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当通气不均匀时，观测的肺泡示踪气体浓度低于其实际平均肺泡气浓度，因此，常规的洗出示踪气体法低估了肺功能残气量（ＦＲＣ）。我们研究了一种改进的洗出示踪气体方法以纠正这种低估：在洗出ＳＦ６的最后几次呼气期间，观测示踪气体浓度同累积呼出的示踪气体量近于线性关系。因此ＦＲＣ等于上述线性关系的截距除以洗入末肺泡示踪气体的浓度。使用六氟化硫（ＳＦ６）作为示踪气体证明了常规的洗出法低估了ＦＲＣ，以及陷闭气量（ＶＴＧ）包括２部分：被深呼吸激起的真正的陷闭气量（ＶＴＧＭ）以及由于肺通气不均匀而被低估掉的ＦＲＣ的一部分，后者是由于肺通气不均匀而引起的陷闭气量（ＶＴＧＩ），它是修正后的ＦＲＣ同常规法洗出末示踪气体浓度为洗入末示踪气体浓度的１／４０时测量的ＦＲＣ之差，１０名健康受检者的ＶＴＧＩ随年龄增加而增加，这说明肺通气的均匀性同健康人的年龄有正相关。
When the ventilation is not uniform, the observed concentration of alveolar tracer gas is lower than its actual mean concentration of alveolar gas, so conventional washout tracer gas method underestimates the amount of lung functional residual volume (FRC). We investigated an improved method of washing out the tracer gas to correct this underestimation: during the last few expirations of the SF6 washout, the observed tracer gas concentration is nearly linear with the cumulative expired tracer gas volume. FRC is therefore equal to the intercept of the above linear relationship divided by the concentration of gas traced to the end of the alveolus. The use of sulfur hexafluoride (SF6) as the tracer gas proved that conventional washout methods underestimated the FRC and that the trapped volume (VTG) consisted of two parts: the true trapped volume of gas (VTGM) provoked by deep breathing, Ventilation unevenly underestimated part of the FRC, which is caused by uneven ventilation of the lung volume of trapped gas (VTGI), which is corrected FRC with the conventional method of washing out the tracer gas concentration at the end of wash The difference in FRC measured at 1/40 of the tracer gas concentration and VTGI in 10 healthy subjects increased with age, indicating that the homogeneity of lung ventilation is positively correlated with the age of healthy people.