with (fluid/air)
FLUID
YOU MUST LUBE THE LUNGS
What is the area between the visceral and parietal pleura called?
The pleural space
What is the pleura that touches the lungs
visceral pleura
what is the pleura that touches the chest cavity
parietal pleura
The fluid that fills the intra-pleural space is called what?
Serous fluid
it is only 10-20mL
Elastic properties of the lung are driven by what two factors?
Surface tension of airways
Elastic properties of cells and tissue (elastin (primarily), fibrillin, collagen, etc)
According to the chest wall/lung volume relationship, pressures below zero are __(expanding/collapsing)__ and pressures above zero are (expanding/collapsing)
Expanding/collapsing
At the end of expiration, the chest wall is experiencing a (expanding/collapsing) force, and why?
Expanding. You’ve forced the system to be really small and it wants to recoil. When you fill the lungs really big at total lung capacity there is a huge pressure now forcing it to collapse.
How much of the lung volume is within the expanding forces for the chest wall/pressure within lung volume relationship?
2/3
When considering the lungs/lung volume relationship, how often do we see a collapsing force?
ALWAYS
The lungs ALWAYS want to be smaller
Describe this image
When we summate the chest wall and lung vs lung volume lines, we get the red line in the middle. The point at which the line crosses zero on the X axis is the functional residual capacity, which is the equilibrium point in lungs where we get to at lung relaxation. This is where the lungs and the chest wall equally try to pull at each other. To get past this point, we require muscles. The collapsing force increases as you move toward total lung capacity.
The pleural space, even at rest, is not at “zero” pressure compared to the outside (this would lead to lung collapse). What the pressure relative to the outside? Positive, or negative?
Negative
Transmural pressure
Pressure inside relative to outside of a container wall (push pressure)
How many pressures do we have to consider when thinking about lung mechanics?
3:
Transmural pressure across lung wall (transpulmonary/translung pressure)
Transmural pressure across chest wall (transthoracic pressure)
Pressure across the entire respiratory system
What happens if you puncture the chest wall through the parietal pleura?
This will collapse the lungs, as it will normalize the intrapleural space pressure to the outside.
the same problem would happen if you punctured the lung
What is the pressure INSIDE THE LUNGS (not pleural space) relative to the outside at rest
Equal
What happens to the volume of air in our lungs during inspiration and expiration
Starts at a baseline; as we inhale it increases, as we exhale it decreases
What happens to the pressure inside the pleural space as we inspire an expire?
During inspiration, the pressure in the pleural space becomes more negative. this is due to the diaphragm and external intercostals generating a larger space in the chest cavity. During expiration, the opposite occurs, so pressure becomes less negative.
What happens to flow of air during inspiration and expiration? Consider air flow relative to air leaving the lungs.
As we breathe in, the flow of air is going into the lungs, so this appears negative on the chart. Then as we stop breathing in, this flow reaches zero. As we breathe out, the air is pushed out, leading to a positive outward flow that diminishes near the end of the breath.
during inspiration/expiration what happens to alveolar pressure
At the beginning of a breath we are at equilibrium with the atmosphere. Then we begin to go negative. However, this doesn’t follow the same trend as in pleural space pressure because air is flowing inside. Thus by the end of inspiration we equilibrate with the outside. during expiration, the pressure becomes positive as air is pushed passively out through the activity of the chest cavity becoming smaller. Then, as this becomes less pronounced, and pressure equilibrates with the outside again, it returns to zero.
What contributes to the sedimentation of medium particles in the bronchioles?
A decrease in air velocity
