Frequency-domain band-pass filtering enhanced pulsation method for pulmonary embolism diagnosis and risk stratification: a two-center retrospective study

BACKGROUND: Pulmonary embolism (PE) remains a major cause of morbidity and mortality in critical care, yet traditional diagnostic methods face limitations, especially in critically ill patients. This study introduces a novel frequency-domain band-pass filtering enhanced electrical impedance tomography (EIT) pulsation method for rapid, non-invasive PE diagnosis and risk stratification. METHODS: In a two-center retrospective study, 106 participants (53 PE patients, 53 healthy controls) were enrolled. A 16-electrode EIT system recorded pulmonary blood flow pulsation signals, and a heart rate-adaptive band-pass filter with its lower cutoff frequency set slightly below the estimated heart rate was applied to extract perfusion-related pulsatility while separating it from ventilation-related low-frequency components. Key parameters (Matching Index (MI), Dead space index (DI), Shunt Index (SI), Electrical Impedance VQ ratio(EIVQ)) were analyzed for PE diagnosis and risk stratification. RESULTS: Compared with healthy controls, PE patients had significantly lower MI (P < 0.001) and higher DI (P < 0.001) and SI (P = 0.005). For risk stratification, intermediate-high-risk PE patients showed lower MI and higher DI than lower-risk patients, with the strongest differences versus low-risk patients (both adjusted P < 0.001).Among the EIT-derived parameters, the combined MI + DI+SI model achieved the highest AUC (0.820, 95% CI: 0.741-0.899), although the improvement over MI alone was marginal; it outperformed DI and SI. EIVQ showed no significant discriminative value. CONCLUSIONS: The enhanced EIT pulsatility method shows promise for non-invasive bedside assessment of PE-related perfusion abnormalities. MI, DI, and SI differentiated PE patients from healthy controls, while MI and DI were associated with risk stratification. These findings support the diagnostic and risk-stratification potential of EIT-derived pulsatility parameters and warrant further validation in consecutive patients with suspected PE.