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Abstract #3672

Comparison Between End-Tidal CO2 and Tidal Volume Changes Calculated from the Respiratory Motion Tracing Used for Correction of Respiratory Fluctuations in a Functional MRI Experiment with Normal Breathing and Hyperventilation

Keith Michael Vogt1, James W. Ibinson2, Robert H. Small1, Petra Schmalbrock3

1Anesthesiology, The Ohio State University, Columbus, OH, USA; 2Anesthesiology, University of Pittsburgh Medical Center, Pittsburgh, PA, USA; 3Radiology, The Ohio State University, Columbus, OH, USA

Functional MRI data was acquired during normal ventilation and paced hyperventilation that caused a 35% decrease in end-tidal CO2 (ETCO2). Respiratory motion and expired CO2 data were collected and respiratory volume over time (RVT) and ETCO2 values were calculated. Although negatively correlated, the RVT and ETCO2 timecourses did not strictly mirror each other. RVT and ETCO2 values were convolved with appropriate response functions and regressed against each voxel timecourse. The ETCO2 regressor was more strongly and diffusely correlated to the FMRI data, suggesting that ETCO2 monitoring may be warranted in studies with large changes in respiration.