Oxygen Treatment

Question 1

How does the body tellus weare breathless

Answer 1

Peripheral and central chemoreceptors tell us we need to improve oxygen supply to tissue.

Detect rising CO2 or H+ concentrations
Detecting falling O2 concentrations

Question 2

At what partial pressure of oxygen is Hb fully saturated?

Answer 2

100mmHg

Question 3

What are some causes of hypoxaemia?

Answer 3

• Low PiO2
• Hypoventilation
• Diffusion limitation
• Right-left shunt
• V/Q mismatch

Question 4

What is a right-left shunt?

Answer 4

Allows deoxygenated blood to bypass the lungs and return to the body

Question 5

What is hypercapnic respiratory failure?

Answer 5

Chronic hypercapnia desensitised chemoreceptors to rising CO2 levels.

Question 6

Why must you be careful in oxygen supplementation in COPD?

Answer 6

Too little is bad obviously.

Too much oxygen can be dangerous.
O2 supplementation causes a decrease in respiratory rate, without oxygen saturation changing that much,
This causes CO2 accumulation, causing CO2 narcosis from low pH.

Question 7

What are the O2 saturation targets for normocapnic and hypercapnic patients?

Answer 7

Normocapnic - acute asthma, acute pulmonary oedema. Aim for 94%-96%

Hypercapnic - chronic lung disease with high risk of CO2 insensitivity. Aim for 88% - 92% to avoid CO2 accumulation/narcosis.