Unidad de Pacientes Críticos, Departamento de Medicina, Hospital Clínico Universidad de Chile, Dr. Carlos Lorca Tobar 999, Independencia, Santiago, Chile.
Divisao de Pneumologia, Faculdade de Medicina, Instituto do Coração, Hospital das Clinicas HCFMUSP, Universidade de São Paulo, São Paulo, Brazil.
Crit Care. 2023 Nov 24;27(1):457. doi: 10.1186/s13054-023-04748-4.
In the acute distress respiratory syndrome (ARDS), specific lung regions can be exposed to excessive strain due to heterogeneous disease, gravity-dependent lung collapse and injurious mechanical ventilation. Computed tomography (CT) is the gold standard for regional strain assessment. An alternative tool could be the electrical impedance tomography (EIT). We aimed to determine whether EIT-based methods can predict the dynamic relative regional strain (DRRS) between two levels of end-expiratory pressure (PEEP) in gravity-non-dependent and dependent lung regions.
Fourteen ARDS patients underwent CT and EIT acquisitions (at end-inspiratory and end-expiratory) at two levels of PEEP: a low-PEEP based on ARDS-net strategy and a high-PEEP titrated according to EIT. Three EIT-based methods for DRRS were compared to relative CT-based strain: (1) the change of the ratio between EIT ventilation and end-expiratory lung impedance in arbitrary units ([ΔZ/EELI]/[ΔZ/EELI]), (2) the change of ΔZ/EELI ratio calibrated to mL ([ΔZ/EELI]/[ΔZ/EELI]) using CT data, and (3) the relative change of ∆Z (∆Z/∆Z). We performed linear regressions analysis and calculated bias and limits of agreement to assess the performance of DRRS by EIT in comparison with CT.
The DRRS assessed by (ΔZ/EELI)/(ΔZ/EELI) and ∆Z/∆Z showed good relationship and agreement with the CT method (R of 0.9050 and 0.8679, respectively, in non-dependent region; R of 0.8373 and 0.6588, respectively, in dependent region; biases ranging from - 0.11 to 0.51 and limits of agreement ranging from - 0.73 to 1.16 for both methods and lung regions). Conversely, DRRS based on EELI ([ΔZ/EELI]/[ΔZ/EELI]) exhibited a weak negative relationship and poor agreement with the CT method for both non-dependent and dependent regions (R ~ 0.3; bias of 3.11 and 2.08, and limits of agreement of - 2.13 to 8.34 and from - 1.49 to 5.64, respectively).
Changes in DRRS during a PEEP trial in ARDS patients could be monitored using EIT, based on changes in ΔZ/EELI and ∆Z. The relative change ∆Z offers the advantage of not requiring CT data for calibration.
在急性呼吸窘迫综合征（ARDS）中，由于疾病的异质性、重力依赖性肺萎陷和损伤性机械通气，特定的肺区域可能会受到过度的应变。计算机断层扫描（CT）是评估区域应变的金标准。替代工具可能是电阻抗断层成像（EIT）。我们旨在确定 EIT 能否预测重力非依赖区和依赖区在两种呼气末正压（PEEP）水平之间的动态相对区域应变（DRRS）。
14 名 ARDS 患者在两种 PEEP 水平下进行 CT 和 EIT 采集（吸气末和呼气末）：一种是基于 ARDS-net 策略的低 PEEP，另一种是根据 EIT 滴定的高 PEEP。比较了三种基于 EIT 的 DRRS 方法与基于 CT 的应变：（1）任意单位（[ΔZ/EELI]/[ΔZ/EELI]）中 EIT 通气与呼气末肺阻抗比值的变化，（2）使用 CT 数据校准到毫升的[ΔZ/EELI]比值（[ΔZ/EELI]/[ΔZ/EELI]），（3）[ΔZ]的相对变化（∆Z/∆Z）。我们进行了线性回归分析，并计算了偏差和一致性区间，以评估 EIT 与 CT 相比在评估 DRRS 方面的性能。
（ΔZ/EELI）/（ΔZ/EELI）和 ∆Z/∆Z 评估的 DRRS 与 CT 方法具有良好的相关性和一致性（非依赖区的 R 分别为 0.9050 和 0.8679，依赖区的 R 分别为 0.8373 和 0.6588；两种方法和两种肺区的偏差范围为-0.11 至 0.51，一致性区间范围为-0.73 至 1.16）。相反，基于 EELI 的 DRRS（[ΔZ/EELI]/[ΔZ/EELI]）在非依赖区和依赖区与 CT 方法的相关性均较弱且一致性较差（R 约为 0.3；偏差为 3.11 和 2.08，一致性区间为-2.13 至 8.34 和-1.49 至 5.64）。
ARDS 患者在 PEEP 试验期间，可基于[ΔZ/EELI]和[ΔZ]的变化，使用 EIT 监测 DRRS 的变化。相对变化[ΔZ]的优势在于无需 CT 数据进行校准。
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