Ventilation And Gas Exchange Flashcards
Might wanna note bank this one?
Yes
What are some of the main lung volumes and capacities? (On the graph)
Inspiration reserve volume
Tidal volume
Exploratory reserve volume
Residual volume
Functional residual capacity
Inspirational capacity
Vital capacity
These volumes are discreet and don’t overlap
Capacities are the sun of two or more volumes
What is minute ventilation?
Tidal volume (L) x breathing frequency (breaths/min)
This is the gas entering and leaving the lungs
What is alveolar ventilation?
(Tidal volume -dead space)x breathing frequency
This is gas entering and leaving the alveoli
What factors affect lung volumes and capacities?
Body size (height/shape)
Sex
Disease
Age
Fitness
What is the dead space in the lungs?
Includes:
Conducting zone - 16 generations, no gas exchange, around 150ml. This is anatomical dead space
Non perfused parenchyma - alveoli without a blood supply, no gas exchange, negligible (0ml). This is alveolar dead space
Physiological dead space is the sum of these
The rest of the space in the lungs is the respiratory zone - 7 generations, gas exchange, 350ml in adults, air reaching here is equivalent to alveolar ventilation
What is the chest wall relationship?
The chest wall has a tendency to spring outwards
The lung has a tendency to recoil inwards
These forces are in equilibrium at end tidal respiration (functional residual capacity,FRC). This is the neutral position of the intact chest
Chest recoil = Lung recoil
Adding an inspiratory or expiratory effort to this results in inhalation of exhalation
What is the basic anatomy of the chest wall?
Lungs are surrounded by a visceral pleural membrane
The inner surface of the chest wall is covered by the parietal pleural membrane
The pleural cavity (gap between the two) is a fixed volume and contains protein rich pleural fluid
Pleural cavity integrity can be affected by a haemothorax (blood, lung shrinks). Or a pneumothorax (perforated chest wall, lung goes tiny)
What are transmural pressures?
P inside - P outside
A negative transrespiratory will lead to inspiration
Positive will lead to expiration
(This involves the three compartment model, google it)
What are the potions of the inspiratory muscles?
Diaphragm - pulling force in one direction (like a syringe)
Other respiratory muscles - upwards and outwards swinging force
What are the 5 key gas laws?
Dalton - pressure did a gas mixture is equal to the sun of all the partial pressures of gasses in the mixture
Fick - molecules diffuse from regions of high to low concentration depending on: the concentration gradient, exchange surface area, and the diffusion capacity of the gas. And inversely proportional to the thickness of the exchange surface
Henry - 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
Boyle - at a constant temperature the volume of the gas is inversely proportional to the pressure of that gas
Charles - at a constant pressure, the volume of the gas is proportional to the temperature of that gas
What is the composition of the air at sea level?
Nitrogen (N2) - 78.09%
O2 - 20.95%
Ar - 0.93%
CO2 - 0.04%
Ne, He, H2, Kr etc - <0.01%
At high altitude the proportions are the same but there is just less air altogether
How is inspired gas modified in the airways?
It is warmed, humidified, slowed and mixed as it passes down the respiratory tree
What is haemoglobin?
Haemoglobin monomers consist of a ferrous iron ion at the centre of a tetrapyrole porphyrin ring connected to a protein chain (globin), covalently bonded at the proximal histamine residue
There are 4 haem groups in one molecule of haemoglobin
How does haemoglobin bond oxygen?
Reversibly
First oxygen is the hardest, second third and fourth get progressively easier due to a conformational change. This is called COOPERATIVITY
This gives a sigmoid oxygen dissociation curve
It is an allostsric protein (when 4 oxygens are bound a binding site in the central opens up for 2,3-DPG)
