EIT Assessment of Lung Volume and Tidal Distribution: A Comparison of Non-Invasive Ventilation Devices

Mechanical ventilation is life-saving technology but it can also inadvertently induce lung injury and increase morbidity and mortality. There currently is not an easy method of assessing the impact ventilator settings have on the degree of lung inflation. Computed tomography (CT), the gold standard for visually monitoring lung function, can provide detailed regional information of the lung. Unfortunately, it necessitates moving critically ill patients to a special diagnostic room and involves exposure to radiation like an X-ray. A technique introduced in the 1980's, electrical impedance tomography (EIT), can non-invasively provide similar monitoring of lung function, and without the exposure to radiation. This imaging technique applies small alternating currents of electricity to surface electrodes to construct cross-sectional images of the lung. Over that past several decades EIT has moved from the research lab to commercially available devices that are used at the bedside. EIT has also been applied to study the effects of various devices used to provide non-invasive ventilation. EIT may prove useful to optimally adjust non-invasive ventilation settings to improve ventilation and oxygenation. One such EIT system is manufactured by Draeger Medical. It is available in Europe and Canada but is not yet FDA approved for use in the United States. This study is being done with healthy volunteers to further the investigators' knowledge of the EIT system and to see if measures between two non-invasive ventilation systems routinely used clinically are equivalent. As this is a preliminary study looking at the EIT system vs 2 other devices, outcomes measures may be modified as the study progresses.