Reply to Wang and Zhong: Bedside Evaluation of Pulmonary Embolism by Saline Contrast–enhanced Electrical Impedance Tomography: Considerations for Future Research

He, Huaiwu; Long, Yun; Chi, Yi; Yuan, Siyi; Zhao, Zhanqi

doi:10.1164/rccm.202010-3768le

Cited by 2 publications

(4 citation statements)

References 6 publications

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“…Different airway pressures at end-inspiration and end-expiration could cause variation in lung perfusion. It is debatable whether lung perfusion by EIT should be measured at end-inspiration or end-expiration [ 46 ] or whether it matches average perfusion during normal tidal breathing. Inspiratory hold could be more readily implemented for patients with mild sedation, but a higher airway pressure at end-inspiration may cause an impairment of global circulation.…”

Section: Discussionmentioning

confidence: 99%

Three broad classifications of acute respiratory failure etiologies based on regional ventilation and perfusion by electrical impedance tomography: a hypothesis-generating study

Chi

Long

et al. 2021

Ann. Intensive Care

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Background The aim of this study was to validate whether regional ventilation and perfusion data measured by electrical impedance tomography (EIT) with saline bolus could discriminate three broad acute respiratory failure (ARF) etiologies. Methods Perfusion image was generated from EIT-based impedance–time curves caused by 10 ml 10% NaCl injection during a respiratory hold. Ventilation image was captured before the breath holding period under regular mechanical ventilation. DeadSpace%, Shunt% and VQMatch% were calculated based on lung perfusion and ventilation images. Ventilation and perfusion maps were divided into four cross-quadrants (lower left and right, upper left and right). Regional distribution defects of each quadrant were scored as 0 (distribution% ≥ 15%), 1 (15% > distribution% ≥ 10%) and 2 (distribution% < 10%). Data percentile distributions in the control group and clinical simplicity were taken into consideration when defining the scores. Overall defect scores (DefectV, DefectQ and DefectV+Q) were the sum of four cross-quadrants of the corresponding images. Results A total of 108 ICU patients were prospectively included: 93 with ARF and 15 without as a control. PaO2/FiO2 was significantly correlated with VQMatch% (r = 0.324, P = 0.001). Three broad etiologies of ARF were identified based on clinical judgment: pulmonary embolism-related disease (PED, n = 14); diffuse lung involvement disease (DLD, n = 21) and focal lung involvement disease (FLD, n = 58). The PED group had a significantly higher DeadSpace% [40(24)% vs. 14(15)%, PED group vs. the rest of the subjects; median(interquartile range); P < 0.0001] and DefectQ score than the other groups [1(1) vs. 0(1), PED vs. the rest; P < 0.0001]. The DLD group had a significantly lower DefectV+Q score than the PED and FLD groups [0(1) vs. 2.5(2) vs. 3(3), DLD vs. PED vs. FLD; P < 0.0001]. The FLD group had a significantly higher DefectV score than the other groups [2(2) vs. 0(1), FLD vs. the rest; P < 0.0001]. The area under the receiver operating characteristic (AUC) for using DeadSpace% to identify PED was 0.894 in all ARF patients. The AUC for using the DefectV+Q score to identify DLD was 0.893. The AUC for using the DefectV score to identify FLD was 0.832. Conclusions Our study showed that it was feasible to characterize three broad etiologies of ARF with EIT-based regional ventilation and perfusion. Further study is required to validate clinical applicability of this method. Trial registration clinicaltrials, NCT04081142. Registered 9 September 2019—retrospectively registered, https://clinicaltrials.gov/show/NCT04081142.

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Section: Discussionmentioning

confidence: 99%

Three broad classifications of acute respiratory failure etiologies based on regional ventilation and perfusion by electrical impedance tomography: a hypothesis-generating study

Chi

Long

et al. 2021

Ann. Intensive Care

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“…Variation was found among different impedance-time curve analysis methods in two patients (He et al, 2021a), and further study is required to optimize the analysis methods.…”

Section: Eit Data Analysismentioning

confidence: 99%

“…The mean lung transit time, which is defined as the time required for blood flow transfer from the right ventricle to the left atrium, should be taken into consideration regards to the length of the breath-hold. However, the apnea time does not need to be as long as the pulmonary transit time (PTT) for lung perfusion (He et al, 2021a). Recent experimental explorations suggested that it took ∼3-5 s from the injection for the saline to enter the lungs and ultimately concentrate (Hentze et al, 2018).…”

Section: Breath Holdingmentioning

confidence: 99%

“…On the other hand, end-inspiratory holding with maximal inflation of the lungs can suppress respiratory drive and dilute carbon dioxide (CO 2 ) levels, and it is considered to be more readily implemented. However, the higher airway pressure at end-inspiration may cause an impairment of global circulation and lung perfusion (He et al, 2021a). Further exploration is necessary to compare the clinical applicability of end-inspiration and end-expiration occlusion methods.…”

Section: Breath Holdingmentioning

confidence: 99%

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Lung Perfusion Assessment by Bedside Electrical Impedance Tomography in Critically Ill Patients

Long

2021

Front. Physiol.

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As a portable, radiation-free imaging modality, electrical impedance tomography (EIT) technology has shown promise in the bedside visual assessment of lung perfusion distribution in critically ill patients. The two main methods of EIT for assessing lung perfusion are the pulsatility and conductivity contrast (saline) bolus method. Increasing attention is being paid to the saline bolus EIT method in the evaluation of regional pulmonary perfusion in clinical practice. This study seeks to provide an overview of experimental and clinical studies with the aim of clarifying the progress made in the use of the saline bolus EIT method. Animal studies revealed that the saline bolus EIT method presented good consistency with single-photon emission CT (SPECT) in the evaluation of lung regional perfusion changes in various pathological conditions. Moreover, the saline bolus EIT method has been applied to assess the lung perfusion in a pulmonary embolism and the effect of positive end-expiratory pressure (PEEP) on regional ventilation/perfusion ratio (V/Q) and acute respiratory distress syndrome (ARDS) in several clinical studies. The implementation of saline boluses, data analyses, precision, and cutoff values varied among different studies, and a consensus must be reached regarding the clinical application of the saline bolus EIT method. Further study is required to validate the impact of the described saline bolus EIT method on decision-making, therapeutic management, and outcomes in critically ill patients.

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Reply to Wang and Zhong: Bedside Evaluation of Pulmonary Embolism by Saline Contrast–enhanced Electrical Impedance Tomography: Considerations for Future Research

Cited by 2 publications

References 6 publications

Three broad classifications of acute respiratory failure etiologies based on regional ventilation and perfusion by electrical impedance tomography: a hypothesis-generating study

Three broad classifications of acute respiratory failure etiologies based on regional ventilation and perfusion by electrical impedance tomography: a hypothesis-generating study

Lung Perfusion Assessment by Bedside Electrical Impedance Tomography in Critically Ill Patients

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