Letter questions pulsatility-based EIT for pulmonary embolism diagnosis

A letter in Critical Care challenges the interpretation and clinical readiness of a pulsatility-based electrical impedance tomography (EIT) method for pulmonary embolism (PE) diagnosis. The method uses heart rate-adaptive filtering to extract cardiac-synchronous impedance signals and derive matching, dead space, and shunt indices. The letter discusses a two-center retrospective study comparing 53 patients with PE against 53 healthy controls; it presents no new data.

According to the letter, the combined three-index model achieved 66.0% sensitivity and 84.9% specificity, despite statistically significant differences between groups. The authors argue that healthy controls do not represent the clinical challenge of distinguishing PE from pneumonia, heart failure, COPD exacerbation, or other symptomatic conditions. Exclusion of patients with arrhythmias and unstable hemodynamics further limits applicability to critically ill patients.

The central concern is that pulsatility does not directly measure regional blood flow. Citing international consensus documents, the letter notes that heartbeat-related impedance changes reflect multiple sources, including blood volume changes, vessel distensibility, and cardiac motion. Hemodynamic disturbances and regional lung compression may also alter these signals independently of embolic occlusion.

The authors recommend positioning the technique as a research tool rather than a clinical PE diagnostic test. They call for prospective studies in consecutive patients with suspected PE, including CT pulmonary angiography-negative controls, direct comparison with saline contrast EIT, and assessment of hemodynamic confounders. These conclusions represent a methodological critique, not a new diagnostic validation study.