EIT-based non-invasive measurements correlate with pulmonary arterial pressure in patients
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Objective
To investigate associations between electrocardiogram (ECG)-referenced timing markers derived from electrical impedance tomography (EIT) and invasively measured mean pulmonary artery pressure (mPAP) in patients with cardiovascular disease.
Approach
EIT, ECG and pulmonary artery pressure were recorded in seven patients during a protocol combining apnoea and phenylephrine administration. Four waveform landmarks were considered: the maximum, the maxima of the first and second derivatives, and the tangent intersection. Their delays from ECG R waves defined eight markers across the heart and lung regions. Within-patient Pearson and Spearman correlations were calculated against unsmoothed invasive mPAP.
Main results
Across 56 patient–marker combinations, the mean absolute Spearman coefficient was 0.74. Absolute coefficients reached 0.70 in 40 combinations and 0.80 in 27. Each patient had at least one marker with an absolute coefficient above 0.79. The lung second-derivative timing marker exceeded 0.90 in four patients, more often than any other marker, but showed weaker associations in the remaining three. Associations were positive in 25 combinations and negative in 31. Their strength and direction varied across patients and landmarks.
Significance
These exploratory findings support studying regional EIT timing as a non-invasive correlate of pulmonary haemodynamics. Validation in independent recordings is required before using these markers to estimate pressure. EIT timing markers are associated with PAP changes in patients; however, there is significant variation between patients.
