Mechanical ventilation is essential for patients with acute lung injury (ALI) in ICU. Inadequate me-chanical ventilation can sometimes develop ventilator-induced lung injury (VILI) which has high mortal-ity of 41%. To prevent VILI, a real-time lung monitoring system is needed to find lung tidal volume and optimal positive end-expiratory pressure for individual settings of ventilator. The chest x-ray CT can provide images containing regional information of lung, but it is not suitable for continuous moni-toring at bedside and cannot guide the appropriate ventilation in real-time. Electrical impedance to-mography (EIT) is particularly useful for measuring the changes of intra-thoracic impedance distribu-tion as a method for lung ventilation monitoring since the impedance of lung increases and decreas-es several-fold between inhalation and exhalation. EIT is an imaging technique which calculates the distribution of electrical impedance within the body from the electrodes applied on the body surface. EIT system is composed of 3 components, the electrode array to contact the skin, the electronic cir-cuits to inject current and read out the voltage along the electrode array, and the computing device with display to reconstruct the tomographic images.
For the lung ventilation monitoring, we proposed a belt-type portable ventilation monitoring system. It is possible because of the proposed EIT SoC which enables low power and real-time imaging of the user’s ventilation. With the help of the proposed SoC, the EIT system has very small form factor and can be operated with battery, and images can be displayed even on the mobile devices. The SoC preprocesses the impedance signals, and through the standard USB-OTG cable, it transmits digital signals for more accurate image without noise degradation. With the tablet computer or even smart phones, the EIT SoC can display the lung tomographic images.