Oxygen

Question 1

What are the physiological risks to supplemental
oxygen therapy?

Answer 1

1. Worsened V/Q mismatch.
2. Absorption atelectasis.
3. Coronary and cerebral vasoconstriction.
4. Reduced cardiac output.
5. Damage from oxygen free radicals.
6. Increased systemic vascular resistance.

Question 2

What are the clinical risks to overoxygenation?

Answer 2

2. Delay in recognition of clinical deterioration.
3. Potentially worse outcomes in mild-to-moderate stroke.
4. Specific risk in patients with previous bleomycin lung
   damage or with paraquat poisoning or acid aspiration.
5. Unknown risk–benefit balance in acute coronary artery
   disease with normal oxygen saturation.
6. Association with increased risk of death in survivors of
   cardiac arrest and among patients on ICUs.
7. harmful to patients who are at risk of hypercapnic respiratory failure,especially if the PaO2 is raised above 10 kPa.
8. associated with increased risk of death in some patient groups eg, patients with mild and moderate strokes

Question 3

What is the Haldane effect?

Answer 3

Deoxygenated haemoglobin has a higher carbon dioxide buffering capacity than oxygenated haemoglobin. This favours carbon dioxide pick-up in the systemic venous circulation and carbon dioxide offloading in the lungs.