Ventilation and Gas Exchange Flashcards
What is minute ventilation?
The volume of air expired in one minute (VE) or per minute (V”E)
Gas entering and leaving the lungs
What is respiratory rate?
The frequency of breathing per minute (Rf)
What is alveolar ventilation?
The volume of air reaching the respiratory zone per minute (Valv)
Gas entering and leaving the alveoli
What is respiration?
The process of generating ATP either with an excess of oxygen (aerobic) and a shortfall (anaerobic)
What is anatomical dead space?
The capacity of the airways incapable of undertaking gas exchange
What is alveolar dead space?
What is physiological dead space?
Equivalent to the sum of alveolar and anatomical dead space
What is hypoventilation?
Deficient ventilation of the lungs; unable to meet metabolic demand (increased PO2 – acidosis)
What is hyperventilation?
Excessive ventilation of the lungs atop of metabolic demand (results in reduced PCO2 - alkalosis)
What is hyperpnoea?
Increased depth of breathing (to meet metabolic demand)
What is hypopnoea?
Decreased depth of breathing (inadequate to meet metabolic demand)
What is apnoea?
Cessation of breathing (no air movement)
What is dyspnoea?
Difficulty in breathing
What is bradypnoea?
Abnormally slow breathing rate
What is tachypnoea?
Abnormally fast breathing rate
What is orthopnoea?
Positional difficulty in breathing (when lying down)
What is alveolar dead space?
Capacity of the airways that should be able to undertake gas exchange but cannot (e.g. hypoperfused alveoli)
What is represented on a time (s) to lung volume (ml) graph? (8)
Inspiratory reserve volume
Tidal volume
Expiratory reserve volume
Residual volume
Functional residual capacity
Inspiratory capacity
Vital capacity
Total lung capacity
What are volumes on the time/volume graphs?
they are discrete sections of the graph and don’t overlap
What are capacities on the time/volume graphs?
they are the sum of 2 or more volumes
What is vital capacity?
the air you have access to
What is tidal volume?
it starts at the default reference point of the graph
It is not just about rest, it is how much you need in that given time
- e.g., during exercise it increases
What happens during functional capacity?
where lung recoil and chest recoil are same effort
Why is there residual volume?
due to mechanical properties of the lungs
What is the expiratory reserve volume?
what you can get out after a normal breath
Why is there this weird descent on the blue line, when taking max inspiratory and expiratory effort?
because a person requires a couple seconds to reach maximum and minimum
When testing someone’s breathing to put on the graph, what are the 3 stages encountered?
Light respiratory effort
Max inspiratory effort
Max expiratory effort
How do you calculate minute ventilation?
Minute ventilation (L/min)
= tidal volume (L) x breathing frequency (breaths/min)
How do you calculate alveolar ventilation?
alveolar ventilation (L/min)
= (tidal volume (L) - dead space (L)) x breathing frequency (breath/min)
What are the factors affecting lung volumes and capacities?
Body size (not really mass, mostly height)
Fitness (innate, training)
Age (chronological, physical)
Disease (pulmonary, neurological)
Sex (male, female)
What is the respiratory zone?
7 generations
Gas exchange
Air reaching here is equivalent to alveolar ventilation
What is the conducting zone?
16 generations
No gas exchange
Typically 150 mL in adults at FRC (functional residual capacity)
Equivalent to anatomical dead space
What is the non-perfused parenchyma?
Alveoli without a blood supply
No gas exchange
Typically 0 mL in adults
Called alveolar dead space
What procedures can decrease the normal volume of dead space?
tracheostomy
cricothyrotomy
(they decrease airway space)
What procedures can increase volume dead space?
anaesthetic circuit (extending tube)
snorkelling
bronchodilation increases dead space
What is the chest wall relationship with the lungs?
The chest wall has a tendency to spring outwards, and the lung has a tendency to recoil inwards
These forces are in equilibrium at end tidal expiration (functional residual capacity; FRC), which is the ‘neutral’ position of the intact chest.
What combination results in inspiration?
inspiratory muscle effort + chest recoil > lung recoil
What combination results in expiration?
lung recoil + expiratory muscle effort > chest recoil
describe the chest wall anatomy.
The lungs are surrounded by a visceral pleural membrane
The inner surface of the chest wall is covered by a parietal pleural membrane
The pleural cavity (the gap between pleural membranes) is a fixed volume and contains protein-rich pleural fluid
What fluid do the pleuras have to benefit the lungs?
