EIT-based non-invasive measurements correlate with pulmonary arterial pressure in patients

Abstract Objective. To investigate the relationship between cardiac synchronized timing of electrical impedance tomography (EIT) signals and invasively measured mean pulmonary artery pressure (mPAP) in patients with cardiovascular disease. Approach. EIT, ECG and mPAP were recorded in seven patients as part of routine surgery during an apnoea phase, while pressure changes were induced with phenylephrine. Four waveform timings 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. Main results. Across 56 patient marker combinations, the mean absolute Spearman coefficient was 0.74. Marker strength and direction varied across patients and landmarks. Each patient had at least one timing marker with an absolute value 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. Significance. These findings represent the first study of EIT timing and mPAP in patients; it suggests that EIT could be a useful non invasive predictor of clinical pulmonary haemodynamics. However, work is required to combine information from timing markers and to relate EIT values to pressure.