肺泡-动脉氧梯度

肺泡：动脉氧梯度是衡量跨肺泡膜气体传输效率的指标。它是跨肺泡膜的氧张力差。

• Aa（梯度）= PAO2（肺泡 O2 分压）- PaO2（动脉 O2 分压）

肺泡氧分压 PAO2 计算如下：

• PAO2 = (FiO2 - PCO2)/R，其中 R 约为 0.8，FiO2 在室内空气中为 20 kPa。

否则，Aa 梯度可以通过以下公式估算：

• PiO2 (吸入氧分压 PO2) - ( PaO2 (动脉氧分压 PO2) + PaCO2 (动脉氧分压 PCO2) )

吸入氧的分压大约为 100 kPa 的百分比。

该梯度的上限随年龄变化，在 1.5 kPa 和 3.0 kPa 之间。梯度超过 3.0 kPa 表明气体交换受损。

 

 

The Alveolar : arterial oxygen gradient is an index of the efficiency of gas transfer across the alveolar membrane. It is the difference in oxygen tension across the alveolar membrane.

• A-a (gradient) = PAO2 (partial pressure alveolar O2) - PaO2 (partial pressure arterial O2)

The alveolar partial pressure of oxygen, PAO2 is given as:

• PAO2 = (FiO2 - PCO2)/R where R is approximately 0.8 and FiO2 is 20 kPa on room air.

Otherwise the A-a gradient may be estimated by the formula:

• PiO2 (inspired PO2) - ( PaO2 (arterial PO2) + PaCO2 (arterial PCO2) )

The partial pressure of inspired O2 is approximately its percentage in kPa.

 

The upper limit for this gradient varies with age between 1.5 kPa and 3.0 kPa. A gradient in excess of 3.0 kPa suggests impaired gas exchange.