Smit Henk J, Vonk-Noordegraaf Anton, Marcus J Tim, van der Weijden Saskia, Postmus Pieter E, de Vries Peter M J M, Boonstra Anco
Department of Pulmonary Medicine, Vrije Universiteit Medical Center, Amsterdam, the Netherlands.
Chest. 2003 Jun;123(6):1803-9. doi: 10.1378/chest.123.6.1803.
Electrical impedance tomography (EIT) is a noninvasive imaging technique using impedance to visualize and measure blood volume changes.
To examine the validity of EIT in the measurement of hypoxic pulmonary vasoconstriction (HPV) and hyperoxic pulmonary vasodilation in healthy volunteers and COPD patients.
Group 1 consisted of seven healthy volunteers (mean age, 46 years; age range, 36 to 53 years). Group 2 comprised six clinically stable COPD patients (mean age, 65 years; age range, 50 to 74 years).
EIT measurements were performed in healthy subjects while they were breathing room air, 14% oxygen (ie, hypoxia), and 100% oxygen (ie, hyperoxia) through a mouthpiece. Maximal impedance change during systole (DeltaZsys) was used as a measure of pulmonary perfusion-related impedance changes. Stroke volume (SV) was measured by means of MRI. In the COPD group, EIT and SV also were determined, but only in room air and under hyperoxic conditions.
The data were statistically compared to data for the room air baseline condition. In the volunteers, the mean (+/- SD) DeltaZsys for the group was 352 +/- 53 arbitrary units (AU) while breathing room air, 309 +/- 75 AU in hypoxia (p < 0.05), and 341 +/- 69 AU in hyperoxia (not significant [NS]). The mean MRI-measured SV was 83 +/- 21 mL while breathing room air, 90 +/- 29) mL in hypoxia (NS), and 94 +/- 19 mL in hyperoxia (p < 0.05). In the COPD patients, the mean DeltaZsys for this group was 222 +/- 84 AU while breathing room air and 255 +/- 83 AU in hyperoxia (p < 0.05). In this group, the SV was 59 +/- 16 mL while breathing room air and 61 +/- 13 mL in hyperoxia (NS). Thus, the volunteer EIT response to hypoxia is not caused by decreased SV, because SV did not show a significant decrease. Similarly, in COPD patients the EIT response to hyperoxia is not caused by increased SV, because SV showed only a minor change.
EIT can detect blood volume changes due to HPV noninvasively in healthy subjects and hyperoxic vasodilation in COPD patients.
电阻抗断层成像（EIT）是一种利用阻抗来可视化和测量血容量变化的非侵入性成像技术。
检验EIT在测量健康志愿者和慢性阻塞性肺疾病（COPD）患者的低氧性肺血管收缩（HPV）和高氧性肺血管舒张方面的有效性。
第1组由7名健康志愿者组成（平均年龄46岁；年龄范围36至53岁）。第2组包括6名临床稳定的COPD患者（平均年龄65岁；年龄范围50至74岁）。
对健康受试者通过咬嘴分别吸入室内空气、14%氧气（即低氧）和100%氧气（即高氧）时进行EIT测量。将收缩期最大阻抗变化（DeltaZsys）用作肺灌注相关阻抗变化的指标。通过磁共振成像（MRI）测量每搏输出量（SV）。在COPD组中，也测定了EIT和SV，但仅在室内空气和高氧条件下进行。
将数据与室内空气基线条件下的数据进行统计学比较。在志愿者中，该组在吸入室内空气时DeltaZsys的平均值（±标准差）为352±53任意单位（AU），低氧时为309±75 AU（p<0.05），高氧时为341±69 AU（无显著性差异[NS]）。MRI测量的SV在吸入室内空气时平均为83±21 mL，低氧时为90±29 mL（无显著性差异），高氧时为94±19 mL（p<0.05）。在COPD患者中，该组在吸入室内空气时DeltaZsys的平均值为222±84 AU，高氧时为255±83 AU（p<0.05）。在该组中，SV在吸入室内空气时为59±16 mL，高氧时为61±13 mL（无显著性差异）。因此，志愿者对低氧的EIT反应不是由SV降低引起的，因为SV没有显著下降。同样，在COPD患者中，对高氧的EIT反应也不是由SV增加引起的，因为SV仅显示出微小变化。
EIT能够在健康受试者中无创检测由HPV引起的血容量变化，以及在COPD患者中检测高氧性血管舒张。
