Lecture 23: Hypoxia Flashcards
What is hypoxia?
Low oxygen content
What is hypoxaemia?
Low PaO2
___________ produces ________ but the converse is not true
Hypoxaemia produces Hypoxia
What is cyanosis?
Blue colour from deoxygenated Hb that occurs in tissue hypoxia and hypoxaemic hypoxia
What are 5 causes of hypoxaemia?
- Low PiO2 (inspired)
- Hypoventilation
- Diffusion limitation
- Right-Left Shunt
- V’/Q’ mismatch
___% of people who drown don’t get water in the lungs. Instead they die because of ___________.
60
Laryngeospasm
What happens when you get fresh water in the lungs?
- Fresh water is hypotonic and so rapidly diffuses and causes epithelial cell rupture
- However the fluid gets absorbed by the blood
- Eventually leads to haemolysis
- Dilution of the blood
What happens when you get salt water in the lungs?
- Salt water is Hypertonic and thus draw water out of the cells causing oedema
- Causes electrolyte issues due to electrolyte absorption
- Slows or halts diffusion of gases
- reduces ventilation because it’s filled with fluid
What causes hypoventilation?
- Respiratory muscle failure
- Restrictive disease (↓ compliance)
- Obstructive disease (↑ Resistance)
Hypoventilation makes you _________ and _________.
Hypoxic and Hypercapnic
Alveolar CO2 is proportional to _________
PACO2 ∝ V’CO2/V’A
During hypoventilation PAO2 always ______ and is _______ to PaO2
Falls
PAO2 equal to PaO2
During hypoventilation PACO2 always ________ and is ______ to PaCO2
Increases
PACO2 equal to PaCO2
What is the Alveolar Gas Equation
PAO2 = PiO2 - PACO2/RQ
How is RQ calculated?
V’CO2/V’O2
