Blood supply, gas exchange and ventilation Flashcards
Where is the biggest compliance?
At the base of lungs
Where is the greatest alveolar ventilation?
At the base of the heart
What is called systemic circulation in the lungs?
Bronchial circulation, arise from systemic, forms bronchial arteries
Describe pulmonary circulation
In series with heart, pulmonary artery arise from right ventricle, to lungs, pulmonary vein to left atrium
Describe the pressure and flow in pulmonary circulation
High flow, low pressure circulation
What is the systolic and diastolic pressure in pulmonary circulation ?
25 mmHg and 8 mmHg
What is the gradient between the arteries and veins?
10 mmHg, very small gradient, only very small change can cause big disruption
What is PAO2, PaO2, PvO2 ?
Partial pressure of O2 in alveoli, arteries and veins respectively
What is PAO2 and PACO2?
100 mmHg (13.3 kPa) and 40 mmHg (5.3 kPa)
What is PaO2 and PaCO2?
100 mmHg and 40 mmHg
What is PvO2, PvCO2 ?
40 mmHg and 46 mmHg
What affects diffusion?
It is directly proportional to partial pressure gradient, gas solubility, surface area, inversely proportional to the thickness of membrane and diffusion distance
What is the gradient between partial pressure of O2 and CO2 ?
60 mmHg and 6 mmHg, O2 gradient is 10 times bigger
What is the amount of O2 absorbed and CO2 excreted ?
250 ml of O2 and 200 ml of CO2 per minute
What happens to partial pressure of O2 in emphysema?
PAO2 is normal or low, in blood PO2 is low
What happens to partial pressure of O2 in lung fibrosis?
PAO2 is normal or low, in the blood is low
What happens to partial pressure of O2 in pulmonary oedema?
PAO2 is normal, in blood low
What happens to partial pressure of O2 in asthma?
PO2 is low both in alveoli and blood
Describe blood flow at the base of lungs
Most of the blood at the base due to gravity, compromising the alveoli, the arterial pressure is bigger than alveolar pressure, low vascular resistance, the blood flow is bigger than ventilation.
Describe the blood flow at the apex of lungs
Less blood than at the bottom, arterial pressure is less than alveolar, resistance is increased, ventilation is bigger than blood flow
On what factors is blood flow dependent upon?
It depends on the resistance. the biggest resistance is at the apex of lungs as the hydrostatic pressure of arteries is lower that the alveolar pressure. Blood flow declines with heigh from the bottom
Describe what is happening to the blood flow and ventilation from the base to the apex of lungs
Both blood flow and ventilation decrease from base to the apex, this is due to gravity. However, the rate of decline for blood flow is bigger and so at the top the ventilation is bigger than the blood flow.
Where does the crossover over ventilation and blood flow happens ?
Over rib 3
Describe the ventilation and perfusion ratio in the lungs
Rib 3 and below the ratio is very close to 1, it decreases slightly as the blood flow is bigger at the base. above rib 3 the ventilation/ perfusion ratio increases and is a lot bigger than 1, there is big mismatch
What is mismatch ratio <1?
The perfusion is bigger than ventilation
What is mismatch > 1?
The ventilation is bigger than perfusion
Where does the majority of mismatch happen?
At the apex of lungs, 75% of lung performs well in terms of the ventilation/perfusion ratio
Describe shunt
Hyperventilated alveoli, there is decrease in PO2 but increase in PCO2, this results is blood not being oxygenated, this blood than mixes with oxygenated blood and dilutes it
How is the mismatch in shunt corrected (ventilation
The area where hypoxia is detected the vessels constrict directing blood to bettie ventilated alveoli, this is the opposite to the systemic circulation. The increase in PCO2 causes bronchial dilation
When is ventilation > perfusion ?
In pulmonary embolism
What is alveolar dead space?
Alveoli that are ventilated but not perfused
What happens when the ventilation is bigger than perfusion?
The PO2 in increased, but the alveolar PCO2 is decreased, this causes dilation of blood vessels and constriction of bronchi, the end result is to increase perfusion and decrease ventilation
What is physiological dead space?
It is the sum of anatomical and alveolar dead space
What is anatomical dead space?
The air in conduction airways
