Wrigge H, Sydow M, Zinserling J, Neumann P, Hinz J, Burchardi H
Zentrum Anaesthesiologie, Rettungs- u. Intensivmedizin, Göttingen, Germany.
Intensive Care Med. 1998 May;24(5):487-93. doi: 10.1007/s001340050601.
Validation of an open-circuit multibreath nitrogen washout technique (MBNW) for measurement of functional residual capacity (FRC). The accuracy of FRC measurement with and without continuous viscosity correction of mass spectrometer delay time (TD) relative to gas flow signal and the influence of baseline FIO2 was investigated.
Laboratory study and measurements in mechanically ventilated patients.
Experimental laboratory and anesthesiological intensive care unit of a university hospital.
16 postoperative patients with normal pulmonary function (NORM), 8 patients with acute lung injury (ALI) and 6 patients with chronic obstructive pulmonary disease (COPD) were included.
Change of FIO2 from baseline to 1.0.
FRC was determined by MBNW using continuous viscosity correction of TD(TDdyn), a constant TD based on the viscosity of a calibration gas mixture (TD0) and a constant TD referring to the mean viscosity between onset and end of MBNW (TDmean). Using TDdyn, the mean deviation between 15 measurements of three different lung model FRCs (FRCmeasured) and absolute volumes (FRCmodel) was 0.2%. For baseline FIO2 ranging from 0.21 to 0.8, the mean deviation between FRCmeasured and FRCmodel was -0.8%. However, depending on baseline FIO2, the calculation of FRC using TDmean and TD0 increased the mean deviation between FRCmeasured and FRCmodel to 2-4% and 8-12%, respectively. In patients (n = 30) the average repeatability coefficient was 6.0%. FRC determinations with TDmean and TD0 were 0.8-13.3% and 4.2-23.9% (median 2.7% and 8.7%) smaller than those calculated with TDdyn.
A dynamic viscosity correction of TD improves the accuracy of FRC determinations by MBNW considerably, when gas concentrations are measured in a sidestream. If dynamic TD correction cannot be performed, the use of constant TDmean might be suitable. However, in patient measurements this can cause an FRC underestimation of up to 13%.
验证用于测量功能残气量（FRC）的开路多次呼吸氮冲洗技术（MBNW）。研究了在对质谱仪延迟时间（TD）相对于气流信号进行连续粘度校正和不进行校正的情况下FRC测量的准确性，以及基线FIO₂的影响。
对机械通气患者进行实验室研究和测量。
大学医院的实验实验室和麻醉重症监护病房。
纳入16例肺功能正常的术后患者（NORM）、8例急性肺损伤（ALI）患者和6例慢性阻塞性肺疾病（COPD）患者。
将FIO₂从基线值改为1.0。
通过MBNW使用TD的连续粘度校正（TDdyn）、基于校准气体混合物粘度的恒定TD（TD0）以及参考MBNW开始和结束之间平均粘度的恒定TD（TDmean）来测定FRC。使用TDdyn时，对三种不同肺模型FRC（FRC测量值）进行15次测量与绝对体积（FRC模型）之间的平均偏差为0.2%。对于基线FIO₂范围为0.21至0.8的情况，FRC测量值与FRC模型之间的平均偏差为-0.8%。然而，根据基线FIO₂，使用TDmean和TD0计算FRC会使FRC测量值与FRC模型之间的平均偏差分别增加到2%-4%和8%-12%。在患者（n = 30）中，平均重复性系数为6.0%。使用TDmean和TD0测定的FRC分别比使用TDdyn计算的结果小0.8%-13.3%和4.2%-23.9%（中位数分别为2.7%和8.7%）。
当在旁流中测量气体浓度时，对TD进行动态粘度校正可显著提高MBNW测定FRC的准确性。如果无法进行动态TD校正，使用恒定的TDmean可能是合适的。然而，在患者测量中，这可能导致FRC低估高达13%。
