Fox W W, Schwartz J G, Shaffer T H
Pediatr Res. 1979 Jan;13(1):60-4. doi: 10.1203/00006450-197901000-00013.
The present study evaluates a new closed circuit helium (He) dilution technique for determination of endotracheal (ET) tube leakage and functional residual capacity (FRC) in neonates with ET tubes. By analytically relating the fall in He concentration due to mixing with that due to leakage, it is possible to predict the final equilibration concentration of He and, therefore, correct for ET tube leaks. The system (120 ml) contains an air pump, He meter, breathing bag in cyclinder, a strip chart readout, and solenoid valve. Continuous positive airway pressure (CPAP) or ventilator pressure can be applied during testing. FRC measurements were performed on 13 neonates (799--4500 g) on CPAP with ET tubes. Leak rates were significantly higher (P less than 0.001) on 3 cm H2O CPAP compared to O cm H2O CPAP. The mean measured FRC was 53.5 ml at 3 cm H2O and 46.3 ml at 0 cm H2O CPAP. If gas leakage had not been considered in FRC calculations, the error in FRC could have been as high as 39% at 3 cm H2O CPAP and 18% at 0 cm H2O CPAP.
本研究评估了一种新的闭路氦气（He）稀释技术，用于测定气管插管新生儿的气管内（ET）导管漏气情况和功能残气量（FRC）。通过分析因混合导致的He浓度下降与因漏气导致的He浓度下降之间的关系，可以预测He的最终平衡浓度，从而校正ET导管漏气情况。该系统（120毫升）包括一个气泵、He测量仪、圆柱形呼吸袋、带状图表读数器和电磁阀。测试期间可施加持续气道正压通气（CPAP）或呼吸机压力。对13例使用CPAP并带有ET导管的新生儿（体重799 - 4500克）进行了FRC测量。与0厘米水柱CPAP相比，3厘米水柱CPAP时的漏气率显著更高（P < 0.001）。在3厘米水柱CPAP时，测得的平均FRC为53.5毫升，在0厘米水柱CPAP时为46.3毫升。如果在FRC计算中未考虑气体泄漏，在3厘米水柱CPAP时FRC的误差可能高达39%，在0厘米水柱CPAP时为18%。
