How is the bronchus supplied with blood?
Via bronchial arteries (nutritive)
What type of circulation supplies the bronchus?
What tissues are supplied in the bronchus by the bronchial arteries?
- Smooth muscle - Nerves - Lung tissue
How are the lungs supplied with the vessels that exchange gas?
- Pulmonary arteries
Where do the pulmonary arteries originate from?
What is the function of the pulmonary vein?
- Returning oxygenated blood to the heart
What is the systolic pressure of the pulmonary artery
What is the flow of the pulmonary artery?
How much blood goes through your lungs every minute?
What is gas exchange said to travel down?
A partial pressure gradient?
What is the partial pressure of CO2 in venous circulation and the pulmonary artery?
What is the partial pressure of O2 in venous circulation and the pulmonary artery?
What does the partial pressure of gases in the venous blood give an indication into?
What is going on with gas exchange in the tissue
What is the partial pressure of CO2 in the arterial circulation and the pulmonary vein?
What is the partial pressure of O2 in the arterial circulation and the pulmonary vein?
What will the partial pressures of these gases in arterial circulation give an indication to?
What is going on with gas exchange in the lungs
What does PA stand for?
What does Pa stand for?
Arterial blood pressure
What does Pṽ stand for?
Mixed venous blood pressure (pulmonary artery)
What 3 things is the rate of diffusion directly proportional to?
- Partial pressure across the membrane - Gas solubility - Surface area
What is rate of diffusion inversely proportional to?
Thickness of the membrane
What is the partial pressure GRADIENT of O2 in the alveoli to the vessels of deoxygenated blood?
60mmHg (100 in the alveoli, 40 in the blood)
How much O2 diffuses across the alveoli per minute?
What is the partial pressure GRADIENT of CO2 in the alveoli to the vessels of deoxygenated blood?
6mmHg (46 in the blood, 40 in the alveoli)
How much CO2 diffuses across the alveoli per minute?
Why is the rate of diffusion of CO2 not 10 times less than O2 if the partial pressure gradient is?
CO2 is more soluble in water
How does pulmonary oedema affect gas exchange?
- Fluid inbetween vessels and alveoli
- Since O2 doesn't dissolve well in water it reduces the movement of O2
- Also increases distance between membranes so diffusion is reduced
How does emphysema reduce gas exchange?
Reduces surface area
How does fibrosis reduce gas exchange?
- Increases membrane thickness
- Reduces ventilation and compliance
How is pulmonary fibrosis confirmed?
Is radioopaque so shows up on chest X ray
How does emphysema increase surface area?
- Imagine the lungs are like a net and have loads of small holes
- If you tear the barrier between one of the holes you get 1 bigger hole
- This is what emphysema does to the lungs
What is ventilation?
Air getting to the alveoli (L/min)
What is perfusion?
Locol blood flow (L/min)
What is the relationship between ventilation and perfusion?
They are equal
Where in the lung are ventilation and perfusion both higher?
Bottom of the lung
Why are ventilation and perfusion higher in the bottom of the lung?
Where in the lung are ventilation and perfusion the lowest?
Where does arterial pressure exceed alveolar pressure in the lungs?
Bottom of the lung
What is distribution of blood flow influenced by?
What other reasons are there for pulmonary artery perfusion decreasing as you go up the lung?
Because the pressure is lower, it is MORE susceptible to gravity
Moving up the lung, at roughly what rib does alveolar pressure become equal to blood flow (ratio = 1)?
Above rib 3, which is higher out of alveolar pressure and Pa?
What is blood flow (Pa) directly proportional to?
What is mismatch 1?
- At the apex
- Ventilation > perfusion
What is mismatch 2?
- At the base of the lung
- Perfusion > ventilation
Why is apex Pa lower?
- Alveoli squash blood vessels
What is shunt?
Blood shifting from the right to left side of the heart through the pulmonary vessels withouth being oxygenated
What happens to most blood vessels in the body in response to hypoxic conditions?
What happens to vessels in the lungs when they detect hypoxic conditions?
Why do the vessels in the lungs contract in response to hypoxic conditions?
So that less blood travels to the alveoli that have low oxygen and therefore more blood travels to areas with higher O2 conc.
What does a higher pressure of CO2 in the lungs cause?
Bronchodilation to increase ventilation
What is an example of a condition in which perfusion will be higher that PA?
What is a condition which may cause higher ventilation?
What is the name given to the aspect of higher ventilation that means a lot of the air won't be used in gas exchange? (alveoli that are ventilated but not perfused?)
Alveolar dead space
What does an increase in alveolar PO2 do to pulmonary circulatory vessels?
When alveoli are ventilated but not perfused, alveolar PCO2 is reduced; what effect will this have on the brochus?
What is physiological dead space?
ALVEOLAR Dead Space + ANATOMICAL Dead Space
How much O2 dissolves per litre of plasma?
To what value does haemoglobin increase blood O2 capacity to?
What does arterial partial pressure refer to?
ONLY O2 in solution
What is O2 concentration determined by?
