3 - ventilation Flashcards
What is chest-wall relationship?
If you split the two components of the chest:
- the ribcage naturally recoils outwards
- lung tissue naturally recoils inwards
at FRC (functional residual capacity), the lung-chest forces are in equilibrium - they are attached through the pleural cavity, therefore are always under pressure
What are the two components of the chest walls?
- bone + muscle + fibrous tissue
- lungs
What is FRC?
Functional Residual Capacity
at the end of tidal respiration- the point at which the elastic recoil of the lungs and the the outward recoil of the ribcage are in equilibrium
what are the skeletal muscles of them lungs?
peck major and minor
intercostal muscles
diaphragm
for inspiration and expiration, give the equations that contain chest and lung recoil
inspiration: inspiratory muscle effort+ chest recoil> lung recoil
expiration: chest recoil< lung recoil + expiratory muscle effort
NOTE: when the two components are in this equilibrium, you need muscular effort to push equilibrium in one direction or another
the pleural cavity has a _____ volume
fixed
the pleural cavity is at _____ pressure
negative
what is the parenchyma?
the functional tissue of the lungs that takes part in gas exchange
if you puncture the chest wall or lungs (and it will eventually lead to a pneumothorax), what happens to the pleural cavity?
the fixed volume of the pleural cavity is compromised
NOTE: a haemothorax will occur much slower
What is tidal breathing?
the amount of inspiration and expiration that meets the metabolic demand
(usually nasal)
What does the end of a tidal breath mark?
Functional Residual Capacity (FRC)
Why can the lungs not be emptied fully?
due to the surfactant in the alveoli (you don’t want the alveoli to stick together and not fully open)
Define the 4 volumes of the lung
INSPIRATORY RESERVE VOLUME (IRV)
TIDAL VOLUME (TV) - the amount of air coming in to meet the demand of the body
EXPIRATORY RESERVE VOLUME (ERV)
RESERVE/RESIDUAL VOLUME (RV) - default amount of air that cannot physically be expelled
Define a capacity
a combination of volumes
Name the 4 capacities of the lung
TOTAL LUNG CAPACITY (TLC)
VITAL CAPACITY (VC)
FUNCTIONAL RESIDUAL CAPACITY (FRC)
INSPIRATORY CAPACITY (IC)
What is total lung capacity?
all volumes combined
the maximal volume of the lung
not very clinically useful because it is very difficult to measure
What is vital capacity?
How much air is within the confines of what we are able to inspire/expire
TLC-RV
What is functional residual capaciity?
the volume of air in the lungs when the outwards recoil of the rib cage and the inward recoil of the lungs are in equilibrium (i.e. at the end of a tidal breath)
ERV+RV
What is inspiratory capacity?
how much air can be inspired on top of the FRC
IRV+TV
What factors affect lung volumes and capacities?
body size sex age disease (pulmonary, neurological) age (chronolgical and physical) fitness
what is the unit for lung volumes (for measuring in respiratory physiology)
cm H2O
what are transmural pressures?
(general)
the pressure across a tissue or several tissues
compares 2 compartments
how is transmural pressure calculated?
Pinside-Poutside
what is transrespiratory pressure?
most important
will tell us if there will be airflow in/out of the lungs
what is negative pressure breathing?
when the pressure in the lungs is lower than atmospheric pressure
normal breathing
what is negative pressure breathing?
when the pressure in the lungs is lower than atmospheric pressure
normal breathing
What is positive pressure breathing? Give some examples
involves increasing the pressure outside the lungs
this can be done using a ventilator or CPR
What is dead space?
the part of the airways that does not participate in gas exchange
(normal DS= 150 mL)
Which parts of the conducting zone and respiratory zone are dead space?
- all of the conducting zone is dead space- anatomical dead space
- alveoli that are not perfused or have collapsed are the alveolar dead space
alveolar dead space= the parts of the lungs that could participate in gas exchange but do not
NOTE: in most healthy individuals, the alveolar dead space is zero so the physiological dead space is equal to the anatomical dead space
what 2 processes can alter the dead space?
- tracheostomy - the upper airways are cut off so are not dead space
- ventilator - the extra tubing becomes dead space
What specific properties allow the lung to be pulled with the chest wall as it expands?
the pleural cavity has a fixed volume and a negative pressure
What is the chest wall pressure at FRC (functional residual capacity)?
What is the lung pressure?
-5 cm H2O
5 cm H2O
hence the FRC is 0 and in equilibrium
