Lecture 4: Resp failure Flashcards
What are the 4 types of hypoxia?
Cytotoxic - reduced ability to utilise O2
Circulatory - reduced ability to deliver O2
Anaemic - reduced ability to deliver O2
Hypoxaemic - reduced ability to deliver O2
What are the 5 mechanisms of hypoxaemia?
Reduced PIO2 Hypoventilation Diffusion limitations Mismatch Shunt
Where is ventilation lowest?
At the apex
Where is ventilation highest?
At the base
Where is perfusion lowest?
At the apex
Where is perfusion highest?
At the base
What is the order of Pa, Pv and PA at the apex (zone 1)?
PA>Pa>Pv
What is the order of Pa, Pv and PA in the centre (zone 2)?
Pa>PA>Pv
What is the order of Pa, Pv and PA at the base (zone 3)?
Pa>Pv>PA
Which is greater at the apex, ventilation or perfusion?
Ventilation > Perfusion
V/Q > 1
Which is greater in the middle of the lung, ventilation or perfusion?
Ventilation = Perfusion
V/Q = 1
Which is greater at the base, ventilation or perfusion?
Ventilation < Perfusion
V/Q < 1
What is the normal range of V/Q ratios?
0.3 to 10
What is meant by V/Q = 0?
When no ventilation occurs in a given area
Extreme version of V/Q mismatch that is called shunt
Decreased PAO2 - hypoxaemia
Unable to compensate with increased FIO2
What is meant by V/Q «_space;1?
Ventilation substantially reduced in a given area - V/Q mismatch
Decreased PAO2 - hypoxaemia
Able to compensate with increased FIO2
What is meant by V/Q»_space; 1?
Wasted ventilatory effort
How would lung failure present?
Gas exchange failure manifested by hypoxaemia
How would pump failure present?
Ventilatory failure manifested by hypercapnia