- O2 solubility
- Partial Pressure of O2 in the gaseous phase
What are the values of partial pressure of a gas in solution equal to?
The partial pressure of the gas in the gaseous phase that is DRIVING the gas into solution
EXAMPLE OF PARTIAL PRESSURE AND ARTERIAL O2 PRESSURE
- O2 solubility in water is low (0.03ml/L/mmHg)
- We have 3ml/L of O2 in the plasma therefore the partial pressure driving O2 into the plasma must be 100mmHg
- VOLUME IN SOLUTION/SOLUBILITY = PARTIAL PRESSURE
- 3/0.03 = 100mmHg
What is the partial pressure that drives oxygen into solution sometimes known as?
What would happen if O2 travelled as gas in the blood?
Air Embolism - fatal
What is the O2 demand for resting tissue?
Without haemoglobin, how much O2 would tissue get using just arterial oxygen?
- Arterial O2 = 3ml/L
- Cardiac output = 5L/min
NOT ENOUGH TO MAINTAIN TISSUE
How much haemoglobin do we have on average in our blood?
How much O2 is carried per gram of haemoglobin?
With haemoglobin, how much O2 is carried in the blood to tissues?
- 150 x 5 = 750
- 1.34 ml of O2 per gram
- Roughly 1000ml/min
What percentage of O2 in the blood is extracted by tissue?
How many alpha and beta chains are in haemoglobin?
- 2 A
- 2 B
What is the name given to the fact that if an O2 binds to one of the polypeptide chains, it increases the affinity for O2 of the others?
What are the 4 different types of haemoglobin?
- Adult haemoglobin (HbA)
- Fetal haemoglobin (HbF)
- Glycosylated haemoglobin
What percentage of total haemoglobin is HbA?
How does HbA2 differ from HbA?
Delta chains replace beta chains
How does HbF differ from HbA?
Gamma chains replace beta chains
What are the three types of glycosylated haemoglobin?
What is the major determinant of haemoglobin saturation with oxygen?
Partial pressure of O2 in arterial blood
What condition is testing for glycosylated haemoglobin useful for?
How does haemoglobin help maintain the partial pressure gradient needed to draw O2 out of the alveoli?
- Essentially mops up the O2 in the plasma
- This means more O2 is drawn out to try to reach equilibrium until the haemoglobin is saturated
What saturation is haemoglobin at at normal systemic arterial PO2?
What is the saturation of haemoglobin at venous pressure?
What has a higher affinity for O2, HbA or HbF?
Why does HbF need a higher affinity?
Used to capture O2 from maternal blood
What has a higher affinity, HbF or myoglobin?
Which type of muscle fibres have more myoglobin?
Definition of anaemia?
Condition where O2 carrying capacity of the blood is compromised
What is the PaO2 during anaemia?
What effect does acidosis have on affinity for oxygen and therefore the haemoglobin saturation curve?
Lowers O2 affinity so more O2 moves out into the muscles, graph shifts right
What effect does alkalosis have on affinity for oxygen and therefore the haemoglobin saturation curve?
Increases affinity for O2, graph shifts left
What effect does increased body temperature have on affinity for oxygen and therefore the haemoglobin saturation curve?
Reduces affinity and shifts the curve to the right
What effect does low body temperature have on affinity for oxygen and therefore the haemoglobin saturation curve?
Increases affinity and shifts the curve left
How much more attracted to haemoglobin is carbon monoxide than oxygen?
What effect does 2,3 - DPG have on affinity for oxygen and therefore the haemoglobin saturation curve?
- Is released during hypoxia
- Reduces affinity and shifts the curve right
Once someone has breathed carbon monoxide in why is it hard to treat them?
Dissociates very slowly
What is a typical sign of carbon monoxide poisoning?
Cherry red skin
What is the treatment for CO poisoning?
- 100% oxygen
- Sometimes ventilate CO2 to encourage increased ventilation
What are the 5 main types of hypoxia?
- Hypoxic hypoxia - reduced O2 gas exchange
- Anaemic hypoxia - reduction in O2 carrying capability
- Ischaemic hypoxia - heart disease with innefficient circulation
- Histotoxic hypoxia - poisoning that prevents cells using O2
- Metabolic hypoxia - O2 delivery doesn't reach tissue demand
What 3 places does CO2 reside when being transported in the blood
- Plasma (7%)
- Combines with deoxyhaemoglobin (23%)
- Reacts with water in erythrocytes to form carbonic acid (70%)
What does the carbonic acid dissociate into?
Bicarbonate and H+ ions
What does the bicarbonate "swap" with to move out of the cell and what is this process called?
- Chlorine shift
What do the dissociated H+ ions do?
Bind to deoxyhaemoglobin
Why is CO2 able to change ECF pH?
It dissociates into a base and H+ ions which both alter the pH
When would CO2 alter pH?
What will hypoventilation cause?
CO2 retention - acidosis
What will hyperventilation cause?
CO2 will be lost more - alkalosis