Human Phys 6.8 Flashcards
What do our lungs aim at?
Keeping ventilated alveoli in areas that are well perfused
How can keeping ventilated alveoli in areas that are well perfused be accomplished?
Compensatory bronchoconstriction (controls V)
Compensatory hypoxic vasoconstriction (controls Q)
What results when small regions of alveoli are not well perfused? (Pulmonary embolus)
Dead space
What does compensatory bronchoconstriction do when regions of alveoli are not well perfused?
Send air to other well perfused areas of the lungs
What results when small regions of alveoli are not ventilated? (Airway collapse or obstruction)
Right to left shunt
What does the compensatory hypoxic vasoconstriction do when small regions of alveoli are not ventilated?
Sends blood to other well ventilated areas of the lungs
Why is blood flow higher at base?
Due to impact of gravity and hydrostatic pressure
What is ventilation higher at base?
Gravity and weight of lung reduce alveolar volume but alveoli at base is more compliant and capable of oxygen exchange
What is normal ventilation?
4 L/min
What is normal perfusion?
5 L/min
What is the normal ventilation/perfusion ratio for the lung as a whole?
0.8
What does it mean when V/Q is higher than 0.8?
Ventilation exceeds perfusion
What is the V/Q at the apex of the lung?
Higher (less Q)
What is the V/Q at the middle of the lung?
Even
What is the V/Q at the base of the lung?
Lower (too much Q)
