Department of Neonatology and Paediatric Intensive Care, University Hospital Carl Gustav Carus, Dresden, Germany.
PLoS One. 2011;6(6):e21003. doi: 10.1371/journal.pone.0021003. Epub 2011 Jun 7.
Electrical Impedance measurements can be used to estimate the content of intra-thoracic air and thereby give information on pulmonary ventilation. Conventional Impedance measurements mainly indicate relative changes, but no information concerning air-volume is given. The study was performed to test whether a 3-point-calibration with known tidal volumes (VT) during conventional mechanical ventilation (CMV) allows subsequent calculation of VT from total Tidal-Impedance (tTI) measurements using Quadrant Impedance Measurement (QIM). In addition the distribution of TI in different regions of the thorax was examined.
QIM was performed in five neonatal piglets during volume-controlled CMV. tTI values at three different VT (4, 6, 8 ml/kg) were used to establish individual calibration curves. Subsequently, each animal was ventilated with different patterns of varying VT (2-10 ml/kg) at different PEEP levels (0, 3, 6, 9, 12 cmH(2)O). VT variation was repeated after surfactant depletion by bronchoalveolar lavage. VT was calculated from tTI values (VT(calc)) and compared to the VT delivered by the ventilator (VT(PNT)). Bland-Altman analysis revealed good agreement between VT(calc) and VT(PNT) before (bias -0.08 ml; limits of agreement -1.18 to 1.02 ml at PEEP = 3 cmH(2)O) and after surfactant depletion (bias -0.17 ml; limits of agreement -1.57 to 1.22 ml at PEEP = 3 cmH(2)O). At higher PEEP levels VT(calc) was lower than VT(PNT), when only one fixed calibration curve (at PEEP 3 cmH(2)O) was used. With a new calibration curve at each PEEP level the method showed similar accuracy at each PEEP level. TI showed a homogeneous distribution over the four assessed quadrants with a shift toward caudal regions of the thorax with increasing VT.
Tidal Impedance values could be used for precise and accurate calculation of VT during CMV in this animal study, when calibrated at each PEEP level.
电阻抗测量可用于估计胸腔内的空气含量，从而提供有关肺通气的信息。传统的阻抗测量主要指示相对变化，但没有给出关于气量的信息。本研究旨在测试在常规机械通气（CMV）期间使用已知潮气量（VT）进行 3 点校准是否允许随后使用四象限阻抗测量（QIM）从总潮气量阻抗（tTI）测量值计算 VT。此外，还检查了 TI 在胸部不同区域的分布。
在五头新生仔猪中进行了 QIM 测量，在容量控制的 CMV 期间进行。使用三个不同 VT（4、6、8 ml/kg）的 tTI 值来建立个体校准曲线。随后，每只动物在不同的 PEEP 水平（0、3、6、9、12 cmH2O）下以不同的 VT（2-10 ml/kg）进行通气。在通过支气管肺泡灌洗耗尽表面活性剂后，重复 VT 变化。从 tTI 值计算 VT（VT(calc)）并与呼吸机提供的 VT（VT(PNT)）进行比较。Bland-Altman 分析显示，在表面活性剂耗尽之前（偏差 -0.08 ml；在 PEEP = 3 cmH2O 时，一致性界限为 -1.18 至 1.02 ml）和之后（偏差 -0.17 ml；在 PEEP = 3 cmH2O 时，一致性界限为 -1.57 至 1.22 ml），VT(calc) 和 VT(PNT) 之间具有良好的一致性。在较高的 PEEP 水平下，当仅使用一个固定的校准曲线（在 PEEP 3 cmH2O 时）时，VT(calc) 低于 VT(PNT)。当在每个 PEEP 水平下使用新的校准曲线时，该方法在每个 PEEP 水平下均显示出相似的准确性。TI 在四个评估象限中呈均匀分布，随着 VT 的增加，向胸部的尾部区域转移。
在这项动物研究中，当在每个 PEEP 水平下进行校准时，潮气量阻抗值可用于 CMV 期间 VT 的精确和准确计算。
