Regional lung perfusion estimated by electrical impedance tomography in a piglet model of lung collapse

Abstract

The assessment of the regional match between alveolar ventilation and perfusion in critically ill patients requires simultaneous measurements of both parameters. Ideally, assessment of lung perfusion should be performed in real-time with an imaging technology that provides, through fast acquisition of sequential images, information about the regional dynamics or regional kinetics of an appropriate tracer. We present a novel electrical impedance tomography (EIT)-based method that quantitatively estimates regional lung perfusion based on first-pass kinetics of a bolus of hypertonic saline contrast. Pulmonary blood flow was measured in six piglets during control and unilateral or bilateral lung collapse conditions. The first-pass kinetics method showed good agreement with the estimates obtained by single-photon-emission computerized tomography (SPECT). The mean difference (SPECT minus EIT) between fractional blood flow to lung areas suffering atelectasis was -0.6%, with a SD of 2.9%. This method outperformed the estimates of lung perfusion based on impedance pulsatility. In conclusion, we describe a novel method based on EIT for estimating regional lung perfusion at the bedside. In both healthy and injured lung conditions, the distribution of pulmonary blood flow as assessed by EIT agreed well with the one obtained by SPECT. The method proposed in this study has the potential to contribute to a better understanding of the behavior of regional perfusion under different lung and therapeutic conditions.

In-vitro evaluation of contrast media for assessment of regional perfusion distribution by Electrical Impedance Tomography (EIT)

“…This approach was later on used in animal experiments in view of estimation of local ventilation and perfusion distribution (V˙/Q˙ ratio) [4]. In an actual publication a 20% solution was applied [5]. Extremely hypertonic sodium solutions may cause major water shift and changes of resistance in pulmonary circulation.…”

Ventilation/perfusion distributions revisited

“…Featuring high temporal resolution but limited spatial resolution, the method is well suited for measuring regional ventilation, and recent developments have included the use of hypertonic saline washin-washout kinetics for regional perfusion [17].…”

Lung imaging: how to get better look inside the lung

“…EIT has been validated as a tool to estimate several respiratory parameters, such as the end-expiratory lung volume versus nitrogen washout test and plethysmography (49), and the distribution of lung volumes compared to CT (50). EIT can also provide indirect quantification of lung perfusion, either measuring the signal pulsatility due to the blood flow, or temporarily increasing the conductance of perfused lung areas with an injection of hypertonic saline in a central venous line (51).…”