Graf Michael, Riedel Thomas
Division of Paediatric Pulmonology, Department of Paediatrics, Inselspital, University Children's Hospital and University of Bern, Bern, Switzerland.
Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, Ecole polytechnique federal de Lausanne, Lausanne, Switzerland.
PLoS One. 2017 Nov 16;12(11):e0188313. doi: 10.1371/journal.pone.0188313. eCollection 2017.
Electrical impedance tomography (EIT) is used on the thorax to measure impedance changes due to the presence of air and blood in the lung. This experimental study was performed to investigate the effect of posture on cardiac and respiratory related impedance changes.
EIT measurements were performed on 14 healthy subjects in left-, right lateral, prone, supine and upright positions. Simultaneously, tidal volume was recorded with an ultrasonic flowmeter. For image reconstruction, the classic Sheffield back-projection and three variants of the modern GREIT algorithm were applied with two different reference frames. Amplitudes of cardiac- and respiratory impedance changes were extracted and compared between the positions.
We found significant differences in both cardiac and respiratory amplitudes between postures. Especially, supine and upright positions showed dramatic changes in amplitude. These differences between postures were unaffected by the change of reference frames in all reconstruction methods except of the classic Sheffield back projection. Possible sources that explain the observed posture dependency are discussed.
Researchers and clinicians need to be aware of this phenomenon when comparing EIT amplitudes in different body positions.
电阻抗断层成像（EIT）用于胸部，以测量由于肺部存在空气和血液而引起的阻抗变化。本实验研究旨在调查姿势对心脏和呼吸相关阻抗变化的影响。
对14名健康受试者在左侧卧位、右侧卧位、俯卧位、仰卧位和直立位进行EIT测量。同时，用超声流量计记录潮气量。对于图像重建，应用经典的谢菲尔德反投影法和现代GREIT算法的三种变体，并采用两种不同的参考框架。提取不同体位下心脏和呼吸阻抗变化的幅度并进行比较。
我们发现不同姿势下心脏和呼吸幅度均存在显著差异。特别是，仰卧位和直立位的幅度变化显著。除经典的谢菲尔德反投影法外，在所有重建方法中，姿势之间的这些差异不受参考框架变化的影响。讨论了解释观察到的姿势依赖性的可能原因。
研究人员和临床医生在比较不同体位的EIT幅度时需要意识到这一现象。
