Special circumstances

Long standing anaemia

[WG21: p642]

In otherwise healthy individual

• Hb<75g/L --> Exertional dyspnoea
• Hb<60g/L --> Weakness
• Hb<30g/L --> Dyspnoea at rest
• Hb<20g/L --> Heart fails

Special circumstances

• Hypovolemia
• Haemorrhage
• Pregnancy
• Foetal/newborn
• Exercise
• Supine --> standing
• Valsalva
• Anaesthetics
• IPPV/PEEP

Artificial respiration

Lung inflation by positive pressure
--> Increase in intrathoracic pressure
--> Decrease in venous return to heart