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Respiratory 4
Respiratory 4
22
Physiology
Undergraduate 4
11/26/2016

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Term
If PO2 is low, what does that mean?
Definition
lower concentration of oxygen in the air = lower oxygen partial pressure
Term
What is oxygen tension?
Definition
concentration of oxygen in the air (PO2)
Term
Why is PO2 of inspired air lower than environmental air?
Definition
because it gets humidified, and the added water vapour 'dilutes' the oxygen concentration
Term
What is PA CO2?
Definition
alveolar partial pressure of carbon dioxide
Term
Why is alveolar oxygen tension (PA O2) lower than that of inspired air?
Definition
because oxygen is diffusing out of the alveoli into the blood, and CO2 is diffusing in
Term
If PA CO2 rises, what happens to PA O2?
Definition
PA O2 must drop
Term
What is alveolar hypoventilation?
Definition
decrease in ventilation of the alveoli, resulting in an increased PA CO2 and decreased PA O2
Term
What effect does alveolar hyperventilation have on PA CO2 / PA O2?
Definition
increased ventilation will mean more CO2 is removed from the blood than is being produced, so PA CO2 will decrease while PA O2 increases
Term
Will hypoxia lead to hypo or hyper ventilation?
Definition
hyper (lack of oxygen will increase breath per minute to try and compensate)
Term
Is gas exchange active or passive?
Definition
passive
Term
What factors affect diffusion of gases across the alveolar & endothelial walls?
Definition
Diffusion coefficient of the gas
Surface area available for diffusion
Distance between air and blood
Pressure gradient
Term
Why does gas exchange between capillaries & tissues improve during exercise?
Definition
More capillaries are recruited, reducing the distance between tissues & capillaries and as the number of dilating vessels increases, blood flow slows which allows more time for gas exchange
Term
What causes 'normal' ventilation mistmatch?
Definition
Gravity's effects on perfusion

-ventral areas have a lower V/Q than dorsal areas
Term
What does V/Q represent?
Definition
ventilation/perfusion ratio
Term
What is 'normal' V/Q in animals?
Definition
0.8
Term
What does a low V/Q mean?
Definition
blood is circulating but not becoming fully oxygenated
Term
What does a low V/Q mean?
Definition
the alveolus is well ventilated but not receiving enough blood
Term
Impaired ventilation is associated with (high/low) V/Q ratios
Definition
low
Term
What type of problem can be addressed by providing oxygen, ventilation or perfusion?
Definition
ventilation
Term
What is a right-to-left shunt
Definition
When blood flows through an unventilated region of the lung (or bypasses the lung completely) and picks up no O2
Term
Impaired perfusion is associated with (high/low) V/Q ratios
Definition
high
Term
If ventilation is normal but blood flow in the lungs is impaired, PO2 will be (high/low), while PCO2 will be (high/low)
Definition
high
low
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