2. Ventilation Flashcards
Define minute ventilation
The volume of air expired in one minute or per minute
Define respiratory rate
The frequency of breathing per minute
Define alveolar ventilation
The volume of air reaching the respiratory zone. The number of breath take per minute multiplied by the volume of breath reaching the alveoli with each breath.
Define respiration
The process of generating ATP either with an excess of oxygen (aerobic) and a short fall (anaerobic)
Define anatomical dead space
The capacity of the airways incapable of undertaking gas exchange
Define alveolar dead space
Capacity of the airways that should be able to undertake gas exchange but cannot (hypoperfused alveoli)
Define physiological dead space
Equivalent to the sum of alveolar and anatomical dead space
Define hypoventilation
Deficient ventilation of the lungs
Define hyperventilation
Excessive ventilation of the lungs
Define Hyperpnoea
Increased depth of breathing (to meet metabolic demand)
Define Hypopnoea
Decreased depth of breathing (inadequate to meed metabolic demand)
Define Apnoea
Cessation of breathing
Define Bradypnoea
Abnormally slow breathing rate
Define Tachypnoea
Abnormally fast breathing rate
Define Orthopnoea
Positional difficulty in breathing (When lying down)
What are the two components to the chest wall?
1) Lungs
2) Bone + Muscle + Fibrous tissue
What is FRC?
Functional residual capacity
When the ribcage and lungs are in equilibrium what is required to push the equilibrium?
Muscular effort
What is the pleural cavity?
The space between the parietal and visceral pleura
What does the pleural cavity contain?
A fixed volume of protein rich pleural fluid. The pleural cavity is at negative pressure
How does the lung and chest wall expand and recoil together as one?
It is held together by the negative pressure of the pleural cavity
What happens when the chest wall or lung is compromised?
The fixed volume of the pleural cavity is compromised so air will fill the pleural cavity causing lung collapse
Define haemothorax
Collection of blood in the pleural cavity due to intrapleural bleeding
Define tidal breathing
The amount of inspiration and expiration that meets metabolic demand. Usually nasal
When happens to tidal breathing when you exercise?
The tidal volume increases
What does the end of a tidal breath mark?
FRC
Why can you not empty the lungs fully?
Due to the surfactant in the alveoli - prevents the alveoli from sticking together and not reopening
Define residual volume
The volume in the lungs which cannot be emptied
Define functional residual capacity
The volume of air in the lungs when the outwards recoil of the rib cage and the inwards recoil of the lungs are in equilibrium. At the end of tidal expiration.
Define total lung capacity
When you inspire all the way and fill your lungs as much as possible, the volume of air in the lungs in the TLC
Define vital capacity
How much air is within the confines of what we are inspire and expire
TLC - RV
Define inspiratory capacity
How much extra air you can take on top of the FRC
What are the four main volumes?
Inspiratory reserve volume
Expiratory reserve volume
Tidal volume
Reserve volume
When talking about lung volumes what is the unit?
cm H20
What are transmural pressures?
Pressure cross a tissue or several tissues
P inside - P outside
Define transpulmonary pressure
Difference between alveolar and intrapleural pressure
What pressure results in expiration?
Positive transmural pressures
What is transrespiratory pressure?
This is the pressure that says whether there will be airflow into or out of the lung
What is the pressure in the lung when you inspire?
The pressure is lower inside of the lung - negative pressure breathing
In terms of transpulmonary pressure, when there is no volume change there is…
No transpulmonary pressure
What does the expansion of the chest wall create?
It creates negative pressure so more air flows in
What type of gradient does airflow move down?
Pressure gradient
What are the two zones in the lungs?
Conducting Zone
Respiratory Zone
What zone is dead space?
Conducting Zone
What is the alveolar dead space like in healthy individuals?
There should be zero alveolar dead space - physiological dead space about equal to anatomical dead space
What is the normal physiological dead space?
150 mL
What varies the anatomical dead space?
The size of the conducting zone
What is a clinical procedures which can reduce a patients dead space?
Tracheostomy - cutting off the upper part of the airway so it is no longer dead space
What is shape of an intact lungs volume-pressure graph?
Sigmoid shape
Why is the volume pressure graph a lung sigmoid?
It takes relatively little pressure to get the chest wall to expand to 6L, because the chest wall wants to expand. However to get the elastic lung to expand the bigger the volume the more pressure needed.
In a healthy person how much air is expelled in the first second from TLC?
75%
Define forced vital capacity
The amount of air which can be forcibly exhaled from the lungs after TLC
Define FET
Forced expiratory time - The time taken to expel all the air from the lungs
What is FEV1
The amount (volume) of air expelled from the lungs in 1 second
In obstructive lung disease (COPD) what would the FEV1, FET and FVC be?
FEV1 would be much lower
FET would be much higher
FVC would be much lower
In restrictive lung disease what would be what would the FVC and FEV1 be?
Restrictive lung disease limits the expansion of the thorax
FVC is lower
FEV1, is relatively high because their conducting airways are quite clear they can expel air relatively easily
What are the FEV1/FVC of normal, restrictive and obstructive patients?
Normal = 73 Restrictive = 87 Obstructive = 53
How can you assess lung function in the GP?
Wright peak flow meter
Describe the shape of flow-volume loop in a patient with obstructive disease
The last bit of expiration is usually a straight line however people with obstructive disease have an indentation (coving). The size of indentation depends on the severity of the disease.
The flow-volume loop is also shifted to the left due to an increase in the volume of the lungs and the expansion of residual volume
Why would the residual volume expand in obstructive lung disease?
Because there is air trapped in the alveoli as small airways connecting these alveoli may have collapsed
Why would there be in increase in the volume of the lungs
Emphysema can degrade the alveolar resulting in one large alveolus.
Describe the shape of flow-volume loop in a patient with restrictive disease
Narrower flow-volume loop
The loop moves to the right
Why would there be a narrower flow-volume loop in restrictive disease?
This is because getting to a high TLC is difficult because of the restriction to expansion of the lung
Describe the flow volume loop of a patient with variable extrathoracic obstruction
Flattened inspiratory curve
Describe the flow volume loop of a patient with variable intrathoracic obstruction
Flattened expiratory curve
Describe the flow volume loop of a patient with fixed airway obstruction
Both the inspiratory and expiratory curves are flattened
Why when we exercise do we not use the whole of our VC?
It is inefficient to use the whole of our vital capacity because a lot of energy and effort is required to utilise the inspiratory and expiratory muscles to the maximum
