The Science Journal of the American Association for Respiratory Care

2010 OPEN FORUM Abstracts

EVALUATION OF ELECTRICAL IMPEDANCE TOMOGRAPHY IN VARIOUS MODES AND SETTINGS OF MECHANICAL VENTILATION

Roger W. Reichenbach1, Mark Stronati1, Rena Laliberte1, Shirley Smith1, Nikolai Pamukov1, Michael Malian2; 1Department of Respiratory Therapy, Henry Ford Health System, Detroit, MI; 2Department of Acute Care Surgery, Henry Ford Health System, Detroit, MI

BACKGROUND: Electrical Impedance Tomography (EIT) is a non-invasive radiation- free monitoring tool. EIT generates cross-sectional images of the chest from measurements of transthoracic electrical conductivity. The device monitors impedance changes in regional lung ventilation with the use of an electrode belt applied around the chest wall. We hypothesized that increases in impedance should correlate to increases in measured tidal volumes on the Evita XL ventilator (Draeger Medical) with various changes in Continuous Positive Airway Pressure (CPAP) and Pressure Support Ventilation(PSV) during mask ventilation. METHODS: After obtaining IRB approval, 10 volunteers (n=10) were mask fit and placed on the following settings for one minute: CPAP 0/PSV 0; CPAP 5/ PSV 0; CPAP 5 / PSV 5; and PSV 5/CPAP 0 while data was recorded using the Draeger Medical EIT Evaluation Kit 2. We also recorded an average tidal volume (Vt) obtained by the minute ventilation for the corresponding ventilator settings. For data analysis a Pearson correlation coefficient was calculated for each individual and is summarized in Table I. RESULTS: For the study we anticipated a positive correlation of measured Vt and global tidal variations (impedance changes). The pooled correlation was 0.168 with a positive slope of 0.0125, meaning that correlation was small and that the two variables (global tidal variations and measured Vt) are not well correlated. Our data shows that increases in global tidal variations, obtained from the EIT device, do not consistently reflect a simultaneous increase in tidal volume as measured on the ventilator. CONCLUSION: Draeger Medical makes no claim to a numeric correlation between global tidal variations ( unitless number ) to volume measurements. The use of EIT bedside for graphic images of ventilation can be useful. However, using the data from the EIT device and ventilator to quantify any changes would require additional methods. Future clinical studies are needed to assist in finding those methods which would be most beneficial to the bedside clinician. Sponsored Research - None

Table I : (N=10) Summary of Results of Correlation and Slope

Grateful Acknowledgement to Ed Peterson PhD. ; Department of Biostatistics and Research Epidemiology, Henry Ford Health System