Feasibility of the dynamic EIT technique for non-invasive monitoring of V/Q: a preliminary study

Ventilation/perfusion (V/Q) matching represents a crucial indicator of lung function. The current for assessing V/Q in a clinical setting are inadequate for bedside monitoring purposes. They are characterised by invasiveness and an increased risk of infection. Accordingly, the present study was based on a high-performance electrical impedance tomography (EIT) system developed by our team, with the objective of exploring the feasibility of using it for non-invasive assessment of V/Q at the bedside. This was achieved by acquiring and imaging pulmonary blood flow pulsation signals and combining them with pulmonary ventilation impedance information. Continuous lung EIT imaging data were acquired at 40 fps through different body positions and breath-holding in anaesthetised domestic pigs (N = 8, 17.50 ± 1.51 kg). By analysing the blood flow pulsation impedance information, lung perfusion-related data were extracted and combined with lung ventilation impedance data to establish a pulsatility V/Q assessment method. Furthermore, the monitoring of pulmonary perfusion using hypertonic saline (5 ml of 10% NaCl) was employed as a control experiment. The results demonstrate that the V/Q results obtained through the utilisation of both methodologies exhibit a notable degree of variability in response to alterations in body position and the state of breath holding. The V/Q results obtained using the pulsatility method and the saline method were subjected to analysis using the Bland-Altman agreement test. During end-expiration breath-holding in the supine position, the results were as follows: 95% CI = 2.36% to 10.26%, bias = 6.309%. During end-inspiration breath-holding in the supine position, the results were as follows: 95% CI = 0.07% to 12.23%, bias = 6.150%. During end-expiration breath-holding in the prone position, the results were as follows: 95% CI = -0.40% to 14.43%, bias = 7.014%. During end-inspiration breath-holding in the prone position, the results were as follows: 95% CI = 1.92% to 11.17%, bias = 6.541%. Moreover, a Pearson correlation analysis revealed a significant correlation between the V/Q match% of the two methods (r = 0.7248; 95% CI = 0.50% to 0.86%; p < 0.0001). Consequently, EIT imaging based on the pulsatility method is capable of assessing V/Q alterations resulting from diverse body positions and changes during breath-holding. This approach offers a novel concept for bedside monitoring of patients.