Pulsatile Electrical Impedance Tomography for Diagnosis and Monitoring of Acute Pulmonary Embolism

Pulmonary embolism is an important type of venous thromboembolism and may be associated with substantial morbidity and mortality. CT pulmonary angiography is commonly used as the reference standard for diagnosis, but it has limitations, including radiation exposure, use of iodinated contrast agents, and limited feasibility for continuous bedside monitoring in some critically ill patients.

Electrical impedance tomography is a noninvasive functional imaging technique that can be performed at the bedside and does not involve radiation. This study will evaluate a pulsatile EIT-based approach for assessing pulmonary ventilation and perfusion. The main EIT-derived parameters include the ventilation-perfusion matching index, dead-space ventilation index, and intrapulmonary shunt index.

The retrospective phase will collect existing clinical and EIT data from patients with CTPA-confirmed acute pulmonary embolism and healthy controls. These data will be used to compare EIT parameters between groups, evaluate diagnostic performance, and explore optimal cutoff values.

The prospective phase will enroll patients newly diagnosed with acute pulmonary embolism and healthy volunteers. EIT examinations will be performed during routine clinical evaluation and follow-up. EIT parameters will be compared with CTPA findings, clinical risk stratification, D-dimer levels, echocardiographic indicators, and clinical outcomes. For patients with pulmonary embolism, serial EIT measurements may be used to evaluate dynamic changes during treatment and follow-up.

This is an observational study. Participants will not be assigned to any treatment by the study protocol, and clinical management will be determined by the treating physicians according to routine clinical practice.

Inclusion criteria

• Adults aged 18 years or older. For retrospective PE cases: patients with acute pulmonary embolism confirmed by CT pulmonary angiography, with completed pulsatile electrical impedance tomography examination, adequate image data, and available clinical information.

For retrospective healthy controls: adults without evidence of lower-extremity venous thrombosis, with normal D-dimer levels, simplified Wells score ≤1, and no pulmonary embolism-related symptoms or history.

For prospective PE patients: patients newly diagnosed with pulmonary embolism by CT pulmonary angiography or CT pulmonary angiography plus CT venography, with body mass index less than 50 kg/m², who voluntarily participate and provide written informed consent.

For prospective non-PE controls: patients with suspected acute pulmonary embolism who undergo CT pulmonary angiography or CT pulmonary angiography plus CT venography, but in whom pulmonary embolism is not confirmed, who voluntarily participate and provide written informed consent.

Exclusion criteria

• Previous diagnosis of chronic pulmonary embolism or idiopathic pulmonary arterial hypertension.

Acute exacerbation of chronic obstructive pulmonary disease, acute heart failure, acute myocardial infarction, or other severe cardiopulmonary diseases that may interfere with study assessment.

Pregnancy or lactation. Thoracic deformity. Contraindications to EIT examination, including automatic implantable cardioverter defibrillator, chest wounds limiting electrode belt placement, implanted pumps, or other conditions unsuitable for EIT electrode belt placement.

Participation in another clinical trial during the same period, for prospective participants.

Unstable vital signs requiring emergency rescue, leaving no time to complete EIT examination, for prospective participants.

Any other condition considered unsuitable for participation by the investigators.