Distribution of inspired gases and gas transfer (self directed) Flashcards
How does airway resistance changed in supine position compared to upright position
Airway resistance is increases in supine compared to upright position
What is the compliance like in high pressures and why
At high pressure, the lung is stiffer, hence compliance is lower (eg like a balloon)
Which part of the lung are more compliant and what does this mean
Lung bases are more compliant (>volume) than the apex so there is better ventilation
What is decreased compliance because of
pulmonary fibrosis and alveolar oedema
What is increased compliance due to
Normal ageing of lung
What happens to lung compliance as you age, and why
Compliance increases with age due to a loss in elastic recoil
What does a loss in elastic recoil prevent
complete exhalation
What is characteristic of emphysema and what does this prevent
increased compliance and decreased elastic recoil
-prevents complete exhalation
What is characteristic of pulmonary fibrosis and what does this mean
Decreased compliance
-Extra work required for ventilation
What does oedema fluid in the interstitial space or fibrosis of the lung mean
Increased diffusion resistance which means there’s an interference with normal gas exchange
Out of oxygen and Co2, which moves faster through gas and why
O2 moves faster because larger molecules diffuse more slowly
Out of O2 and Co2, which moves faster in liquid and why
Co2 diffuses faster because it is more soluble than O2
How is gas transfer and respiration controlled
Neural regulation
Chemical regulation
Where is voluntary breathing controlled
Cerebral cortex
Where is involuntary breathing controlled
Pons
Medulla
Where does chemical regulation of gas transfer and respiration take place
Central chemoreceptors
Peripheral chemoreceptors
Where are central chemoreceptors found
Medulla
Where are peripheral chemoreceptors found
Carotid arteries and aortic arch
What is perfusion ratio
ratio of alveolar ventilation to blood flow
What are the normal values for perfusion ration
Va=normal=5
Q=normal=1
Va/Q=normal=1
What is the normal partial pressure of o2 in alveoli
13.3kPa
What is the normal partial pressure of Co2 in alveoli
5.3kPa
What happens in dead space in relation to ventilation
No capacity to carry O2 away or to bring CO2 to the alveoli
No gas exchange between the alveoli and the blood; alveoli equilibrates with atmosphere
What happens in shunt in relation to ventilation
No ventilation, normal perfusion
No new O2 into the system; alveoli equilibrates with venous blood
Why is there regional variation for Va/Q ratio in different areas of the lung
Due to gravity
In the apex, what Is blood flow and ventilation like
Decreased blood flow
Increased ventilation
In the base, what is the blood flow and ventilation like
Increased blood flow
Decreased ventilation
How would you diagnose a pulmonary embolism and how is this measured
Va/Q
-measured by V/Q scan using radioisotopes
What does hypoxia do to vessels
Low O2 constricts pulmonary arterioles
What does High O2 do to vessels
Dilates pulmonary arterioles
What does high CO2 (caused by lung disease) do to vessels
Dilates bronchioles
What does low O2 (hypocapnia) do to vessels
Constricts bronchioles
