Hypoxia Flashcards
What is hypoxia?
Low tissue partial pressure of oxygen = organ/tissue dysfunction or cell death
How does PaO2 change with age?
Decreases
What are the causes of hypoxia? (3)
- Hypoxaemia
- Reduction in oxygen supply
- Inability to use it
What are the two types of hypoxia? (2)
- Single organ=impaired blood flow
- Global=whole body
What is hypoxaemia?
Low arterial partial pressure of oxygen (low PaO2)
What does hypoxia lead to locally?
Ischaemia and eventual infarction
List the causes of hypoxaemia (5)
- High altitude
- Opioid overdose (hypoventilation)
- Diffusion defect e.g fibrosis
- V:Q mismatch e.g PE
- Right to left cardiac shunt - e.g congenital cyanotic heart disease
List 2 broad causes of hypoxaemia that are type I resp failures. What happens to AA difference in these conditions? Does O2 help?
- Diffusion defect e.g fibrosis/puemonia
- V:Q mismatch e.g PE
AA differennce = increased
O2 helps
What is hypoxaemia in high altitude caused by? What is AA difference like - does O2 help? (4)
- Fall in barometric pressure leads to decreased PIO2
- Decreased PaO2
- Normal AA difference
- O2 helps
What is hypoxaemia in opioid overdose caused by? What is AA difference like - does O2 help? (3)
- Interrupted resp transport leads to decrease in PA(arterial)O2
- Normal AA
- O2 helps
What type of resp failure is opiod overdose? And why?
- Type 2 resp failure
- Hypoventilation causes hypercapnia
Explain why a right to left cardiac shunt causes hypoxaemia? What is AA difference like - does O2 help? (5)
- Shunted blood bypasses alveoli
- Cannot be ventilated
- Very low PaO2
- Increased AA difference
- O2 help limited: only non shunted blood
Give an example of a right to left cardiac shunt
Congenital cyanotic heart disease
What are the causes of tissue hypoxia? (4)
- Hypoxaemia
- Stagnant hypoxia
- Anaemic hypoxia
- Histotoxic hypoxia
Why does pulmonary fibrosis/puenmonia lead to type I resp failure? (2)
- Decreased diffusion distance
- Decrease in PaO2
