血气和氧合

PaO2 的正常范围是 11.3-13.3 kPa。分压低于 8 kPa 定义为呼吸衰竭。

动脉低氧血症通常是由于肺部疾病引起的：

• 气体交换不良：
  • I型呼吸衰竭
  • PaCO2 通常较低
• 通气不足：
  • II型呼吸衰竭
  • PaCO2 通常会升高

当肺部正常时，可能会发生动脉低氧血症：

• 吸入氧分压低，如海拔
• 通气-血流灌注失配
• 右向左分流：
  • 先天性心脏病
  • 肺血管动静脉畸形

测量肺泡-动脉 (Aa) 梯度对缺氧患者很有用，可能有助于区分肺部疾病引起的缺氧血症与其他原因引起的缺氧血症。

 

The normal range for PaO2 is 11.3-13.3 kPa. A partial pressure less than 8 kPa defines respiratory failure.

Arterial hypoxaemia is commonly due to pulmonary disease:

• poor gas transfer:
  • type I respiratory failure
  • PaCO2 is typically low
• hypoventilation:
  • type II respiratory failure
  • PaCO2 is typically raised

Arterial hypoxaemia may occur when the lungs are normal:

• low inspired partial pressure of oxygen e.g. altitude
• ventilation-perfusion mismatch
• right to left shunts:
  • congenital heart disease
  • arteriovenous malformation of the pulmonary vessels

 

Measurement of the alveolar-arterial (A-a) gradient is useful in hypoxic patients and may help to distinguish hypoxaemia due to pulmonary disease from other causes of hypoxaemia.