Oxygen therapy

Question 1

When should oxygen therapy be administered?

Answer 1

When oxygen supply to tissues is reduced to avoid anaerobic respiration

Question 2

What are the key indicators for oxygen therapy?

Answer 2

SpO₂ < 93%
PaO₂ < 70 mmHg
Lactate > 2.0 mmol/L

Question 3

What are examples of conditions requiring oxygen therapy?

Answer 3

Ventilation/perfusion mismatch or diffusion impairment
- Pleural space pathology e.g. pneumothorax
- Lung pathology e.g. pneumonia
- Perfusion abnormalities e.g. hypovolaemic shock

Reduced global delivery of oxygen (DO2)
- Distributive shock e.g. sepsis/SIRS
- Anaemia
- Acid Base disturbances affection Hb/Sat curve

Right to left shunts (de-ox blood into circulation)

Question 4

How do acidosis & alkalaemia affect oxygen delivery?

Answer 4

Acidosis reduces Hb affinity -> increases O2 offloading

Alkalaemia increases Hb affinity -> decreases O2 offloading

Question 5

What are the pros and cons of flow-by oxygen?

Answer 5

✅ Easy, non-invasive, rapid delivery, no sedation required

❌ Poor oxygen delivery (FiO₂ = 25-30%), requires high gas flow, ineffective if not breathing

Question 6

What are the pros and cons of mask oxygen?

Answer 6

✅ FiO₂ = 40-50%, self-humidifying, non-invasive, no sedation, rapid

❌ CO₂ rebreathing risk, poorly tolerated, must be correctly sized, doesn’t bypass problem

Question 7

What are the pros and cons of an oxygen tent/cage?

Answer 7

✅ FiO₂ = 50%, easy, no sedation needed

❌ Delayed oxygen therapy (takes time to build up), can’t monitor patient, unsuitable for large animals, not appropriate before diagnosis (start again if cage opened)

Question 8

What are the pros and cons of nasal prongs?

Answer 8

✅ FiO₂ = 50-60%, well tolerated, good for brachycephalics (bypass nares)

❌ Ineffective if patient is not breathing through nose, prone to displacement

Question 9

What are the pros and cons of a nasal catheter?

Answer 9

✅ FiO₂ = 60%, permanent oxygen source, humidified, stable placement, suitable for long term

❌ Stressful placement, requires training

Question 10

What are the pros and cons of intubation?

Answer 10

✅ Bypasses airway obstruction, provides 100% FiO₂, allows ventilation

❌ Requires general anaesthesia, difficult in recovery, not ideal for pneumonia cases