Ventilation ****** Flashcards
(36 cards)
What are the two components of the chest-wall?
Independent Lung
Independent rib cage and muscles ( bone, muscle and fibrous tissue)
what would happen if we spilt up the components of the chest wall and how is this different to normal?
Rib cage would naturally recoil OUTWARDS.
The lungs have a tendency to recoil INWARDS.
What is Functional Residual Capacity?
FRC = ERV + RV
ERV: additional air that can be forcibly exhaled after the expiration of a normal tidal volume.
RV: volume of air still remaining in the lungs after the expiratory reserve is exhaled
It is the volume of air remaining in the lungs at the end of a tidal breath. At FRC, the recoil inwards of the lungs and the recoil outwards of the chest wall are in equilibrium.
Describe how the pleural cavity allows the chest wall and the lungs to move in unison.
The pleural cavity has a fixed volume and is at negative pressure.
This means that when the chest wall expands, the lung gets pulled with it..
The pleural cavity contains protein-rich pleural fluid.
How may the fixed volume of the pleural cavity be compromised?
The pleural lining could get punctured in the case of a haemothorax (happens much more slowly) or pneumothorax.
what is tidal volume?
Tidal breathing is usually nasal.
Tidal breathing= the amount of inspiration and expiration that meets metabolic demand.
-When exercising the tidal volume increases.
what does the end of a tidal breath mark?
It marks the Functional Residual Capacity (FRC)
why can’t we empty the lungs fully and what is this remaining volume called?
Due to surfactant in the the alveoli, you can’t empty the lungs fully because you don’t want the alveoli to stick together and not reopen.
Remaining volume is the RESIDUAL VOLUME
Which volumes make up each of the following capacities: Total Lung Capacity Vital Capacity Functional Residual Capacity Inspiratory Capacity
Total Lung Capacity - all the volumes together. (When you inspire all the way in and fill your lungs up as much as possible, the volume of air in the lungs is the TLC)
Vital capacity + residual volume (RV)
Vital Capacity - expiratory reserve volume+ inspiratory reserve volume + tidal volume
IRV+TV+ERV
or
TLC- RV
How much air is within the confined of what we are able to inspire and expire.
Functional Residual Capacity - ERV + RV
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.
Inspiratory Capacity - TV + IRV
How much extra air you can take in on top of the FRC
What unit is commonly used when describing lung pressures?
Unit: cm H2O
What are the three main lung pressures involved in respiratory mechanics? Define them.
Transmural Pressure = pressure across a tissue or several tissues
Transpulmonary Pressure = difference between alveolar and intrapleural pressure
Transrespiratory Pressure = tells us the direction of airflow in the airways.
How do you work out the orientation of the gradient?
You always do the pressure inside MINUS the pressure outside
what is the normal reason we breathe?
Due to lower pressure inside the lung- this is NEGATIVE pressure breathing.
Give two examples of positive pressure breathing.
CPR and Ventilators
Define Dead Space.
Parts of the airways and lungs that do not participate in gas exchange.
What is the difference in alveolar pressure between the end of a tidal expiration and the end of tidal inspiration? Explain your answer.
NO DIFFERENCE - during inspiration, the thoracic cavity expands and so the alveoli expand and the pressure decreases. Air is drawn in to the alveoli and the pressure becomes the same as it was at the end of expiration.
what is the conducting zone
Is the Dead space.
What are the two different types of dead space?
Anatomical Dead Space
Alveolar Dead Space= the parts of the lung that could participate in gas exchange but do not.
What is the normal physiological dead space of a healthy individual?
150 mL - physiological dead space is usually equivalent to anatomical dead space because normal healthy people don’t have alveolar dead space
State two reversible procedures that can change dead space.
Tracheostomy = cutting off the upper part of the airway so it is no longer dead space ventilators= the extra tubing becomes dead space
Explain the chest wall relationship diagram (volume against pressure).
Expanding the chest wall to 6 L takes relatively little pressure because its natural tendency is to expand. Expanding the lungs to 6 L takes a lot more effort and pressure because its natural tendency is to recoil inwards.
what shape does the intact lung have?
It has a sigmoid shape in terms of its volume-pressure relationship.
Define FVC, FEV1 and FET.
Forced Vital Capacity - volume of air that can be expelled from the lungs after a full inspiration
Forced Expiratory Volume 1 - maximum volume of air that can be expired within 1 second
Forced Expiratory Time - time taken to fully empty the lungs (except residual volume)
How would these values change for a) someone with obstructive lung disease, b) someone with restrictive lung disease?
Obstructive lung disease: FVC = lower, FEV1 = lower, FET = higher
Restrictive lung disease: FVC = decrease, FEV1 = relatively high because their conducting airways are quite clear they can expel air relatively easily.