Parietal pleura and visceral pleura have serous fluid to lubricate
What does the pressure gradient help with the flow?
drive it
What is normal breathing in terms of pressure?
negative pressure breathing
What are the types of breathing in terms of pressure, and how do they correlate to Palv and Patm?
What are examples of negative pressure breathing?
mechanical ventilation
CPR
Fighter pilots
What is the result of the inspiratory muscle the diaphragm?
it is like a syringe, a pulling force in one direction
diaphragm induced breathing
What is the effect of the other respiratory muscles?
it is like a bucket handle
an upwards and outwards swinging force
Do you know what the symbols
P
F
S
C
Hb
mean?
How can you describe the pleural cavity?
a partial vacuum
What does maximum ventilation involve?
full inspiratory muscle recruitment (syringe and bucket handle movement)
What is Dalton’s law that describes gas behaviour?
Pressure of a gas mixture is equal to the sum (Σ) of the partial pressures (P) of gases in that mixture
𝑷𝑮𝒂𝒔 𝒎𝒊𝒙𝒕𝒖𝒓𝒆 = #𝑷𝑮𝒂𝒔𝟏 + 𝑷𝑮𝒂𝒔𝟐 + ⋯ + 𝑷𝑮𝒂𝒔𝒏
What is Fick’s law that describes gas behaviour?
Molecules diffuse from regions of high concentration to low concentration at a rate proportional to the concentration gradient (P1-P2), the exchange surface area (A) and the diffusion capacity (D) of the gas, are inversely proportional to the thickness of the exchange surface (T)
What is Henry’s law that describes gas behaviour?
At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid
What is Boyle’s law that describes gas behaviour?
At a constant temperature, the volume of a gas is inversely proportional to the pressure of that gas
What is Charle’s law that describes gas behaviour?
At a constant pressure, the volume of a gas is proportional to the temperature of that gas
What is the percentage of each gas in the air and their partial pressures (relatively) ?
What is the most soluble gas in the air?
CO2 (by a lot)
How much is a patient breathing of each gas at high altitudes, idea wise?
still 21% O2 and 78% nitrogen, etc. but it is proportional, so there is just less of the air overall
What is your patient breathing in a smoke (house fire)?
lot more CO2, more CO, less O2
What can increase your oxygen intake?
oxygen therapy
How is inspired gas modified in the airways?
warmed, humidified, slowed and mixed as air passes down the respiratory tree
What is the difference ,idea wise, in the partial pressures of O2, CO2, and H2O as it goes down the airway?
Dry air at sea level…
conducting airways…
Respiratory airways…
What is the total O2 delivery ar rest?
about 16 mL.min-1
What is resting VO2?
It is approximately 250 mL.min-1
- so obviously relying on dissolved oxygen alone is not conducive with life
- so we have more effective transport mechanisms
What is haemoglobin structure like?
Haemoglobin monomers consist of a ferrous iron ion (Fe2+; haem- ) at the centre of a tetrapyrrole porphyrin ring connected to a protein chain (-globin); covalently bonded at the proximal histamine residue
What type of protein is Hb?
al allosteric protein
How does Hb bind to oxygen?
reversibly
- binding to one makes it more accepting, have a greater affinity for O2
- that is why it has a sigmoid shape
- quaternary shape changes to reveal a binding site
Is saturation enough to know if someone is ok, I.e., they have high saturation?
No, it is important to know the amount of Hb because blood can still be very saturated you just don’t have a lot of Hb.
What does an Oxygen dissociation curve look like?
What can cause a leftward shift in the dissociation curve?
increased affinity loading
What can cause a rightward shift in the dissociation curve?
decreased loading
What does hypercapnia entail?
increased CO2
What can cause an upward or downward shift in the dissociation curve?
assume 20 is normal Hb
What happens when there is CO in the dissociation curve?
Unloading of O2 is harder
What happens to the dissociation curve with foetal haemoglobin and myoglobin?
Where is myoglobin found?
in our skeletal muscle for high intensity low time stuff
What is the transit time for gas exchange?
0.75s
What does fick state affects gas exchange?
partial pressure gradient, surface area, diffusion capacity, membrane thickness
How is carbon dioxide transported pt.1, what are the reactions it has and where do they occur?
How is carbon dioxide transported pt.2, the chloride shift?
How is carbon dioxide transported pt.3, the total CO2 flux?
How is O2 transported around the blood % wise?
2% in solution, roughly 98% bound to hb
How is CO2 transported around the blood?
as bicarbonate molecules (HCO3-) and as carbamino compounds (e.g., HbCO2)
What is the shape of the oxygen dissociation curve?
sigmoid shape
