估计肺功能的办法很多,护士要从众多的信息中找出那些是最有用的。例如动脉氧分压(PaO_2)是指示肺功能不全的最常用的检验之一,但若孤立地看PaO_2水平可能没多大帮助,甚至给人以错觉。建议使用动脉—肺泡氧比例(a/A)。为便于理解和使用a/A比值并用以解释PaO_2水平,首先就要复习影响PaO_2的因素。影响PaO_2水平最基本的原理是肺换气与灌注之间的失衡,当肺泡气流减少时,注入到受损肺泡毛细血管的血液就不能充分地氧合。静脉血经过肺没有很好被氧合就“短路”回到大循环。这些没有氧合的血与氧合了的血混合时,使PaO_2下降。静脉血与动脉血的混合可用QS/QT来表示。QS表示单位时间内“短 There are many ways to estimate lung function, and it is most useful for nurses to find those out of so much information. For example, PaO 2 is one of the most commonly used tests to indicate pulmonary insufficiency, but looking at PaO 2 levels in isolation may not help much or even give the wrong impression. It is recommended to use arterio-alveolar oxygen ratio (a / A). To understand and use the a / A ratio and to explain the PaO_2 level, we first review the factors that affect PaO_2. The most fundamental principle that affects PaO 2 levels is the imbalance between lung ventilation and perfusion. When alveolar airflow is reduced, the blood injected into damaged alveolar capillaries can not be fully oxygenated. Veins through the lungs are not well oxygenated to “short circuit” back to the big circle. PaO2 is decreased when these non-oxygenated blood mix with oxygenated blood. The mixture of venous blood and arterial blood can be expressed by QS / QT. QS that unit time "short