Schaffartzik W
Klinik für Anaesthesiologie und operative Intensivmedizin, Freie Universität Berlin.
Anaesthesist. 1993 Jan;42(1):3-10.
When arterial and mixed venous blood gas tensions, inspired and expired O2 and expired CO2 concentrations are known, it is possible to calculate the alveolar-arterial PO2 difference, intrapulmonary right-to-left shunt and dead space ventilation. However, because arterial hypoxemia is caused by ventilation/perfusion mismatching in most cases, a method allowing analysis of ventilation/perfusion ratios is needed. The "multiple inert gas elimination technique" (MIGET) is a powerful method that is useful for this purpose. This technique is based on measurements of arterial, venous and expired levels of inert gases spanning a wide range of solubility and analysis of the lung for the ventilation/perfusion ratios from true shunt to dead space ventilation. True shunt, with ventilation/perfusion ratios of 0, can be differentiated from ventilation/perfusion ratios of 0.005, and dead space ventilation can be distinguished from ventilation/perfusion ratios over 10 and under 100. Ventilation/perfusion ratios between these extremes can also be differentiated. It is not unusual for results yielded by MIGET to differ from those obtained with O2-dependent methods: O2 shunt generally exceeds MIGET shunt, for example, because O2 shunt includes low ventilation/perfusion units.
当动脉血和混合静脉血的血气张力、吸入和呼出的氧气以及呼出的二氧化碳浓度已知时，就可以计算肺泡-动脉血氧分压差、肺内右向左分流和死腔通气。然而，由于大多数情况下动脉低氧血症是由通气/灌注不匹配引起的，因此需要一种能够分析通气/灌注比值的方法。“多种惰性气体清除技术”（MIGET）就是一种适用于此目的的强大方法。该技术基于对一系列具有广泛溶解度的惰性气体的动脉、静脉和呼出水平的测量，并分析肺从真正分流到死腔通气的通气/灌注比值。真正的分流，通气/灌注比值为0，可以与通气/灌注比值为0.005区分开来，死腔通气可以与通气/灌注比值超过10和低于100区分开来。这些极端值之间的通气/灌注比值也可以区分。MIGET得出的结果与依赖氧气的方法获得的结果不同并不罕见：例如，氧气分流通常超过MIGET分流，因为氧气分流包括低通气/灌注单位。
